Accumulation Of Photosynthetic Pigments Research Articles

Drought priming improves subsequent more severe drought in a drought-sensitive cultivar of olive cv. Chétoui

Drought is a major factor limiting crop production worldwide. The objective of this study was to test whether pre-exposure to drought can enhance the subsequent drought response of a drought–sensitive variety of olive cv. Chétoui.Seven-months old olive plants were grown in a controlled conditions and divided into control plants (irrigated daily), primed plants (PP, primed by exposure to drought for 21days, re-watered for 60days and then exposed to water depletion for 30days) and non-primed plants (NPP, well watered for 81days and immediately followed by intermediate drought as PP). Compared to the non-primed plants, primed plants showed an improvement in biomass production and healthy values of photosynthesis parameters with a higher accumulation of photosynthetic pigments. Additionally, the data of chlorophyll fluorescence were significantly similar to those of control, implying that no photodamage was occurred. Moreover, primed plants exhibited high accumulation of total sugar and proline which lead to the better water status maintenance. The lower level of oxidative status measured in term of hydrogen peroxide (H2O2), malondiadehyde (MDA) and electrolyte leakage (EC) in primed plants confirmed the alleviation of oxidative stress. Furthermore, the primed plants possessed more effective oxygen scavenging systems as exemplified by the increased activities of CAT, SOD, GP and high accumulation of polyphenols, resulting in a better maintenance in homeostasis of ROS production. Our investigation is indicative of the result of the benefit memory effects caused by stress pre-exposure in young olive plants cv.’Chétoui’ to overcome subsequent stress.

Nitrogen or phosphorus repletion strategies for enhancing lipid or carotenoid production from Tetraselmis marina

The objective of this study was to investigate the accumulation of lipid and photosynthetic pigments from Tetraselmis marina. When the cells were grown in F/2-medium for seven days in the first stage, the carotenoid and lipid contents, and productivity were 44g/kg (DW), 27% and 31mg/L/d, respectively. After second stage of cultivation of T. marina for further 3-days under N-replete condition (4.41mM NaNO3) increased biomass concentration of 1900mg/L and lipid content of 50% were observed, with an enhanced lipid productivity of 86.36mg/L/d and SFA and MUFA fractions of 70.76 and 13.14%, respectively. However, under P-repletion (2.08mM NaH2PO4), its carotenoid content increased to 89.23g/kg and its PUFA for 65% of total lipids. Results showed that N and P-replete conditions decreased SOD activity and increased H2O2 and TBARS levels of T. marina. Thus, this native microalga strain could be a potent candidate for feed, food or biofuel production.

Photosynthetic recovery and acclimation to excess light intensity in the rehydrated lichen soil crusts.

As an important successional stage and main type of biological soil crusts (BSCs) in Shapotou region of China (southeastern edge of Tengger Desert), lichen soil crusts (LSCs) often suffer from many stresses, such as desiccation and excess light intensity. In this study, the chlorophyll fluorescence and CO2 exchange in the rehydrated LSCs were detected under a series of photosynthetically active radiation (PAR) gradients to study the photosynthetic acclimation of LSCs. The results showed that although desiccation leaded to the loss of photosynthetic activity in LSCs, the fluorescence parameters including Fo, Fv and Fv/Fm of LSCs could be well recovered after rehydration. After the recovery of photosynthetic activity, the effective photosynthetic efficiency ΦPSII detected by Imaging PAM had declined to nearly 0 within both the lichen thallus upper and lower layers when the PAR increased to 200 μE m-2 s-1, however the net photosynthesis detected by the CO2 gas analyzer in the LSCs still appeared when the PAR increased to 1000 μE m-2 s-1. Our results indicate that LSCs acclimating to high PAR, on the one hand is ascribed to the special structure in crust lichens, making the incident light into the lichen thallus be weakened; on the other hand the massive accumulation of photosynthetic pigments in LSCs also provides a protective barrier for the photosynthetic organisms against radiation damage. Furthermore, the excessive light energy absorbed by crust lichens is also possibly dissipated by the increasing non-photochemical quenching, therefore to some extent providing some protection for LSCs.

Characterization and evaluation of some Mung bean genotypes for drought tolerance

To study the mean performance of characterization and evaluate the response drought tolerance for 21 Vigna radiate (Mung bean) genotypes. The results showed that the genotypes (L19) had a highest significant some characters plant height (cm), number of branches, number of pods, number of seeds and number of fruiting nods per plant, while the best yield was recorded with L14 and L15 genotypes. An effort to screening basis on growth parameters, physiological and biochemical characteristics, such as plant height, leaflet area, fresh and dry weight, leaf relative water content, cell membrane stability and chlorophyll (a and b) content, proline biomarker and some antioxidant enzyme activities, under different levels of drought stress. The results showed that different genotypes of mung bean exhibited distinct and significant response during screening for drought tolerance under different water-deficiency in plant growth stage. The tolerant genotypes showed less reduction in length, shoot fresh and dry weight, membrane stability, chlorophyll a and b contents, under high drought level (50 %) with respect to susceptible genotypes plants. On the basis of growth parameters of the each genotypes under high drought levels, total 6 genotypes L2, L4, L8, L18, L19 and L21 were selected for study the physiological and biochemical response to low water condition in different Mung bean genotypes plants. Drought stress showed that the best genotypes for partially drought tolerance were L4, L18, L19 and L21. Total physiological and biochemical parameters (maintenance of turgor cells, proline accumulation, and content of photosynthetic pigments and increase of some antioxidant enzyme expression) is an important physiological and biochemical mechanisms and adaptation for minimizing the detrimental effects of drought stress.

Sodium nitroprusside and indole acetic acid improve the tolerance of tomato plants to heat stress by protecting against DNA damage

ABSTRACTClimate change represents a major threat to agriculture. High ambient temperatures, as a result of global warming, are currently limiting plant growth and development. The aim of the present study was to investigate the effect of sodium nitroprusside (SNP) in combination with indole acetic acid (IAA) on tomato (Lycopersicon esculentum Mill.) plants under heat stress (HS) and non-heat stress (non-HS) conditions. HS is suggested to induce the formation of reactive oxygen species, such as superoxide and hydrogen peroxide, which may lead to genotoxicity by damaging DNA, which can be detected by the comet assay (single-cell gel electrophoresis). HS substantially enhanced proline (Pro), malondialdehyde accumulation, electrolyte leakage (EL), growth reduction, and reduced physiological and biochemical parameters. However, the co-application of SNP and IAA alleviated the adverse effects of HS by promoting catalase, peroxidase, and superoxide dismutase activities and enhancing the accumulation of photosynthetic pigments (chlorophyll a and b) and Pro with a concomitant decrease in H2O2 and content, EL, and DNA damage. Conversely, the treatment of tomato plants with the NO scavenger cPTIO [2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide] along with SNP and IAA further reduced the SNP signal. Therefore, these results suggest that the application of SNP with IAA improves plant defense mechanisms against HS.

Identification of a Halotolerant Mutant via In Vitro Mutagenesis in the Cyanobacterium Fremyella diplosiphon.

Energy metabolism and photosynthetic pigment accumulation are affected by salt stress in cyanobacteria leading to cessation of growth. In this study, the effect of salinity on the freshwater cyanobacterium, Fremyella diplosiphon, was investigated and mutagenesis-based efforts were undertaken to enhance salt tolerance. Salinity at a concentration of 10g/L sodium chloride (NaCl) inhibited growth of wildtype F. diplosiphon under white, red, and green light. Efforts to enhance halotolerance resulted in a mutant that could survive in 20g/L NaCl for 15 generations with no significant reduction in phycobiliproteins (phycocyanin, phycoerythrin, and allophycocyanin) or chlorophyll a. Gene expression measured by quantitative reverse transcription-polymerase chain reaction revealed a three-fold increase in tripartite ATP-independent periplasmic transporters (TRAP) solute receptor transcript in the mutant compared to wild type. Our discovery of a TRAP transporter system in F. diplosiphon and its possible role in salinity response enables growth in brackish waters, which enhances its potential for biotechnological applications.

Endophytic Fungi from Frankincense Tree Improves Host Growth and Produces Extracellular Enzymes and Indole Acetic Acid.

Boswellia sacra, an economically important frankincense-producing tree found in the desert woodlands of Oman, is least known for its endophytic fungal diversity and the potential of these fungi to produce extracellular enzymes and auxins. We isolated various fungal endophytes belonging to Eurotiales (11.8%), Chaetomiaceae (17.6%), Incertae sadis (29.5%), Aureobasidiaceae (17.6%), Nectriaceae (5.9%) and Sporomiaceae (17.6%) from the phylloplane (leaf) and caulosphere (stem) of the tree. Endophytes were identified using genomic DNA extraction, PCR amplification and sequencing the internal transcribed spacer regions, whereas a detailed phylogenetic analysis of the same gene fragment was made with homologous sequences. The endophytic colonization rate was significantly higher in the leaf (5.33%) than the stem (0.262%). The Shannon-Weiner diversity index was H′ 0.8729, while Simpson index was higher in the leaf (0.583) than in the stem (0.416). Regarding the endophytic fungi’s potential for extracellular enzyme production, fluorogenic 4-methylumbelliferone standards and substrates were used to determine the presence of cellulases, phosphatases and glucosidases in the pure culture. Among fungal strains, Penicillum citrinum BSL17 showed significantly higher amounts of glucosidases (62.15±1.8 μM-1min-1mL) and cellulases (62.11±1.6 μM-1min-1mL), whereas Preussia sp. BSL10 showed significantly higher secretion of glucosidases (69.4±0.79 μM-1min-1mL) and phosphatases (3.46±0.31μM-1min-1mL) compared to other strains. Aureobasidium sp. BSS6 and Preussia sp. BSL10 showed significantly higher potential for indole acetic acid production (tryptophan-dependent and independent pathways). Preussia sp. BSL10 was applied to the host B. sacra tree saplings, which exhibited significant improvements in plant growth parameters and accumulation of photosynthetic pigments. The current study concluded that endophytic microbial resources producing extracellular enzymes and auxin could establish a unique niche for ecological adaptation during symbiosis with the host Frankincense tree.

Meeting the challenge of stevioside production in the hairy roots of Stevia rebaudiana by probing the underlying process

Agrobacterium rhizogenes mediated “hairy root cultures” of the renowned bio-sweetener producing plant—Stevia rebaudiana, were generated to explore their yet undetected biosynthetic potentials concerning the low calorie diterpene glycoside—stevioside. Four stable rhizoclones were studied under light and dark conditions showing better growth under dark. Two of these rhizoclones revealed substantially higher photosynthetic pigment accumulation under light. Evidently, capitalization on the available inter-clonal variability first time showed the stevioside synthesizing exclusivity in the SRA4 rhizoclone under light condition, while the rest failed. The dualities of the glycoside synthesizing power amongst the two photosynthetically active rhizoclones were resolved through quantitative RT-PCR analysis of UGT85C2 gene showing positive expression in the stevioside producing rhizoclone. These findings elucidated the decisive role of UGT85C2 in combination with photosynthetic proficiency of the studied hairy root cultures in regulating the biosynthetic pathway of S. rebaudiana.

Alleviation of salinity-induced damage on wheat plant by an ACC deaminase-producing halophilic bacterium Serratia sp. SL- 12 isolated from a salt lake

Plant growth promoting bacteria (PGPB) with 1-aminocyclopropane-1-carboxylate deaminase (ACC deaminase) activity can be used to ameliorate salt stress in plants. The aim of this study was to characterize a salt-tolerant PGP bacterium Serratia sp. SL-12 isolated from a salt lake, and to evaluate its capability to promote growth in wheat plants (Triticum aestivum L) under conditions of salt stress. The isolate SL-12 exhibited other plant growth promoting properties such as the production of indole-3-acetic acid, and enabling solubilization of inorganic phosphate. An analysis of fatty acid composition of the isolate grown at different salt concentrations (150–200 mM) indicated that salt concentration strongly influenced the fatty acid composition, and increased the proportion of unsaturated fatty acids. Inoculation of SL-12 into wheat plants growing under salt stress (150–200 mM NaCl) resulted in a significant increase in plant growth, as measured by parameters such as shoot/root length, fresh/dry weight, and photosynthetic pigment accumulation. In addition, application of isolate SL-12 decreased the levels of Na+ by (65 %) and increased the uptake of K+ by (39 %), indicating a role in maintaining ionic homeostasis, and minimizing toxic ionic effects in host wheat plants. The growth of wheat seedling under salinity stress was improved by SL-12 by inducing accumulation of osmolytes such as total soluble sugar and total protein content, while reducing the salt-induced malondialdehyde content. This has been found by other researchers. The present study indicates the potential of isolate SL-12 as a biofertilizer for enhancing the growth of wheat and other crops under salt stress conditions.

Proline levels, oxidative metabolism and photosynthetic pigments during in vitro growth and acclimatization of Pitcairnia encholirioides L.B. Sm. (Bromeliaceae).

This study aimed to evaluate the variation in the levels of proline, oxidative metabolism and photosynthetic pigments in plants of Pitcairnia encholirioides grown in vitro under different conditions and after acclimatization. The analyses were performed after 150 days of in vitro cultivation in MS media supplemented with 10 µM GA3 or 0.2 µM NAA, sucrose at 15 or 30 g L-1, in test tubes which allowed gas exchange or in a hermetically sealed system, and 180 days after acclimatization. The in vitro maintenance in hermetically sealed flasks, with GA3 and 15 g L-1 sucrose had adverse metabolic effects, which was demonstrated by the lower proline and photosynthetic pigments accumulation and by the increase in antioxidant enzymes activities. After acclimatization, differences for proline and photosynthetic pigments were no longer found and the enzymatic activities ranged unevenly. The results suggest that the in vitro cultivation in media with 0.2 µM NAA and 30 g L-1 sucrose, in test tubes capped with closures which allowed gas exchange, is more suitable for micropropagation of P. encholirioides, providing a prolonged maintenance of in vitro cultures and plantlets with superior quality for ex vitro development.

The chloroplastic DEVH-box RNA helicase INCREASED SIZE EXCLUSION LIMIT 2 involved in plasmodesmata regulation is required for group II intron splicing.

INCREASED SIZE EXCLUSION LIMIT 2 (ISE2) encodes a putative DEVH-box RNA helicase originally identified through a genetic screening for Arabidopsis mutants altered in plasmodesmata (PD) aperture. Depletion of ISE2 also affects chloroplasts activity, decreases accumulation of photosynthetic pigments and alters expression of photosynthetic genes. In this work, we show the chloroplast localization of ISE2 and decipher its role in plastidic RNA processing and, consequently, PD function. Group II intron-containing RNAs from chloroplasts exhibit defective splicing in ise2 mutants and ISE2-silenced plants, compromising plastid viability. Furthermore, RNA immunoprecipitation suggests that ISE2 binds in vivo to several splicing-regulated RNAs. Finally, we show that the chloroplast clpr2 mutant (defective in a subunit of a plastidic Clp protease) also exhibits abnormal PD function during embryogenesis, supporting the idea that chloroplast RNA processing is required to regulate cell-cell communication in plants.

Dynamics of accumulation of coumarin-related compounds in leaves of Matricaria chamomilla after methyl jasmonate elicitation

The effect of methyl jasmonate (MeJA) treatment on diploid and tetraploid plants of Matricaria chamomilla and the changes of the main physiological parameters and secondary metabolites content was studied. Leaf rosettes from 7-week-old plants were harvested at four different time points (24, 48, 72, 96 h) after foliar application of 0.4 mM MeJA. The treatment led to a moderate biomass accumulation accompanied by an accumulation of photosynthetic pigments and decrease in the total soluble proteins. The content of hydrogen peroxide and superoxide radical was most elevated at 24 and 72 h after the treatment. Although the values of stress parameters were higher in tetraploid plants (such as in control so in treated plants), their total increase after the MeJA application was similar. The absolute level of total soluble phenols and flavonoids in the controls was similar in both cultivars and their content was enhanced in 24- and 48-h variants, more rapidly in diploid plants. MeJA has been found to trigger different responses of the secondary metabolites accumulation. Almost all studied metabolites were higher in control plants in the tetraploid cultivar, but their biosynthesis was more stimulated in diploids. Significant changes, mainly increasing trends with a maximum between 24 and 48 h after elicitation, in the content of free coumarin herniarin and its glycosidic precursors (Z)- and (E)-2-β-d-glucopyranosyloxy-4-methoxycinnamic acid were observed. The umbelliferone level increased over time. The maximum values for chlorogenic acid and 1,5-dicaffeoylquinic acid were at 24-h and between the 24–72 h time points. Among dicycloethers, the amounts of (E)-form decreased with time, and for (Z)-form an opposite trend was observed, with a maximum of 96 h for diploid and 24 h for tetraploid after elicitation.

AJUSTAMENTO OSMÓTICO EM MUDAS DE JATOBÁ SUBMETIDAS À SALINIDADE EM MEIO HIDROPÔNICO

RESUMOEm ambientes naturais, a salinidade representa grande empecilho ao desenvolvimento dos vegetais. Visando à melhor compreensão dos efeitos que ela provoca na fisiologia de espécies arbóreas nativas, este trabalho objetivou avaliar o comportamento fisiológico de mudas de jatobá (Hymenaea courbaril L.) submetidas à salinidade em meio hidropônico. Portanto, um experimento foi realizado em casa de vegetação do Laboratório de Fisiologia Vegetal da Universidade Federal Rural de Pernambuco, adotando-se um delineamento experimental inteiramente casualizado em arranjo fatorial 3 x 2, composto por três tratamentos salinos: Controle (solução nutritiva sem adição de NaCl), Estresse moderado (adição de 50 mM de NaCl) e Estresse severo (adição de 100 mM de NaCl) e duas épocas de avaliação (1ª época: constatação do fechamento estomático; e 2ª época: após a verificação da abertura estomática das plantas submetidas à salinidade), com 20 repetições em cada tratamento. Durante o estudo, foram verificadas as trocas gasosas, as relações hídricas, os teores de pigmentos fotossintéticos e o acúmulo de solutos orgânicos e inorgânicos. Ao final do experimento, observou-se que as mudas de jatobá se ajustaram osmoticamente após a indução do estresse severo, uma vez que acumularam solutos orgânicos que promoveram a elevação da turgescência foliar, resultando na estabilização das trocas gasosas, mesmo após a submissão ao estresse severo.

Arbuscular mycorrhizal symbiosis ameliorates the optimum quantum yield of photosystem II and reduces non-photochemical quenching in rice plants subjected to salt stress

Rice is the most important food crop in the world and is a primary source of food for more than half of the world population. However, salinity is considered the most common abiotic stress reducing its productivity. Soil salinity inhibits photosynthetic processes, which can induce an over-reduction of the reaction centres in photosystem II (PSII), damaging the photosynthetic machinery. The arbuscular mycorrhizal (AM) symbiosis may improve host plant tolerance to salinity, but it is not clear how the AM symbiosis affects the plant photosynthetic capacity, particularly the efficiency of PSII. This study aimed at determining the influence of the AM symbiosis on the performance of PSII in rice plants subjected to salinity. Photosynthetic activity, plant gas-exchange parameters, accumulation of photosynthetic pigments and rubisco activity and gene expression were also measured in order to analyse comprehensively the response of the photosynthetic processes to AM symbiosis and salinity. Results showed that the AM symbiosis enhanced the actual quantum yield of PSII photochemistry and reduced the quantum yield of non-photochemical quenching in rice plants subjected to salinity. AM rice plants maintained higher net photosynthetic rate, stomatal conductance and transpiration rate than nonAM plants. Thus, we propose that AM rice plants had a higher photochemical efficiency for CO2 fixation and solar energy utilization and this increases plant salt tolerance by preventing the injury to the photosystems reaction centres and by allowing a better utilization of light energy in photochemical processes. All these processes translated into higher photosynthetic and rubisco activities in AM rice plants and improved plant biomass production under salinity.

Effect of pre-sowing treatments with chemical mutagens on seed germination and growth performance of jamun (Syzygium cuminiL. Skeels) under different potting substrates

Introduction. Jamun, propagated through seed for raising rootstock, involves a lot of cost and risk for maintenance until attainment of graftable size. Use of suitable growing substrates is essential for production of quality nursery plants. Chemical mutagenesis is a simple approach to create mutation in plants for improvement of potential agronomic traits in rootstock materials. Materials and methods. Seeds originating from a single ‘elite’ tree were soaked in 0.1 and 0.5% ethyl methane sulfonate and colchicine solutions for 24 h prior to sowing in different propagation substrates (Arka fermented coco-peat and a mixture of sand, soil and farmyard manure). Morphological, physiological and biochemical analyses were performed after 3 months. Results and discussion. The Arka fermented coco-peat substrate resulted in earlier and higher seed germination, higher polyembryony, greater accumulation of photosynthetic pigments and total carbohydrates, and lower synthesis of stress-induced metabolites in leaves. These performances were probably due to a better balance between the water and air capacity than in the other growth substrate. Among different doses of chemicals, colchicine at 0.1% concentration was found to stimulate early seedling emergence, improve plant morphological characters and enhance production of total chlorophyll and total carbohydrates in leaves. Conclusion. The graftable stage can be attained rapidly if jamun seeds are treated with 0.1% colchicine and sown in Arka fermented coco-peat substrate.

Physiological responses of blackberry cultivar ‘Ningzhi 1’ to drought stress

In order to study the potential antioxidant defense mechanisms, the blackberry cultivar ‘Ningzhi 1’, a new floricane-fruiting hybridberry (Rubus sp.), was subjected to 20-day drought stress by withholding irrigation, followed by rewatering for 5 days, then the leaf water content (LWC), membrane electrolyte leakage, contents of photosynthetic pigments, protein, soluble sugar, hydrogen peroxide (H2O2), and MDA, activities of superoxide dismutase (SOD) and peroxidase (POD), and the levels of antioxidants such as ascorbate (AsA) and reduced glutathione (GSH) in leaves were investigated. The results showed that LWC was greatly decreased during the 20-day drought treatment period. After rewatering, water content restored. Drought stress induced significant accumulation of photosynthetic pigments, protein, soluble sugar, H2O2, and MDA as well as an increase in membrane electrolyte leakage, which were all decreased after rewatering. The activities of SOD and POD were elevated under drought stress, which were still at higher levels compared with control after rewatering. The contents of AsA and GSH ascended first and were then followed by a decline during the whole drought period, after rewatering, the contents increased and remained at a higher level than that of controls. The plants showed a rapid and almost complete recovery after rewatering, and the physiological alterations could represent a set of adaptive mechanisms employed by ‘Ningzhi 1’ to cope with drought stress. It was suggested that increased drought tolerance of ‘Ningzhi 1’ was due to higher antioxidant enzymes, reduced lipid peroxidation, better accumulation of osmolytes, and maintenance of tissue water content.

Insecticides induced biochemical changes in freshwater microalga Chlamydomonas mexicana.

The effect of insecticides (acephate and imidacloprid) on a freshwater microalga Chlamydomonas mexicana was investigated with respect to photosynthetic pigments, carbohydrate and protein contents, fatty acids composition and induction of stress indicators including proline, superoxide dismutase (SOD) and catalase (CAT). C. mexicana was cultivated with 1, 5, 10, 15, 20 and 25 mg L(-1) of acephate and imidacloprid. The microalga growth increased with increasing concentrations of both insecticides up to 15 mg L(-1), beyond which the growth declined compared to control condition (without insecticides). C. mexicana cultivated with 15 mg L(-1) of both insecticides for 12 days was used for further analysis. The accumulation of photosynthetic pigments (chlorophyll and carotenoids), carbohydrates and protein was decreased in the presence of both insecticides. Acephate and imidacloprid induced the activities of superoxide dismutase (SOD) and catalase (CAT) and increased the concentration of proline in the microalga, which play a defensive role against various environmental stresses. Fatty acid analysis revealed that the fraction of polyunsaturated fatty acids decreased on exposure to both insecticides. C. mexicana also promoted 25 and 21% removal of acephate and imidacloprid, respectively. The biochemical changes in C. mexicana on exposure to acephate and imidacloprid indicate that the microalga undergoes an adaptive change in response to the insecticide-induced oxidative stress.

Functional Analysis of Two Orthologous NAC Genes, CarNAC3, and CarNAC6 from Cicer arietinum, Involved in Abiotic Stresses in Poplar

Abiotic stresses such as drought and high salinity inhibit plant growth and productivity. NAC transcription factors play a variety of important roles in plant development and abiotic stress responses. To date, the transformation of NAC genes into poplar plants has not been reported. In this study, we introduced the CarNAC3 and CarNAC6 salinity and drought tolerant genes from Cicer arietinum (chickpea) into Populus deltoides × Populus euramericana ‘Nanlin895’ (poplar) plants using Agrobacterium tumefaciens-mediated transformation. We verified the integration of the two genes into the poplar genome using polymerase chain reaction (PCR) and their stable expression was confirmed at the transcript level using real-time (RT)-PCR. The growth rates of roots and shoots and the clawed root rate increased in transformed plants grown in agar medium or in soil and increased in response to drought and salt stress conditions. Proline and photoprotectant pigment accumulation and antioxidant enzyme activities increased in response to abiotic stress, but the accumulation of photosynthetic pigments and malondialdehyde (MDA) decreased in transgenic lines relative to wild-type control plants. The CarNAC3 transgene was expressed at higher levels than the CarNAC6 transgene. Our results showed that the CarNAC3 and CarNAC6 genes enhanced the capacity for osmotic adjustment and increased antioxidant enzyme activity and suggest that these genes could play a significant role in improving drought and salt tolerance when expressed in poplar plants.

The dual effects of two inorganic selenium forms on the growth, selected physiological parameters and macronutrients accumulation in cucumber plants

The boundary between beneficial and phytotoxic levels of selenium (Se) is narrow, and both induce alteration in plant growth and their physiology. In this study, the influence of two Se forms (selenite or selenate) with different concentrations (2–80 µM) on cucumber plants was investigated. The toxicity threshold for selenate and selenite was determined at the concentrations of 80 and 20 µM, respectively. In the Se-exposed plants, the growth-promoting effect was found at 6 µM of selenite and at 6–20 µM of selenate. The root activity considerably increased with increasing selenite concentrations suggesting the upregulation of mitochondrial dehydrogenases activity. Selenite treatment also impaired photosynthetic pigments accumulation and chlorophyll fluorescence parameters. Moreover, Se exerted a dual effect on lipid peroxidation in roots: at low concentrations it inhibited this process, whereas at high concentrations it enhanced the accumulation of harmful lipid peroxides. Under low Se concentrations (<10 µM), the accumulation of Se in shoots was similar in the presence of selenate and selenite. When Se concentration was >10 µM, the accumulation of Se in shoots was greater in selenate-exposed than selenite-exposed plants. However, in the roots the Se concentrations were always higher after selenite exposure comparing to selenate. The N level in plants was generally maintained constant, while the remaining macronutrients (especially K, P, and S) concentrations were significantly changed depending on the form and concentrations of Se. These results imply that an application of either selenate or selenite at concentrations <10 µM may be potentially used for biofortification of cucumber with Se and changes in plant macronutrient contents are not expected under these conditions.

Identification of genes involved in spontaneous leaf color variation in Pseudosasa japonica.

Spontaneous leaf color variation in bamboo provides the opportunity to study the mechanisms of leaf color formation and the breeding of ornamental bamboos. Despite the fact that many genes are known to be involved in leaf color variation in model plants, molecular mechanisms governing natural leaf color variation in bamboo have remained obscure. This study aimed to identify the genes responsible for the occurrence of such phenomena in bamboo using the suppression subtractive hybridization (SSH) method between green and albino leaves in Pseudosasa japonica f. A total of 1062 and 1004 differentially expressed transcripts were obtained from the forward and reverse SSH libraries, respectively. Subsequently, 59 differentially expressed unigenes with potential roles in leaf color formation, predicted via computational analysis of their functional relevance, were selected for further analysis using qPCR. Ten genes, involved in photosynthesis, plastid development, and cation signal transduction, showed 2-fold changes in expression levels between green and albino leaves. Further expression pattern analyses of these genes at three developmental stages revealed much lower expression abundance of Lhca1-encoded chlorophyll a/b binding protein in the albino leaves than in the green leaves. Our results suggest that, together with the concatenated negative pressure for subsequent photosynthetic processes, the albino phenotype is at least partly attributable to chloroplast inner membrane damage or to the impairment of photosynthetic pigment accumulation, which results from low Lhca1 expression.