Osmotic Adjustment Capacity Research Articles

An intronless sucrose:fructan-6-fructosyltransferase (6-SFT) gene from Dasypyrum villosum enhances abiotic tolerance in tobacco

Fructans play vital roles in enhancing plant abiotic stress tolerance by reducing oxidative damage, stabilizing cell membranes, improving the osmotic adjustment capacity, and lowering the freezing point. In this study, a sucrose: fructan-6-fructosyltransferase (6-SFT) gene involved in the synthesis of fructans was isolated from Dasypyrum villosum, Dv-6-SFT, using genomic walking and reverse transcription (RT)-PCR. Alignment of the cDNA sequence with its genomic counterpart showed that no introns were present in the Dv-6-SFT gene, and thus it differs from all other plant 6-SFTs that have been cloned previously. Sequence analysis showed that the cDNA of the Dv-6-SFT sequence comprised 2 175 bp with a 1 863 bp open reading frame, and its deduced protein comprised 620 amino acids with a predicted molecular mass of 68.47 kDa. The Dv-6-SFT gene was transferred into tobacco (Nicotiana tabacum L.) cv. W38 via Agrobacterium-mediated transformation. The screened plants were tested by PCR and semi-quantitative RT-PCR, and the transgenic plants were evaluated under drought, cold, and salt stresses. The Dv-6-SFT transgenic tobacco plants had higher resistance to drought, cold, and salt stress than the non-transgenic plants. Further analysis showed that the transgenic plant expressing Dv-6-SFT had increased content of saccharides and proline, but reduced content of malondialdehyde in leaves. The results of this study demonstrate that the Dv-6-SFT gene is a potential candidate for conferring abiotic stress tolerance in plants and it could be used in crop improvement breeding programs.

Ameliorative Effect of Salicylic Acid on Growth, Minerals and Nitrogenous Compounds ofVicia fabaL. Plants under Salt Stress

This study aimed to identify the salt tolerance of three broad bean genotypes (Vicia faba L.) and to elucidate the stimulatory role of salicylic acid on the studied bean genotypes under salt stress. Growth, photosynthetic pigments, minerals, membrane integrity and some nitrogenous compounds were evaluated. The three studied broad bean genotypes varied in their salt tolerance and in their response to salicylic acid application. Salinity reduced the shoot growth, the photosynthetic pigments, K+ contents and total proteins while it improved proline, total amino acids, soluble proteins and Na+ contents. Increasing the NaCl-salt level caused more cell membrane injury and electrolyte loss. The Na+/K+ ratio increased with increasing salt concentration in old leaves than in young leaves of bean genotypes. Foliar application of 0.5 mM salicylic acid to the bean genotypes under the different salinity levels improved these attributes significantly. Exogenous salicylic acid succeeded to ameliorate the oxidative stress in bean salt-stressed genotypes especially at the most sensitive genotype Assiut84/4. It can be concluded that broad bean plants could be possibly cultivated in moderate saline soils due to its capacity for osmotic adjustment. Moreover, salicylic acid could be used as a promising compound in broad bean cultivation under salt stress conditions.

Bioinformatic Analyses of Subgroup-A Members of the Wheat bZIP Transcription Factor Family and Functional Identification of TabZIP174 Involved in Drought Stress Response.

Extensive studies in Arabidopsis and rice have demonstrated that Subgroup-A members of the bZIP transcription factor family play important roles in plant responses to multiple abiotic stresses. Although common wheat (Triticum aestivum) is one of the most widely cultivated and consumed food crops in the world, there are limited investigations into Subgroup A of the bZIP family in wheat. In this study, we performed bioinformatic analyses of the 41 Subgroup-A members of the wheat bZIP family. Phylogenetic and conserved motif analyses showed that most of the Subgroup-A bZIP proteins involved in abiotic stress responses of wheat, Arabidopsis, and rice clustered in Clade A1 of the phylogenetic tree, and shared a majority of conserved motifs, suggesting the potential importance of Clade-A1 members in abiotic stress responses. Gene structure analysis showed that TabZIP genes with close phylogenetic relationships tended to possess similar exon–intron compositions, and the positions of introns in the hinge regions of the bZIP domains were highly conserved, whereas introns in the leucine zipper regions were at variable positions. Additionally, eleven groups of homologs and two groups of tandem paralogs were also identified in Subgroup A of the wheat bZIP family. Expression profiling analysis indicated that most Subgroup-A TabZIP genes were responsive to abscisic acid and various abiotic stress treatments. TabZIP27, TabZIP74, TabZIP138, and TabZIP174 proteins were localized in the nucleus of wheat protoplasts, whereas TabZIP9-GFP fusion protein was simultaneously present in the nucleus, cytoplasm, and cell membrane. Transgenic Arabidopsis overexpressing TabZIP174 displayed increased seed germination rates and primary root lengths under drought treatments. Overexpression of TabZIP174 in transgenic Arabidopsis conferred enhanced drought tolerance, and transgenic plants exhibited lower water loss rates, higher survival rates, higher proline, soluble sugar, and leaf chlorophyll contents, as well as more stable osmotic potential under drought conditions. Additionally, overexpression of TabZIP174 increased the expression of stress-responsive genes (RD29A, RD29B, RAB18, DREB2A, COR15A, and COR47). The improved drought resistance might be attributed to the increased osmotic adjustment capacity. Our results indicate that TabZIP174 may participate in regulating plant response to drought stress and holds great potential for genetic improvement of abiotic stress tolerance in crops.

Males exhibit competitive advantages over females of Populus deltoides under salinity stress.

Sexual competition among dioecious plants affects sex ratios and the spatial distribution of the sexes in different environments. At present, little is known about sexual dimorphisms induced by different competition patterns under salinity stress. We employed Populus deltoides as a model to investigate sex-related growth as well as physiological and biochemical responses to salinity stress under conditions of intrasexual and intersexual competition. Potted seedlings (two seedlings per pot; two females, two males, or one female and one male) were exposed to two salt levels (0 and 50 mM NaCl) and salinity- and competition-driven differences in growth, assimilation rate, water use, contents of leaf pigments and osmotica, hydrogen peroxide (H2O2), and antioxidant enzyme and nitrate reductase activity were examined. In the absence of salinity, no significant differences in competitive ability between males and females subjected to intrasexual competition were observed, although the growth of females was moderately greater under intersexual competition. The salinity treatment significantly increased the sex differences in competitive ability, especially under intersexual competition. Under salinity stress, males showed decreased height, but displayed greater capacity for osmotic adjustment, enhancement of long-term water-use efficiency and increase in antioxidant enzyme activities. The absolute values of these traits were greater in salt-stressed males than in females under intersexual competition. In addition, salt-stressed males accumulated less Cl- and had lower H2O2 contents than females. These data collectively demonstrate that the competitive advantage of females in non-stressed conditions is lost under salinity. Greater salinity resistance of males growing intermixed with females under salt stress can importantly affect the sex ratio of P. deltoides populations.

Enzymatic and Biochemical Responses of Sesame to Sodium Chloride at Germination and Early Seedling Growth

ABSTRACTSesame (Sesamum indicum L) is used for its leaves as a vegetable and its oil in Africa but soil salinity is a major abiotic stress limiting growth and productivity. Seed of sesame from cvs. Maroc (from Morocco), Tunisie (from Tunisia), and Ispahan (from Iran) were evaluated for enzymatic and biochemical responses to 0, 2, 4, 6, 8, and 10 g·L−1 of NaCl for 7 days to determine how germination and early seedling development were affected. Final germination percentage decreased in all cultivars at 10 g·L−1. Water content, lengths of radicles and plumules and, chlorophyll a and b contents were decreased when NaCl concentration was above 6 g·L−1. Enzyme activities were associated with elevated proline, total soluble sugars, and protein concentrations for cvs. Tunisie and Ispahan and total soluble sugars and proteins decreased for cv. Maroc. Protease activity was increased as NaCl concentration increased for all cultivars and was highest for cv. Maroc, which could indicate involvement of these enzymes in synergic adjustment. ‘Tunisie’ exhibited better germination and growth, which may be attributed to its capacity for osmotic adjustment and to mobilize higher sugars and reserve proteins during germination.

Exogenous application of hydrogen peroxide alleviates drought stress in cucumber seedlings

Drought limits plant growth and crop yield worldwide and more frequent occurrences of water shortages are expected according to climate change projections. However, relatively little is known about whether the spraying of plants leaves with hydrogen peroxide (H2O2) would alleviate the symptoms of drought stress. In this study, 3-week-old cucumber seedlings exposed to different soil water contents (non-limiting soil water conditions, medium drought, and severe drought) were foliar-sprayed with 1.5mM H2O2. Growth, photosynthesis and oxidative defense system were determined after one week of treatment. Results showed that exogenous H2O2 significantly increased biomass, leaf relative water content (RWC) and chlorophyll content, coupled with increased net photosynthetic rate (Pn), especially under medium drought. Meanwhile, superoxide anion radicals (O2−), electrolyte leakage and malondialdehyde (MDA) levels decreased whereas the activities of key antioxidant enzymes superoxide dismutase (SOD) and peroxidase (POD) as well as soluble sugar and proline contents increased in H2O2-treated plants. Hence, exogenously applied H2O2 considerably improved drought tolerance of cucumber plants by increasing the plant antioxidative defense system and the capacity for osmotic adjustment to alleviate membrane lipid peroxidation and to reestablish cell turgor, and thereby increasing photosynthesis, particularly under medium drought.

Relationships between foliar carbon isotope composition and elements of C3 species in grasslands of Inner Mongolia, China

Foliar elements and their ratios can be related to foliar carbon isotope composition (δ13C) through their involvement in plant transpiration, photosynthesis, and osmotic adjustment. In order to investigate these relationships in grasslands of Inner Mongolia, China, δ13C and element contents of dominant C3 species at 47 grassland sites were determined. For C3 species, δ13C showed no correlation with carbon (C), positive correlations with nitrogen (N), nitrogen:phosphorus ratio (N/P) and carbon:phosphorus ratio (C/P), and negative correlations with phosphorus (P), potassium (K), and carbon:nitrogen ratio (C/N), while correlation with P was subsidiary to positive correlation between P and K. These correlations indicate that plants in Inner Mongolia that survive in dry conditions may profit from their higher water use efficiency via stomatal regulation and N-related photosynthetic capacity rather than K-related osmotic adjustment and P-related photosynthetic capacity. Further, plants adapt to severe environments by having higher water and phosphorus use efficiency at the expense of nitrogen use efficiency. However, these correlations differed among plant functional groups (PFGs), e.g., δ13C was negatively correlated with N in shrubs in contrast to other life forms. A possible explanation is that shrubs adapt to low N availability by having lower photosynthetic nitrogen use efficiency (PNUE), so that N is not positively related to photosynthetic rate in shrubs. Obviously, data on stomatal conductance, PNUE, and cell osmotic pressure are needed to fully understand these correlations and the strategies of plants adapted to arid environments.

Rhizobium symbiosis contribution to short-term salt stress tolerance in alfalfa (Medicago sativa L.)

Salt stress negatively affects alfalfa (Medicago sativa L.) production and biological nitrogen fixation. We investigated whether rhizobium symbiosis has an effect on host plant tolerance to salt stress. We determined the survival rate, oxidative damage level, activities of antioxidant enzymes, and contents of osmotic solutes in the leaf and root of 4-month-old alfalfa with active nodules, inactive nodules or without nodules, and under short-term salt stress. Alfalfa with active nodules showed higher survival rate. Higher survival rate was associated with reduced lipid peroxidation, higher activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) as well as higher concentrations of reduced glutathione (GSH) and soluble sugar, especially in roots under salt stress. Variance analysis indicated nodulation affected the activities of SOD, CAT, POD, and APX along with concentrations of GSH, soluble sugar, and soluble protein. Inoculation also resulted in higher basal levels of superoxide anion radical (O2 −·) without salt stress. Rhizobium symbiosis had a positive effect on alfalfa salt tolerance by improving the activity of antioxidant enzymes and osmotic adjustment capacity.

The effect of salinity stress on survival percentage and physiological characteristics in three varieties of pistachio (Pistacia vera)

Abstract Greenhouse pot experiments were conducted to investigate the effect of salinity stress on survival percentage and physiological parameters in three varieties of Pistacia vera L.; including ‘Sarakhs’, ‘Badami’ and ‘Akbari’. To impose salinity stress, the plants were watered with NaCl solution (250 mM). The physiological characters were investigated at 3rd, 6th and 9th days of salinity induction. Based on our results, Badami showed a greater survival percentage among the other varieties. The highest level of proline, soluble sugar, anthocyanin and glycine-betaine contents and the lowest amount of H2O2 and MDA were also detected in Badami. Large quantities of H2O2, MDA and phenolic compounds were detected in Sarakhs. The highest level of superoxide dismutase (SOD) and catalase (CAT) activity was detected in Badami, while the highest activity of polyphenol oxidase (PPO) was seen in Sarakhs. All physiological characters increased during 3rd to 9th days of salinity induction, except CAT and SOD. In conclusion, Badami was more tolerant to salinity stress in comparison with other varieties due to it’s high capacity for osmotic adjustment and antioxidant protection. The physiological parameters including proline and H2O2 contents, besides the activity of CAT can be used as biochemical markers for identification of tolerant varieties of Pistacia vera.

Drought stress tolerance mediated by zinc-induced antioxidative defense and osmotic adjustment in cotton (Gossypium Hirsutum)

Zinc, as one of the essential microelements in crop plant, plays a crucial role in resistance to drought stress. To acquire a comprehensive of the physiological mechanism of resistance to drought stress enhanced by supplemental Zn in cotton, a hydroponic trial was conducted to investigate the changes in antioxidants and osmoregulation substances under zinc def icient and zinc sufficient conditions after 0, 3, 6 and 48 h of polyethylene glycol 6000-simulated drought stress. The present research showed that supplemental Zn significantly enhanced photosynthetic rate, chlorophyll a, chlorophyll b and dry matter of cotton under polyethylene glycol 6000 simulated drought stress, indicating that supplemental zinc improved the cotton growth. The antioxidant enzymes activities such as catalase, ascorbate peroxidase and superoxide dismutase, and non-enzymatic antioxidants such as carotenoid, reduced glutathione and ascorbic acid were all significantly enhanced and malonaldehyde content was remarkably reduced by supplemental zinc under polyethylene glycol 6000 simulated drought stress, indicating that the capacity of scavenging active oxygen species was improved by supplemental zinc in cotton. The osmoregulation substances such as soluble sugar, proline and soluble protein were all enhanced by supplemental zinc under Polyethylene glycol 6000 simulated drought stress, suggesting that zinc enhanced the osmotic adjustment capacity of cotton. It is implied that supplemental zinc could enhance the resistance to drought stress by inducing the buildup of antioxidative defences and osmotic adjustment ability in cotton.

Effects of water deficit on radicle apex elongation and solute accumulation in Zea mays L

In this study, we examined the effects of water deficit on the elongation of radicles of maize seedlings and on the accumulation of solutes in the radicle apices of two maize varieties: VS-22 (tolerant) and AMCCG-2 (susceptible). Sections of radicle corresponding to the first 2 mm of the primary roots were marked with black ink, and the seedlings were allowed to grow for 24, 48, and 72 h in polyvinyl chloride (PVC) tubes filled with vermiculite at three different water potentials (Ψw, −0.03, −1.0, and −1.5 MPa). The radicle elongation, sugar accumulation, and proline accumulation were determined after each of the growth periods specified above. The Ψw of the substrate affected the dynamics of primary root elongation in both varieties. In particular, the lowest Ψw (−1.5 MPa) inhibited root development by 72% and 90% for the VS-22 and AMCCG-2 varieties, respectively. The osmotic potential (Ψo) was reduced substantially in both varieties to maintain root turgor; however, VS-22 had a higher root turgor (0.67 MPa) than AMCCG-2 (0.2 MPa). These results suggest that both varieties possess a capacity for osmotic adjustment. Sugar began to accumulate within the first 24 h of radicle apex growth. The sugar concentration was higher in VS-22 root apices compared to AMCCG-2, and the amount of sugar accumulation increased with a decrease in Ψw. Significant amounts of trehalose accumulated in VS-22 and AMCCG-2 (29.8 μmol/g fresh weight [FW] and 5.24 μmol/g FW, respectively). Starch accumulation in the root apices of these two maize varieties also differed significantly, with a lower level in VS-22. In both varieties, the proline concentration also increased as a consequence of the water deficit. At 72 h, the proline concentration in VS-22 (16.2 μmol/g FW) was almost 3 times greater than that in AMCCG-2 (5.19 μmol/g FW). Trehalose also showed a 3-fold increase in the tolerant variety. Accumulation of these solutes in the root growth zone may indicate an osmotic adjustment (OA) to maintain turgor pressure.

Photosynthetic carbon and nitrogen metabolism and the relationship between their metabolites and lipid peroxidation in dwarf bamboo (Fargesia rufa Yi) during drought and subsequent recovery

Differential regulations of C and N metabolism in dwarf bamboo improve the capacity of osmotic adjustment, and also their metabolites may play an important role for protection against membrane lipid peroxidation under drought, thus accelerating recovery after rewatering. Dwarf bamboo (Fargesia rufa Yi), is a staple food for the endangered giant panda, but little is known about the impact of drought on bamboo species and its recovery mechanism. This study investigated the response of carbon (C) and nitrogen (N) metabolism to drought and subsequent recovery, and the relationship of their metabolites with lipid peroxidation. Photochemistry was reversibly down-regulated after drought, but a longer recovery time is needed. The accelerated degradation of starch due to a rapid increase in amylase activity resulted in higher soluble sugar only in severe drought-stressed plants after 30 days of drought. Sucrose content was not affected by drought because of the relative increases in activities of invertase, sucrose synthase, and sucrose phosphate synthase. As nitrate concentration increased in parallel with nitrate reductase activity, ammonium (NH4 +) production was enhanced by drought. Also, activated glutamine synthetase/glutamate synthase cycle stimulated NH4 + assimilation, while hydrolysis of soluble proteins was accelerated, resulting in accumulation of amino acids. After rewatering, re-balancing of C metabolism has gradually begun, but a stronger N metabolism was still observed. The notable positive correlations between MDA and the contents of starch and proline after 15 days of drought as well as between MDA and the contents of soluble sugar, NSC and proline after 30 days of drought were displayed. We conclude that dwarf bamboo may not only differently regulate its C and N metabolism to improve the capacity of osmotic adjustment but also employ its different metabolites protect against membrane lipid peroxidation under different intensities and duration of drought, thus accelerating its recovery after rewatering.

Regulation of invertase activity in different root zones of wheat (Triticum aestivum L.) seedlings in the course of osmotic adjustment under water deficit conditions

Osmotic adjustment of roots is an essential adaptive mechanism to sustain water uptake and root growth under water deficit. In this paper, the role of invertases (β-fructofuranosidase, EC 3.2.1.26) in osmotic adjustment was investigated in the root tips (cell division and elongation zone) and the root maturation zone of wheat (Triticum aestivum L. cv. Josef) in the course of osmotic stress imposed by 20% polyethylene glycol (PEG) 6000. The two root zones investigated differed distinctly in the response of invertases to water deprivation. In the root tips, the activity of the vacuolar and cell wall-bound invertases increased markedly under water stress resulting in the accumulation of hexoses (glucose and fructose) that contributed significantly to osmotic adjustment. A transient rise in hydrogen peroxide (H2O2) preceded the enhancement of invertases upon exposure to osmotic stress. Treatment with the NADPH oxidase inhibitor diphenylene iodonium (DPI) abolished the stress induced H2O2 production and suppressed the stimulation of the vacuolar invertase activity, whereas the activity of the cell wall-bound invertase was not influenced by DPI. As a consequence of the inhibitory effect of DPI on the vacuolar invertase, hexose levels and osmotic adjustment were also markedly decreased in the root tips under water deficit in the presence of DPI. These data suggest that H2O2 probably generated by a NADPH oxidase is required as a signalling molecule for the up-regulation of the vacuolar invertase activity in the root tips under osmotic stress, thereby enhancing the capacity for osmotic adjustment. In the root maturation zone, an early H2O2 signal could not be detected in response to PEG application. Only an increase in the glucose level that was not paralleled by fructose and a slight stimulation of the activity of the vacuolar invertase occurred in the maturation zone after water deprivation. The stress induced accumulation of glucose in the maturation zone was not affected by DPI and thus seems to be not regulated by NADPH oxidase-derived H2O2. Altogether, osmotic adjustment was considerably smaller in the maturation zone than in the root tips.

MORPHOLOGICAL CHARACTERISTICS AND WATER STATUS OF SOME TUNISIAN BARLEY GENOTYPES SUBMITTED TO WATER STRESS

Tunisia has been qualified as a country vulnerable to climate change that will be unregistered a great drop of annual rainfall and an increase of evaporation. Response strategies of agriculture to drought will be critical because drought is one of the major abiotic stresses which adversely affect crop growth and yield. Among strategies to be developed to cope with the effect of climate change, recourse of genetic diversity and new varietal creation can be a solution among other methods.
 In this study, four barley genotypes were cultivated in semi-controlled conditions and submitted to three levels of water stress. Data were recorded on number of grain per plant (NGP), one thousand grains weight (PMG), total leaf surface (TLS), plant height (HAT), stomata density (DS), leaf water content (RWC) and leaf water potential (LWP).
 Results showed that morphological characteristics (HAT, TLS, DS), yield components (NGP, PMG) and water status (LWP, RWC) of barley genotypes were decreased significantly. However, moderate water deficit didn’t affect significantly the most of parameters studied. Study had demonstrated also that barley genotypes developed different strategies and mechanisms to cope with water deficit, based essentially on their osmotic adjustment capacity.

The effect of salinity stress on survival percentage and physiological characteristics in three varieties of pistachio (Pistacia vera L)

Greenhouse pot experiments were conducted to investigate the effect of salinity stress on survival percentage and physiological parameters in three varieties of Pistacia vera L.; including 'Sarakhs', 'Badami' and 'Akbari'. To impose salinity stress, the plants were watered with NaCl solution (250 mM). The physiological characters were investigated at 3rd, 6th and 9th days of salinity induction. Based on our results, Badami showed a greater survival percentage among the other varieties. The highest level of proline, soluble sugar, anthocyanin and glycine-betaine contents and the lowest amount of H2O2 and MDA were also detected in Badami. Large quantities of H2O2, MDA and phenolic compounds were detected in Sarakhs. The highest level of superoxide dismutase (SOD) and catalase (CAT) activity was detected in Badami, while the highest activity of polyphenol oxidase (PPO) was seen in Sarakhs. All physiological characters increased during 3rd to 9th days of salinity induction, except CAT and SOD. In conclusion, Badami was more tolerant to salinity stress in comparison with other varieties due to it's high capacity for osmotic adjustment and antioxidant protection. The physiological parameters including proline and H2O2 contents, besides the activity of CAT can be used as biochemical markers for identification of tolerant varieties of Pistacia vera. © 2015 Institute of Botany, Slovak Academy of Sciences.

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.

Exogenous 24-Epibrassinolide Elevates the Salt Tolerance Potential of Pea (Pisum sativum L.) by Improving Osmotic Adjustment Capacity and Leaf Water Relations

Salinity, as a wide spread problem around the globe, can drastically limits the crop growth and productivity. Therefore, there is a growing need to mitigate the drastic effects of this abiotic stress through the use some sustaiable short-term or long term approaches. An investigation was carried out to assess the potential role of 24-epibrassinolide (EBL) in mitigating the drastic effects of salt stress on growth, water relations, osmolytes, and ions accumulation of salt-tolerant and salt-sensitive pea genotypes. EBL treatment significantly altered the leaf water status and accumulation of osmolytes and various ions in salt-stressed [with sodium chloride (+NaCl)] plants. The plants of both salt-tolerant and salt-sensitive genotypes, subjected to +NaCl conditions had a significant reduction in plant fresh and dry weights, internodal distance, leaf area (LA), leaf water potential (w), leaf osmotic potential (o), leaf turgor potential (t), relative water content (RWC), number of seeds pod−1, seed weight, root/leaf inorganic osmolytes (Ca2+, K+ and Mg2+), while increased the levels of root/leaf proline, glycinebetaine, total free amino acids, total soluble sugars, sodium (Na+), and chloride (Cl−). There was non-significant effect of EBL on number of pods plant−1 both under saline and non-saline conditions. However, the foliar application of EBL significantly alleviated the deleterious effects of salinity by improving the plant biomass, water relations and concentration of organic/inorganic osmolytes and yield attributes. However, EBL minimized the drastic effects of salt stress by limiting the root/leaf Na+ and Cl− contents. It can be concluded that EBL efficiently alleviated the salinity-induced drastic effects by improving the water status of plant tissues, which led to salt dilution within plant tissues, thus minimized the ion-toxicity, ultimately elevated the plant growth by minimizing the toxic action of Na+ and Cl−. Secondly, EBL augmented the salt-tolerance capacity of tested pea genotypes by enhancing their osmotic adjustment potential, in terms of high accumulation of organic and inorganic osmolytes within leaf and root tissues.

MORPHOLOGICAL CHARACTERISTICS AND WATER STATUS OF SOME TUNISIAN BARLEY GENOTYPES SUBMITTED TO WATER STRESS

Tunisia has been qualified as a country vulnerable to climate change that will be unregistered a great drop of annual rainfall and an increase of evaporation. Response strategies of agriculture to drought will be critical because drought is one of the major abiotic stresses which adversely affect crop growth and yield. Among strategies to be developed to cope with the effect of climate change, recourse of genetic diversity and new varietal creation can be a solution among other methods. In this study, four barley genotypes were cultivated in semi-controlled conditions and submitted to three levels of water stress. Data were recorded on number of grain per plant (NGP), one thousand grains weight (PMG), total leaf surface (TLS), plant height (HAT), stomata density (DS), leaf water content (RWC) and leaf water potential (LWP). Results showed that morphological characteristics (HAT, TLS, DS), yield components (NGP, PMG) and water status (LWP, RWC) of barley genotypes were decreased significantly. However, moderate water deficit didn’t affect significantly the most of parameters studied. Study had demonstrated also that barley genotypes developed different strategies and mechanisms to cope with water deficit, based essentially on their osmotic adjustment capacity.

海滨滨麦叶片和根对不同厚度沙埋生理响应差异分析

PDF HTML阅读 XML下载 导出引用 引用提醒 海滨滨麦叶片和根对不同厚度沙埋的生理响应差异分析 DOI: 10.5846/stxb201312172966 作者: 作者单位: 鲁东大学生命科学学院 山东烟台 264025,鲁东大学生命科学学院 山东烟台 264025,鲁东大学生命科学学院 山东烟台 264025,鲁东大学生命科学学院 山东烟台 264025,鲁东大学生命科学学院 山东烟台 264025,鲁东大学生命科学学院 山东烟台 264025 作者简介: 通讯作者: 中图分类号: 基金项目: 烟台市科技局资助课题(2013ZH351);国家973课题(2009CB421303);国家自然科学基金项目 (30972422) Analysis of the different physiological responses of Leymus mollis (Trin.) Hara leaves and roots to sand burial on the coast of Yantai, China Author: Affiliation: Ludong University,Ludong University,Ludong University,Ludong University,Ludong University,Ludong University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以烟台海岸抗风沙植物滨麦为研究材料,通过对不同厚度沙埋下其叶片和根部抗氧化酶活力(超氧化物歧化酶(SOD)、过氧化物酶(POD)、 过氧化氢酶(CAT))、丙二醛(MDA)含量和渗透调节物含量变化的分析,探讨了叶片和根部对沙埋生理响应的差异。 试验按滨麦成株株高(约40 cm)对其进行了轻度沙埋(在株高1/4 处)、中度沙埋(2/4 处)和重度沙埋(3/4 处)。在沙埋第6天,分别测定了不同厚度沙埋处理下,植株各段叶片和根抗氧化酶活力、MDA和渗透调节物含量。结果表明,轻度和中度沙埋均加速植株生长。与对照相比,经轻度、中度沙埋处理6 d,叶片平均MDA含量增加,在重度沙埋下降低。不同厚度沙埋6 d, 叶片平均SOD活力和脯氨酸含量增加, 而CAT活力、可溶性糖和可溶性蛋白质含量下降。 但不同厚度沙埋均使沙上叶片MDA、脯氨酸、可溶性蛋白质含量和SOD和CAT活力增加,尤其是叶片顶部增加最为明显,使沙下叶片MDA、可溶性糖、可溶性蛋白质含量和CAT活力下降,导致同株沙上和沙下叶片MDA、脯氨酸、可溶性糖、可溶性蛋白质含量和SOD和CAT活力差异显著(P<0.05)。与叶片相比,根中MDA、可溶性蛋白质含量和SOD和CAT活力较低, 而POD活力和可溶性糖含量较高并与叶片差异显著(P<0.05)。不同厚度沙埋6 d,滨麦根中MDA和可溶性蛋白质含量变化较小,可溶性糖含量和CAT、POD、SOD活力略有降低。研究表明,滨麦根和叶片对不同厚度沙埋的生理响应不同。沙埋直接作用于叶片并诱发叶内氧自由基积累,但叶片通过快速激活的抗氧化酶保护系统(CAT、SOD)维持氧自由基代谢平衡,以及渗透调节物(脯氨酸、可溶性糖)的积累维护细胞水分代谢平衡,并满足能量的需求和快速生长。但在不同厚度沙埋下,由于根系不受沙埋直接影响而生理变化较小,并且还维持较低的膜脂过氧化水平,这可能是根能维持正常的吸水输水功能并在沙埋处理过程中和沙埋后地上叶片快速生长摆脱沙埋的重要物质基础。 Abstract:In this study, we tested the physiological responses of Leymus mollis (Trin.) leaves and roots to sand burial on the Yantai coast of China to understand the biochemical and physiological adaptive mechanisms of this species to sand burial. Based on the height of L. mollis (about 40 cm) four levels of sand burial treatments were set up: no-sand burial (control), light sand burial (1/4 plant height), moderate sand burial (1/2 plant height), and severe sand burial (3/4 plant height). After 6 days of sand burial, samples were taken from the leaves and roots of plants in each treatment. Changes in malonaldehyde (MDA) content, an osmotic regulator, in addition to antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activity, were measured in the leaves above and below the sand and in the roots at various depths. Plants under light and moderate sand-burial grew fast until they protruded from the sand, becoming taller than control plants after 6 days. Compared to the control, the average MDA content increased in whole leaves under light and moderate sand burial, but and decreased in leaves subject to severe sand burial. In all three sand burial treatments, SOD activity and proline content increased in whole leaves, whereas CAT activity and soluble sugar and soluble protein contents decreased. In all three burial treatments, MDA, proline, and soluble protein content increased in leaves above the sand, along with SOD and CAT activity, especially in the top section of the leaves. In contrast, MDA, soluble sugar, and soluble protein content, in addition to CAT activity, decreased in the leaves beneath the sand. This resulted in significant differences in MDA, proline, soluble sugar, and soluble protein content, in addition to SOD and CAT activity, between leaves above and below the sand (P< 0.05). Compared to above ground leaves, underground roots had lower MDA and soluble protein content, in addition to lower SOD and CAT activity, but higher POD activity and soluble sugar content. After 6 days of sand burial, there was a small change in MDA and soluble sugar content, with soluble sugar content and CAT, POD, and SOD content slightly decreasing in the roots. On the same plant, leaves above ground had significantly higher (P<0.05) MDA and soluble protein content, along with higher CAT and SOD activity, than the underground roots. This result indicates that sand burial had a greater effect on the aboveground structures (branches and leaves) above ground compared to the underground structures. Sand-burial caused the accumulation of oxygen free radicals in the cells, which induced lipid peroxidation and activated the antioxidant enzymatic protection system to scavenge oxygen free radicals and maintain the metabolic balance of oxygen free radicals. This action also promoted osmotic adjustments to maintain the balance of water metabolism and provide energy and nutrition. Thus, under sand burial, it may be important to enhance cell antioxidant and osmotic adjustment capacity rapidly to maintain the balance of oxygen free radical metabolism and metabolic water balance, a key physiological regulation strategy for L. mollis for sand burial adaptation. Moreover, the root system was not affected by the different levels of sand burial, and continued to sustain lower levels of lipid peroxidation, allowing the roots to maintain normal functions of water suction and transportation, and to support the fast growth of leaves out of the sand. 参考文献 相似文献 引证文献

Effect of picloram herbicide on physiological responses of Eupatorium adenophorum Spreng

Eupatorium adenophorum Spreng., a major invasive weed in southwestern China, has caused great economic losses. In order to find a new herbicide to control E. adenophorum, experiments were conducted to study its physiological and biochemical responses to low and high doses of picloram herbicide (4-amino-3,5,6-trichloropyridine-2-carboxylic acid). Electrolyte leakage, malondialdehyde, and free proline were stimulated by picloram, showing a remarkably increase (p < 0.05) with high herbicide concentration (60, 120, and 240 g ai ha-1). The treated plants exhibited lower osmotic adjustment capacity, high dosage lipid peroxide levels and more free-proline accumulation. It was found that low doses (12 and 24 g ai ha-1) of picloram initially increased catalase, peroxidase, superoxide dismutases and protein, but these indicators decreased (p < 0.05) with the increase of treating time (after 3 d) and dose (120 and 240 g ai ha-1). In addition, the structures of chloroplasts and mitochondria were seriously deformed. These results indicated E. adenophorum can improve its herbicide-tolerance by increasing the antioxidative system activity at the initial period of low picloram stress. However, this protective function disappeared with increasing of treating time and picloram dosage. Eupatorium adenophorum responded differently to low and high concentrations of picloram and ultrastructural changes are an important cause of death in E. adenophorum.