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Branchlets with scale and needle leaves of Juniperus sabina L.
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Savin juniper has green, photosynthetic branchlets with scale and/or needle leaves and these heteromorphic forms may contribute differentially to its success in open, arid environments. To test differences in photoprotection between fully sun-exposed scale-holding branchlets (SHB) and needle-holding branchlets (NHB), we measured gas exchange, chlor...
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... 500 individuals at the study site. Based on a random sampling of 45 plants, the stem diameter at ground level was 3.01 ± 0.58 cm (mean ± SD), the height was 116.0 ± 11.6 cm, crown breadth from east to west was 161.1 ± 32.1 cm, and crown breadth from north to south was 166.9 ± 33.7 cm. The proportion of foliage as viewed vertically from the side ( Fig. 1) that consisted of branchlets with scale leaves was estimated to be 79 ± 2% and that of branchlets with needle leaves was 21 ± 2%. The study site is characterized by a continental monsoon climate with four distinct seasons, dry and windy spring, hot and rainy summer, cool autumn, and a cold and relatively dry winter. Mean annual ...
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... mass area: Because scale leaves are more succulent than needle leaves (Fig. 1), we estimated fresh mass over dry mass ratios and ʻleafʼ mass per unit area of the different branchlet types to check whether patterns would change if results were expressed on a different basis. Branchlet fresh mass was measured and then area was determined using an image scanner (EPSON Expression 10000XL) and image processing ...
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... in photoprotection. Table 2 shows the main photosynthetic pigment concentrations and their ratios in SHB and NHB. The concentrations of Chl a, Chl b, and Chl (a+b) in the NHB were significantly higher than those measured in the SHB, however, SHB had a higher Chl a/b ratio. The higher Chl in NHB was consistent with their higher photosynthetic rate (Fig. 1A). Significantly higher total Car concentration and Car/Chl ratio were observed in the SHB than that in the ...
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Citations
... Photosynthetic pigments were measured according to the study of Zhang et al. with a few modifications [59]. Three seedlings were randomly selected from each treatment, and the leaves in the same position were selected, wiped clean, and mixed. ...
... The whole experiment was carried out in low light. Finally, chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid concentrations were calculated by using the equation described by Zhang et al. [59]. There were three replicates from each treatment. ...
Korean pine (Pinus koraiensis Sieb. et Zucc.), as the main tree species in northeast China, has important economic and ecological values. Currently, supplementary light has been widely used in plant cultivation projects. However, the studies about different supplementary light sources on the growth and development of Korean pine are few. In this study, the one with no supplementary light was used as the control, and two kinds of light sources were set up: light-emitting diode (LED) and incandescent lamp, to supplement light treatment of Korean pine. The spectrum and intensity of these two light sources were different. The results showed that the growth and physiological–biochemical indicators were significantly different under different supplementary light treatments. The biomass of supplementary light treatment was significantly lower than the control. Compared with the control, IAA and GA were lower, and JA, ABA, ZT, and ETH were higher under supplementary light conditions. Photosynthetic parameters in supplementary light conditions were significantly lower than the control. Supplemental light induces chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid accumulation. From RNA-seq data, differentially expressed genes (DEGs) were observed in all the comparison groups, and there were 487 common DEGs. The expression levels of DEGs encoding transcription factors were also changed. According to GO and KEGG analysis, the plant hormone signal transduction, circadian rhythm-plant, and flavonoid biosynthesis pathways were the most enriched. These results provided a theoretical basis for the response of Korean pine to different supplementary lights.
... For photosynthetic pigments analysis, pigments were extracted by grinding leaves in 95% ethanol in the dark. For detailed steps, improved by the method of Zhang et al. (2019b). Samples mixed with random three seedlings. ...
... After standing, absorbed the supernatant and measured the absorbance values at 470, 649, 664 nm, respectively. Concentrations of photosynthetic pigments were calculated using the following equation (Zhang et al., 2019b): ...
Light is not only a very important source of energy for the normal growth and development of plants, but also a regulator of many development and metabolic processes. The mechanism of plant growth and development under low light conditions is an important scientific question. With the promulgation of the law to stop natural forest cutting, understory regeneration is an important method for artificial forest afforestation. Here, the growth and physiological indexes of Juglans mandshurica, an important hardwood species in Northeast China, were measured under different shade treatments. In addition, transcriptome and metabolome were compared to analyze the molecular mechanism of shade tolerance in J. mandshurica. The results showed that the seedling height of the shade treatment group was significantly higher than that of the control group, and the 50% light (L50) treatment was the highest. Compared with the control group, the contents of gibberellin, abscisic acid, brassinolide, chlorophyll a, and chlorophyll b in all shade treatments were significantly higher. However, the net photosynthetic rate and water use efficiency decreased with increasing shade. Furthermore, the transcriptome identified thousands of differentially expressed genes in three samples. Using enrichment analysis, we found that most of the differentially expressed genes were enriched in photosynthesis, plant hormone signal transduction and chlorophyll synthesis pathways, and the expression levels of many genes encoding transcription factors were also changed. In addition, analysis of differentially accumulated metabolites showed that a total of 470 differential metabolites were identified, and flavonoids were the major differential metabolites of J. mandshurica under light stress. These results improved our understanding of the molecular mechanism and metabolite accumulation under light stress in J. mandshurica.
... Photosynthesis chlorophyll a, chlorophyll b, total chlorophyll and carotenoid contents were determined with the method described by Zhang et al. [93] with few modifications. The leaves of three seedlings were randomly selected and mixed, then frozen in liquid nitrogen immediately. ...
... The absorbance values of the supernatant were measured at 470, 649 and 664 nm after centrifugation (5000× g for 10 min). The pigment contents were calculated using the previous study [93], seen in the equations as follows: ...
Light is one of the most important environmental cues that affects plant development and regulates its behavior. Light stress directly inhibits physiological responses and plant tissue development and even induces mortality in plants. Korean pine (Pinus koraiensis) is an evergreen conifer species widely planted in northeast China that has important economic and ecological value. However, the effects of light stress on the growth and development of Korean pine are still unclear. In this study, the effects of different shading conditions on physiological indices, molecular mechanisms and metabolites of Korean pine were explored. The results showed that auxin, gibberellin and abscisic acid were significantly increased under all shading conditions compared with the control. The contents of chlorophyll a, chlorophyll b, total chlorophyll and carotenoid also increased as the shading degree increased. Moreover, a total of 8556, 3751 and 6990 differentially expressed genes (DEGs) were found between the control and HS (heavy shade), control and LS (light shade), LS vs. HS, respectively. Notably, most DEGs were assigned to pathways of phytohormone signaling, photosynthesis, carotenoid and flavonoid biosynthesis under light stress. The transcription factors MYB-related, AP2-ERF and bHLH specifically increased expression during light stress. A total of 911 metabolites were identified, and 243 differentially accumulated metabolites (DAMs) were detected, among which flavonoid biosynthesis (naringenin chalcone, dihydrokaempferol and kaempferol) metabolites were significantly different under light stress. These results will provide a theoretical basis for the response of P. koraiensis to different light stresses.
... The needle-like juvenile leaves have a higher photosynthetic rate than scale-like adult leaves under the same sunlight conditions. It provides the former with more opportunity for photochemical quenching (Zhang et al., 2019). ...
Pine seedlings exhibit heteroblastic foliage (primary and secondary needles) during seedling development. However, few trials have studied how heteroblastic foliage influences pine seedling growth by seasonal variation. This study first investigated the anatomical differences between the primary and secondary needles of one-year-old Pinus massoniana seedlings. We measured chlorophyll fluorescence (ChlF) and evaluated the photoprotective mechanisms and light energy partitioning of these heteroblastic leaves from September to November. The results showed that the primary needles, as juvenile foliage, had a greater fraction of mesophyll tissue and stomata. In addition, the primary needles had two vascular bundles, and shorter distance from xylem and phloem to mesophyll cells, exhibiting a luxury growth strategy of rapidly obtaining high returns. The ChlF parameters indicated that the primary needles maintained a relatively high level of photoprotection by thermal dissipation (nonphotochemical quenching (NPQ)) and nonregulated energy dissipation (Y(NO)). The secondary needles, representing mature foliage, had greater area of xylem and phloem tissues. The contents of Chl b and carotenoids (Car) significantly increased in November, promoting φPo and photoprotection, which suggested that the secondary needles were more resistant to low temperatures. During the whole light response process of secondary needles, the increases in the electron transfer rate (ETR) and light energy utilization efficiency (α) helped to increase the actual photosynthetic quantum yield (Y(II)) by reducing energy dissipation by decreasing the proportion of regulated energy dissipation (Y(NPQ)) and Y(NO). Given the sensitivity of this heteroblastic foliage to environmental changes, the practical use and extension of P. massoniana for afforestation purposes should be carried out with caution.
(Share Link: https://authors.elsevier.com/a/1eE6D3VH9X2Ijx, expiring in January 30, 2022)
... Foliage from the upper outer canopy of three plants per treatment was randomly sampled from 14:00 to 15:00 h in every month on the same days as photosynthesis was measured, and frozen in liquid nitrogen (−80 ℃) for pigment determination following Zhang et al. (2019). A TU-1901 Spectrophotometer (Beijing Purkinje General, Beijing, China) was used for measuring the absorbance, and chlorophyll a (Chla), chlorophyll b (Chl-b), total chlorophyll (Chl) and total carotenoid (Car) concentrations were calculated following Lichtenthaler (1987). ...
... Carotenoid concentrations were measured according to Lee (2001) as modified by Zhang et al. (2019). Carotenoids were separated on a C30 (Devolosil, Nomura Chemical, Nagoya, Japan) column with a 1525 (Waters, Milford, MA, USA) High-Performance Liquid Chromatograph equipped with a Waters 2707 automatic sampler, a Waters 2998 twolevel array detector, and Empower chromatogram management software. ...
Key message
In savin juniper, age and season can affect photosynthesis, chlorophyll fluorescence and photoprotective pigments. In spring, 2-year-old plants had more lutein than 5-year-olds, but the reverse occurred during summer and autumn.
Abstract
Savin juniper is an endemic evergreen shrub in the Mu Us Desert, where it establishes only with the protection of larger plants. Ultimately, established plants emerge into full sunlight as they grow. To explore how photoprotection responses change during this transition, a pot study was established under field conditions with three sunlight regimes (10%, 50% and 100% light transmittance) and two age cohorts (1- and 4-year-old rooted scions). To avoid potentially confounding effects of differences in leaf form, after one year we measured photosynthesis, chlorophyll fluorescence and foliar pigments of 2- and 5-year-old savin juniper on a monthly basis from April to October. For gas exchange and fluorescence variables, there were no interactions between cohort and sunlight except for intrinsic water-use efficiency in June; however, there were many interactions regarding pigment concentrations and ratios. Generally, 5-year-old plants had higher mean chlorophyll, total carotenoids, and chlorophyll a/b ratios than 2-year-old plants, but lower mean β-carotene/α-carotene ratio, zeaxanthin and lutein. Plants under brighter light had lower mean lutein. There were obvious changes in β-carotene/α-carotene, zeaxanthin and lutein in June, July and August, respectively. Under 100% sunlight, lutein concentration was higher in 2-year-old than 5-year-old plants from April to June, but this pattern reversed from July to October. The effects of age and season, in addition to the prevailing light regime, need to be considered when investigating the role of carotenoids in photoprotection.
... Branchlets (close to branchlets used to measure leaf parameters) comparable to those measured for other variables, were randomly sampled from the upper outer canopy of three plants per treatment from 14:00-15:00 h in every month on the same day as leaf parameters and photosynthesis were measured, then frozen in liquid nitrogen (-80°C) for pigment analysis following Zhang et al. (2019). A TU-1901 spectrophotometer (Beijing Purkinje General, Beijing, China) was used to measure the absorbance and calculate Chl a, Chl b, total Chl and Car concentrations, following the equations in Lichthentaler (1987). ...
... Carotenoid concentrations were measured according to Lee et al. (2001) as modified by Zhang et al. (2019). Carotenoids were separated on a C30 (Devolosil, Nomura Chemical, Nagoya, Japan) column with a 1525 (Waters, Milford, MA, USA) High-Performance Liquid Chromatograph equipped with a Waters 2707 automatic sampler, a Waters 2998 twolevel array detector and Empower chromatogram management software. ...
... Plants of these two age groups growing under moderate shade (50% light) or under full sunlight (100% light) typically had scale leaves (Fig. 2e,f,h,i,k,l,n,o,q,r). These results are consistent with previous research showing that scale leaves of savin juniper are better adapted to high light, whereas needle leaves are more appropriate to shade conditions (He & Zhang 2001;Tanaka-Oda et al. 2010;Zhang et al. 2019). Interestingly, in this study, scale and needle leaves occurred under all light conditions and at all ages, but in different proportions. ...
• Savin juniper is an excellent species for desertification control in arid and semi‐arid areas, where it typically establishes under the protection of nurse plants. Ultimately, established plants emerge into full sunlight as they grow, and this transition is accompanied by an increase in the preponderance of scale‐like vs. needle‐like leaf forms.
• To test how age and variable sunlight environments affect shade tolerance in savin juniper, we established a pot study under field conditions with two age cohorts (1‐ and 4‐year‐old rooted scions) and three sunlight regimes (10%, 50% and 100% light transmittance). We measured growth, leaf parameters, photosynthesis, chlorophyll fluorescence and foliar pigments on a monthly basis (seven growing months per year, from 2015 to 2017).
• Overall, there was little interaction for all variables, and both cohort and light regime had significant effects. Leaf form and spacing varied continuously, tending towards shorter, more closely spaced and more appressed scale leaves with higher dry leaf mass per area in older plants or under higher sunlight. There were no clear age‐related patterns in carotenoids but both cohort and light had significant effects on gas exchange and chlorophyll fluorescence variables.
• Savin juniper shows an intermediate tolerance to shade that changes with growth in that younger plants were less tolerant of full sun than older plants, consistent with its reliance on nurse plants for ultimate establishment in the open.
... Foliar dimorphism has been studied in different genera such as Juniperus and Taxus [8,9], but most of the investigations, especially related to heteroblasty, have been carried out in species of Pinus: P. pinea, P. canariensis, P. halepensis, P. brutia and also P. pinaster [6,[10][11][12]. Primary pine needles of those species are typically single and with different cross-sectional shape than secondary needles. ...
Great variation in shape and size between primary (juvenile) and secondary (adult) needles, so-called leaf-heteroblasty, occurs in several Pinus species. Most of them loss primary needles during the juvenile-to-adult transition of the tree. An exception to this is Pinus canariensis (a Canary Islands endemism) in which basal resprouting twigs of adult trees frequently wear both primary and secondary needles. Taking advantage of this extraordinary study-case-species, we conducted an exhaustive comparison of both needle types through quantitative analyses of needle anatomy, photochemical performance, gas exchange, and resistance to extreme dehydration and to extreme needle temperature. We hypothesized that primary needles would show lower investment to leaf structure but higher photosynthetical efficiency. Primary needles had less stomatal density and thicker and less wettable cuticles. In cross section, primary needles showed smaller structural fraction (e.g., percent of hypodermis, endodermis and vascular tissue) and higher fraction of photosynthetic parenchyma. Significant differences between primary and secondary needles were not found in net carbon assimilation not in their leaf mass area values. Interestingly, secondary needles showed higher electron transport rate, and they were additionally much more efficient in retaining water under severe and controlled desiccant conditions. When subjected to extreme temperatures (−10° to +50 °C), primary needles recovered better their photochemical efficiency than secondary needles, after +46° and +48 °C heat-shock treatments. Our results indicate that both needle types broaden the diversity of physiological responses against environmental constrains in basal twigs of adult P. canariensis trees. Considering that this is a fire-resistant and resprouting species, this advantage could be particularly useful after a drastic environmental change such a fire or a gap opening in the forest.
