Some physiological responses of chickpea cultivars to arbuscular mycorrhiza under drought stress

A factorial experiment based on RCB design with three replicates was conducted to investigate changes in some physiological responses of two chickpea (Cicer arietinum L.) cultivars (Pirouz from Desi type and ILC482 from Kabuli type) to arbuscular mycorrhiza (Glomus etunicatum Becker and Gerdman) under different irrigation treatments. The experiment was carried out in the greenhouse of the Agricultural Faculty of Kurdistan University from April to August 2009. The results showed that leaf chlorophyll content of chickpea cultivars was significantly increased by arbuscular mycorrhiza (AM) under both well and limited irrigation conditions. Proline accumulation in chickpea leaves under moderate and severe drought stresses was significantly stronger than that under optimum irrigation. Inoculation of chickpea with mycorrhizal fungi caused an increase in the activities of polyphenol oxidase and peroxidase, but a decrease in the activity of catalase. Comparisons among different irrigation levels showed that chickpea plants under drought stress had the most active lipid peroxidation. Non-AM plants showed stronger lipid peroxidation under moderate and severe water stresses than AM plants. Lipid peroxidation was more active in Pirouz leaves than in ILC₄₈₂ leaves. It seems that Kabuli-type cultivar responded better to mycorrhizal symbiosis under drought stress than Desitype cultivar.     

Antioxidant enzymes and physiological characteristics in two Jerusalem artichoke cultivars under salt stress

The effects of NaCl stress on the activity of antioxidant enzymes, lipid peroxidation, cell membrane stability, net photosynthetic rate, gas-exchange, and chlorophyll content were investigated in two Jerusalem artichoke cultivars, Dafeng (salt-tolerant) and Wuxi (salt-sensitive), grown under control (nutrient solution) or salt stress (nutrient solution containing 75, 150, and 225 mM NaCl) conditions for 7 days. In leaves of salt-tolerant cv. Dafeng, superoxide dismutase (EC 1.15.1.1), peroxidase (EC 1.11.1.7), and catalase (EC 1.11.1.6) activities significantly increased as compared to the controls, whereas no significant change was observed in cv. Wuxi. Lipid peroxidation and cell membrane injury were enhanced in both cultivars. Net photosynthesis and stomatal conductance decreased in response to salt stress, but cv. Dafeng showed a smaller reduction in photosynthesis than cv. Wuxi. The results indicated that stomatal aperture limited leaf photosynthetic capacity in the NaCl-treated plants of both cultivars. However, significant reduction in the leaf chlorophyll content due to NaCl stress was observed only in cv. Wuxi. These results suggested that salt-tolerant Jerusalem artichoke varieties may have a better protection against reactive oxygen species, at least in part, by increasing the activity of antioxidant enzymes under salt stress.     

Gas exchange,chlorophyll fluorescence,and osmotic adjustment in two mango cultivars under drought stress

The responses of photosynthetic gas exchange, chlorophyll fluorescence, content of pigments, main osmolytes, and malondialdehyde (MDA) to water-withholding for 15 days and re-hydration in seedlings of two mango cultivars (Mangifera indica L. var. “Choke Anand’ and var. “Khieo Sawoei”) under 50% sunlight and full sunlight were investigated. For both cultivars, the water-witholding resulted in progressively decreases in leaf relative water content, net photosynthesis (P _n), stomatal conductance (g _s), and increases in the conversion of xanthophyll cycle pigments estimated by an index of leaf spectral reflectance (ΔPRI), carotenoid to chlorophyll ratio, non-photochemical quenching (NPQ), the contents of malondialdehyde (MDA) and compatible solutes (total soluble sugar and proline). The effect of the water stress was more pronounced in full sunlight than 50% sunlight. The maximum photochemistry efficiency measured at dawn was fairly constant during the period of the treatment for both cultivars under both light regimes. The water stress caused less pronounced inhibition of photosynthesis in “Choke Anand” than in “Khieo Sawoei” cultivar under both light regimes. After re-hydration, the recovery was relatively quicker in “Choke Anand” than in “Khieo Sawoei” cultivar. Both cultivars in both 50% and full sunlight showed complete recovery in photochemistry after 5 days of re-watering but photosynthesis did not show a complete recovery as indicated by gas exchange rates. As the results of lower NPQ, ΔPRI and osmotic adjustment in the cultivar “Khieo Sawoei” compared to the cultivar “Choke Anand”, the former cultivar was less tolerant to drought than the latter. Our study further showed that partial shading (e.g., 50% of sunlight) significantly alleviated the harmful effect of drought stress on mango cultivars but in fact stomata of seedlings grown in partial shade was more responsive to water deficit than in full light.     

Hsp transcript induction is correlated with physiological changes under drought stress in Indian mustard

Physiology and Molecular Biology of Plants - Brassica juncea is an important oilseed crop and drought stress is major abiotic stress that limits its growth and productivity. RH0116 (drought...     

Comprehensive physiological analyses and reactive oxygen species profiling in drought tolerant rice genotypes under salinity stress

Rice being a staple cereal is extremely susceptible towards abiotic stresses. Drought and salinity are two vital factors limiting rice cultivation in Eastern Indo-Gangetic Plains (EIGP). Present study has intended to evaluate the consequences of salinity stress on selected drought tolerant rice genotypes at the most susceptible seedling stage with an aim to identify the potential multi-stress (drought and salt) tolerant rice genotype of this region. Genotypic variation was obvious in all traits related to drought and salt susceptibility. IR84895-B-127-CRA-5-1-1, one of the rice genotypes studied, exhibited exceptional drought and salinity tolerance. IR83373-B-B-25-3-B-B-25-3 also displayed enhanced drought and salt tolerance following IR84895-B-127-CRA-5-1-1. Variations were perceptible in different factors involving photosynthetic performance, proline content, lipid peroxidation, K⁺/Na⁺ ratio. Accumulation of reactive oxygen species (ROS) disintegrated cellular and sub-cellular membrane leading to decreased photosynthetic activities. Therefore, accumulation and detoxification of reactive oxygen species was also considered as a major determinant of salt tolerance. IR84895-B-127-CRA-5-1-1 showed improved ROS detoxification mediated by antioxidant enzymes. IR84895-B-127-CRA-5-1-1 seedlings also displayed significant recovery after removal of salt stress. The results established a direct association of ROS scavenging with improved physiological activities and salt tolerance. The study also recommended IR84895-B-127-CRA-5-1-1 for improved crop performance in both drought and saline environments of EIGP. These contrasting rice genotypes may assist in understanding the multiple stress associated factors in concurrent drought and salt tolerant rice genotypes.     

Growth and physiological responses to ozone and mild drought stress of tree species with different ecological requirements

An open-top chamber experiment was carried out in Curno (Northern Italy) in 2004 and 2005 on seedlings of Fagus sylvatica (FS), Quercus robur (QR), and an ozone-sensitive Populus (POP) clone, to investigate the role of two stress factors: tropospheric ozone and water shortage. Treatments were filtered air to achieve a 50% reduction in the environmental ozone concentrations (charcoal filtered, CF); and non-filtered air, with a 5% reduction in the environmental ozone concentrations (non-filtered, NF). Overall ozone exposure (AOT40) in open air (April–September) was 26,995 ppb h in 2004 and 25,166 ppb h in 2005. The plants were either watered (W) or not watered (dry, D). We investigated the above-ground biomass, tree-ring growth, stable carbon isotopes ratio, i.e. δ¹³C of tree rings, and the photosynthetic parameter Driving forces (DF_ABS), derived from chlorophyll a fluorescence analysis. Ozone-induced growth reduction (in terms of biomass) in POP, and that reduction was more pronounced in D plots. A synergistic effect of ozone and drought stress was evidenced by DF_ABS in POP and QR, but not in FS. The water availability was revealed as the main factor influencing the isotopic ratio δ¹³C. In drought-stressed seedlings, the increase in δ¹³C value was accompanied by the reduction in stomatal conductance and increased DF_ABS. Fast-growing plant species with high water requirements are more susceptible to ozone and drought stress.     

Photosynthesis by six Portuguese maize cultivars during drought stress and recovery

Photosynthesis, chlorophyll fluorescence, and leaf water parameters were measured in six Portuguese maize (Zea mays L.) cultivars during and following a period of drought stress. The leaf relative water content (RWC) responded differently among cultivars but except for cultivar PB369, recovered close to initial values after watering was restored. Photosynthetic rate and stomatal conductance decreased with drought but more slowly in cultivars PB269 and PB260 than in cultivars AD3R, PB64, PB304 and PB369. Water use efficiency (WUE) decreased during the water stress treatment although with cultivar PB260 the decrease was marked only when the RWC fell below 40%. Recovery of WUE was seen with all cultivars except PB369. The maximum quantum efficiency of photosystem II, the photochemical quenching coefficient, the electron transport rate in PSII and the estimated functional plastoquinone pool tended to decrease with drought, while the non-photochemical quenching coefficient increased. The parameters estimated from chlorophyll fluorescence did not recover in PB369, during re-watering. The results show that PB260 and PB269 were the most tolerant and PB369 was the least tolerant cultivars to water stress. The variation found among the cultivars tested suggests the existence of valuable genetic resources for crop improvement in relation to drought tolerance.     

Effect of drought stress implemented at pre- or post-anthesis stage on some physiological parameters as screening criteria in chickpea cultivars

Drought is one of the most important factors limiting chickpea production in arid and semi-arid regions. There is little information regarding genotypic variation for drought tolerance in chickpea cultivars. Screening for drought tolerance is very important. It is essential to identify the physiological mechanisms of drought tolerance to complete conventional breeding program. Glasshouse experiment was carried out to study the genotypic variation among 11 chickpea (Cicer arietinum L.) cultivars. Plants were grown either under optimum conditions or drought stress was implemented at pre-or post-anthesis stages. The drought susceptibility index (DSI) was used as the measure of drought tolerance. Relationships between DSI and excised-leaf water loss (RWL), relative water content (RWC), membrane permeability, ascorbic acid, proline, and chlorophyll contents, lipid peroxidation, and hydrogen peroxide concentrations were determined in order to find out whether these physiological parameters could be used as the genotypic selection criteria for drought tolerance. The results of this study indicated that there was a wide variation in tolerance to drought stress among the chickpea cultivars, which could be exploited in breeding new chickpea cultivars with high drought tolerance. The results also demonstrated that drought-tolerant cultivars had a higher RWC, ascorbic acid and proline concentrations, but lower RWL and membrane permeability in comparison to drought-sensitive cultivars. The significant and a well defined relationships between DSI and RWC, RWL, ascorbic acid, proline, and membrane permeability were found. It was concluded that these parameters could be instrumental in predicting the drought tolerance of chickpea cultivars. This text was submitted by the authors in English.     

Salicylic acid induces physiological and biochemical changes in Torreya grandis cv. Merrillii seedlings under drought stress

Key message

SA treatment effectively ameliorated the negative effect of moderate drought stress on T. grandis Seedlings through increasing the water content, Pn, proline content, antioxidant enzymes activity and reducing MDA.

Abstract

Water availability is one of the most critical factors that limits the growth and development of plants. Salicylic acid (SA) is an important signal molecule that modulates plant responses to abiotic stress. To elucidate the regulating mechanism of exogenous SA on Torreya grandis cv. Merrillii under different water stresses, a pot experiment was conducted in a greenhouse. Exposure of T. grandis seedlings to drought conditions resulted in reduced growth rate that was associated with a decline in water content and CO₂ assimilation. Foliar application of SA effectively increased the water content, net CO₂ assimilation rate, proline content and antioxidant enzymes activity in the plants, which helped T. grandis to acclimate to moderate drought stress and increase the shoot dry matter. However, when the plants were under severe drought stress, the relative water content and CO₂ assimilation in the SA-treated plants were significantly lower than those in the control plants. Therefore, our results indicated that SA can effectively ameliorate the negative effect of moderate drought stress on T. grandis seedling growth.     

Differential antioxidative responses of indica rice cultivars to drought stress

The present study investigated the linkages between drought stress, oxidative damages and variations in antioxidants in the three rice varieties IR-29 (salt-sensitive), Pokkali (salt-tolerant) and aromatic Pusa Basmati (PB), to elucidate the antioxidative protective mechanism governing differential drought tolerance. Water deficit, induced by 20% (w/v) polyethylene glycol (PEG-6000), provoked severe damages in IR-29 and PB in the form of huge chlorophyll degradation and elevated H₂O₂, malondialdehyde and lipoxygenase (LOX, EC 1.13.11.12) levels as compared to Pokkali. The protein oxidation was more conspicuous in IR-29. Increment in antioxidants, particularly flavonoids and phenolics was several folds higher over control in Pokkali, while much lesser in IR-29 and PB. The activity of catalase (CAT, EC 1.11.1.6) and superoxide dismutase (SOD, EC 1.15.1.1) were decreased in IR-29 and PB, but unaltered in Pokkali. However, marked drought-induced increase in guaiacol peroxidase (GPX, EC 1.11.1.7) activity was noted in both IR-29 and PB. Induction in radical scavenging activity, being the maximum in IR-29, and increased reducing power ability in all the cultivars, accompanied with drought stress, were observed as a defense mechanism. The novelty of our work is that it showed the aromatic rice PB behaving more closely to IR-29 in greater susceptibility to dehydration stress, while the salt-tolerant Pokkali also showed effective drought tolerance properties.     

Differential growth, physiological and biochemical responses of niger (Guizotia abyssinica Cass.) cultivars to water-deficit (drought) stress

The present study demonstrates the effect of polyethylene glycol-8000 (PEG) and percent field capacity (FC%)-induced water-deficit stress on growth, water status, productivity and various biochemical parameters in Guizotia abyssinica Cass. cultivars (IGP 76, GA 10, No. 71 and IGPN 2004) at seedling and maturity stages of the plant. Cultivar GA 10 showed higher, IGP 76 and No. 71 moderate, and IGPN 2004 least reduction in percent seed germination given PEG stress treatments (0, 10 and 20%). A similar pattern was observed for decreased growth and water content of the seedlings and plants of the cultivars exposed to both kinds of water-deficit stresses. The productivity (number of capitula per plant, number of seeds per capitula and 1,000-seed weight) and total chlorophyll content of cultivar IGPN 2004 was significantly higher in comparison to other cultivars given different FC% treatments (100, 80 and 60%). Significantly higher accumulation of proline, glycine betaine and total soluble sugars and lower damage to membrane lipids under increased water-deficit stress (i.e., at 80 and 60% FC) conditions in cultivar IGPN 2004 suggested its more tolerance capacity to water-deficit stress in comparison to other cultivars. Besides, antioxidant enzyme activities (superoxide dismutase, catalase, ascorbate peroxidase and guaiacol peroxidase) partially demonstrated variations in the tolerance of the cultivars to water-deficit stress. The results suggest that cultivar IGPN 2004 could be considered as more tolerant, and IGP 76 and No. 71 as moderately tolerant, whereas GA 10 was more sensitive to water-deficit stress.     

Comparing symbiotic performance and physiological responses of two soybean cultivars to arbuscular mycorrhizal fungi under salt stress

The presented experiments evaluated the symbiotic performance of soybean genotypes with contrasting salt stress tolerance to arbuscular mycorrhizal fungi (AMF) inoculation. In addition, the physiological stress tolerance mechanisms in plants derived from mutualistic interactions between AMF and the host plants were evaluated. Plant growth, nodulation, nitrogenase activity and levels of endogenous growth hormones, such as indole acetic acid and indole butyric acid, of salt-tolerant and salt-sensitive soybean genotypes significantly decreased at 200 mM NaCl. The inoculation of soybean with AMF improved the symbiotic performance of both soybean genotypes by improving nodule formation, leghemoglobin content, nitrogenase activity and auxin synthesis. AMF colonization also protected soybean genotypes from salt-induced membrane damage and reduced the production of hydrogen peroxide, subsequently reducing the production of TBARS and reducing lipid peroxidation. In conclusion, the results of the present investigation indicate that AMF improve the symbiotic performance of soybean genotypes regardless of their salt stress tolerance ability by mitigating the negative effect of salt stress and stimulating endogenous level of auxins that contribute to an improved root system and nutrient acquisition under salt stress.     

Influence of silicon on antioxidant mechanisms and lipid peroxidation in chickpea (Cicer arietinum L.) cultivars under drought stress

Abstract

The effects of exogenous silicon (Si) on leaf relative water content (RWC), and the growth, Si concentrations, lipid peroxidation (MDA), lipoxygenase (LOX) activity, proline and H₂O₂ accumulation, non-enzymatic antioxidant activity (AA) and the activity of some antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT; ascorbate peroxidase, APX) in shoots of ten chickpea cultivars grown under drought were investigated. Drought stress decreased the growth of all the cultivars while applied Si improved the growth at least five of the 10 chickpea cultivars. Silicon applied to the soil at 100 mg kg^?1 significantly increased Si concentrations of the cultivars and counteracted the deleterious effects of drought in 5 of the ten chickpea cultivars by increasing their RWC. In most cultivars tested H₂O₂, proline and MDA content and LOX activity were increased by drought whereas application of Si decreased their levels. APX activity was increased by drought but it was depressed by Si. In general, SOD and CAT activities of the cultivars were decreased by drought. Depending on cultivars, the CAT activity was decreased, and increased or unchanged in response to applied Si, while the SOD activity of the cultivars increased or unchanged by Si. The non-enzymatic antioxidant activity of the cultivars was also increased by Si. These observations implied an essential role for Si in minimizing drought stress-induced limitation of the growth and oxidative membrane damage in chickpea plants.     

黄连木对干旱胁迫的生理响应

研究了自然干旱条件下黄连木（Pistacia chinensis Bunge）的生理变化。结果表明,随土壤含水量的减少,叶绿素b含量、光合速率、叶片相对含水量与叶水势均下降;叶绿素a和可溶性糖含量、叶绿素a和b的比值及总叶绿素含量呈现上升的趋势;超氧化物歧化酶活性先升后降;丙二醛含量干旱胁迫前期升高,后期变化不明显;净光合速率、气孔导度和蒸腾速率随土壤含水量的减少逐步降低。气孔和可溶性糖含量都是影响黄连木光合速率的关键因子,干旱胁迫前12d光合速率主要受气孔限制,之后为非气孔限制。干旱胁迫前期渗透调节物质以可溶性糖为主,干旱胁迫较重时脯氨酸含量急剧升高,与可溶性糖同时起渗透调节作用。     

Influence of exogenously applied paclobutrazol on some physiological traits and growth of Stevia rebaudiana under in vitro drought stress

This investigation was carried on to find out the changes occurred in Stevia rebaudiana in response to paclobutrazol (PBZ; 0–4 mg L^?1) treatment and drought stress. Polyethylene glycol (PEG; 0–6 % w/v) was used to stimulate drought stress. Drought stress reduced fresh and dry weight, water content, chlorophylls, carotenoids, anthocyanins, water soluble carbohydrates, reducing sugar and proline amounts. Electrolyte leakage, MDA, α-tocopherol and glycine betaine contents increased in drought-stressed plants. The activity of P5CS and PDH enzymes and protein content showed no significant changes under drought stress. PBZ (with or without PEG) treatments decreased fresh and dry weight and water content. In PBZ-treated plants, less pigments was damaged by drought stress. PBZ treatment reduced the negative effect of drought stress on lipid peroxidation which resulted in lower electrolyte leakage and MDA content, compared to the same PEG level without PBZ. PBZ (with or without PEG) treatments increased glycine betaine, α-tocopherol, proline and protein contents. The amount of water soluble carbohydrates, reducing sugar and activity of P5CS and PDH were not affected by PBZ treatments. SDS-PAGE analysis revealed that drought stress increased a 25 kD protein with a critical function in plant development under stresses. According to the results, PEG provoked a severe drought stress in S. rebaudiana that could partly be restored by PBZ treatment.     

Expression profiling of rice cultivars differing in their tolerance to long-term drought stress

Understanding the molecular basis of plant performance under water-limiting conditions will help to breed crop plants with a lower water demand. We investigated the physiological and gene expression response of drought-tolerant (IR57311 and LC-93-4) and drought-sensitive (Nipponbare and Taipei 309) rice (Oryza sativa L.) cultivars to 18 days of drought stress in climate chamber experiments. Drought stressed plants grew significantly slower than the controls. Gene expression profiles were measured in leaf samples with the 20 K NSF oligonucleotide microarray. A linear model was fitted to the data to identify genes that were significantly regulated under drought stress. In all drought stressed cultivars, 245 genes were significantly repressed and 413 genes induced. Genes differing in their expression pattern under drought stress between tolerant and sensitive cultivars were identified by the genotype x environment (G x E) interaction term. More genes were significantly drought regulated in the sensitive than in the tolerant cultivars. Localizing all expressed genes on the rice genome map, we checked which genes with a significant G x E interaction co-localized with published quantitative trait loci regions for drought tolerance. These genes are more likely to be important for drought tolerance in an agricultural environment. To identify the metabolic processes with a significant G x E effect, we adapted the analysis software MapMan for rice. We found a drought stress induced shift toward senescence related degradation processes that was more pronounced in the sensitive than in the tolerant cultivars. In spite of higher growth rates and water use, more photosynthesis related genes were down-regulated in the tolerant than in the sensitive cultivars.