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Effect of plastic mulches on yield and fruit quality of strawberry plants grown under high tunnels

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Shahrokh Khanizadeh at ELM Consulting
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Medina, Y., Gosselin, A., Desjardins, Y., Harnois, R., Gauthier, L., and Khanizadeh, S. (2011). Effect of plastic mulches on yield and fruit quality of strawberry plants grown under high tunnels, Acta Horticulturae (ISHS), 893, pp. 1327-1332.
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1327
Effect of Plastic Mulches on Yield and Fruit Quality of Strawberry
Plants Grown under High Tunnels
Y. Medina, A. Gosseli
n
a and Y. Desjardins
Horticultural Research Center
Laval University
Québec, G1K 7P4
Canada
L. Gauthie
r
Les Fraises de l’Île d’Orléans inc.
199, côte Gosselin, St-Laurent d’Orléans
Québec, G0A 3Z0
Canada
R. Harnois
Industries Harnois inc.
1044, rue principale, St-Thomas de Joliette
Québec, J0K 3L0
Canada
S. Khanizadeh
Agriculture and Agri-Food Canada
Boul. Gouin, St-Jean-sur-Richelieu
Québec, J3B 3E6
Canada
Keywords: growth conditions, phenolics content, small fruits, sugars content
Abstract
High tunnels are gaining in popularity in Canadian northern climates to
prolong the growing season, increase yields and improve the quality of fruits and
vegetables. An experiment in 2006 and 2007 was conducted under high tunnels and
open fields to determine the effects of various plastic mulches on microclimate
conditions, growth, yields and fruit quality of day-neutral strawberry. High tunnels
(8.4 m wide, 4.8 m high and 145 m long) developed by Industries Harnois inc. were
used at Les Fraises de l’Île d’Orléans inc. near Quebec City, Canada (latitude 47°,
altitude 137 m). Four plastic mulches (green, grey on grey, white on black and black)
obtained from Ginegar Plastics Products Ltd. were compared. Treatments were
replicated four times and each experimental unit consisted of 26 strawberry plants
of cultivar ‘Seascape’. Soil at a depth of 10 cm and air temperatures at a height of 20
cm were measured with Hobo temperature sensors obtained from MicroDaq Ltd.
Plant growth was measured periodically, while yields were measured three times per
week. All mulch treatments under the high tunnels produced higher yield than the
outdoor control. Black mulch caused excessive soil and air temperatures in tunnels,
but was found adequate for the open field.
INTRODUCTION
Strawberry culture is one of the most widespread fruit production in the world
(4,068,454 T) (FAOSTAT, 2008). The strawberry is a much appreciated food crop and is
consumed for its pleasant flavor as well as its nutrient content (Loughrin and
Kasperbauer, 2002; Carlen et al., 2005). In recent years, there have been interests to study
bioactive compounds of strawberries with an impact on human health such as ascorbic
and ellagic acids (Wang et al., 2002). In Canada, the culture of day-neutral strawberry
prolongs harvesting from July to October (Parent, 2003). Growing day-neutral strawberry
using plastic mulches stimulates growth of young plants, increases soil temperature,
reduces evapotranspiration and restrains heat loss during cold nights (Lieten, 1991) while
it improves the profitability by increasing the yield and/or early fruit production. It also
has a positive effect on photosynthesis (Atkinson et al., 2006), daughter and runner
development, early production and fruit quality (Orzolek and Murphy, 1993).
High tunnels are very common in the Mediterranean regions and Asia (Espí et al.,
2006) as they prolong the harvesting period and improve fruit quality. A high tunnel fruit
growing system provides a competitive edge in the market, compared with a field
growing system (Kadir et al., 2006). Despite recent commercial construction of high
tunnels in Canada, few investigations have been made on high tunnels for the production

a andre.gosslin@fsaa.ulaval.ca
Proc. IS on High Technology for Greenhouse Systems - GreenSys2009
Ed.: M. Dorais
Acta Hort. 893, ISHS 2011
1328
of small fruits. A joint collaborative project started in 2005 with Les Industries Harnois
inc. and Les Fraises de l'Île d’Orléans inc. to investigate the effect of high tunnels on
yield, fruit quality and its adaptability to Northern Canadian climates.
MATERIALS AND METHODS
Plug plants provided by NorCal Nurseries Inc. enterprise (http://sakumabros.com/
index.html) were planted for four weeks in a greenhouse on 15 April 2006 or on 10 April
2007 and then transplanted under high tunnels or outdoor on 5 May 2006, and on 12 May
2007, respectively. The experiment was a randomized complete block, and the treatments
consisted of four color plastic mulches (green, grey on grey white on black and black)
replicated four times. Each experimental unit consisted of 26 ‘Seascape’ strawberry plug
plants. The beds measured 182 cm long, 112 cm width and 20 cm high. The strawberry
plugs plants were spaced by 30 cm. The type of soil was sandy loam. An outdoor control
treatment was added in 2006 using black mulch and all plastic mulches in 2007. Data
were analyzed using analysis of variance of SAS (1990) and differences among means
were tested by the least significant difference (LSD) using Fisher’s protected at 5% level.
Soil at a depth of 10 cm and air temperatures at a height of 20 cm were measured
with Hobo temperature sensors. The first and last harvests in 2006 were 28 June and 30
October, respectively, while in 2007 the first and last harvests were 3 July and 28
September. Fruits were harvested three times per week and yield was measured
periodically.
Marketable fruits were counted and weighed, and separated from those
unmarketable with diseases, small fruits or physical damage. In 2006, the numbers of
leaves, crowns and runners per plant were determined on 8 June and on 28 October, while
in 2007 these measurements were made on 27 June and on 30 September. Leaves, shoots
and roots were dried at 70°C for 72 h, and total shoot and root biomass was determined.
Sugars were measured in the strawberry fruits which were crushed and the
obtained juice was used for the °Brix measurements using a hand refractometer (Atago
Co., Ltd.). This measurement was made on 18 July 2006 while in 2007 the observations
were made weekly in August. The lyophilized strawberries were used to measure the total
phenols and the antioxidant activity by HPLC, according to the protocols of Gil et al.
(2000) and of Fogliano et al. (1999), respectively.
RESULTS AND DISCUSSION
Effect of High Tunnels on Marketable Yield, Fruit Size of Strawberry Plants Grown
on Black Plastic Mulch
During the two years of experiments, we observed significant differences in
marketable yield and in fruit size, between strawberries grown in the high tunnel and
outside. In 2006, a very marked significant difference for marketable yield and fruit size
was found in plants grown under high tunnels in relation to outdoors (21.5 vs. 12.5 t/ha
and 12.4 vs. 8.4 g, respectively) (Table 1). In 2007, the significant differences were
observed only for the marketable yield (20.3 vs. 14.2 t/ha), while for other variables there
was no significant difference found in fruit size (Table 2). High tunnels enhanced the
yield by 72% and fruit size by 47.6% in 2006, while in 2007, the yield was increased by
48.6%. High tunnels extend the production season and increase fruit quality (Wittwer and
Castilla, 1995; Cavins et al., 2000). Our results confirm these findings since in 2006 the
production period under high tunnels was extended till October, one month longer than
outdoors. In 2007, we stopped harvesting in September because of a Verticillium dahliae
outbreak, but the production season in high tunnels could be extended also by one month.
The verticilium infection was particularly visible in the cultivar ‘Seascape’ which is very
sensitive. Some plants were withered and the old leaves dried out, some leaves remained
green and turgid.
We noted that the growing season of 2007 was warmer than in 2006 with
maximum, minimum and average temperatures of 32.5, 11.1 and 19.8°C, respectively.
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There were daily extreme temperatures of 35-38°C recorded several times during the
growing season in 2007. Leblanc (1988) denoted that very high temperatures hindered the
development of fruits and reduced the growth and biomass of day-neutral strawberries. In
general, our results suggest that the microclimate under high tunnels has a positive effect
on strawberry growth. Our results also confirm those of Kadir et al. (2006).
Effect of Different Plastic Mulches on the Growth, Yield, Fruit Size and Fruit
Quality
The effect of mulch color was only significant on fruit size, but not on the other
growth parameters measured (Table 3). When our measurements were made, the foliage
was already dense and covered more than 80% of the plastic mulch area. As a
consequence, the effects of light reflection by mulch were lower than earlier in the
growing season. Growth could have been significantly affected earlier in the growing
season. These results confirm those of Karhu et al. (2006), who used the white on black
and black plastic mulches in the growth of seven genotypes of strawberries (Fragaria
ananasa) and concluded that color of plastic mulches does not affect either the yield, or
the number of leaves, or the number of crowns of different cultivars. However, our results
showed that fruit size is significantly increased (11 vs. 10.4 g) with the white on black
plastic mulch. Likewise, polyphenol concentration in the fruits. These results confirm
those obtained for Atkinson et al. (2006) with reflective plastic mulches. These
researchers observed an increase of ellagic acid concentration and of ascorbic acid with
the utilization of reflective plastic mulch. This response could be attributable to a
stimulation of phytochrome by the reflective cover, would regulate the allocation of
photosynthates to the fruit (Kasperbauer, 2000). It is also possible that the increase of the
reflected light has augmented photosynthesis and the highest quantity of sugars has
increased the synthesis of polyphenols. In addition, the polyphenols are present on the
cuticule to give an effective protection against UV radiation; then these biomolecules are
in the epidermic cells in high quantities. Therefore, these cells are more exposed to the
high radiation (Schemelzer et al., 1988). The utilization of white on black plastic mulch in
our experiment probably reflected more of this radiation.
In 2007, we evaluated the effect of different plastic mulches that were installed
under high tunnels and outdoors. The results show that there was no interaction between
plastic mulches and their environment, but that high tunnels had a positive effect on the
marketable yield, fruit size and on the fruit sugar content (Table 4).
CONCLUSION
Plastics mulches used in this experiment modified the pattern of soil and air
temperatures. High tunnels prolonged the growing season of strawberry plants, increased
yield and improved fruit quality. Our results suggest that it is possible to adopt cultural
practices in the strawberry culture in order to improve the total and marketable yields and
increase the bioactive compounds content.
ACKNOWLEDGEMENTS
The authors thank “Les Industries Harnois inc.” and “Les Fraises de l’Île
d’Orléans inc.” for the technical and financial assistance.
Literature Cited
Atkinson, C.J., Dodds, P.A.A., Ford, Y.Y., Le Mière, J., Taylor, J.M., Blake, P.S. and
Paul, N. 2006. Effects of cultivar, fruit number and reflected photosynthetically active
radiation on Fragaria ananassa productivity and fruit ellagic acid and ascorbic acid
concentrations. Ann. Bot. 97:429-441.
Carlen, C., Potel, A.M., Bellon, C. and Ançay, A. 2005. Qualité des fraises: effets de la
variété, du rapport feuille/fruit, de la période de récolte et du stade de maturité. Revue
Suisse Vitic. Arboric. Hort. 37:87-93.
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antioxidant activity and its application to monitoring the antioxidant capacity of
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Gil, M.I., Tomas-Barberan, F.A., Hess-Pierce, B., Holcroft, D.M. and Kader, A.A. 2000.
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Kadir, S., Carey, E. and Ennahli, S. 2006. Influence of high tunnel and field conditions on
strawberry growth and development. HortScience 41:329-335.
Karhu, S.T., Puranen, R. and Aflatuni, A. 2006. White mulch and a south facing position
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Leblanc, M. 1988. Influence du système de plantation, de l’espacement entre les plants et
de la période d’enlèvement des fleurs sur la productivité des fraisiers à production
continue (day-neutral strawberries). Mémoire de maîtrise. 83p. Université Laval.
Lieten, P. 1991. Multi-coloured crop production. Grower 116:9-10.
Loughrin, J.H. and Kasperbauer, M.J. 2002. Aroma of fresh strawberries is enhanced by
ripening over red versus black mulch. J. Agri. Food Chem. 50:161-165.
Orzolek, M.D. and Murphy, J.H. 1993. The effect of colored polyethylene mulch on the
yield of squash and pepper. Proc. Nat. Agri. Plastics Cong. 24:157-161.
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http://www.agrireseau.qc.ca/petitsfruits/Documents/fraise%20climat%20nordique.pdf.
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Tables
Table 1. Marketable yield and fruit size of ‘Seascape’ strawberry grown under high
tunnels and outdoor (2006).
Treatments Marketable yield Fruit size
(t ha-1) (g fruit-1)
High tunnels 21.5 12.4
Outdoor 12.5 8.4
t 0.05 ** **
** Significant difference at 0.05.
Table 2. Marketable yield and fruit size of ‘Seascape’ strawberry grown under high
tunnels and outdoors (2007).
Treatments Marketable yield Fruit size
(t ha-1) (g fruit-1)
High tunnels 20.3 a 10.2 a
Outdoor 14.2 b 10.9 b
t 0.05 ** NS
** Significant difference at 0.05; NS: non significant.
Table 3. Marketable yield, fruit size, number of leaves, of runners, of crowns and dry
weight of ‘Seascape’ grown on different plastic mulches under high tunnels in 2006
and 2007.
Plastic mulches Marketable
yield
(t ha-1)
Fruit
size
(g fruit-1)
Leaves
(#) Runners
(#) Crowns
(#)
Dry weight
Root
(g) Shoot
(g)
Green 28.0 10.1 26.9 2.3 4.4 36.3 34.3
Grey on grey 28.0 10.2 27.9 2.1 4.4 35.5 29.9
White on black 28.4 11.0 26.4 2.1 4.2 38.5 28.1
Black 27.6 10.4 28.7 2.3 3.8 37.1 30.3
LSD 0.05 NS ** NS NS NS NS NS
**Significant difference at 0.05; NS: Non significant.
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Table 4. Marketable yield, fruit size and sugar content of strawberries grown with
different plastic mulches under high tunnels and outdoors conditions in 2007.
Environment Plastic mulch Marketable yield
(t ha-1) Fruit size
(g fruit-1) °Brix
High tunnels
Green 23.3 9.8 6.8
Grey on grey 24.4 9.8 6.6
White on black 24.7 10.9 6.9
Black 24.8 10.2 6.9
Outdoors
Green 21.3 10.8 6.5
Grey on grey 20.5 11.2 6.2
White on black 19.6 10.9 6.4
Black 20.4 10.9 6.3
LSD 0.05 ** ** **
Interaction treat. vs. env. NS NS NS
** Significant difference at 0.05; NS: Non significant.
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Full-text available
  • Feb 2018
  • SCI HORTIC-AMSTERDAM
The effect of rain shelters on the performance of the day-neutral strawberry (Fragaria × ananassa) Monterey cultivar was studied in northern Québec in trials extending over 2 years. The main objective of the study was to evaluate the benefits of growing strawberry crops under plastic rain shelters in terms of yield, fruit quality, disease incidence and economical returns for soilless strawberry production. Five treatments were carried out and these included four − under rain shelters cultivation (T1 to T4) and one under open-air conditions (the Control, C). Under rain shelters conditions, plants were grown in either peat (PE; T1 treatment) or peat-sawdust (PS25; T2 treatment) substrates. Early forcing of bare-root plants (T3) in combination with a rain shelter cover was also carried out in an attempt to generate consistent early yields by the end of July as such would allow producers to capture a niche market for strawberries in Québec. Finally in T4, the PE substrate was laid onto a capillary mat to determine the potential of sub-surface water retention technology to minimize water use. In comparison to the Control treatment, protected cultivation led to a significantly lower incidence of strawberry mildew [Sphaerotheca macularis (Wall. ex Fries)] and consistently higher marketable yields which largely compensated for the initial costs associated with the rain shelters. When grown under greenhouse conditions, forced plants had a significant production peak earlier, coinciding with the period of high prices for fresh strawberries in 2013. However, the economical analysis revealed that this method was not always profitable. Balancing economical and environmental considerations, the conditions of the T4 treatment were found to be best for generating both consistent water savings and profits (CAD $ 724–1356 per 0.1 ha) compared to the Control. Taken together, our results highlight the potential for rain shelters for soilless strawberry production, and should be a more profitable and environmentally friendly cultivation method for strawberry producers.
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Kuşburnu Çeşitlerinin Çelikle Çoğaltımı Üzerine Bir Araştırma
Conference Paper
Full-text available
  • Nov 2019
BAHÇE 48 (Özel Sayı 1: 6. Ulusal Üzümsü Meyveler Sempozyumu):
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Investigation of the Soil Depths Temperature Trend Using Parametric and Non-Parametric Methods (Shahrud Station)
Article
Full-text available
  • Jan 2019
سابقه و هدف: استفاده از مالچها، بهویژه مالچهاي پلاستیکی نه تنها سبب زودرسی میوه، بلکه در افزایش مقدار محصول، کیفیت میوه، عطر و طعم آن مؤثر است. مالچ پلاستیکی افزون بر افزایش باردهی و کیفیت میوه سبب کاهش تلفات آب از راه تبخیر، جلوگیري از رشد علفهاي هرز و در نهایت کاهش مصرف شیمیایی میشود. هدف از این پژوهش، بررسی تأثیر مالچ پلاستیکی قرمز بر ویژگیهاي کیفی و فعالیت آنتیاکسیدانی سه رقم مختلف توتفرنگی است. مواد و روشها: در این پژوهش، بهمنظور بررسی تأثیر مالچ پلاستیکی قرمز بر خصوصیات کیفی ارقام مختلف میوه توتفرنگی، آزمایشی در قالب طرح بلوكهاي کامل تصادفی با سه تیمار آزمایشی شامل (سه رقم کاماروسا، سیلوا و گاویتا) در سه تکرار در مزرعه پژوهشی دانشگاه علوم کشاورزي و منابع طبیعی ساري در سال زراعی 94-1393 انجام شد. میوهها، در یک دوره زمانی 4 روزه برداشت شدند و پس از هر برداشت، میوههاي هر بوته به دقت توزین شد فعالیت آنتیاکسیدانی، ترکیبات فنلی و فلاونوئید میوه اندازهگیري شد. دادههاي بهدست آمده در پایان آزمایش، با بهرهگیري از نرمافزار SAS تجزیه و از آزمون SNK براي مقایسه میانگینها استفاده شد. یافتهها: نتایج نشان داد، مالچ پلاستیکی قرمز اثر معنیداري بر عملکرد وزن میوه و خصوصیات کیفی میوه در سه رقم توتفرنگی داشت. بهطوريکه عملکرد وزن میوه توتفرنگی رقم سیلوا (35/17859 گرم در 300 بوته) بیش از دو رقم دیگر بود. بیشترین عملکرد کل تعداد میوه در رقم سیلوا (1767 (و کمترین آن مربوط به رقم گاویتا (798 (بود. میزان آنتوسیانین میوه در رقمهاي کاماروسا و گاویتا بهترتیب با (56/80 میلیگرم بر 100 گرم) و (2/77 میلیگرم بر 100 گرم) بالاتر از رقم سیلوا (26/69 میلیگرم بر 100 گرم) بود، اما تفاوت معنیداري میان این دو رقم دیده نشد. محتواي فنل کل و فلاونوئید میوه رقم کاماروسا بهترتیب با مقادیر (53/55 میلیگرم بر گرم) و (16/60 میلیگرم بر گرم) نسبت به دو رقم دیگر بالاتر بود. همچنین نتایج نشان داد که، مالچ پلاستیکی قرمز اثر معنیداري بر فعالیت آنتیاکسیدانی (IC50 (سه رقم مختلف، نداشت. نتیجهگیري: بر پایه یافتههاي این پژوهش، عملکرد کل میوه توتفرنگی در رقم سیلوا در مقایسه با ارقام کاماروسا و گاویتا، بالاتر بود. همچنین بالاتر بودن محتواي آنتوسیانین کل، محتواي فنل و فلاونوئید میوه توتفرنگی رقم کاماروسا در مقایسه با دیگر ارقام را میتوان به پتانسیل ژنتیکی رقم کاماروسا و کیفیت نور بازتابی از مالچ قرمز نسبت داد. در این پژوهش گمان بر این است که، پتانسیل ژنتیکی مطلوب ارقام و تأثیر رنگ مالچ پلاستیکی قرمز بر کیفیت محیط نوري پیرامون گیاه، نقش بهسزایی را در افزایش کیفیت میوه توتفرنگی ایفا میکند. واژههاي کلیدي: توتفرنگی، زمان برداشت، فعالیت آنتیاکسیدانی، مالچ پلاستیکی
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Sawdust and Bark-Based Substrates for Soilless Strawberry Production: Irrigation and Electrical Conductivity Management
Article
Full-text available
The objective of this work was to optimize a soilless growing system for producing bare-root strawberry transplants in three organic substrates. Three trials were conducted in the Quebec City area to determine the productivity potential of a peat-sawdust mixture (PS25) and an aged bark (AB) material compared to conventional coconut fiber (CF) substrate. A first experiment was carried out to define appropriate irrigation set points for each substrate that allowed optimal plant growth and fruit yields. For all substrates, wetter conditions (irrigation started at -1.0 kPa for CF; -1.5 kPa for AB and PS25, relative to -1.5 kPa for CF; -2.5 kPa for AB and PS25) enhanced plant growth and fruit production. The second trial was carried out to test the productivity potential for commercial production of the three substrates using high-tunnels. After the addition of an initial fertilizer application to PS25, we successfully established bare-root plants that gave similar fruit yields than those in CF and AB. The productivity potential of PS25 and AB were further confirmed during a third trial under greenhouse conditions. The critical factor for plant establishment in PS25 was attributed to consistent N, P and S immobilization by microorganisms, as well as the retention of other elements (Mg2+, K+) in the growth media. Taken together, our results showed that PS25 and AB are promising alternative substrates to coconut coir dust for strawberry cultivation. This paper also provides a useful guide for strawberry cultivation in Quebec, and suggests future research that might be conducted to optimize soilless systems for cold-climate strawberry production in Northern America.
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Influence of High Tunnel and Field Conditions on Strawberry Growth and Development
Article
Full-text available
  • Apr 2006
Plant growth, yield, and fruit quality of two strawberries (Fragaria xananassa Buch.) - 'Chandler' and 'Sweet Charlie' - grown under high tunnels (HTs) were compared with that of field plants during 2002-03 and 2003-04 growing seasons. Plug plants were planted in mid-October 2002 and mid-September 2003 on raised beds covered with black polyethylene mulch. Microclimate of the HTs protected strawberry crowns from winter damage and advanced fruit production 5 weeks earlier than that of plants grown under field conditions. From December to February, average minimum and maximum crown temperatures under the HTs were 5 and 12°C warmer than those of the field crowns, respectively. The earliest HT fruit were harvested on 7 Apr. 2003 and 11 Mar. 2004. Yield and fruit quality under the HTs were superior to that of field-grown plants. HT plants, especially 'Sweet Charlie', bloomed earlier than did field plants, but 'Chandler' produced higher yield than 'Sweet Charlie' late in the season. Larger fruit with higher soluble solids concentration (SSC) were produced inside the HTs than outside. HT 'Sweet Charlie' fruit were sweeter than 'Chandler' fruit, but 'Chandler' produced larger fruit. Larger leaf area, greater number of leaves and shoot biomass, more branch-crowns, and fewer runners were developed under HTs than field conditions. Total leaf area, leaf production, total shoot biomass, and number of branch-crowns of HT 'Chandler' were greater than HT 'Sweet Charlie'. Results of this study indicate that strawberry plants under HTs were not only precocious, but also produced higher yields and superior quality to that of field plants. HT conditions suppressed runner growth, but enhanced branch-crown development.
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PLastic Films for Agricultural Applications
Article
Full-text available
  • Apr 2006
The most important agricultural applications of plastic films are greenhouse, walk-in tunnel and low tunnel covers, and mulching. The raw materials are usually low density polyethylene (LDPE) and ethylene-vinyl acetate (EVA) or ethylene-butyl acrylate (EBA) copolymers for the covers and linear low density polyethylene (LLDPE) for mulching. The market is explosively growing in China, and slowly growing in the rest of the world. The key properties for these applications are durability, optical (ultraviolet, visible, near infrared, and middle infrared) properties, and the antidrip or antifog effect. Recent developments in this area include UV-blocking, NIR-blocking, fluorescent, and ultrathermic films.
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Antioxidant Activity of Pomegranate Juice and Its Relationship with Phenolic Composition and Processing
Article
Full-text available
  • Nov 2000
The antioxidant activity of pomegranate juices was evaluated by four different methods (ABTS, DPPH, DMPD, and FRAP) and compared to those of red wine and a green tea infusion. Commercial pomegranate juices showed an antioxidant activity (18-20 TEAC) three times higher than those of red wine and green tea (6-8 TEAC). The activity was higher in commercial juices extracted from whole pomegranates than in experimental juices obtained from the arils only (12-14 TEAC). HPLC-DAD and HPLC-MS analyses of the juices revealed that commercial juices contained the pomegranate tannin punicalagin (1500-1900 mg/L) while only traces of this compound were detected in the experimental juice obtained from arils in the laboratory. This shows that pomegranate industrial processing extracts some of the hydrolyzable tannins present in the fruit rind. This could account for the higher antioxidant activity of commercial juices compared to the experimental ones. In addition, anthocyanins, ellagic acid derivatives, and hydrolyzable tannins were detected and quantified in the pomegranate juices.
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In situ localization of light-induced chalcone synthase messenger-RNA, chalcone synthase, and flavonoid end products in epidermal-cells of Parsley leaves
Article
Full-text available
  • Jun 1988
Methods involving in situ RNA hybridization, immunohistochemistry, and microspectrophotometry of individual cells were used to localize the mRNA encoding chalcone synthase (the key enzyme of flavonoid biosynthesis), the enzyme protein, and the biosynthetic end products in cross sections of parsley leaves (Petroselinum crispum). The light-dependent, sequential occurrence of all three components was restricted to epidermal cells. The results are in agreement with the putative function of flavonoids (transcriptionally inducible, UV-protective pigments) and suggest that all biosynthetic steps occur in those cells in which the products accumulate.
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White mulch and a south facing position favour strawberry growth and quality in high latitude tunnel cultivation
Article
  • Apr 2007
  • CAN J PLANT SCI
Polyethylene mulches with black or white surface were compared in seven strawberry (Fragaria x ananassa Duch.) genotypes in a 2-yr experiment. The plants were covered by an unheated walk-in tunnel at the beginning of the first harvest season. The effects of a south-west versus north-east position of plants within the double-row beds were also studied. Soil temperatures were higher under black mulch, especially mid-day temperatures on the bed surface in the southward position. White mulch favoured root and crown growth in the first year, and the southwest position increased plant growth in both years. With black mulch, lower carbohydrate reserves were observed after transplanting, and a decreased chlorophyll content of leaves was detected in the second year. Mulch colour did not affect yield quantity. The first-year harvest was advanced with black mulch, but in the second year, the harvest season was earliest on the south side of beds with white mulch. Black mulch decreased fruit size in the first year and the concentration of fruit soluble solids in both years. The results suggest that in northern latitudes white mulch improves strawberry plant growth and fruit quality over that obtained using black mulch, but enhanced yield is not to be expected when a double-row tunnel cultivation system is used.
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Method for Measuring Antioxidant Activity and Its Application to Monitoring the Antioxidant Capacity of Wines
Article
  • Feb 1999
A novel method for measuring the antioxidant activity using N,N-dimethyl-p-phenylenediamine (DMPD) was developed. The radical cation of this compound gives a stable colored solution and a linear inhibition of color formation can be observed in the presence of 0.2−11 μg of TROLOX. The experimental protocol, which is rapid and inexpensive, ensures sensitivity and reproducibility in the measure of antioxidant activity of hydrophilic compounds. The effectiveness of the DMPD method on real foods was verified by evaluating the antioxidant ability of wine samples coming from different areas of Campania, Italy. Antioxidant capacity of wines is strictly related to the amount of phenolic compounds. The results obtained by the DMPD method are very similar to those obtained on the same samples when the radical cation of 2,2‘-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) (Miller et al., 1996) was used. Keywords: Antioxidant activity; DMPD; radical cation; ABTS; wine
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Strawberry Yield over Red versus Black Plastic Mulch
Article
Plastic mulches are frequently used in raised-bed culture of strawberry (Fragaria x ananassa Duch) to conserve water, control weeds with less herbicides, and keep fruit clean. The most commonly used plastic mulch color is black. It was hypothesized that a specially formulated red plastic mulch that reflects a higher far-red to red photon ratio could regulate photosynthate allocation enough to increase yield of strawberry. Yields over the red plastic (SRM-Red) were compared with those over standard black plastic in field experiments at a research center and on a commercial strawberry farm. Yield per plant and size per berry were greater over the red than over the black plastic at both locations. The yield advantage of red mulch relative to black occurred whether the red plastic was placed directly over the soil or over a layer of black plastic. It is concluded that strawberries were larger over the new red plastic mulch because reflected far-red and red light affected phytochrome-mediated allocation of photosynthate, and more was directed to developing fruit.
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Aroma of Fresh Strawberries Is Enhanced by Ripening over Red versus Black Mulch
Article
  • Feb 2002
Strawberry (Fragaria ananassa Duch) is a high-value food crop, the aroma of which is important in consumer satisfaction. We hypothesized that the concentration of fresh strawberry aroma compounds could be enhanced by growing the berries over a red plastic mulch that was formulated to reflect more far-red (FR) and red light (R) and a higher FR/R photon ratio than is reflected by standard black plastic mulch. Strawberries of the cultivars "Chandler" and "Sweet Charlie" were grown in trickle-irrigated field plots over the two colors of mulch. The berries were harvested when ripe, and aroma compounds were isolated by dynamic headspace sampling. Entrained compounds were quantified by gas chromatography and identified by gas chromatography/mass spectroscopy. Twenty-three compounds were identified, and most of them were aliphatic esters. Strawberries that ripened over the red mulch during periods of sunny weather had significantly higher concentrations of aroma compounds than berries grown over the black plastic mulch. Total levels of aroma compounds from berries grown over red plastic mulch were higher for both Chandler and Sweet Charlie. We postulate that FR and R in light reflected from the red mulch acted through the natural phytochrome system to modify gene expression enough to result in greater concentration of aroma compounds in fresh strawberries.
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Cultural System Affects Fruit Quality and Antioxidant Capacity in Strawberries
Article
  • Nov 2002
Cultural system [hill plasticulture (HC) versus matted row (MR)] and genotype interactions affected strawberry fruit quality. In general, fruit soluble solids content, total sugar, fructose, glucose, ascorbic acid, titratable acid, and citric acid contents were increased in the HC system. Fruit from HC also had higher flavonoid contents and antioxidant capacities. Strawberry fruit contains flavonols as well as other phenolic compounds such as anthocyanins and phenolic acids. Pelargonidin-based anthocyanins such as pelargonidin 3-glucoside, pelargonidin 3-rutinoside, and pelargonidin 3-glucoside-succinate were the predominant anthocyanins in strawberry fruit. The content of cyanidin-based anthocyanins, cyanidin 3-glucoside and cyanidin 3-glucoside-succinate, was much lower than that of pelargonidin-based anthocyanins in either system. Strawberry fruit from the HC system had significantly higher amounts of p-coumaroylglucose, dihydroflavonol, quercetin 3-glucoside, quercetin 3-glucuronide, kaempferol 3-glucoside, kaempferol 3-glucuronide, cyanidin 3-glucoside, pelargonidin 3-glucoside, pelargonidin 3-rutinoside, cyanidin 3-glucoside-succinate, and pelargonidin 3-glucoside-succinate. Fruits from plants grown in the MR system generally had the lowest contents of phenolic acids, flavonols, and anthocyanins. Strawberry fruit grown under HC conditions had significantly higher peroxyl radicals (ROO*) absorbance capacity (ORAC).
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