Chlorophyll Accumulation Research Articles

Methyl jasmonate and selenium synergistically mitigative cadmium toxicity in hot pepper (Capsicum annuum L.) plants by improving antioxidase activities and reducing Cd accumulation.

Methyl jasmonate (MeJA) or selenium (Se)-mediated response to cadmium (Cd) stress in plant has been widely reported, but the combined effects both on plant growth in response to Cd stress and the underlying mechanisms remain obscure. Here, we showed the combined effects of MeJA (2.5μM) and Se (7μM) on hot pepper growth under Cd stress (CdCl2, 5μM). The results showed Cd suppressed the accumulation of total chlorophyll and carotenoid and reduced the photosynthesis, while it increased the content of endogenous signaling molecules, e.g. nitric oxide (NO) and hydrogen peroxide (H2O2), as well as Cd content in leaves. The combined application of MeJA and Se significantly decreased the malondialdehyde (MDA) accumulation and improved the activities of antioxidant enzymes (AOEs, e.g. SOD and CAT) and defense-related enzymes (DREs, POD and PAL). Additionally, the synergistic application of MeJA and Se also obviously improved photosynthesis in hot pepper plants under Cd stress compared with those treated with MeJA or Se respectively or not. Moreover, the treatment of MeJA associated with Se also effectively reduced the Cd accumulation in hot pepper leaves under Cd stress compared with the plants treated with MeJA or Se separately, which implied a potentially synergistic role of MeJA and Se in alleviating Cd toxicity in hot pepper plants. This study provides a theoretical reference for the further analysis of the molecular mechanism of MeJA and Se in jointly mediating the response to heavy metals in plants.

The Effect of Salinity on the Chlorophyll Content of Wheat

Abiotic stress caused by salinity soil affects the development and plant growth, seed production and quality in a negative way. Salinity is an important factor influencing the quality of water. Saline stress causes negative reactions in plants both morphologically, biochemically and physiologically. The chlorophyll content is an important indicator of photosynthetic capacity of plants. Amount of chlorophyll is very influenced by nutrients reserve and by environment stress. Salinity in soil occurs as a result of the factors such as improper irrigation, lack of drainage, excessive accumulation of soluble salts. The research aims to study the behavior of an assortement of wheat varieties in terms of variability in salinity tolerance. To this end, an indirect test method for salinity tolerance, based on the determination of the influence of saline stress on chlorophyll accumulation, was pursued. Determination of chlorophyll content was performed at 7, 14, 21 days after saline stress induction. The duration of stress had the highest contribution (41.72%) to the variability of the chlorophyll content, followed by the saline (10.88%) and the varieties 7.63% respectively. At the level of the whole experiment it is observed that the chlorophyll content decreased progressively as saline stress prolongation. The change in the concentration from 200 to 240 Mm showed the highest influence on this property, materialized by a significant decrease in photosynthetic capacity. A good way to understand the plant photosynthetic regime is to determine the chlorophyll content as an indirect method. A selection criterion in screening for salt tolerance can be considered the physiological features that are positively associated with production under conditions of saline stress.

Iron nanoparticle regulate succinate dehydrogenase activity in canola plants under drought stress

Application of nutrients as nanoparticle (NP) is an operative manner of nutrient supply for plants, especially under stress conditions. The present study was designed to highlight the role of iron NP on drought tolerance and elucidate the underlying mechanisms in drought-stressed canola plants. Drought stress was imposed by polyethylene glycol different concentrations (0, 10 and 15% (W/V)) with or without iron NP (1.5 and 3 mg/l). A comparative study of several physiological and biochemical parameters have been carried out in canola plants treated by drought and iron NP. Stressed-canola plants showed a reduction in growth parameters, whereas iron NP mostly stimulated growth of stressed plants, which was accompanied by reinforcement in defense mechanisms. Regarding impacts on compatible osmolytes, the data revealed that iron NP was able to regulate osmotic potential by increasing protein, proline and soluble sugar contents. The iron NP application was activated the enzymatic defense system (catalase and polyphenol oxidase) and promoted the non-enzymatic antioxidants (phenol, flavonol and flavonoid). Both of these adaptive responses declined free radicals as well as lipid peroxidation and enhanced the membrane stability and drought tolerance of the plants. Enhanced chlorophyll accumulation via induction of protoporphyrin, magnesium protoporphyrin and protochlorophyllide, by iron NP also contributed towards better stress tolerance. Enzymes of Krebs cycle, namely succinate dehydrogenase and aconitase, were induced by iron NP in canola plants grown under drought stress. These results propose a multifaceted involvement of iron NP, through regulation of activity of respiratory enzymes and antioxidant enzymes, production of reactive oxygen species, osmoregulation and secondary metabolites metabolism, in response to drought stress.

Exploring key physiological attributes of grapevine cultivars under the influence of seasonal environmental variability

Seasonal climatic variability is a key challenge in many grape-growing regions across the globe, affecting phenology, growth, physiological responses, and yield at harvest. Unfavourable climatic conditions impair the plant's physiological processes, such as chlorophyll accumulation, gas exchange and photosynthesis in grapevine leaves. It is critical to unlock the complex physiological behaviour of grapevine cultivars at key phenological stages and under varying environmental conditions. The present study was designed to evaluate the key physiological processes, such as gas exchange, chlorophyll contents and water use efficiency (WUE), of four table grape cultivars at key growth stages under varying environmental conditions of the Pothwar region, in a factorial experimental set up (Location× Year × Cultivar × Phenological stage). The physiological responses of the table grape cultivars were recorded at the 5-leaf stage, full bloom, berry set, veraison and harvest during two consecutive vintages (2019 and 2020) in two locations (Islamabad and Chakwal). The results show that the mean photosynthetic activity in colder Islamabad was 30.7 % higher than in Chakwal, and the transpiration rate and WUE were 10.4 % and 28.6 % higher. Similarly, 12 % higher photosynthetic activity, with 13 % more WUE, was observed in the colder vintage of 2020 compared to that of 2019. The vine physiological activity also varied among cultivars; for example, cv. Sugraone was found to have 12 % more chlorophyll and 30 % higher photosynthetic activity than cv. Kings Ruby. Similarly, higher photosynthetic activity and transpiration rates were recorded at the berry set stage, while WUE peaked near blooming. The biplot analysis for the first two principal components also showed cv. Sugraone to be a highly responsive and physiologically efficient cultivar. The findings of the present research will help to better assess the effect of seasonal variability on vine physiological performance and to identify genotypes with higher photosynthetic potential and WUE. It could also assist in devising vineyard management strategies to better adapt to varying environmental conditions.

Expression of RsPORB Is Associated with Radish Root Color.

Radish (Raphanus sativus) plants exhibit varied root colors due to the accumulation of chlorophylls and anthocyanins compounds that are beneficial for both human health and visual quality. The mechanisms of chlorophyll biosynthesis have been extensively studied in foliar tissues but remain largely unknown in other tissues. In this study, we examined the role of NADPH:protochlorophyllide oxidoreductases (PORs), which are key enzymes in chlorophyll biosynthesis, in radish roots. The transcript level of RsPORB was abundantly expressed in green roots and positively correlated with chlorophyll content in radish roots. Sequences of the RsPORB coding region were identical between white (948) and green (847) radish breeding lines. Additionally, virus-induced gene silencing assay with RsPORB exhibited reduced chlorophyll contents, verifying that RsPORB is a functional enzyme for chlorophyll biosynthesis. Sequence comparison of RsPORB promoters from white and green radishes showed several insertions and deletions (InDels) and single-nucleotide polymorphisms. Promoter activation assays using radish root protoplasts verified that InDels of the RsPORB promoter contribute to its expression level. These results suggested that RsPORB is one of the key genes underlying chlorophyll biosynthesis and green coloration in non-foliar tissues, such as roots.

Influence of combined stress by salinity (NaCl) and heavy metals (Pb(NO3)2) on the proline, chlorophyll and lead accumulation in the tissues of the Atriplex canescens (Pursh ) Nutt.

Abstract. Salinity and heavy metals pollution are the root causes of many environmental problems. This study aims to determine the effect of NaCl-induced salinity and Pb(NO3)2 on chlorophyll, proline content, and lead accumulation in shoots and roots of Atriplex canesens. Sowing was carried out in plastic pots (16 cm in diameter and 13.8 cm high) containing a mixture of sand/compost. The irrigation of plants was performed with distilled water and Hoagland nutrient solution. After four months of growth, the plants were subjected to either 0.50 or 3% of NaCl combined with 800, 1600, and 2400 ppm of Pb(NO3)2 for a duration of one month, then we performed biochemical and chemical analyses on the plants. Results showed that the combined influence of strong salinity and lead caused a reduction of chlorophyll and increased proline and lead accumulation in plant tissues. Lead significantly accumulated in the roots compared to the shoots of the plants.

Metabolome and Transcriptome Analyses Reveal the Differences in the Molecular Mechanisms of Oat Leaves Responding to Salt and Alkali Stress Conditions

Plant growth and production are more severely inhibited by alkalinity than by salinity. However, the metabolites responsible for the reduced growth caused by alkalinity are largely unknown. Here, the Illumina RNA-Seq analysis and targeted metabolome were used to identify the differentially expressed genes and metabolites responding to salt and alkali stresses. The expression levels of eight genes related to photosynthesis and some genes related to chlorophyll synthesis decreased under alkali stress, whereas no changes were detected under salt stress, which may explain the observed lower level of photosynthetic rate in alkalinity than in salinity. Under alkali stress, significant decreases in the relative abundances of cis-cinnamic acid and scopoline were observed, which correlated with the high levels of reactive oxygen species (ROS). The levels of protocatechuic acids decreased, correlating with the observed decrease in the chlorophyll content. Alkalinity markedly increased the production of o-coumaric acid, which contributes to growth inhibition. No significant changes in cis-cinnamic acid, scopoline, and o-coumaric acid were detected in salinity, which may be the reason for the stronger growth inhibition due to alkali stress than salt stress. The accumulation of citric acid, serotonin, pyroglutamic acid, L-citrulline, ferulic acid, and caffeic acid was detected under salt and alkali stress conditions, indicating high free radical scavenging capacity. The enhancement of mevalonic acid and salicylic acid levels was detected under alkali stress, which could have facilitated chlorophyll accumulation. Salt and alkali stress conditions also led to the accumulation of cyclic AMP related to inorganic ion regulation and betaine-related osmoregulation. Benzamide, phenethylamine, N-feruloyltyramine, chrysoeriol 6-C-hexoside, 1,3-o-di-p-coumaroyl glycerol, cordycepin, and 1-o-p-cumaroylglycerol were identified to be accumulated in response to alkali stress.

A multi-omics approach identifies bHLH71-like as a positive regulator of yellowing leaf pepper mutants exposed to high-intensity light.

Light quality and intensity can have a significant impact on plant health and crop productivity. Chlorophylls and carotenoids are classes of plant pigments that are responsible for harvesting light energy and protecting plants from the damaging effects of intense light. Our understanding of the role played by plant pigments in light sensitivity has been aided by light-sensitive mutants that change colors upon exposure to light of variable intensity. In this study, we conducted transcriptomic, metabolomic, and hormone analyses on a novel yellowing mutant of pepper (yl1) to shed light on the molecular mechanism that regulates the transition from green to yellow leaves in this mutant upon exposure to high-intensity light. Our results revealed greater accumulation of the carotenoid precursor phytoene and the carotenoids phytofluene, antheraxanthin, and zeaxanthin in yl1 compared with wild-type plants under high light intensity. A transcriptomic analysis confirmed that enzymes involved in zeaxanthin and antheraxanthin biosynthesis were upregulated in yl1 upon exposure to high-intensity light. We also identified a single basic helix-loop-helix (bHLH) transcription factor, bHLH71-like, that was differentially expressed and positively correlated with light intensity in yl1. Silencing of bHLH71-like in pepper plants suppressed the yellowing phenotype and led to reduced accumulation of zeaxanthin and antheraxanthin. We propose that the yellow phenotype of yl1 induced by high light intensity could be caused by an increase in yellow carotenoid pigments, concurrent with a decrease in chlorophyll accumulation. Our results also suggest that bHLH71-like functions as a positive regulator of carotenoid biosynthesis in pepper.

OsDERF8 regulates rice leaf senescence through involvement in jasmonate signaling

Plant leaf senescence is regulated by complicated signaling network involving endogenous and environmental factors. Appropriate leaf senescence processing plays important roles in plant growth and stress response and contributes to crop production. The regulatory mechanism of leaf senescence has been widely investigated but still remains elusive. Here we identified the rice transcription factor OsDERF8 as the positive regulator of leaf senescence. Overexpression of OsDERF8 resulted in shortened reproductive stage and earlier leaf senescence, as well as lower grain yield. The knockout lines of OsDERF8 exhibited the “stay-green” phenotype and higher grain yield per plant. Dark induced senescence assays confirmed the function of OsDERF8 in senescence regulation. The leaves of OsDERF8 knockout lines showed less sensitivity to dark treatment with slighter chloroplast damage. OsDERF8 knockout mutants also exhibited less sensitivity to jasmonate (JA) treatment with higher chlorophyll accumulation and less root inhibition. Transcriptomic analysis and promoter-luciferase assays indicated that OsDERF8 regulated multiple senescence related genes, plant hormone related genes and photosynthesis genes. Taken together, OsDERF8 positively regulates rice leaf senescence through JA signaling and might be used for molecular breeding to increase grain yield.

Determination of green and red spinach microgreen chlorophyll content using visible spectroscopy and wavelength selection

Microgreens are quickly-grown greens that are suitable for urban areas. The accumulation of chlorophyll in plants is essential for both nutritional compounds and the microgreen’s attractive appearance. A plant factory is a controlled-environment cultivation method that employs LEDs to enhance photosynthesis, vegetative development, seed germination, and chlorophyll accumulation. This work used VIS-NIR for the quantitative determination of chlorophyll content in green and red spinach microgreens grown under four different LED light intensities with four different ratios, with 100% blue, red, and white LED, and 67%:20%:13% of red:blue: white LED, as artificial grow for 12 hours illumination. The performance of MSC, AN, SNV, smoothing, and the first and second Savitzky-Golay’s derivatives (SGD) were examined. PLSR explained accurately predicted R2C, R2P, RMSEC, and RMSEP up to 0.957, 0.892, 1.054, and 1.661 for chlorophyll a using SGD 1st; 0.813, 0.652, 0.979, and 1.338 for chlorophyll b using SNV; and 0.931, 0.876, 1.155, and 1.550 for total chlorophyll using SNV. The wavelength region of 400 to 700 nm was dominant based on the best regression coefficient (β) for predicting green and red spinach microgreens. Results demonstrated that VIS-NIR spectroscopy, combined with chemometric techniques, PLSR, can be used to evaluate the chlorophyll content of green and red spinach microgreens.

IReenCAM: automated imaging system for kinetic analysis of photosynthetic pigment biosynthesis at high spatiotemporal resolution during early deetiolation.

Seedling de-etiolation is one of the key stages of the plant life cycle, characterized by a strong rearrangement of the plant development and metabolism. The conversion of dark accumulated protochlorophyllide to chlorophyll in etioplasts of de-etiolating plants is taking place in order of ns to µs after seedlings illumination, leading to detectable increase of chlorophyll levels in order of minutes after de-etiolation initiation. The highly complex chlorophyll biosynthesis integrates number of regulatory events including light and hormonal signaling, thus making de-etiolation an ideal model to study the underlying molecular mechanisms. Here we introduce the iReenCAM, a novel tool designed for non-invasive fluorescence-based quantitation of early stages of chlorophyll biosynthesis during de-etiolation with high spatial and temporal resolution. iReenCAM comprises customized HW configuration and optimized SW packages, allowing synchronized automated measurement and analysis of the acquired fluorescence image data. Using the system and carefully optimized protocol, we show tight correlation between the iReenCAM monitored fluorescence and HPLC measured chlorophyll accumulation during first 4h of seedling de-etiolation in wild type Arabidopsis and mutants with disturbed chlorophyll biosynthesis. Using the approach, we demonstrate negative effect of exogenously applied cytokinins and ethylene on chlorophyll biosynthesis during early de-etiolation. Accordingly, we identify type-B response regulators, the cytokinin-responsive transcriptional activators ARR1 and ARR12 as negative regulators of early chlorophyll biosynthesis, while contrasting response was observed in case of EIN2 and EIN3, the components of canonical ethylene signaling cascade. Knowing that, we propose the use of iReenCAM as a new phenotyping tool, suitable for quantitative and robust characterization of the highly dynamic response of seedling de-etiolation.

CsRVE1 promotes seasonal greening of albino Camellia sinensis cv. Huangkui by activating chlorophyll biosynthesis.

Seasonal greening is a crucial survival strategy for albino tea cultivars, during which dysfunctional chloroplasts recover and chlorophyll biosynthesis increases in albino leaves. However, the regulatory mechanisms of seasonal greening in albino tea plants remain unclear. Here, we report that CsRVE1, a nuclear-located Myb-like transcription factor, can positively modulate the seasonal greening of albino Camellia sinensis cv. Huangkui leaves by activating the expression of genes involved in light harvesting and chlorophyll biosynthesis. The transcriptional expression of CsRVE1 increased during seasonal greening and was tightly correlated with increases in the expression of genes involved in light harvesting (CsLhcb) and chlorophyll biosynthesis (CsCHLH, CsHEMA1 and CsCAO). In vivo and in vitro molecular analyses showed that CsRVE1 can directly bind to the promoters of CsLhcb, CsCHLH and CsPORA, eventually leading to chlorophyll accumulation in tea leaves. Furthermore, transient suppression of CsRVE1 in tea leaves led to a decrease in target gene expression. In contrast, the overexpression of CsRVE1 in Arabidopsis led to chlorophyll increases and the activation of AtLhcb, AtPORA, AtCHLH, etc. These results identify CsRVE1 as an important promoter of seasonal greening that functions by regulating genes involved in chlorophyll biosynthesis in albino tea plants and shed new light on the regulatory mechanisms of leaf phenotypes in plants.

Auxin inhibits chlorophyll accumulation through ARF7-IAA14-mediated repression of chlorophyll biosynthesis genes in Arabidopsis.

Auxin is a well-known important phytohormone in plant that plays vital roles in almost every development process throughout plant lifecycle. However, the effect of auxin on the metabolism of chlorophyll, one of the most important pigments involved in the photosynthesis, was intertwined and the underlying mechanism remained to be explored. Here, we found the auxin-defective yuc2 yuc6 double mutant displayed dark-green leaf color with higher chlorophyll content than wildtype, suggesting a negative regulatory role of auxin in chlorophyll biosynthesis. The chloroplast number and structure in mesophyll cells were altered and the photosynthetic efficiency was improved in yuc2 yuc6. In addition, the chlorophyll level was significantly improved during seedling de-etiolation in yuc2 yuc6 mutant, and decreased dramatically under IAA treatment, confirming the inhibitory role of auxin in chlorophyll biosynthesis. The analyses of gene expression in mature leaves and de-etiolation seedlings suggested that auxin suppressed the expression of many chlorophyll biosynthesis genes, especially PROTOCHLOROPHYLLIDE OXIDOREDUCTASE A (PORA) and GENOMES UNCOUPLED 5 (GUN5). Yeast-one-hybrid and luciferase assays demonstrated that the AUXIN RESPONSE FACTOR 2 (ARF2) and ARF7 bind to the promoter of PORA and GUN5 to suppress their expression with the help of INDOLE-3-ACETIC ACID14 (IAA14). Collectively, our research explicitly unraveled the direct inhibitory role of auxin in chlorophyll biosynthesis, and provided new insight into the interplay between auxin signaling and chlorophyll metabolism.

The influence of increased seawater HCO3− concentration on the survival, growth and physiology of the eelgrass Zostera marina

Inorganic resources are a key determining factor in the growth process of seagrass; however, the process and mechanisms involved in the promoting effect of increased seawater HCO3− concentration on seagrass growth and propagation under controlled conditions are poorly understood. We subjected shoots of the eelgrass Zostera marina to different seawater HCO3− levels [2 (control), 5, 10, 15 and 20 mmol L−1] for 6 weeks under controlled, mesocosm conditions. We measured eelgrass response in terms of survivorship, growth, propagation, productivity, carbonic anhydrase, leaf pigmentation and carbohydrate concentrations. The ramet frequency of Z. marina reached 58.7% when exposed to 5 mmol L−1, which was 1.3 times higher than that of shoots under the control condition. Survival analysis combined with growth assessment suggested that the optimal range of seawater HCO3− concentration for the propagation of Z. marina shoots was 4.8–5.5 mmol L−1. The promotion of survival and propagation of Z. marina that stemmed from seawater HCO3− concentration mainly depended on the increase in chlorophyll content and accumulation of nonstructural carbohydrate. The total chlorophyll content of Z. marina leaves exposed to 5 mmol L−1 was 1.1 times higher than that of shoots under the control condition. The results provide valuable data that could prove helpful in the development of efficient artificial propagation technology for Z. marina shoots.

Effect of ultra-violet light radiation on Scenedesmus vacuolatus growth kinetics, metabolic performance, and preliminary biodegradation study.

This study presents the effect of ultra-violet (UV) light radiation on the process kinetics, metabolic performance, and biodegradation capability of Scenedesmus vacuolatus. The impact of the UV radiation on S. vacuolatus morphology, chlorophyll, carotenoid, carbohydrates, proteins, lipid accumulation, growth rate, substrate affinity and substrate versatility were evaluated. Thereafter, a preliminary biodegradative potential of UV-exposed S. vacuolatus on spent coolant waste (SCW) was carried out based on dehydrogenase activity (DHA) and total petroleum hydrocarbon degradation (TPH). Pronounced structural changes were observed in S. vacuolatus exposed to UV radiation for 24h compared to the 2, 4, 6, 12 and 48h UV exposure. Exposure of S. vacuolatus to UV radiation improved cellular chlorophyll (chla = 1.89-fold, chlb = 2.02-fold), carotenoid (1.24-fold), carbohydrates (4.62-fold), proteins (1.44-fold) and lipid accumulations (1.40-fold). In addition, the 24h UV exposed S. vacuolatus showed a significant increase in substrate affinity (1/Ks) (0.959), specific growth rate (µ) (0.024h-1) and biomass accumulation (0.513g/L) by 1.50, 2 and 1.9-fold respectively. Moreover, enhanced DHA (55%) and TPH (100%) degradation efficiency were observed in UV-exposed S. vacuolatus. These findings provided major insights into the use of UV radiation to enhance S. vacuolatus biodegradative performance towards sustainable green environment negating the use of expensive chemicals and other unfriendly environmental practices.

The effect of fungicides on the physiological and biochemical state of lupine plants after seed treatment

Goal. To assess the effect of fungicides on the content of chlorophyll and the activity of antioxidant enzymes (peroxidase, catalase) in lupine plants after seed treatment.
 Methods. Laboratory and vegetation studies were carried out in the laboratory of analytical chemistry of pesticides of pesticides of the Institute of Plant Protection. The seeds of yellow lupine (Lupinus luteus L., variety Obriy) were treated with combined fungicides from different chemical classes: triazoles (cyproconazole, difenoconazole, tebuconazole, prothioconazole), phenylpyrroles (fludioxonil), carboxamides (carboxin), dithiocarbamates (thiram). Determination of the content of fungicides in plants was carried out using chromatographic methods of analysis. Chlorophyll content, peroxidase and catalase activity were determined by physicochemical methods according to generally accepted methods.
 Results. Fungicides activated the antioxidant systems of plants, depending on their physicochemical properties (in particular, the octanol-water partition coefficient Kow) and their content in plants (C, mg/kg). An increase in peroxidase activity (up to 89% compared to the control) was established within 30 days, which indicates the activation of antioxidant processes aimed at maintaining oxidative homeostasis in plants. The change in catalase activity under the influence of fungicides was inversely correlated with peroxidase activity, which is explained by the formation of adaptive mechanisms of ROS homeostasis. The high activity of peroxidase, compared to catalase, testifies to the important role of this enzyme in the redox reactions of plant resistance under the influence of fungicides. The total chlorophyll content under the action of fungicides, increased by 6—20%, compared to the control.
 Conclusions. Seed treatment with fungicides affects the course of redox reactions in plants, causing changes in the activity of key enzymes. The high activity of peroxidase against the background of fluctuations in catalase activity indicates the direct effect of fungicides on the state of antioxidant systems and the important role of peroxidase in maintaining ROS homeostasis. The stimulatory effect of fungicides on the accumulation of chlorophyll at the initial stages of growth of lupine plants was established, the content of which exceeded the control indicator by 6—20% by development phase. Changes in the activity of antioxidant enzymes (catalase and peroxidase) and the content of chlorophyll can serve as criteria for determining the levels of adaptation of lupine plants to the stress effect of fungicides.

Dynamics of accumulation of photosynthetic pigments in leaves <i>Trititrigia Cziczinii</i> Tzvel.

The productivity of plants depends on the efficiency of photosynthetic pigments, of which chlorophyll is the most important. In the conditions of sod-podzolic medium loamy soils of the Moscow region, the features of the accumulation of photosynthetic pigments (chlorophyll a and chlorophyll b) and the photosynthetic apparatus of a new synthetic grain crop Trititrigia cziczinii Tzvel. were studied. (Pamyati Lyubimovoj variety, line № 3202) compared to the winter wheat variety (Rubezhnaya) obtained by remote hybridization. The dynamics of the accumulation of chlorophyll a and chlorophyll b in the leaves of grain crops was measured during the generative development of plants starting from the earing phase (BBCH-scale code 52-53) on a spectrophotometer. The research results showed that all the studied varieties have their peaks of accumulation of the amount of chlorophyll a and chlorophyll b, depending on their biological characteristics. In winter wheat, the maximum amount of the sum of the two pigments fell on July 2 and amounted to 3,3 mg/g of raw leaf mass. In the trititrigia variety of the Pamyati lyubimovoj, the peak of pigment accumulation was noted almost a month later (July 30). The amount of pigments was 4,45 mg/g of raw mass. Trititrigia line № 3202 accumulated the maximum amount of chlorophyll (4,20 mg/g of raw leaf mass) even later than the Pamyati Lyubimovoj variety – August 5. The higher content of photosynthetic pigments in the cells of trititrigia leaves, compared with winter wheat, may indicate its high adaptive characteristics. And the peaks of chlorophyll accumulation, shifted by almost a month, indicate the long-term work of the assimilation apparatus and the uniqueness of the new synthetic culture. The leaf area measured in a straight linear way was different for all the studied objects. The largest leaf area was noted in the variety of trititrigia in Pamyati Lyubimovoj – 21,2 thousand m2/ha on July 13. The maximum leaf area at line № 3202 was 14.4 thousand m2/ha, then it gradually decreased. Rubezhnaya winter wheat had a significantly lower leaf area compared to trititrigia samples (the maximum was 6.1 thousand m2/ha), then the activity of the active assimilating surface decreased.

Comparative Transcriptomic and Physiological Analyses Reveal Key Factors for Interstocks to Improve Grafted Seedling Growth in Tangor.

Interstock is an important agronomic technique for regulating plant growth and fruit quality, and overcoming the incompatibility between rootstocks and scions; however, the underlying mechanisms remain largely unknown. In this study, the effects and regulatory mechanisms of tangor grafting, with and without interstocks, on the growth and development of scions were analyzed by combining morphology, physiology, anatomy and transcriptomics. Morphological and physiological analyses showed that interstocks ('Aiyuan 38' and 'Daya') significantly improved the growth of seedlings, effectively enhanced the foliar accumulation of chlorophyll and carotenoids, and increased the thickness of leaf tissues. Using 'Aiyuan 38' as the interstock, photosynthetic efficiency and starch content of citrus seedlings improved. Transcriptomics showed that genes related to photosynthesis and photosynthetic antenna proteins were upregulated in interstock-treated seedlings, with significant upregulation of photosystem PSI- and PSII-related genes. In addition, multiple key genes may be involved in plant hormone signaling, starch and sucrose metabolism, and transcriptional regulation. Taken together, these findings provide novel insights into the role of interstocks in regulating and contributing to the growth and development of grafted seedlings, and will further define and deploy candidate genes to explore the mechanisms of rootstock-interstock-scion interactions.

Effects of Cd treatment on morphology, chlorophyll content and antioxidant enzyme activity of Elymus nutans Griseb., a native plant in Qinghai-Tibet Plateau

ABSTRACT Cd pollution is a global environmental problem. However, the response mechanism of the alpine plant Pelagia under Cd stress remains unclear. Therefore, in this study, a native plant(Elymus nutans Griseb.) of the Qinghai-Tibet Plateau was used as the material to quantify plant height, leaf number, length of leaf, crown width, root number, biomass, Dry weight malondialdehyde (MDA), free proline, superoxide dismutase (SOD), ascorbate enzyme (APX), catalase (CAT) and chlorophyll contents under different Cd concentrations. The results showed that the growth of Elymus nutans Griseb. was a phenomenon of “low concentration promotes growth, high concentration inhibited growth” under Cd treatment. It meant that 10 mg·L−1 Cd promoted the growth of leaf number, plant height, crown width and tiller number, while 40 mg·L−1 Cd inhibited the growth of root number and biomass of Elymus nutans Griseb. compare with the control. The MDA content, free proline content, SOD activity, APX activity and CAT activity of Elymus nutans Griseb. was increased with the increase of Cd treatment concentration to resist the oxidative damage caused by Cd to the body. At the same time, the accumulation of chlorophyll A, chlorophyll B and chlorophyll AB was decreased with the increase of Cd stress concentration. In addition, the carotenoid content did not change much between the control group and the treatment group, indicating that Cd treatment had little effect on it. The results could provide a reference for the mechanism of heavy metal resistance and the selection and improvement of Cd -resistant varieties of Elymus nutans Griseb.

Exogenous abscisic acid and sodium nitroprusside regulate flavonoid biosynthesis and photosynthesis of Nitraria tangutorum Bobr in alkali stress.

Abscisic acid (ABA) and nitric oxide (NO) are involved in mediating abiotic stress-induced plant physiological responses. Nitraria tangutorum Bobr is a typical salinized desert plant growing in an arid environment. In this study, we investigated the effects of ABA and NO on N.tangutorum seedlings under alkaline stress. Alkali stress treatment caused cell membrane damage, increased electrolyte leakage, and induced higher production of reactive oxygen species (ROS), which caused growth inhibition and oxidative stress in N.tangutorum seedlings. Exogenous application of ABA (15μm) and Sodium nitroprusside (50μm) significantly increased the plant height, fresh weight, relative water content, and degree of succulency in N.tangutorum seedlings under alkali stress. Meanwhile, the contents of ABA and NO in plant leaves were significantly increased. ABA and SNP can promote stomatal closure, decrease the water loss rate, increase leaf surface temperature and the contents of osmotic regulator proline, soluble protein, and betaine under alkali stress. Meanwhile, SNP more significantly promoted the accumulation of chlorophyll a/b and carotenoids, increased quantum yield of photosystem II (φPSII) and electron transport rate (ETRII) than ABA, and decreased photochemical quenching (qP), which improved photosynthetic efficiency and accelerated the accumulation of soluble sugar, glucose, fructose, sucrose, starch, and total sugar. However, compared with exogenous application of SNP in the alkaline stress, ABA significantly promoted the transcription of NtFLS/NtF3H/NtF3H/NtANR genes and the accumulation of naringin, quercetin, isorhamnetin, kaempferol, and catechin in the synthesis pathway of flavonoid metabolites, and isorhamnetin content was the highest. These results indicate that both ABA and SNP can reduce the growth inhibition and physiological damage caused by alkali stress. Among them, SNP has a better effect on the improvement of photosynthetic efficiency and the regulation of carbohydrate accumulation than ABA, while ABA has a more significant effect on the regulation of flavonoid and anthocyanin secondary metabolite accumulation. Exogenous application of ABA and SNP also improved the antioxidant capacity and the ability to maintain Na+/K+ balance of N. tangutorum seedlings under alkali stress. These results demonstrate the beneficial effects of ABA and NO as stress hormones and signaling molecules that positively regulate the defensive response of N. tangutorum to alkaline stress.