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Ozone: Science & Engineering
The Journal of the International Ozone Association
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/bose20
Effect of Elevated Tropospheric Ozone on Vigna
Mungo L. Varieties
Periyasamy Dhevagi, Ambikapathi Ramya, Sengottiyan Priyatharshini &
Ramesh Poornima
To cite this article: Periyasamy Dhevagi, Ambikapathi Ramya, Sengottiyan Priyatharshini &
Ramesh Poornima (2021): Effect of Elevated Tropospheric Ozone on Vigna�Mungo L. Varieties,
Ozone: Science & Engineering, DOI: 10.1080/01919512.2021.2009332
To link to this article: https://doi.org/10.1080/01919512.2021.2009332
Published online: 12 Dec 2021.
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Eect of Elevated Tropospheric Ozone on Vigna Mungo L. Varieties
Periyasamy Dhevagi , Ambikapathi Ramya , Sengottiyan Priyatharshini , and Ramesh Poornima
Department of Environmental Sciences, Tamil Nadu Agricultural University, Coimbatore, India
ABSTRACT
Tropospheric ozone (O
3
) is widely recognized as the most critical, regional atmospheric pollutant
causing signicant losses to agricultural productivity due to its phytotoxicity over agricultural areas
and is expected to increase in future. In view of rising tropospheric ozone concentration over Indian
regions, the present study aimed to evaluate the eect of elevated ozone stress on pulse crop
blackgram (Vigna mungo L.), which contributes the major share of protein. The blackgram varieties
namely CO 6, VBN 1, VBN 2, VBN 3, VBN 5, VBN 6, VBN 7, and VBN 8 were grown in open top
chambers and factorial completely randomized block design was followed. The plants were
exposed to elevated ozone concentration (50 and 100 ppb) from 10.00 h to 17.00 h over 10 days
at owering stage, with a weighted average ozone concentration of 50.1 and 101.2 ppb. Both the
elevated ozone treatments signicantly aected the plant physiological, biochemical, growth, and
yield traits of all test varieties. On an average across eight blackgram varieties, decrease in
chlorophyll content by 33.83 and 42.41%, stomatal conductance by 28.25 and 40.51% and photo-
synthetic rate by 29.43 and 42.30% exposed to 50 and 100 ppb ozone were observed, respectively.
Correspondingly, the number of pods per plant decreased by 30.82 and 32.65%, 100 grain weight
by 7.75 and 21.23% and plant weight by 16.03 and 21.23%, respectively, which were signicant at
5% level. Furthermore in the observed traits, signicantly higher reduction was observed in VBN3,
while the least reduction was observed in VBN8. The path analysis displayed that all the observed
physiological, biochemical, growth, and yield traits positively regulated the yield except leaf injury
percentage, malondialdehyde, and proline content. The principal component analysis of two
elevated ozone treatments conrmed VBN8 as ozone tolerant and VBN3 as ozone sensitive variety.
Hence, cultivation of VBN8 variety at ozone hotspot regions would be the best option to overcome
ozone induced yield loss.
ARTICLE HISTORY
Received 19 April 2021
Accepted 13 November 2021
KEYWORDS
Ozone; blackgram varieties;
crop response; principal
component analysis
Introduction
Rapid industrialization and unregulated urbanization
during the past decades in developing countries caused
tremendous increase in the concentration of primary
and secondary air pollutants. Tropospheric Ozone,
a phytotoxic secondary air pollutant concentration has
more than doubled since Industrial Revolution (Monks
et al. 2015). Although ozone concentrations vary spa-
tially at global scale, many of the world’s agricultural
regions are exposed to high ozone during the crop-
growing season. Simulations for the period 2015
through 2050 project boosts in ozone by 20–25%
(Grewe et al. 2001), and simulations through 2100 indi-
cates that ozone may increase by 40–60% (Hauglustaine
et al. 2005). The impacts are going to be most severe over
many parts of the world and this increase in ozone
pollution reduces the net primary productivity of terres-
trial vegetation by 1–16% globally (Ainsworth et al.
2012). Injudicious urbanization, increase in number of
motor vehicles, increased fuel consumption poor
environmental regulations has led to multifaceted air
pollution problems. In addition, meteorological condi-
tions such as high temperature and high light intensity
with long light duration are favorable to ozone forma-
tion due to long range transport of precursor emissions.
Tropospheric ozone has mounted from approximately
10 ppb in the late 1800s to monthly average daytime
concentrations exceeding 40–50 ppb these days (Brauer
et al. 2016).
A sudden reduction of greenhouse gases (GHGs) has
been observed by many researchers during COVID-19
lockdowns across various regions of the world (Donzelli
et al. 2021). In comparison with the pollutants concen-
tration during pandemic lockdown year (2020) with
respect to previous years, PM
10
, PM
2.5
, NO, NO
2
, and
SO
2
concentrations were decreased with modest
changes. Conversely, due to the significant reduction in
NO levels during the lockdown period, ozone concen-
tration increased in various parts of the world (Donzelli
et al. 2021). According to Brancher (2021), the
CONTACT Periyasamy Dhevagi devagisivaraj@gmail.com Tamil Nadu Agricultural University, Coimbatore 641003, Tamil Nadu, India
OZONE: SCIENCE & ENGINEERING
https://doi.org/10.1080/01919512.2021.2009332
© 2021 International Ozone Association
observation from January to September 2020 showed
slight increase in ozone concentration by 4.3% over
Vienna. Moreover, the daily average ozone concentra-
tion significantly increased during the lockdown year
(2020) by 2.4% in Valencia, 14% in Rome, 24% in
Nice, 27% in Turin, and 36% in Wuhan (Sicard et al.
2020). Correspondingly, in India, Sharma et al. (2020)
reported a rise in ozone concentration by 17% during
lockdown year. The ozone level increased from 26 to
56.4 ppb during pre-lockdown (1 February–
23 March 2020) and lockdown period (24 March–
30 April 2020), respectively in Hyderabad City, India
(Allu et al. 2021). Bera et al. (2021) recorded an increase
of ozone by 4.14% in New Delhi, 3.58% in Mumbai,
2.28% in Kolkata, and 1.26% in Chennai during lock-
down (April 2020) compared to prelockdown
(April 2019) year. Increase in tropospheric ozone
severely affects the human health and vegetation due to
its higher oxidation potential.
Tropospheric ozone enters into the plants through
the photosynthesis and respiration processes causing
phenotypical and physiological changes. The ozone
exposure of 0.2 ppm for 2 min/day for 10 days depicted
a positive impact on the growth traits of the tomato
seedlings with increased leaf area, root and shoot length
and plant biomass (Sudhakar et al. 2008). Sublethal
ozone doses of 2.66 and 3.96 mg L
−1
applied to the
hydroponic float system significantly increased stem
diameter, root and shoot biomass of lettuce plants;
while the ozone doses of 20, 40, and 60 mg L
−1
caused
a rapid leaf tissue darkening and necrosis symptoms
(Vázquez-Ybarra et al. 2015). However, due to
unplanned urbanization and industrialization during
the past few decades, considerable increase in ozone
levels was observed and it has potential impact on
plant growth and yield. The magnitude of response to
ozone in plants varies significantly from crop to crop
(Mills et al. 2007) and from cultivar to cultivar (Sarkar
and Agrawal 2010).
Pulses are one of the important crops in India culti-
vated in an area of 28.3 million hectares with production
of 25.7 million metric tons for the financial year 2020–
2021, thereby supplying a major share of protein
requirement (Statista 2021). It is one of the most sensi-
tive crop against ozone and the critical level (AOT 40)
required for 5% reduction in yield for pulses is 3 ppm
h (Mills et al. 2007). Legumes were subjected to huge
yield loss of about 10–65% in Asian region where mean
ambient ozone concentration varied between 35 and 75
ppb in growing season of the crop (Emberson et al.
2009). In India, ozone pollution already threatens the
crop production where up to 18–79% yield losses in
Vigna radiata was reported (Agarwal et al. 2006).
Recent studies suggest a net reduction in crop yield
due to ozone over the Indian region (Sachin et al.
2014; Sinha et al. 2015). Therefore, it is substantially
manifested that exposure to elevated ozone concentra-
tion causes a range of adverse effects on legume plants
including reduction in photosynthetic activity, altered
carbon allocation, diminished biomass production,
reduced yield and accelerated senescence (Chaudhary
et al. 2013; Singh, Tiwari, and Agrawal 2010).
Based on the literature survey, most of ozone stress
studies were focused on the cultivars grown in Indo-
gangetic plains. In recent decades, the concentration of
ozone increased in many parts of India. However, no
studies have been reported on the sensitivity of black-
gram varieties with respect to increased ozone level in
southern region, where the climatic condition differ
markedly from other regions. With this evidence, the
current study aimed to examine the response of popu-
larly growing blackgram varieties to elevated ozone
stress. Principal component analysis (PCA) is
a multidimensional preference analysis that has been
previously used to classify the sensitive and tolerant
genotypes under various environmental stress (Fatima
et al. 2019; Kakar et al. 2019). This multivariate analysis
is used in this study to identify the principal variables
and correlation patterns within the plant traits that
would best describe the ozone tolerance and sensitivity
among the blackgram varieties. This method of classifi-
cation has more advantages by transforming the large set
of variables into fewer dimensions, which improves the
accuracy of classification model (Kakar et al. 2019). The
present study with ozone-induced stress on blackgram
and varietal screening poses significant importance to
crop production in certain region; on the other hand, it
has wide implication on plant breeding studies for devel-
oping ozone-tolerant breeds to overcome current cli-
mate change impacts. Further, with the evidence of
increasing ozone concentration in future, a detailed
study on the effect of elevated ozone on pulse could
provide a scientific evidence to understand the extent
of damage caused and mechanism underneath as well.
Materials and methods
Plant Materials and Meteorological Conditions
Blackgram varieties (CO 6, VBN 1, VBN 2, VBN 3,
VBN 5, VBN 6, VBN 7, and VBN 8) obtained from
the National Pulses Research Center, Vamban, Tamil
Nadu, India were used for the study (Table 1). The
experimental site is located at Wetland farm (11.00°
N, 76.92° E), Tamil Nadu Agricultural University,
Coimbatore, India. The experiment was conducted
2P. DHEVAGI ET AL.
under controlled condition in Open Top Chamber to
evaluate the elevated ozone stress on blackgram vari-
eties during two crop growing seasons. The experi-
ment I with 50 ppb ozone stress was conducted
during December, 2019 to February, 2020. Monthly
maximum, minimum and average temperature dur-
ing experiment I varied from 29.9 to 30.8, 17.5 to
18.2, and 23.9 to 24.5 °C, respectively and the max-
imum, minimum and average relative humidity ran-
ged from 71 to 85, 48 to 54, and 59 to 70%,
respectively. Similarly, for experiment II with 100
ppb stress, the study was conducted during
November, 2020 to February, 2021. The monthly
maximum, minimum and average temperature dur-
ing experiment II differed from 30.1 to 31.5, 17.1 to
18.2, and 23.5 to 25.0 °C, respectively, and the max-
imum, minimum and average relative humidity var-
ied from 69 to 84, 35 to 51, and 51 to 67%,
respectively (Table 2).
Ozone treatment and growth conditions
The experiment was conducted in two Open Top
Chambers (OTC; 3.5 × 3.5 m), one with ambient
ozone level as control and another with elevated
ozone. The ozone generator (A4G, Faraday, India)
was used to generate ozone and conducted to the
ozone chamber via teflon tube. The generator used
high frequency corona discharge technology for
ozone production, which configured with the ozone
capacity of 4 g/h, maximum concentration of 2% by
weight, reactor pressure of 29 psig and feed gas flow
of 10–12 lpm. The teflon tube with the length of 4 m,
outside diameter of 6 mm and inside diameter of
4 mm was used. The ozone emission through teflon
tube was set in four multiple points of the chamber
and fixed at 30 cm above the plant canopy. The feed
gas flow was set at maximum level (10–12 lpm) and
the outlet ozone emission was regulated by ozone
flow adjustment knob present in ozone generator
according to the concentration measured inside the
OTC to achieve target level of ozone. The ozone
concentration presents in four multiple emission
points inside the chamber was monitored using
handheld ambient ozone monitor (G09-O
3
-3121).
Moreover, the objective was to expose the plants to
ozone pollution which correlated with the actual
meteorological condition. The diurnal concentrations
of ozone are influenced by the intensity of solar
radiation. In troposphere, the trend of ozone concen-
tration increased toward daytime with respect to
increasing solar radiation and declined slowly toward
nighttime. In order to impose actual environmental
circumstance and to create a realistic ozone stress on
plants, the ozone exposure in this study was under-
taken between 10.00 h and 17.00 h. The experimental
setup is displayed in Figure 1.
During experiment I (2019–2020), the blackgram
varieties were exposed to elevated ozone level of 50 ± 5
ppb in one chamber and another with ambient ozone.
The eight backgram varieties, each with 9 replications
Table 1. Agronomic characteristics of blackgram varieties.
Blackgram
varieties Parentage
Agronomic characteristics
Special characters
Duration
(days)
CO 6 DU 2 × VB 20 Moderately resistant to
mungbean yellow mosaic
virus (MYMV), stem
necrosis, and root rot
diseases
60–65
VBN 1 KM 1 × H 76–1 High yielding, tolerant to
YMV
60–65
VBN 2 Spontaneous
mutant
selection from
Type 9
Resistant to YMV 65
VBN 3 LBG 402 × LBG 17 Resistant to YMV 65–70
VBN 5 Vamban 1 × UK
17
High yield, resistant to YMV 65–70
VBN 6 VBN 1 × Vigna
mungo var.
silvestris
High yield, resistant to YMV 65–70
VBN 7 VBN 3 × Vigno
mungo var.
silvestris
High yield, resistant to YMV,
powdery mildew, and leaf
crinkle disease
65–70
VBN 8 VBN 3 × VBG 04–
008
High yield, resistant to YMV,
moderately resistant to
powdery mildew
65–70
Table 2. Meteorological conditions inside the open top chamber.
Study period
Mean temperature (°C) Mean relative humidity (%)
Maximum Minimum Average Maximum Minimum Average
3–31 December, 2019 29.9 17.5 23.9 85 54 70
1–31January, 2019 30.4 17.9 24.0 74 51 64
1–17 February, 2019 30.8 18.2 24.5 71 48 59
26–30 November, 2020 30.1 17.1 23.5 84 49 67
1–31 December, 2020 30.5 17.8 24.4 77 51 65
1–31January, 2020 30.9 17.5 24.3 73 38 57
1–10 February, 2020 31.5 18.1 25.0 69 35 51
OZONE: SCIENCE & ENGINEERING 3
(n = 9) were placed with a spacing of 25 × 10 cm in
control (n = 72) and ozone (n = 72) chambers (Total
N = 144). As per the crop production guide for Tamil
Nadu, all the package of practices were carried out
(CPGA 2020). Before sowing, fertilizer requirement of
25:50:25:40 kg of N:P
2
O
5
:K
2
O:S ha
−1
was applied as
basal and irrigation was given immediately after sowing.
After that, the plants were irrigated at the interval of 3–
5 days till the maturity stage depending upon soil moist-
ure condition and care was taken to avoid water stagna-
tion at all stages. Thirty days after sowing (30 DAS), the
plants were exposed to elevated ozone treatment of
50 ± 5 ppb from 10.00 h to 17.00 h over 10 days at
flowering stage. Ozone feed rate of 0.6 mg/min was
maintained throughout the ozone treatment period as
per calculation described by Van Leeuwen (2015). The
daily average ozone concentration in ozone chamber
ranged from 44 to 58 ppb, and weighted average ozone
was 50.1 ppb (AOT40 = 0.714 ppm h) (Figure 2).
Similarly, for control, the blackgram plants were grown
in control chamber (ambient) where the ozone concen-
tration was <7 ppb.
Similar experimental setup was followed for
experiment II (2020–2021) with eight blackgram vari-
eties exposed to 100 ± 5 ppb ozone in one chamber
(n = 72) and another with ambient ozone (n = 72).
During the ozone exposure period (31–40 DAS),
ozone feed rate of 1.2 mg/min was maintained in
ozone chamber and daily average ozone concentra-
tion varied from 92 to 108 ppb, and weighted average
ozone was recorded to be 101.2 ppb (AOT40 = 4.1
ppm h) (Figure 2). In control chamber (ambient), the
plants were grown without ozone exposure and the
concentration was <5 ppb.
Figure 1. Schematic representation of experimental design.
Figure 2. Contour graph representing the variation of ozone concentration inside the open top chambers.
4P. DHEVAGI ET AL.
Plant analysis
Leaf injury percentage (LIP) was assigned to all eight
blackgram varieties from 0 to 100 as per the method
followed by Chaudhary and Agrawal (2013). The obser-
vation was taken from all plants after 10 days of ozone
exposure at flowering stage. The physiological traits like
photosynthetic rate (A) and stomatal conductance (gs)
were measured using portable photosynthesis system
(ADC BioScientific LCpro-SD System, UK) and chlor-
ophyll content meter (CCM-200+, USA) was used to
assess chlorophyll content (Chl). All the physiological
observations were taken after 10 days of ozone exposure.
These measurements were taken at three different points
of young fully expanded leaves from each treatment
between 9.30 h and 12.00 h.
After 10 days of ozone exposure, fresh leaves were
sampled from each treatment and analyzed for malon-
dialdehyde (MDA) (Heath and Packer 1968), proline
(Bates, Waldren, and Teare 1973) and ascorbic acid
(AsA) contents (Keller and Schwager 1977). The plant
height (PH), root length (RL), number of nodules per
plant (NNP), number of branches per plant (NBP),
number of leaves per plant (NLP), number of pods per
plant (NPP), pod length (PL), number of seeds per plant
(NSP), 100 grain weight (100 GW), and plant weight
(PW) were measured at crop maturity stage for each
treatment.
Statistical analysis
All the statistical analysis was performed using the SPSS
statistical package (SPSS Inc., version 16.0.0). The one-
way ANOVA was used to test the significance between
treatments and cultivars. The two-way ANOVA was
used to test the treatment; cultivar and their interaction
effect of various plant traits and Tukey method was used
to identify the difference among treatment means.
The percentage reduction in observed leaf traits were
calculated by the formula, 100-[(ozone/control)×100].
The degree of correlation was determined based on
Pearson’s correlation coefficient. P values less than 0.05
(P < .05) was considered as significant. The relative plant
physiological, biochemical and yield traits were calcu-
lated using the formula, Relative plant trait = (ozone/
control)×100. The path analysis was performed using
beta standardized coefficients obtained from regression
analysis (Singh et al. 2018). The multivariate analysis,
i.e., Principal component analysis (PCA) was performed
using R software (Version 3.5.1). OriginPro 2019 (ver-
sion 9.6.5) was used to plot the graphs.
Results
Experimental site
The texture of the experimental soil was clay loam with
a pH of 8.05 and EC of 0.39 dS m
−1
. The organic carbon
content was 0.48%, while the available N, P, and
K content were 217, 11.8, and 295 kg ha
−1
, respectively.
Leaf injury percentage
The elevated ozone (50 ppb) exposure to blackgram
varieties showed different levels of leaf injury percen-
tage. Among the test varieties, VBN3, CO6, VBN1, and
VBN2 developed early necrotic spots on younger leaves
(Figure 3). Prolonged elevated ozone increased the leaf
Figure 3. Leaf injury symptoms of blackgram varieties exposed to elevated ozone stress.
OZONE: SCIENCE & ENGINEERING 5
injury symptoms in all test varieties. Ten days of 50 ppb
ozone exposure significantly increased the ozone injury
symptoms in VBN3 (50.67%), CO6 (40.33%), VBN1
(40.00%), and VBN2 (40.00%) clearly depicting its sen-
sitivity toward ozone stress. The blackgram varieties,
VBN7 (36.67%), VBN6 (34.00%), VBN5 (27.00%), and
VBN8 (23.67%) displayed comparatively less injury
symptoms and confirmed its less sensitivity to elevated
ozone (50 ppb) (Table 3).
Similarly, at 100 ppb ozone exposure, VBN3, VBN2,
and VBN6 exhibited early injury symptoms on leaves.
Furthermore, VBN3 (60.00%), VBN2 (56.33%), VBN6
(55.00%), VBN7 (52.33%), and CO6 (52.00%) showed
significantly higher ozone injury percentage compared
to VBN1 (45.33%), VBN5 (38.67%), and VBN8 (34.33%)
(Table 3).
Physiological traits
Blackgram varieties after ten days of 50 ppb ozone
exposure at flowering stage showed significant reduction
in all physiological traits. The photosynthetic rate
reduced significantly, with maximum reduction in
VBN3 (33.55%) and minimum in VBN8 (26.23%).
Ozone exposure caused a marked reduction in stomatal
conductance, where the highest reduction was observed
in VBN5 (33.33%) and least in VBN8 (22.20%). At the
same time, the reduction in chlorophyll content showed
significant variation among the cultivars with the max-
imum reduction of 36.61% in VBN2 and minimum in
VBN8 (31.79%) (Figure 4). At 5% level significant vari-
ety and treatment effect were noticed in photosynthetic
rate; whereas their interaction effect was not significant.
Stomatal conductance and chlorophyll content showed
significant treatment effect; while variety and interaction
effect were insignificant (Table 4).
Under 100 ppb ozone exposure, the photosynthetic
rate showed highest reduction in VBN3 (45.97%) and
the lowest in VBN1 (38.18%) which was at a significant
level compared to control. In regard to stomatal con-
ductance, significant reduction was noticed in all test
varieties with a maximum reduction in VBN2 (48.00%)
and minimum in VBN1 (29.10%). The chlorophyll con-
tent decreased significantly and was higher in VBN3
Table 3. Leaf injury percentage (LIP) of blackgram varieties
exposed to 50 ppb and 100 ppb ozone.
Blackgram varieties 50 ppb ozone 100 ppb ozone
CO 6 40.33 ± 2.65 52.00 ± 3.59
VBN 1 40.00 ± 3.46 45.33 ± 1.58
VBN 2 40.00 ± 1.73 56.33 ± 2.74
VBN 3 50.67 ± 4.36 60.00 ± 3.96
VBN 5 27.00 ± 3.46 38.67 ± 4.28
VBN 6 34.00 ± 3.57 55.00 ± 1.98
VBN 7 36.67 ± 2.65 52.33 ± 4.35
VBN 8 23.67 ± 3.61 34.33 ± 3.45
(n = 9, Total sample size, N = 144)
Figure 4. Plant physiological traits of blackgram varieties exposed to 50 and 100 ppb ozone. Bars indicate ±1 SEM (total sample size,
N = 144). Asterisk denotes significant difference between control and ozone treatment within the cultivar.* ≤ 0.05, ** ≤ 0.01, *** ≤
0.001, and NS = Not Significant.
6P. DHEVAGI ET AL.
(46.47%) and least in VBN7 (39.58%) (Figure 4).
ANOVA results at 5% level of physiological traits
showed significant treatment effect in photosynthetic
rate, stomatal conductance and chlorophyll content.
A significant variety effect was noticed only in photo-
synthetic rate, while the interaction effect between vari-
ety and treatment was insignificant for all physiological
traits (Table 5).
Biochemical traits
Exposure to elevated ozone at 50 ppb, significantly
increased the MDA content in all test varieties which
was found to be maximum in VBN3 (122.44%) and
minimum in VBN8 (78.69%). In the same way, VBN3
showed a significant increase in proline content
(13.46 µmol g
−1
FW), while the minimum was observed
in VBN6 (11.06 µmol g
−1
FW). In case of ascorbic acid
content, the reduction was significant among the black-
gram varieties, where the highest reduction was
observed in VBN2 (41.79%) and minimum in VBN8
(36.31%). All the biochemical traits showed significant
variety and treatment effects at 5% level; whereas variety
and treatment interaction effects were significant only
for proline content (Table 4).
The varieties exposed to 100 ppb ozone for ten days
showed significant increment in MDA content which
was higher in VBN3 (152.42%) and least in VBN8
(99.75%). Concerning proline content, all test varieties
increased at a significant level wherein VBN3 showed
maximum increase of 12.13 µmol g
−1
FW and the mini-
mum increase was observed in VBN1 (11.25 µmol g
−1
FW). In view of ascorbic acid content, the highest reduc-
tion was observed in VBN3 (49.87%) and the lowest in
VBN8 (41.07%) which was at a significant level
(Figure 5). All the biochemical traits under 100 ppb
ozone exposure showed significant variety and treat-
ment effects at 5% level; whereas variety and treatment
interaction effects were insignificant (Table 5).
Growth traits
Fifty ppb ozone exposure showed significant decrease
in plant height of all test varieties, wherein the max-
imum reduction was noticed in VBN6 (13.87%) and
minimum in CO6 (9.39%). The root length and
number of nodules per plant decreased under ozone
stress but not at a significant level in all blackgram
varieties. A significant reduction in number of
branches per plant was found with the greatest
reduction in VBN5 (20.00%) and minimum in
VBN8 (9.09%) at ten days of ozone exposure. The
number of leaves per plant decreased at a significant
level and the highest reduction was recorded in
VBN6 (17.58%) and minimum in VBN8 (11.50%).
The plant weight exhibited a significant reduction
which was maximum in VBN5 (20.17%) and mini-
mum in VBN8 (9.71%). The two-way ANOVA
results at 5% level depicted significant variation
among the varieties for plant height, number of
nodules, branches, leaves per plant and plant weight.
With respect to treatment and their interaction effect,
plant height, number of branches, leaves per plant,
Table 4. ANOVA results of plant physiological and biochemical traits of blackgram varieties exposed to 50 ppb ozone.
ANOVA
(P values)
A
(µmol CO
2
m
−2
s
−1
)
gs
(mol H
2
O m
−2
s
−1
) Chl
MDA
(µmol g
−1
FW)
Proline
(µmol g
−1
FW)
AsA
(mg g
−1
FW)
Varieties <0.001 0.064 0.340 0.015 0.001 <0.001
Treatment <0.001 <0.001 <0.001 <0.001 <0.001 <0.001
Varieties ×Treatment 0.520 0.821 0.964 0.190 0.026 0.870
Treatment means
Control 18.53 ± 1.02 0.49 ± 0.04 29.38 ± 0.93 1.33 ± 0.14 05.52 ± 1.50 1.49 ± 0.12
Ozone 13.67 ± 0.87 0.36 ± 0.09 19.44 ± 0.49 2.65 ± 0.24 11.31 ± 0.98 0.90 ± 0.08
(n = 9, Total sample size, N = 144; A – photosynthetic rate, gs – stomatal conductance, Chl – chlorophyll content, MDA – malondialdehyde content, proline –
proline content, AsA – ascorbic acid content)
Table 5. ANOVA results of plant physiological and biochemical traits of blackgram varieties exposed to 100 ppb ozone.
ANOVA
(P values)
A
(µmol CO
2
m
−2
s
−1
)
gs
(mol H
2
O m
−2
s
−1
) Chl
MDA
(µmol g
−1
FW)
Proline
(µmol g
−1
FW)
AsA
(mg g
−1
FW)
Varieties 0.041 0.371 0.166 0.005 <0.001 0.017
Treatment <0.001 <0.001 <0.001 <0.001 <0.001 <0.001
Varieties ×Treatment 0.965 0.271 0.870 0.394 0.143 0.969
Treatment means
Control 19.99 ± 1.24 0.49 ± 0.05 29.42 ± 0.85 1.28 ± 0.12 05.70 ± 1.02 1.50 ± 0.09
Ozone 11.54 ± 1.03 0.29 ± 0.04 16.94 ± 0.74 2.86 ± 0.16 12.38 ± 1.31 0.83 ± 0.13
(n = 9, Total sample size, N = 144; A – photosynthetic rate, gs – stomatal conductance, Chl – chlorophyll content, MDA – malondialdehyde content, proline –
proline content, AsA – ascorbic acid content)
OZONE: SCIENCE & ENGINEERING 7
and plant weight were found to be significantly dif-
ferent while root length and number of nodules per
plant were insignificant (Table 6).
Plant height displayed highest reduction in VBN3
(14.64%) and the least in VBN8 (11.77%) under 100
ppb ozone exposure, which was at a significant level.
The test blackgram varieties depicted an insignificant
reduction in root length and number of nodules per
plant. In terms of number of branches per plant, sig-
nificant reduction was observed in all test varieties with
a maximum reduction in VBN3 (22.22%) and minimum
in VBN7 and VBN8 (9.09%). The number of leaves per
plant exhibited highest reduction in VBN3 (18.54%) and
lowest in VBN8 (12.97%) which was at a significant
level. The plant weight decreased significantly in all
test varieties which was maximum in VBN5 (30.96%)
and minimum in VBN8 (15.17%). The ANOVA results
at 5% level showed significant difference among the
varieties for all growth traits except root length. In
regard to treatment and interaction effect, plant height,
number of branches, leaves per plant, and plant weight
were significant; whereas root length and number of
nodules per plant were insignificant (Table 7).
Yield traits
All yield parameters were significantly influenced by
elevated ozone treatment. Ten days of 50 ppb ozone
exposure showed reduction in number of pods per
Figure 5. Plant biochemical traits of blackgram varieties exposed to 50 and 100 ppb ozone. Bars indicate ±1 SEM (total sample size,
N = 144). Asterisk denotes significant difference between control and ozone treatment within the cultivar.* ≤ 0.05, ** ≤ 0.01, *** ≤
0.001, and NS = Not Significant.
Table 6. ANOVA results of plant growth and yield traits of blackgram varieties exposed to 50 ppb ozone.
ANOVA results
(P values)
RL
(cm)
PH
(cm) NNP NBP NLP
PW
(g) NPP PL NSP
100 GW
(g)
Varieties 0.051 <0.001 <0.001 0.047 0.023 0.042 <0.001 <0.001 0.055 <0.001
Treatment 0.058 <0.001 0.875 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 0.028
Varieties
×Treatment
0.053 <0.001 0.325 <0.001 <0.001 <0.001 0.012 0.342 0.001 0.052
Treatment
means
Control 14.80 ± 0.81 29.60 ± 2.45 23.58 ± 4.89 3.33 ± 0.81 55.13 ± 6.44 17.43 ± 1.23 13.25 ± 2.43 4.73 ± 0.62 5.79 ± 1.22 4.34 ± 0.42
Ozone 14.36 ± 0.68 26.17 ± 2.06 23.33 ± 3.45 2.83 ± 0.63 46.63 ± 3.91 14.65 ± 1.24 9.17 ± 1.93 4.60 ± 0.41 5.33 ± 0.75 4.00 ± 0.32
(n = 9, Total sample size, N = 144; RL – root length, PH – plant height, NNP – number of nodules per plant, NBP – number of branches per plant, NLP – number of
leaves per plant, PW – plant weight, NPP – number of pods per plant, PL – pod length, NSP – number of seeds per plant, 100 GW – 100 grain weight)
8P. DHEVAGI ET AL.
plant which was significantly maximum in VBN5
(35.56%) and minimum in VBN8 (28.26%). The pod
length of blackgram varieties reduced significantly with
maximum reduction in VBN3 (5.93%) and minimum in
VBN8 (1.36%). Likewise, ozone exposure showed sig-
nificant reduction in number of seeds per pod which was
maximum in VBN7 (15.79%) and minimum in VBN1,
VBN3, and VBN8 (5.88%). With reference to 100 grain
weight, VBN6 exhibited a maximum reduction of
10.92%, while the minimum reduction was observed in
VBN8 (5.22%). Blackgram varieties exposed to 50 ppb
ozone showed significant treatment effect in all yield
traits at 5% level; whereas varietal effect was insignificant
for number of seeds per pod. The interaction effect was
significant for number of pods and seeds per plant, while
pod length and 100 grain weight were insignificant
(Table 6).
Similarly, 100 ppb ozone exposure showed significant
reduction in number of pods per plant in all test vari-
eties, wherein the maximum reduction was noticed in
VBN5 (36.59%) and minimum in VBN8 (28.89%). With
respect to pod length, VBN3 showed maximum reduc-
tion (7.25%) and minimum in CO6 (3.92%), which was
found to be significant. In terms of number of seeds per
pod, all test varieties showed significant reduction which
was maximum in VBN1 and VBN3 (11.76%) and mini-
mum in VBN6 and VBN8 (5.26%). A significant reduc-
tion in 100 grain weight was observed in all varieties,
while the highest reduction was recorded in VBN3
(15.94%) and minimum in VBN8 (10.00%). Ten days
of 100 ppb ozone exposure exhibited significant treat-
ment effect in all yield traits at 5% level; whereas variety
effect was not significant for number of seeds per pod
alone. A significant interaction effect was noticed for
number of pods and seeds per plant; whereas pod length
and 100 grain weight were insignificant (Table 7).
Principal component analysis
All the observed physiological, biochemical, growth and
yield traits were considered for Principal Component
Analysis (PCA), which was used for categorizing the
ozone tolerant and sensitive groups. In 50 ppb ozone
exposed treatment, the first two principal components
(PC1 and PC2) accounted for 41.59% and 19.19% with
a cumulative eigen value of 60.78% and clustered photo-
synthetic rate with growth traits and chlorophyll content
with 100 grain weight which were highly responsible for
grouping of blackgram varieties (Figure 6a). Hence, the
eight blackgram varieties categorized into four major
Table 7. ANOVA results of plant growth and yield traits of blackgram varieties exposed to 100 ppb ozone.
ANOVA results
(P values)
RL
(cm)
PH
(cm) NNP NBP NLP
PW
(g) NPP PL NSP
100 GW
(g)
Varieties 0.058 <0.001 <0.001 0.035 0.015 <0.001 <0.001 <0.001 0.053 <0.001
Treatment 0.053 <0.001 0.993 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 0.047
Varieties
×Treatment
0.074 <0.001 0.811 0.017 0.041 <0.001 <0.001 0.127 <0.001 0.064
Treatment
means
Control 14.71 ± 0.74 29.99 ± 1.98 24.58 ± 3.85 3.42 ± 0.69 54.58 ± 5.36 17.52 ± 1.12 13.42 ± 1.85 4.88 ± 0.51 5.83 ± 1.30 4.27 ± 0.28
Ozone 14.10 ± 0.86 25.95 ± 2.10 24.50 ± 4.42 2.92 ± 0.72 45.54 ± 3.74 13.81 ± 1.36 09.04 ± 2.10 4.61 ± 0.39 5.42 ± 0.87 3.73 ± 0.37
(n = 9, Total sample size, N = 144; RL – root length, PH – plant height, NNP – number of nodules per plant, NBP – number of branches per plant, NLP – number of
leaves per plant, PW – plant weight, NPP – number of pods per plant, PL – pod length, NSP – number of seeds per plant, 100 GW – 100 grain weight)
A
Gs
Chl
MDA
Proline
AsA
SL
RL
NBP
NLP
PW
NPP
NSP
PL
100 GW
LIP
R
-0.4 -0.2 0.0 0.2 0.4
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
PC2 (19.19%)
PC1 (41.59%)
PH
-2 -1 0 1 2
-2
-1
0
1
CO 6 VBN 1
VBN 2
VBN 3
VBN 5
VBN 6
VBN 7
VBN 8
PC 2 (19.19%)
PC 1 (41.59%)
Sensitive Moderately tolerant
Tolerant
Moderately sensitive
Figure 6 (a) Principal component analysis of plant traits of blackgram varieties exposed to 50 ppb ozone. (b) Classification of eight
blackgram varieties into different ozone response groups (50 ppb ozone) based on principal component analysis.
OZONE: SCIENCE & ENGINEERING 9
groups indicates ozone tolerant (VBN8 and VBN5),
moderately ozone tolerant (VBN6 and VBN7), moder-
ately ozone sensitive (CO6, VBN1, and VBN2), and
ozone sensitive (VBN3) groups (Figure 6b).
Similarly, under 100 ppb ozone exposed treatment,
the PC1 and PC2 explained for 53.34% and 18.48% with
a cumulative eigen value of 71.82%. It showed higher
loading for physiological and most of the growth and
yield traits (Figure 7a). All these clustered physiological,
growth, and yield traits were highly accountable for
separating blackgram varieties into four major groups,
i.e., ozone tolerant (VBN8 and VBN5), moderately
ozone tolerant (VBN1 and VBN7), moderately ozone
sensitive (CO6, VBN2, and VBN6) and ozone sensitive
(VBN3) varieties (Figure 7b).
Discussion
Ozone is a strong oxidant that has both positive and
negative impact on plants. In food processing indus-
tries, ozone is widely applied for mycotoxin degrada-
tion, microbial decontamination and insect control in
cereals and foodstuffs viz., fruits, vegetables, meat, and
fish (Sivaranjani et al. 2021). The application of low
dose of ozone (0.01 g of ozone/g for 20 minutes)
increased the germination rate in tomato seeds by
ozone-induced cell signaling process (Sudhakar et al.
2011). Violleau et al. (2007) reported that the ozone
concentration of 20 g/m
3
for 20.5 minutes showed
rapid germination in corn seeds. In limited quantity/
exposure period, ozone enhances seed germination
rate; in contrast, excess concentration causes negative
effects like chlorosis and necrosis on leaves
(Pandiselvam et al. 2020). Apart from the industrial
applications, ozone normally present in troposphere
and considered as toxic air pollutant due to its high
oxidizing nature. The present atmospheric condition
with increasing ozone concentration severely affects
crop growth and yield. In this concern, a detailed
study conducted on blackgram varieties exposed to
elevated ozone stress and the outcome of this investi-
gation is discussed in detail.
Ozone exposure
The tropic region like India has environmental condi-
tions of warm climate, high light intensity, and long
sunshine daily hours which provides a favorable condi-
tion for high ozone formation. Chaudhary and Agrawal
(2014) reported that the ozone concentration varied
from 42.2 to 95.2 ppb with AOT 40 value of 14,029
ppb h at Varanasi during mung bean growing period.
In general, reproductive growth stage of blackgram vari-
eties (flowering and pod formation, ~31 to 40 DAS), are
critical period and more sensitive to external environ-
mental factors (CPGA 2020; De Datta 1981; Van, Hai,
and Ishii 2008). In the present study region, blackgram
varieties are usually cultivated during northeast mon-
soon season (October–December). With these refer-
ences, the test blackgram varieties cultivated in the
month of November and December anticipated to
experience high ozone stress at reproductive stage,
wherein the maximum ozone concentration reached
upto 71.70 ppb (Prabakaran et al. 2017) and 144.13
ppb (Mohan and Saranya 2019) during earlier period.
Moreover, the concentration of ozone varied signifi-
cantly with season to season and the crop experiences
negligible amount of ozone during vegetative stage.
Consequently, the present experimental setup was
designed to mimic the actual circumstances to provide
more precise results. Hence, the ozone concentration
above 40 ppb during the crop growing period of black-
gram would affect the plant yield (Singh et al. 2010).
Based on the literature survey, the elevated ozone
Chl
A
gs
Proline
MDA
AsA
SL
RL
NBP
NPP
NSP
PL
NLP
100 GW
PW
LIP
NNP
-0.4 -0.2 0.0 0.2 0.4
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
PC2 (18.48%)
PC1 (53.34%)
-2 -1 0 1 2
-2
-1
0
1
2
CO 6
VBN 1
VBN 2
VBN 3
VBN 5
VBN 6
VBN 7
VBN 8
PC 2 (18.48%)
PC 1 (53.34%)
Sensitive Moderately tolerant
Tolerant
Moderately sensitive
Figure 7 (a) PCA of plant traits of blackgram varieties exposed to 100 ppb ozone. (b) PCA-based classification of blackgram varieties
into different ozone response groups (100 ppb ozone).
10 P. DHEVAGI ET AL.
concentration for the current experiment was fixed as 50
ppb (AOT40 = 0.714 ppm h) and 100 ppb (AOT40 = 4.1
ppm h).
Leaf injury percentage
The range of leaf injury percentage varied from 23.67 to
50.67% in 50 ppb and from 34.33 to 60.00% for 100 ppb
ozone exposed treatment. In the present experiment, as
a visible response to elevated ozone stress, a significant
increase in leaf chlorotic and necrotic symptoms were
observed in all test varieties with respect to increasing
ozone concentration (Figure 8). The possible explana-
tion of this trend may be attributed due to increased
formation of reactive oxygen species (ROS) like super-
oxide with respect to increase in ozone level thereby
causing leaf injury (Alscher and Hess 1993). According
to Mishra and Agrawal (2014), accumulation of ROS
inside the plant system led to foliar and cellular damage.
Also, cultivar-specific variation in leaf injury percentage
observed in the present study showed that the blackgram
varieties have differential tolerance levels toward ele-
vated ozone exposure. Similar observation was found
by Chaudhary and Agrawal (2013) who reported that
the foliar injury percentage aggravated with prolonged
ozone exposure and also varied based on the sensitivity
of test cultivars.
Physiological traits
The results of the current experiment clearly indicate the
varietal differences in blackgram under elevated ozone
stress. On an average across eight blackgram varieties,
10 days of ozone exposure decreased the chlorophyll
content by 33.83 and 42.41% under 50 and 100 ppb
ozone, respectively. This elevated ozone induced chlor-
ophyll content reduction might be related to destruction
of chloroplast structure that leads to inhibition of chlor-
ophyll synthesis at elevated ozone condition (Biswas and
Jiang 2011; Castagna et al. 2001). The decrease in chlor-
ophyll content is also attributed due to reduction in
photoprotective carotenoid pigments (Salvatori et al.
2013). This significant decrease in chlorophyll content
was not only dependent on elevated level of ozone, but
also displayed varietal variation. Similar observation was
noticed by Tetteh, Yamaguchi, and Izuta (2016) who
reported that chlorophyll content of two African cowpea
(Vigna unguiculata L.) varieties (Blackeye and Asontem)
reduced significantly under 50 ppb ozone.
In general, stomata opening and closing acts
a common entry point into the plant system and plays
a fundamental role in regulating the flux of ozone and
CO
2
in the apoplastic region (Rai 2020). In current
experiment, stomatal conductance decreased by 28.25
and 40.51% and photosynthetic rate by 29.43 and
42.30% in 50 and 100 ppb ozone treated plants, respec-
tively which was associated with counteract mechanism
of plant varieties to limit the entry of pollutant by closing
its stomata and ultimately diminishing the CO
2
entry as
well (Betzelberger et al. 2010; Edwin et al. 2005; Ghosh
et al. 2020). Furthermore, stomatal closure under ele-
vated ozone condition was related with loss of osmotic
potential inside the substomatal region and altered par-
tial pressure in guard cells. As a result of stomatal clo-
sure and decreased CO
2
uptake, the plant system ends
up with reduced photosynthetic rate. Similarly, at 40
DAG mung bean cultivars showed reduction in photo-
synthetic rate and stomatal conductance which was 28.3
and 38.8% in HUM-2 and 19 and 24.8% for HUM-6,
respectively (Mishra and Agrawal 2014, 2015).
20 30 40 50 60 70
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
Frequency
Leaf injury percentage (LIP)
50 ppb Ozone
100 ppb Ozone
Figure 8. Frequency distribution (Histogram) of leaf injury percentage for eight blackgram varieties exposed to 50 and 100 ppb ozone.
OZONE: SCIENCE & ENGINEERING 11
According to Bailey et al. (2019), 70 ppb ozone exposure
resulted in decreased photosynthesis (5%) and stomatal
conductance (30%) of soybean genotype (Fiskeby III).
Various modeling studies indicate that a major factor
affecting plant response to ozone appears to be stomatal
conductance. More rapid closure of stomatal aperture
was reported in intolerant varieties (Yadav et al. 2019).
Reduction in stomatal conductance, in Vigna unguicu-
lata L. cultivars (Tetteh, Yamaguchi, and Izuta 2016)
and soybean cultivars (Rai et al. 2015; Sun, Feng, and
Ort 2014) were noticed under ozone stress.
The relative physiological traits of blackgram varieties
under elevated ozone stress varied among the photosyn-
thetic rate, stomatal conductance and chlorophyll con-
tent. The boxplot of relative physiological traits showed
mean values 71.39, 70.80, and 66.63% under 50 ppb
ozone stress and 56.92, 58.76, and 57.24% for 100 ppb
ozone treatment for photosynthetic rate, stomatal con-
ductance and chlorophyll content, respectively
(Figure 9). The results showed that higher deviation in
stomatal conductance noticed for both the treatments
(50 and 100 ppb) were possibly related to the sensitivity
of blackgram varieties.
Biochemical traits
Ozone enters the plant system via stomatal opening
and it rapidly reacts with apoplastic water and gener-
ates reactive oxygen species (ROS) causing damage to
the membrane/lipid components eventually increasing
the MDA content. In present experiment, greater
induction of MDA, depicts its sensitivity to elevated
ozone (99.66 and 125.15% under 50 and 100 ppb
ozone, respectively). This increased MDA concentra-
tion in all test varieties suggests higher lipid peroxida-
tion of the membrane compared to controlled
condition. Moreover, excess production of ROS due
to the oxidative burst, destructs the structure and func-
tion of the plasma membrane and damages the lipids,
protein, chloroplast and nucleic acids (Alaiz, Hidalgo,
and Zamora 1999; Blokhina, Virolainen, and Fagerstedt
2003), thereby hindering the ability of plant cell in
scavenging of active oxygen species (Sanmartin et al.
2003). The findings coincides with the report of Mishra
and Agrawal (2014) who stated that lipid peroxidation
significantly increased by 30.8 and 21% in mung bean
(Vigna radiata L.) cultivars of HUM-2 and HUM-6,
respectively under averaged elevated ozone concentra-
tion of 68.9 ppb.
In present observation, ascorbic acid content
decreased by 39.54 and 44.76% under 50 and 100 ppb
ozone, respectively. The possible explanation of this
finding may be ascribed to poor non-enzymatic defense
system in blackgram varieties under elevated ozone
stress. To counteract ROS, antioxidant molecules are
produced (Caregnato et al. 2013). In addition, these
results suggest that redox state of AsA may not be
maintained under elevated ozone stress, which would
result in inadequate detoxification of H
2
O
2
by AsA
(Tetteh, Yamaguchi, and Izuta 2016). These results
were supported by Upadhyaya, Khan, and Panda
(2007) who found that oxidative stress decreased the
ascorbate level in plant system. Similarly, Tetteh,
Yamaguchi, and Izuta (2016) reported that two African
cowpea varieties showed a drastic reduction in AsA
content under 50 ppb ozone exposure. Also, total ascor-
bic acid content showed no significant effect in Vigna
radiata L. under 70.9 ppb ozone at 60 DAG (Chaudhary
and Agrawal 2015). On contrary, in mung bean cultivars
under 68.9 ppb ozone exposure, the ascorbic acid con-
tent increased significantly by 5.7 and 3.8% in HUM-2
and HUM-6, respectively, at 40 DAG (Mishra and
A gs Chl
60
62
64
66
68
70
72
74
76
78
80
82
Relative physiological traits
50 ppb Ozone
A gs Chl
50
55
60
65
70
75
Relative physiological traits
100 ppb Ozone
Figure 9. Relative physiological traits of blackgram varieties exposed to 50 ppb and 100 ppb elevated ozone.
12 P. DHEVAGI ET AL.
Agrawal 2014). Moreover, Lee (1991) and Van Hove
et al. (2001) observed a significant positive relationship
between sensitivity and ascorbic acid content.
Proline acts as a scavenger of singlet oxygen and
hydroxyl radicals in response to environmental stress
(Rejeb, Kilani, and Arnould 2014). In current experi-
ment, proline content increased by 105.58 and 122.74%
under 50 and 100 ppb ozone, respectively. This incre-
ment in proline content might participate in ROS
scavenging mechanism under elevated ozone stress
(Gill and Tuteja 2010). The findings also coincides
with the report of Nahar, Sahoo, and Tanti (2018) who
stated that rice cultivars accumulate free proline under
changing external environment.
The boxplot of eight blackgram varieties showed that
under 50 ppb ozone stress, the mean values of relative
biochemical traits were higher for proline content
(202.00%) and malondialdehyde (201.01%) compared
to ascorbic acid content (60.11%). Similarly, the mean
relative traits of proline, malondialdehyde and ascorbic
acid content for 100 ppb ozone treatment were recorded
as 217.00, 224.67, and 55.72%, respectively (Figure 10).
This outcome might be related to increase in production
of malondialdehyde and proline under elevated ozone
stress and decrease in ascorbic acid content.
Furthermore, higher ozone concentration (100 ppb
ozone) increased the malondialdehyde and proline con-
tent, while the ascorbic acid content declined compared
to 50 ppb ozone exposure.
Growth and yield traits
In present observation, all the growth traits decreased
significantly. On an average across all test varieties, the
plant height, root length, number of branches per plant,
number of leaves per plant and plant weight decreased
by 11.75, 2.98, 14.77, 15.53, and 16.03%, respectively
under 50 ppb ozone exposure. Similarly, 100 ppb
ozone exposure decreased the growth traits by 13.51,
4.16, 14.88, 16.63, and 21.23%, respectively. The reduc-
tion in photosynthetic capacity of the plant system
under elevated ozone stress directly reduced the plant
biomass which was due to change in partitioning of
photosynthates to various plant parts (Chaudhary and
Agrawal 2013; Feng et al. 2011; Sarkar and Agrawal
2010). This results coincides with report of Chaudhary
and Agrawal (2015) who observed that the plant height
and number of leaves per plant reduced maximally in
mung bean genotype (HUM-1) by 25.7 and 24.0%,
respectively, at 40DAG under 70.9 ppb ozone exposure.
In current study, 50 ppb ozone exposure decreased
the number of pods per plant, pod length, number of
seeds per pod and 100 grain weight by 30.82, 2.76, 7.20,
and 7.75%, respectively. Similarly, 100 ppb ozone expo-
sure decreased these yield traits by 32.65, 5.51, 7.75,
and 21.23%, respectively. The present findings might be
related due to prolonged stomatal closure and reduced
C-fixation capability of all blackgram varieties thereby
reducing the amount of assimilates allocated to repro-
ductive parts. Ozone induced senescence observed in
VBN 3 and VBN 1, was associated with triggering
senescence associated genes under elevated ozone con-
dition (Miller, Arteca, and Pell 1999). Furthermore, the
cumulative modification in physiological, biochemical
and growth traits end up in altered yield traits. Similar
to the current report, seed weight and number of pods
per plant reduced maximally in mung bean genotype
(HUM-1) by 15.4 and 6.9% under 70.9 ppb ozone
exposure (Chaudhary and Agrawal 2015). Likewise,
elevated ozone stress reduced the grain yield in
Triticum aestivum cv. HD 2967 by 16.2% (Ghosh et al.
2020).
MDA Proline AsA
50
60
170
180
190
200
210
220
230
240
Relative biochemical traits
50 ppb Ozone
Proline MDA AsA
40
60
180
200
220
240
260
Relative biochemical traits
100 ppb Ozone
Figure 10. Relative biochemical traits of blackgram varieties exposed to 50 ppb and 100 ppb elevated ozone.
OZONE: SCIENCE & ENGINEERING 13
The mean relative root length, plant height and num-
ber of nodules per plant were recorded to be 88.32, 96.89
and 100.00%, respectively in 50 ppb ozone treatment
and 86.49, 95.87, and 98.88%, respectively in 100 ppb
ozone treatment. Similarly, number of branches per
plant, number of leaves per plant and plant weight
were registered as 84.66, 83.60, and 83.23%, respectively
under 50 ppb and 86.11, 82.69, and 79.81%, respectively,
under 100 ppb ozone treatment (Figure 11). Among the
growth traits, number of nodules per plant and number
of branches per plant showed higher deviation in both
the elevated ozone treatment, while plant height and
weight showed lesser deviation in 100 ppb ozone treat-
ment as compared to 50 ppb ozone.
In terms of yield traits, number of pods per plant,
number of seeds per pod, pod length and 100 grain
weight were 69.73, 93.93, 97.93, and 91.85%, respec-
tively, in 50 ppb ozone treatment and 67.05, 94.12,
94.62, and 87.66%, respectively, in 100 ppb ozone treat-
ment (Figure 11). The deviations in relative yield traits
were very low in both the treatments, which explains
that the differences among the varieties were negligible
under elevated ozone treatment.
Correlation
The Pearson’s correlation coefficient was tested for all
the observed plant traits under 50 and 100 ppb ozone
stress. The results showed that a significant negative
correlation was observed between LIP and all physiolo-
gical, biochemical and growth traits except for MDA and
proline content under 50 ppb and 100 ppb ozone stress.
Under 50 ppb ozone stress, significant positive correla-
tion was noticed between photosynthetic rate and sto-
matal conductance, and at the same time, chlorophyll
content showed a positive relation with both photosyn-
thetic rate and stomatal conductance. Almost all the
plant traits were negatively related with MDA and pro-
line content. Among the growth traits, number of seeds
per plant and pod length showed highly positive correla-
tion with photosynthetic rate. Number of nodules per
plant was positively correlated with all observed physio-
logical traits and root length. Root length and number of
pods per plants depicted a strong positive correlation
with chlorophyll content. Similarly, plant weight was
positively correlated with number of branches per
plant and number of leaves per plant. In terms of 100
GW, the photosynthetic rate, chlorophyll content, ascor-
bic acid content, root length, and number of leaves per
plants showed significant positive correlation
(Figure 12a).
Under 100 ppb ozone stress, photosynthetic rate
showed a significant positive correlation with stomatal
conductance and chlorophyll content. Furthermore,
photosynthetic rate showed a positive correlation with
most of the plant growth traits, i.e., plant height, root
length, number of branches per plant, plant weight,
number of pods per plant, number of seeds per plant,
and pod length. Similarly, chlorophyll content depicted
a positive correlation with plant height, root length,
number of pods per plant, and pod length. Number of
nodules per plant showed a positive correlation with all
observed physiological traits, root length, and plant
weight. Number of branches per plant also exhibited
a positive correlation with number of leaves per plant,
number of pods per plant, and pod length. In terms of
100 grain weight, a positive correlation was observed
with photosynthetic rate, chlorophyll content, plant
height, root length, number of branches per plant, num-
ber of leaves per plant, and number of pods per plant
(Figure 12b).
In present study, changes in plant metabolism under
elevated ozone condition alters the plant’s physiological,
biochemical, growth, and yield traits which are
PH RL NNP NBP NLP PW NPP NSP PL 100 GW
60
70
80
90
100
110
120
Relative growth and yield traits
50 ppb Ozone
PH RL NNP NBP NLP PW NPP NSP PL 100 GW
50
60
70
80
90
100
110
120
130
Relative growth and yield traits
100
pp
b Ozone
Figure 11. Relative growth and yield traits of blackgram varieties exposed to 50 ppb and 100 ppb elevated ozone.
14 P. DHEVAGI ET AL.
correlated to different extent (Figure 12a,b). Moreover,
ozone sensitive VBN1 variety showed higher leaf injury
percentage and also recorded lower levels of physiologi-
cal traits suggesting higher degree of sensitivity toward
elevated ozone than other varieties (Chaudhary et al.
2013). The limitation of chlorophyll content was well
correlated with photosynthetic rate and stomatal con-
ductance. All the plant traits were negatively related with
MDA and proline content which in turn were positively
related with LIP (Tripathi and Agrawal 2013).
Path analysis
The path analysis showed that the yield component was
directly explained by leaf injury percentage under 50 and
100 ppb elevated ozone concentration and the indirect
effect were observed through physiological, biochemical
and growth traits. Under 50 and 100 ppb ozone stress,
standardized beta values from LIP to photosynthetic
rate, stomatal conductance, chlorophyll content and
ascorbic acid content were found to be negative, i.e.,
−0.182 and −0.290, −0.072 and −0.148, −0.122 and
−0.238, −0.145 and −0.325, respectively, and these traits
showed a positive relation with 100 grain weight ie.,
0.272 and 0.319, 0.142 and 0.299, 0.275, and 0.342,
0.336 and 0.429, respectively. Moreover, LIP to MDA
and proline were recorded to be positive, i.e., 0.156 and
0.276, respectively which showed negative relation with
100 grain weight, i.e., −0.429 and −0.375, respectively. In
terms of growth traits, the relationship between LIP and
root length, plant height, number of nodules per plant,
number of seeds per plant, number of branches per
plant, number of leaves per plant, and plant weight
were also negative for 50 and 100 ppb ozone stress, i.e.,
−0.242 and −0.352, −0.112 and −0.158, −0.029 and
−0.085, −0.277 and −0.858, −0.417 and −0.616, −0.238
and −0.599, −0.284 and −0.385, respectively. All these
traits exhibited a positive relation with 100 grain weight,
i.e., 0.352 and 0.375, 0.232 and 0.318, 0.527, and 0.592,
0.149 and 0.226, 0.851 and 0.957, 1.038 and 1.590, 0.218
and 0.258, under 50 and 100 ppb ozone stress, respec-
tively. The direct effect of 50 and 100 ppb ozone showed
negative influence in 100 grain weight (−0.588 and
−0.753, respectively) (Figure 13a,b). These standardized
coefficients of path analysis depicted the contribution of
various physiological, biochemical and growth traits to
yield component under 50 and 100 ppb ozone stress.
In present study, the standardized beta coefficients
showed the negative effect of elevated ozone (50 and 100
ppb) concentration on blackgram varieties, which was
evidenced through physiological and biochemical traits,
i.e., photosynthetic rate, stomatal conductance, chloro-
phyll content, and ascorbic acid content that would
positively regulate the yield traits. Similarly, the positive
effect observed in malondialdehyde and proline content
negatively influenced the yield. In terms of growth traits,
a negative relationship was noticed in root length, plant
height, number of nodules per plant, number of seeds
per plant, number of branches per plant, number of
leaves per plant and plant weight and all these traits
positively influenced the yield traits in both 50 and 100
ppb ozone concentration. The path analysis for 100 ppb
ozone stress reflected the maximum variability in 100
grain weight compared to 50 ppb ozone stress. These
standardized coefficients of path analysis displayed the
contribution of observed physiological, biochemical and
growth traits to yield component under elevated ozone
(Figure 13a,b).
Principal component analysis
In present study, PCA analysis in 50 ppb and 100
ppb ozone treatment depicted cumulative eigen value
of 60.78 and 71.82%, respectively. Based on the
Figure 12. (a) Pearson’s correlation coefficient for plant traits of blackgram varieties exposed to 50 ppb ozone. (b) Pearson’s correlation
coefficient for plant traits of blackgram varieties exposed to 100 ppb ozone.
OZONE: SCIENCE & ENGINEERING 15
loading in various observed plant traits, all eight
blackgram varieties were separated in four different
groups, i.e., VBN8 and VBN5 were ozone tolerant,
VBN6 and VBN7 were moderately ozone tolerant,
CO6, VBN1 and VBN2 were moderately ozone sen-
sitive and VBN3 was ozone sensitive under 50 ppb
ozone exposed condition (Figure 6b). Similarly,
under 100 ppb ozone exposure, VBN8 and VBN5
were ozone tolerant, VBN1 and VBN7 were moder-
ately ozone tolerant, CO6, VBN2, and VBN6 were
moderately ozone sensitive and VBN3 was ozone
sensitive (Figure 7b). The test varieties showing dif-
ferent ozone sensitivity groups were associated with
various tolerance levels of blackgram varieties under
elevated ozone. Correspondingly, the ozone sensitiv-
ity of Spinach (Spinacia oleracea L.) and Swiss chard
(Beta vulgaris L.) showed differences between culti-
vars of the same species (González-Fernández et al.
2016). Similar to these findings, Singh et al. (2018)
assessed the sensitivity of 14 Indian wheat cultivars
based on various plant traits. Furthermore, Fatima
et al. (2019) used PCA tool to categorize wheat cul-
tivars and respective parameters into different ozone-
sensitive groups.
Ozone stress and plant tolerance
The concentration of tropospheric ozone is highly vari-
able in space and time on seasonal, interannual and
decadal time scales. On an average, ozone concentration
fluctuates from approximately 20 ppb over parts of
Australia and South America to 55–60 ppb in parts of
Asia, Europe and North America (Ainsworth 2017).
Furthermore, higher ozone level of about 100 ppb have
been reported in several parts of China, India,
Bangladesh and Pakistan during summer season
(Brauer et al. 2016). Ozone burden has increased by 3–
6 ppb per decade since the mid 1990s and the level has
increased by 15–20% in India from 1980 to 2016 (IPCC
2021). The highest trend of increase about 3–5.6% per
decade and 0.4 ± 0.4% per year were observed over Indo
Gangetic Plains (IGPs), while increasing trend of 1.2–
2.0% per decade was noticed over southern regions of
India (Lal et al. 2012). In future, the mean surface ozone
is projected to increase by 10–30 ppb through 2100
(Fowler et al. 2008; IPCC 2021).
In developing countries like India, the ozone forming
precursor gases (NOx) showed higher emissions along
the Indo-Gangetic Plains and southernmost regions of
Figure 13 (a) Path analysis describing differential effect of 50 ppb ozone on plant traits of eight blackgram varieties. Values in the
rectangular box denotes the standardized beta values. (b) Schematic representation of path analysis describing differential effect of
100 ppb ozone on plant traits of eight blackgram varieties. Values in the rectangular box denotes the standardized beta values.
16 P. DHEVAGI ET AL.
India. As a result of large industrial, transportation and
biomass burning activities, high NOx emissions also
recorded over the states like Gujarat, Maharashtra,
Andhra Pradesh, and Tamil Nadu (Jena et al. 2015).
Higher the concentrations of NOx resulted in higher
the ozone pollution (45–65 ppb) over these regions
(David and Nair 2013; Deb Roy, Beig, and Ghude
2009) and these regions were considered as ozone
hotspots.
The present-day ozone concentration already exceeds
the accepted threshold limit and it tends to intensify in
future. With these references, the present experiment
conducted with two levels of elevated ozone (50 and
100 ppb) above the threshold limit (40 ppb) showed
significant reduction in physiological, biochemical,
growth, and yield traits of blackgram varieties.
A significant ozone impact is progressed with increasing
concentration. The reduction in plant traits with
response to elevated ozone was maximum for the vari-
eties grown under 100 ppb ozone compared to 50 ppb
ozone stress. According to Mills et al. (2007), the
accepted threshold level of ozone for crop species is 40
ppb; pulses being one among the most sensitive agricul-
tural crop species to 40 ppb ozone and exhibited yield
reduction at AOT40 of 3 ppm h. In this study, mean
concentration of elevated ozone was greater than 40 ppb
and AOT40 values was relatively greater than 3 ppm h,
which could be the reason for ozone-induced negative
impact in the blackgram varieties. The magnitude of
response of blackgram to ozone stress varied signifi-
cantly among the test varieties. Additionally, the ozone
tolerance level for blackgram varieties lies below 40 ppb
and shows ozone-induced negative effect when it
exceeds 40 ppb ozone concentration. Moreover, in pre-
vious studies, the blackgram varieties grown under
ozone stress with a mean of 51 ppb and AOT40 value
of 10.786 ppm h showed significant reduction in phy-
siological, biochemical, growth, and yield traits (Singh
and Agrawal 2011). Similarly, cultivar-specific variations
in mung bean (Chaudhary et al. 2013) and black gram
(Singh and Agrawal 2011) were also observed under
ozone stress.
The plants tolerance to elevated ozone is attributed to
antioxidant metabolites, ascorbic acid, and enzyme con-
tent in the plant species. In present study, the ozone
tolerant variety VBN8 maintains better ascorbic acid
level under elevated ozone stress compared to ozone sen-
sitive variety VBN3. As a consequence, the variety VBN8
showed its tolerance to elevated ozone by retaining higher
physiological, growth, and yield parameters. The mechan-
ism of cellular response and the presence of antioxidants in
the plant system are substantially varied among the species
and within the species which would result in varying ozone
tolerant capacity of the plants (Yendrek, Koester, and
Ainsworth 2015). In this study, among the test varieties,
the presence of antioxidant enzymes and ROS scavenging
capacity might be higher for VBN8 which would enhance
the tolerance against ozone stress. Additionally, lower leaf
injury percentage and MDA content of VBN8 under ele-
vated ozone stress is also an evident for its tolerance.
Conclusion
From the obtained results, it is clear that all blackgram
varieties showed differential behavior in terms of physiol-
ogy, biochemical, growth, and yield traits. The genetic
variation among the test varieties would provide significant
insights related to crop yield loss toward elevated ozone
stress. The present results suggests that the ozone tolerant
blackgram variety, VBN8 may be recommended for culti-
vation in ozone polluted areas; whereas, ozone sensitive
VBN3 variety may be used for monitoring the ozone
pollution. Improved agronomic practices and application
of ozone protectants would alleviate the ozone-induced
negative impact on blackgram varieties. Moreover, the
present outcome would suggest the choice of ozone toler-
ant donor parents in developing ozone specific plant gen-
otypes. With respect to changing environmental
conditions and increasing ozone pollution in future,
further investigation on genome-wide association study
and identification of genetic factor/loci associated with
ozone tolerance in blackgram would provide a rich base
for adaptive breeding.
Acknowledgments
Authors are thankful to Tamil Nadu Agricultural University,
Coimbatore, 641003, Tamil Nadu, India and Physical
Research Laboratory (PRL), Indian Space Research
Organization (ISRO), Ahmedabad for providing facilities to
carry out the research. Authors are grateful to
Dr. S. Karthikeyan, Professor (Microbiology), TNAU for pro-
viding infrastructure facility.
Disclosure statement
The authors declare that they have no known competing
financial interests or personal relationships that could have
appeared to influence the work reported in this paper.
ORCID
Periyasamy Dhevagi http://orcid.org/0000-0001-9212-0242
Ambikapathi Ramya http://orcid.org/0000-0002-8697-
5938
OZONE: SCIENCE & ENGINEERING 17
Sengottiyan Priyatharshini http://orcid.org/0000-0001-
6400-7402
Ramesh Poornima http://orcid.org/0000-0002-2460-4162
References
Ainsworth, Elizabeth A., Craig R. Yendrek, William J. Stephen
Sitch, Collins, L D. Emberson, and Lisa D. Collins. 2012.
“The Effects of Tropospheric Ozone on Net Primary
Productivity and Implications for Climate Change.”
Annual Review of Plant Biology 63 (1): pp. 637–61.
doi:10.1146/annurev-arplant-042110-103829.
Ainsworth, Elizabeth A. 2017. “Understanding and Improving
Global Crop Response to Ozone Pollution.” The Plant
Journal 90 (5): pp. 886–97. doi:10.1111/tpj.13298.
Alaiz, Manuel, Francisco J. Hidalgo, and Rosario Zamora.
1999. “Effect of pH and Temperature on Comparative
Antioxidant Activity of Nonenzymatically Browned
Proteins Produced by Reaction with Oxidized Lipids and
Carbohydrates.” Journal of Agricultural and Food Chemistry
47 (2): pp. 748–52. doi:10.1021/jf980733r.
Allu, Sarat Kumar, Aparna Reddy, Shailaja Srinivasan, Rama
Krishna Maddala, and Gangagni Rao Anupoju. 2021.
“Surface Ozone and Its Precursor Gases Concentrations
during COVID-19 Lockdown and Pre-Lockdown Periods
in Hyderabad City, India.” Environmental Processes 8 (2):
pp. 959–72. doi:10.1007/s40710-020-00490-z.
Alscher, R. G., and J. L. Hess. 1993. Antioxidants in Higher
Plants. Boca Raton: CRC Press.
Bailey, Amanda, Kent Burkey, Matthew Taggart, and
Thomas Rufty. 2019. “Leaf Traits that Contribute to
Differential Ozone Response in Ozone-Tolerant and
Sensitive Soybean Genotypes.” Plants 8 (7): p. 235.
doi:10.3390/plants8070235.
Bates, L. S., S. P. Waldren, and I. D. Teare. 1973. “Rapid
Determination of Proline for Water-Stressed Studies.”
Plant and Soil 39 (1): pp. 205–07. doi:10.1007/BF00018060.
Bera, Biswajit, Sumana Bhattacharjee, Pravat Kumar Shit,
Nairita Sengupta, and Soumik Saha. 2021. “Variation and
Correlation between Ultraviolet Index and Tropospheric
Ozone during COVID-19 Lockdown over Megacities of
India.” Stochastic Environmental Research and Risk
Assessment pp. 1–19. doi: 10.1007/s00477-021-02033-w.
Betzelberger, M., M. Amy Kelly, Justin M. Gillespie, Robert
P. Mcgrath, Randall L. Koester, Nelson, and Elizabeth
A. Ainsworth. 2010. “Effects of Chronic Elevated Ozone
Concentration on Antioxidant Capacity, Photosynthesis
and Seed Yield of 10 Soybean Cultivars.” Plant, Cell &
Environment 33 (9): pp. 1569–81. doi:10.1111/j.1365-
3040.2010.02165.x.
Biswas, D. K., and G. M. Jiang. 2011. “Differential
Drought-Induced Modulation of Ozone Tolerance in
Winter Wheat Species.” Journal of Experimental Botany
62 (12): pp. 4153–62. doi:10.1093/jxb/err104.
Blokhina, Olga, Eija Virolainen, and Kurt V. Fagerstedt. 2003.
“Antioxidants, Oxidative Damage and Oxygen Deprivation
Stress: A Review.” Annals of Botany 91 (2): pp. 179–94.
doi:10.1093/aob/mcf118.
Brancher, Marlon. 2021. “Increased Ozone Pollution
Alongside Reduced Nitrogen Dioxide Concentrations dur-
ing Vienna’s First COVID-19 Lockdown: Significance for
Air Quality Management.” Environmental Pollution 284: p.
117153. doi: 10.1016/j.envpol.2021.117153
Brauer, Michael, Greg Freedman, Joseph Frostad, van
Donkelaar Aaron, Randall V. Martin, Frank Dentener, van
Dingenen Rita, Kara Estep, Joshua S. Heresh Amini,
Kalpana Balakrishnan Apte, et al. 2016. “Ambient Air
Pollution Exposure Estimation for the Global Burden of
Disease 2013.” Environmental Science and Technology
50 (1): pp. 79–88. doi:10.1021/acs.est.5b03709.
Caregnato, Fernanda Freitas, Rafael Calixto Bortolin,
Armando Molina Divan Junior, and Cláudio José. 2013.
“Exposure to Elevated Ozone Levels Differentially Affects
the Antioxidant Capacity and the Redox Homeostasis of
Two Subtropical Phaseolus Vulgaris L. Varieties.”
Chemosphere 93 (2): pp. 320–30. doi:10.1016/j.
chemosphere.2013.04.084.
Castagna, Antonella, S. Cristina Nali, Giacomo
Lorenzini Ciompi, G. F. Soldatini, Annamaria Ranieri,
and A. Ranieri. 2001. “Ozone Exposure Affects
Photosynthesis of Pumpkin (Cucurbita Pepo) Plants.”
New Phytologist 152 (2): pp. 223–29. doi:10.1046/j.0028-
646X.2001.00253.x.
Chaudhary, Nivedita, and S. B. Agrawal. 2013. “Intraspecific
Responses of Six Indian Clover Cultivars under Ambient
and Elevated Levels of Ozone.” Environmental Science and
Pollution Research 20 (8): pp. 5318–29. doi:10.1007/s11356-
013-1517-0.
Chaudhary, Nivedita, and S. B. Agrawal. 2014. “Cultivar Specific
Variations in Morphological and Biochemical Characteristics
of Mung Bean Due to Foliar Spray of Ascorbic Acid under
Elevated Ozone.” Acta Physiologiae Plantarum 36 (7): pp.
1793–03. doi:10.1007/s11738-014-1553-5.
Chaudhary, Nivedita, and S. B. Agrawal. 2015. “The Role of
Elevated Ozone on Growth, Yield and Seed Quality
Amongst Six Cultivars of Mung Bean.” Ecotoxicology and
Environmental Safety 111: pp. 286–94. doi: 10.1016/j.
ecoenv.2014.09.018
Chaudhary, Nivedita, S. B. Suruchi Singh, Agrawal,
Madhoolika Agrawal, and S B. Agrawal. 2013. “Assessment
of Six Indian Cultivars of Mung Bean against Ozone by Using
Foliar Injury Index and Changes in Carbon Assimilation, Gas
Exchange, Chlorophyll Fluorescence and Photosynthetic
Pigments.” Environmental Monitoring and Assessment
185 (9): pp. 7793–97. doi:10.1007/s10661-013-3136-0.
CPGA. 2020. “Crop Production Guide Agriculture.”
Directorate of Agriculture and Tamil Nadu Agricultural
University. https://tnau.ac.in/research/wp-content
/uploads/sites/60/2020/02/Agriculture-CPG-2020.pdf 19
March 2021
David, Liji Mary, and Prabha R. Nair. 2013. “Tropospheric
Column O
3
and NO
2
over the Indian Region Observed by
Ozone Monitoring Instrument (OMI): Seasonal Changes
and Long-Term Trends.” Atmospheric Environment 65:
pp. 25–39. doi: 10.1016/j.atmosenv.2012.09.033
De Datta, S. K. 1981. Principles and Practices of Rice
Production. New York: Wiley-Inter Science.
18 P. DHEVAGI ET AL.
Deb Roy, S., G. Beig, and Sachin D. Ghude. 2009. “Exposure-
Plant Response of Ambient Ozone over the Tropical Indian
Region.” Atmospheric Chemistry and Physics 9 (14): pp.
5253–60. doi:10.5194/acp-9-5253-2009.
Donzelli, Gabriele, Lorenzo Cioni, Mariagrazia Cancellieri,
Agustin Llopis-Morales, and Morales-Suárez-Varela
María. 2021. “Air Quality during Covid-19 Lockdown.”
Encyclopedia 1 (3): pp. 519–26. doi:10.3390/
encyclopedia1030043.
Edwin, Fiscus, L., L. Fitzgerald, Booker, and Kent O. Burkey.
2005. “Crop Responses to Ozone: Uptake, Modes of Action,
Carbon Assimilation and Partitioning.” Plant, Cell &
Environment 28 (8): pp. 997–11. doi:10.1111/j.1365-
3040.2005.01349.x.
Emberson, L. D., P. Büker, M. R. Ashmore, G. Mills,
L. S. Jackson, M. Agrawal, M. D. Atikuzzaman,
S. Cinderby, M. Engardt, and C. Jamir. 2009.
“A Comparison of North American and Asian Exposure–
Response Data for Ozone Effects on Crop Yields.”
Atmospheric Environment 43 (12): pp. 1945–53.
doi:10.1016/j.atmosenv.2009.01.005.
Fatima, Adeeb, Aditya Abha Singh, Arideep Mukherjee,
Tsetan Dolker, Madhoolika Agrawal, and Shashi
Bhushan Agrawal. 2019. “Assessment of Ozone Sensitivity
in Three Wheat Cultivars Using Ethylenediurea.” Plants
8 (4): p. 80. doi:10.3390/plants8040080.
Feng, Zhaozhong, Jing Pang, Kazuhiko Kobayashi,
Jianguo Zhu, and Donald R. Ort. 2011. “Differential
Responses in Two Varieties of Winter Wheat to Elevated
Ozone Concentration under Fully Open-Air Field
Conditions.” Global Change Biology 17 (1): pp. 580–91.
doi:10.1111/j.1365-2486.2010.02184.x.
Fowler, David, Markus Amann, Ross Anderson,
Mike Ashmore, Peter Cox, Michael Depledge,
Dick Derwent, Peringe Grennfelt, Nick Hewitt,
Oystein Hov, et al. 2008. “Ground-Level Ozone in the 21st
Century: Future Trends, Impacts and Policy Implications.”
(RS1276 Ed.) Royal Society Policy Document.” The Royal
Society. http://royalsociety.org/policy/publications/2008/
ground-level-ozone/ 14 January 2021.
Ghosh, A., B. Pandey, M. Agrawal, and S. B. Agrawal. 2020.
“Interactive Effects and Competitive Shift between Triticum
Aestivum L. (Wheat) and Chenopodium Album L. (Fat-hen)
under Ambient and Elevated Ozone.” Environmental
Pollution 265: p. 114764. doi: 10.1016/j.envpol.2020.114764
Gill, Sarvajeet Singh, and Narendra Tuteja. 2010. “Reactive
Oxygen Species and Antioxidant Machinery in Abiotic
Stress Tolerance in Crop Plants.” Plant Physiology and
Biochemistry 48 (12): pp. 909–30. doi:10.1016/j.
plaphy.2010.08.016.
González-Fernández, Ignacio, Susana Elvira,
Vicent Calatayud, Esperanza Calvo, Pedro Aparicio,
Miguel Sánchez, Rocío Alonso, and Victoria
Bermejo Bermejo. 2016. “Ozone Effects on the Physiology
and Marketable Biomass of Leafy Vegetables under
Mediterranean Conditions: Spinach (Spinacia Oleracea L.)
And Swiss Chard (Beta Vulgaris L. Var. Cycla).”
Agriculture, Ecosystems & Environment 235 (1–4): pp.
215–28. doi:10.1016/j.agee.2016.10.023.
Grewe, V., D. Brunner, M. Dameris, J. L. Grenfell, R. Hein,
D. Shindell, and J. Staehelin. 2001. “Origin and
Variability of Upper Tropospheric Nitrogen Oxides and
Ozone at Northern Mid-latitudes.” Atmospheric
Environment 35 (20): pp. 3421–33. doi:10.1016/S1352-
2310(01)00134-0.
Hauglustaine, D. A., J. Lathiere, S. Szopa, and G. A. Folberth.
2005. “Future Tropospheric Ozone Simulated with
a Climate-Chemistry-Biosphere Model.” Geophysical
Research Letters 32 (24): pp. 1–5. doi:10.1029/
2005GL024031.
Heath, Robert L., and Lester Packer. 1968. “Photoperoxidation in
Isolated Chloroplasts. I. Kinetics and Stoichiometry of Fatty
Acid Peroxidation.” Archives of Biochemistry and Biophysics
125 (1): pp. 189–98. doi:10.1016/0003-9861(68)90654-1.
IPCC. 2021. Summary for Policymakers. Climate Change
2021: The Physical Science Basis. Contribution of
Working Group I to the Sixth Assessment Report of the
Intergovernmental Panel on Climate Change.
V. Masson-Delmotte, P. Zhai, A. Pirani,
S. L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen,
L. Goldfarb, and M. I. Gomis, et al.edited by England:
Cambridge University Press. In Press 213
Jena, Chinmay, D. Sachin, Ghude, G. Beig, D. M. Chate,
Rajesh Kumar, G. G. Pfister, D. M. Lal, Divya
E. Surendran, S. Fadnavis, and R.J. van der A. 2015. “Inter-
Comparison of Different NOx Emission Inventories and
Associated Variation in Simulated Surface Ozone in
Indian Region.” Atmospheric Environment 117: pp. 61–73.
doi: 10.1016/j.atmosenv.2015.06.057.
Kakar, Naqeebullah, Salah H. Jumaa, Edilberto Diaz Redoña,
Marilyn L. Warburton, and K. Raja Reddy. 2019.
“Evaluating Rice for Salinity Using Pot-culture Provides
a Systematic Tolerance Assessment at the Seedling Stage.”
Rice 12 (1): pp. 1–14. doi:10.1186/s12284-019-0317-7.
Keller, T., and H. Schwager. 1977. “Air Pollution and Ascorbic
Acid.” European Journal of Forest Pathology 7 (6): pp.
338–50. doi:10.1111/j.1439-0329.1977.tb00603.x.
Lal, D. M., Sachin D. Ghude, S. D. Patil, Santosh H. Kulkarni,
Chinmay Jena, Suresh Tiwari, and K. Srivastava Manoj.
2012. “Tropospheric Ozone and Aerosol Long-Term
Trends over the Indo-Gangetic Plain (IGP), India.”
Atmospheric Research 116: pp. 82–92. doi: 10.1016/j.
atmosres.2012.02.014
Lee, Edward H. 1991. “Plant Resistance Mechanisms to Air
Pollutants: Rhythms in Ascorbic Acid Production during
Growth under Ozone Stress.” Chronobiology International
8 (2): pp. 93–02. doi:10.3109/07420529109059161.
Miller, Jennifer D., Richard N. Arteca, and Eva J. Pell.
1999. “Senescence-associated Gene Expression during
Ozone-Induced Leaf Senescence in Arabidopsis.” Plant
Physiology 120 (4): pp. 1015–24. doi:10.1104/
pp.120.4.1015.
Mills, G., A. Buse, B. Gimeno, V. Bermejo, M. Holland,
L. Emberson, and H. Pleijel. 2007. “A Synthesis of
AOT40-Based Response Functions and Critical Levels of
Ozone for Agricultural and Horticultural Crops.”
Atmospheric Environment 41 (12): pp. 2630–43.
doi:10.1016/j.atmosenv.2006.11.016.
Mishra, A. K., and S. B. Agrawal. 2014. “Cultivar Specific
Response of CO
2
Fertilization on Two Tropical Mung Bean
(Vigna Radiata L.) Cultivars: ROS Generation, Antioxidant
Status, Physiology, Growth, Yield and Seed Quality.” Journal of
Agronomy and Crop Science 200 (4): pp. 273–89. doi:10.1111/
jac.12057.
OZONE: SCIENCE & ENGINEERING 19
Mishra, Amit Kumar, and S. B. Agrawal. 2015. “Biochemical
and Physiological Characteristics of Tropical Mung Bean
(Vigna Radiata L.) Cultivars against Chronic Ozone Stress:
An Insight to Cultivar-Specific Response.” Protoplasma
252 (3): pp. 797–11. doi:10.1007/s00709-014-0717-x.
Mohan, S., and Packiam Saranya. 2019. “Assessment of
Tropospheric Ozone at an Industrial Site of Chennai
Megacity.” Journal of the Air & Waste Management
Association 69 (9): pp. 1079–95. doi:10.1080/
10962247.2019.1604451.
Monks, P.S., A.T. Archibald, A. Colette, O. Cooper, M. Coyle,
R. Derwent, D. Fowler, C. Granier, K. S. Law, G. E. Mills,
et al. 2015. “Tropospheric Ozone and Its Precursors from the
Urban to the Global Scale from Air Quality to Short-Lived
Climate Forcer.” Atmospheric Chemistry and Physics 15 (15):
pp. 8889–73. doi:10.5194/acp-15-8889-2015.
Nahar, Shamsun, Lingaraj Sahoo, and Bhaben Tanti. 2018.
“Screening of Drought Tolerant Rice through
Morpho-Physiological and Biochemical Approaches.”
Biocatalysis and Agricultural Biotechnology 15: pp. 150–59.
doi: 10.1016/j.bcab.2018.06.002
Pandiselvam, R., V. P. Mayookha, L. Anjineyulu Kothakota,
S. V. Sharmila, C. P. Ramesh, Bharathi, K. Gomathy,
V. Srikanth, and V. Srikanth. 2020. “Impact of Ozone
Treatment on Seed Germination–A Systematic Review.”
Ozone: Science & Engineering 42 (4): pp. 331–46.
doi:10.1080/01919512.2019.1673697.
Prabakaran, P., V. Krishnasamy, A. Manikandan, and
V. Rambabu. 2017. “Consequence of Meteorological
Factors on Gaseous Pollutants and Seasonal Erraticism in
the Ambient Air of Chennai City.” Journal of
Environmental Protection 37 (6): pp. 461–74.
Rai, Richa. 2020. “Threat Imposed by O 3-Induced ROS on
Defense, Nitrogen Fixation, Physiology, Biomass Allocation,
and Yield of Legumes.” In The Plant Family Fabaceae, edited
by M. Hasanuzzaman, S. Araújo, and S. Gill, pp. 503–17.
Singapore: Springer. doi:10.1007/978-981-15-4752-2_19.
Rai, Richa, Madhoolika Agrawal, Choudhary, S. Krishna Kumar,
B. Agrawal, Lisa Emberson, and Büker Patrick. 2015.
“Application of Ethylene Diurea (EDU) in Assessing the
Response of a Tropical Soybean Cultivar to Ambient O
3
:
Nitrogen Metabolism, Antioxidants, Reproductive
Development and Yield.” Ecotoxicology and Environmental
Safety 112: pp. 29–38. doi: 10.1016/j.ecoenv.2014.10.031
Rejeb, Ben, Chedly Abdelly Kilani, and Savouré Arnould.
2014. “How Reactive Oxygen Species and Proline Face
Stress Together.” Plant Physiology and Biochemistry 80:
pp. 278–84. doi: 10.1016/j.plaphy.2014.04.007
Sachin, Ghude, D., D. M. Chinmay Jena, Chate, G. Beig,
G. G. Pfister, Rajesh Kumar, V. Ramanathan, and
V. Ramanathan. 2014. “Reductions in India’s Crop Yield
Due to Ozone.” Geophysical Research Letters 41 (15): pp.
5685–91. doi:10.1002/2014GL060930.
Salvatori, Elisabetta, Lina Fusaro, Simone Mereu,
Alessandra Bernardini, Gigliola Puppi, and Fausto Manes.
2013. “Different O
3
Response of Sensitive and Resistant
Snap Bean Genotypes (Phaseolus Vulgaris L.): The Key
Role of Growth Stage, Stomatal Conductance, and PSI
Activity.” Environmental and Experimental Botany 87: pp.
79–91. doi: 10.1016/j.envexpbot.2012.09.008
Sanmartin, Maite, Pavlina D. Drogoudi, Tom Lyons,
Irene Pateraki, Jeremy Barnes, and Angelos K. Kanellis.
2003. “Over-Expression of Ascorbate Oxidase in the
Apoplast of Transgenic Tobacco Results in Altered
Ascorbate and Glutathione Redox States and Increased
Sensitivity to Ozone.” Planta 216 (6): pp. 918–28.
doi:10.1007/s00425-002-0944-9.
Sarkar, Abhijit, and S. B. Agrawal. 2010. “Elevated Ozone and
Two Modern Wheat Cultivars: An Assessment of Dose
Dependent Sensitivity with respect to Growth,
Reproductive and Yield Parameters.” Environmental and
Experimental Botany 69 (3): pp. 328–37. doi:10.1016/j.
envexpbot.2010.04.016.
Sharma, Shubham, Mengyuan Zhang, Jingsi Gao,
Hongliang Zhang, Sri Harsha Kota, and S H. Kota. 2020.
“Effect of Restricted Emissions during COVID-19 on Air
Quality in India.” Science of the Total Environment 728: p.
138878. doi: 10.1016/j.scitotenv.2020.138878
Sicard, Pierre, Alessandra De Marco,
Evgenios Agathokleous, Zhaozhong Feng, Xiaobin Xu,
Elena Paoletti, José Jaime, Diéguez Rodriguez, and
Vicent Calatayud. 2020. “Amplified Ozone Pollution in
Cities during the COVID-19 Lockdown.” Science of the
Total Environment 735: p. 139542. doi: 10.1016/j.
scitotenv.2020.139542
Singh, Aditya Abha, Adeeb Fatima, Amit Kumar Mishra,
Nivedita Chaudhary, Arideep Mukherjee,
Madhoolika Agrawal, and Shashi Bhushan Agrawal.
2018. “Assessment of Ozone Toxicity among 14
Indian Wheat Cultivars under Field Conditions:
Growth and Productivity.” Environmental Monitoring
and Assessment 190 (4): pp. 1–14. doi:10.1007/s10661-
018-6563-0.
Singh, Era, Supriya Tiwari, and Madhoolika Agrawal. 2010.
“Variability in Antioxidant and Metabolite Levels, Growth
and Yield of Two Soybean Varieties: An Assessment of
Anticipated Yield Losses under Projected Elevation of
Ozone.” Agriculture, Ecosystems & Environment 135 (3):
pp. 168–77. doi:10.1016/j.agee.2009.09.004.
Singh, Shalini, S., B. Agrawal, Poonam Singh, and M. Agrawal.
2010. “Screening Three Cultivars of Vigna Mungo
L. Against Ozone by Application of Ethylenediurea
(EDU).” Ecotoxicology and Environmental Safety 73 (7):
pp. 1765–75. doi:10.1016/j.ecoenv.2010.05.001.
Singh, Shalini, and S. B. Agrawal. 2011. “Ambient Ozone and
Two Black Gram Cultivars: An Assessment of Amelioration
by the Use of Ethylenediurea.” Acta Physiologiae Plantarum
33 (6): pp. 2399–411.
Sinha, B., K. Singh Sangwan, Y. Maurya, V. Kumar, C. Sarkar,
B. P. Chandra, and V. Sinha. 2015. “Assessment of Crop
Yield Losses in Punjab and Haryana Using 2 Years of
Continuous in Situ Ozone Measurements.” Atmospheric
Chemistry and Physics 15 (16): pp. 9555–76. doi:10.5194/
acp-15-9555-2015.
Sivaranjani, S., V. Arun Prasath, R. Pandiselvam,
Anjineyulu Kothakota, and Amin Mousavi Khaneghah.
2021. “Recent Advances in Applications of Ozone in
the Cereal Industry.” LWT - Food Science and
Technology 146: p. 111412. doi: 10.1016/j.
lwt.2021.111412
20 P. DHEVAGI ET AL.
Statista. 2021. “Pulses in India - Statistics and Facts.” Statista
Research Department. https://www.statista.com/topics/
5757/pulses-in-India/#dossierSummary__chapter2 11
March 2021.
Sudhakar, N., D. Nagendra-Prasad, N. Mohan, M. Bradford
Hill, Gunasekaran, K. Murugesan, and M. Gunasekaran.
2011. “Assessing Influence of Ozone in Tomato Seed
Dormancy Alleviation.” American Journal of Plant
Sciences 2 (3): p. 443. doi:10.4236/ajps.2011.23051.
Sudhakar, Natesan, Durairaj Nagendra-Prasad,
Natrajan Mohan, and Kandasamy Murugesan. 2008.
“A Preliminary Study on the Effects of Ozone Exposure
on Growth of the Tomato Seedlings.” Australian Journal
of Crop Science 2 (1): pp. 33–39.
Sun, Jindong, Zhaozhong Feng, and Donald R. Ort. 2014.
“Impacts of Rising Tropospheric Ozone on Photosynthesis
and Metabolite Levels on Field Grown Soybean.” Plant
Science 226: pp. 147–61. doi: 10.1016/j.plantsci.2014.06.012
Tetteh, R., M. Yamaguchi, and T. Izuta. 2016. “Effect of
Ambient Levels of Ozone on Photosynthetic Components
and Radical Scavenging System in Leaves of African
Cowpea Varieties.” African Crop Science Journal 24 (2):
pp. 127–42. doi:10.4314/acsj.v24i2.2.
Tripathi, Ruchika, and Shashi B. Agrawal. 2013. “Interactive
Effect of Supplemental Ultraviolet B and Elevated Ozone on
Seed Yield and Oil Quality of Two Cultivars of Linseed
(Linum Usitatissimum L.) Carried Out in Open Top
Chambers.” Journal of the Science of Food and Agriculture
93 (5): pp. 1016–25. doi:10.1002/jsfa.5838.
Upadhyaya, H, M. H. Khan, and S. K. Panda. 2007. “Hydrogen
Peroxide Induces Oxidative Stress in Detached Leaves of
Oryza Sativa L.” doi:10.1.1.320.3168. General and Applied
Plant Physiology 33 (1–2): pp. 83–95.
Van Hove, L. W. A., M. E. Bossen, B. G. San Gabino, and
C. Sgreva. 2001. “The Ability of Apoplastic Ascorbate to
Protect Poplar Leaves against Ambient Ozone
Concentrations: A Quantitative Approach.”
Environmental Pollution 114 (3): pp. 371–82. doi:10.1016/
S0269-7491(00)00237-2.
Van Leeuwen, J. H. 2015. “Proposed OS&E Requirement:
Measuring Ozone Dosage.” Ozone: Science & Engineering
37 (2): pp. 191–92. doi:10.1080/01919512.2015.1006467.
Van, Dinh, Thi Hai, and Satoshi Ishii. 2008. “Assessment of
Ozone Effects on Local Rice Cultivar by Portable Ozone
Fumigation System in Hanoi, Vietnam.” Environmental
Monitoring and Assessment 155 (1–4): pp. 569–80.
doi:10.1007/s10661-008-0456-6.
Vázquez-Ybarra, Jorge A., Cecilia B. Peña-Valdivia,
Carlos Trejo, Albino Villegas-Bastida, Sergio Benedicto-
Valdéz, and Sánchez-García Prometeo. 2015. “Promoción
del crecimiento de plantas de lechuga (Lactuca sativa L.)
con dosis subletales de ozono aplicadas al medio de cultivo.”
Revista Fitotecnia Mexicana 38 (4): pp. 405–13.
doi:10.35196/rfm.2015.4.405
Violleau, Frédéric, Kheira Hadjeba, Joël Albet, Roland Cazalis,
and Olivier Surel. 2007. “Increase of Corn Seeds
Germination by Oxygen and Ozone Treatment.” In:
Proceedings of the IOA Conference and Exhibition Spain,
Valencia, pp. 3–4.
Yadav, Durgesh Singh, Richa Rai, Amit Kumar Mishra,
Nivedita Chaudhary, S. B. Arideep Mukherjee, Agrawal,
Madhoolika Agrawal, and S.B. Agrawal. 2019. “ROS
Production and Its Detoxification in Early and Late Sown
Cultivars of Wheat under Future O
3
Concentration.”
Science of the Total Environment 659: pp. 200–10. doi:
10.1016/j.scitotenv.2018.12.352
Yendrek, Craig R., Robert P. Koester, and Elizabeth
A. Ainsworth. 2015. “A Comparative Analysis of
Transcriptomic, Biochemical, and Physiological Responses
to Elevated Ozone Identifies Species-Specific Mechanisms
of Resilience in Legume Crops.” Journal of Experimental
Botany 66 (22): pp. 7101–12. doi:10.1093/jxb/erv404.
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