Eco-physiological response to water stress of drought-tolerant and drought-sensitive tomato genotypes

Water stress is an increasing environmental constraint affecting tomato growth and yield in Mediterranean areas. Solanum pennellii is a wild tomato species that exhibits a higher water use efficiency compared with cultivated S. lycopersicum. In particular, a cultivated line carrying a small S. pennellii region on chromosome 9 (IL 9-2-5) was identified as more tolerant to water deficit. In this work, the tolerant (IL 9-2-5) and the susceptible (M82) genotypes were subjected to three different water regimes: irrigation with 100% (V1), 50% (V2) and 25% (V3) field capacity. To evaluate the physiological response of IL 9-2-5 and M82 to water deficit, leaf functional traits, plant biomass production and maximal PSII photochemical efficiency were measured together with photosynthetic pigments and phenolic compounds. The higher tolerance to water deficiency of IL 9-2-5 was associated with the development of a better antioxidant system, especially in treatment V3. In addition, IL 9-2-5 had higher values of sclerophylly and leaf dry matter content thus confirming that the tolerance of IL 9-2-5 can be attributed to traits related to leaf morphology and physiology. In future, identification of polymorphisms in key-genes controlling these traits can guide breeding efforts aimed at improving susceptible genotypes.     

Physiological and biochemical adaptations in lentil genotypes under drought stress

Drought is a major restrictive factor for declining grain yield in lentil globally. Present investigation was conducted by taking microsperma (HUL-57) and macrosperma (IPL-406) genotypes of lentil (Lens culinaris Medik.) as information regarding physiological and biochemical basis of differences in drought resistance in macrosperma (bold-seeded) and microsperma (small-seeded) are not well understood. Pot grown plants were exposed to drought stress at specific phenophase viz. mid-vegetative, flower initiation and pod formation stage by withholding irrigation till the plants experienced one cycle of permanent wilting (PWP). Genotypes exhibited substantial differences for most of the measured traits under drought irrespective of the phenophase of stress imposed. Under drought HUL-57 had lower CMI, higher CSI, lower values of Δ¹³C, maintained higher SLN, accumulated more N and efficiently remobilized accumulated N to developing seeds. Higher chlorophyll content, increased accumulation of osmotically active solutes viz. soluble sugars and proline under drought stress was evident in HUL-57. Drought induced H₂O₂ accumulation and lipid peroxidation in both genotypes, but increments were of lesser magnitudes in HUL-57. Drought stress of pod formation stage followed by flower initiation stage was most damaging than the stress imposed at mid-vegetative stage in both genotypes. HUL-57 showed a better drought resistance capacity than IPL-406. Drought indices viz. DSI, STI and MP are proposed as criterion to identify and breed lentil genotypes for drought conditions.     

Morphological and physiological characterization of different genotypes of faba bean under heat stress

Heat stress (HS) is the major constraint to crop productivity worldwide. The objective of the present experiment was to select the tolerant and sensitive genotype(s) on the basis of morpho-physiological and biochemical characteristics of ten Vicia faba genotypes. These genotypes were as follows: Zafar 1, Zafar 2, Shebam 1, Makamora, Espan, Giza Blanka, Giza 3, C4, C5 and G853. The experimental work was undertaken to study the effects of different levels of temperature (control, mild, and modest) on plant height (PH) plant⁻¹, fresh weight (FW) and dry weight (DW) plant⁻¹, area leaf⁻¹, content of leaf relative water (RWC), proline content (Pro) and total chlorophyll (Total Chl), electrolyte leakage (EL), malondialdehyde level (MDA), hydrogen peroxide (H₂O₂), and activities of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) enzymes. HS significantly affected growth performance of all genotypes. However, the magnitude of reduction in genotypes ‘C5’ was relatively low, possibly due to its better antioxidant activities (CAT, POD and SOD), and accumulation of Pro and Total Chl, and leaf RWC. In the study, ‘C5’ was noted to be the most HS tolerant and ‘Espan’ most HS sensitive genotypes. It was concluded that the heat-tolerant genotypes may have better osmotic adjustment and protection from free radicals by increasing the accumulation of Pro content with increased activities of antioxidant enzyme.     

Comparative proteome analysis of drought-sensitive and drought-tolerant rapeseed roots and their hybrid F1 line under drought stress

Rapeseed (Brassica napus L.), which is the third leading source of vegetable oil, is sensitive to drought stress during the early vegetative growth stage. To investigate the initial response of rapeseed to drought stress, changes in the protein expression profiles of drought-sensitive (RGS-003) and drought-tolerant lines (SLM-003), and their F1 hybrid, were analyzed using a proteomics approach. Seven-day-old rapeseed seedlings were treated with drought stress by restricting water for 7 days, and proteins were extracted from roots and separated by two-dimensional polyacrylamide gel electrophoresis. In the sensitive rapeseed line, 35 protein spots were differentially expressed under drought stress, and proteins related to metabolism, energy, disease/defense, and transport were decreased. In the tolerant line, 32 protein spots were differentially expressed under drought stress, and proteins involved in metabolism, disease/defense, and transport were increased, while energy-related proteins were decreased. Six protein spots in F1 hybrid were common among expressed proteins in the drought-sensitive and -tolerant lines. Notably, tubulin beta-2 and heat shock protein 70 were decreased in the drought-sensitive line and hybrid F1 plants, while jasmonate-inducible protein and 20S proteasome subunit PAF1 were increased in the F1 hybrids and drought-tolerant line. These results indicate that (1) V-type H⁺ ATPase, plasma-membrane associated cation-binding protein, HSP 90, and elongation factor EF-2 have a role in the drought tolerance of rapeseed; (2) The decreased levels of heat shock protein 70 and tubulin beta-2 in the drought-sensitive and hybrid F1 lines might explain the reduced growth of these lines in drought conditions.     

Changes in chlorophyll fluorescence parameters and oxidative stress responses of bush bean genotypes for selecting contrasting acclimation strategies under water stress

Drought resistance of bean landraces was compared in order to select genotypes with either high morphological or high biochemical-physiological plasticity. The lines in the former group exhibited fast reduction in fresh and dry mass, decreased the water potential in primary leaves after irrigation withdrawal and the biomass mobilized from the senescent primary leaves was allocated into the roots. These genotypes had high frequency of primary leaf abscission under water stress. The genotypes with plasticity at the biochemical level maintained high water potential and photochemical efficiency, i.e. effective quantum yield, high photochemical (qP) and low non-photochemical (NPQ) quenching in primary leaves under drought stress. While superoxide dismutase activity was not influenced by the drought and the genotype, catalase activity increased significantly in the primary leaves of the genotypes with efficient biochemical adaptation. Lines with high morphological plasticity exhibited higher quaiacol peroxidase activity under drought. Proline may accumulate in both cases, thus it may be a symptom of protein degradation or a successful osmotic adaptation. On the basis of contrasting responses, the genetic material cannot be screened for a large-scale breeding program by a single physiological parameter but by a set of the methods presented in this work.     

Water relations of Capsicum genotypes under water stress

Pepper species and cultivars, Capsicum annuum cv. Bell Boy, C. annuum cv. Kulai and C. frutescens cv. Padi, differing in drought tolerance were investigated for their water relations, stomatal responses and abscisic acid (ABA) content during water stress. C. frutescens cv. Padi exhibited a greater osmotic adjustment than C. annuum cultivars. Stomatal conductance of cv. Bell Boy was more sensitive to water stress than that of cvs. Kulai and Padi. In all pepper genotypes, stomatal closure was triggered in the absence of a large decrease in leaf water status. ABA content in xylem sap and leaf was higher in C. annum cultivars compared to C. frutescens cv. Padi. This revised version was published online in July 2006 with corrections to the Cover Date.     

Physiological and biochemical alterations in Anabaena 7120 under iron stress

Various physiological and biochemical process like growth, NO3- -uptake, nitrate reductase, glutamine synthetase and ATPases (Mg2+ and Ca2+ dependent) in the cyanobacterium Anabaena 7120 were observed under iron stress. Growth was found to be maximum in 50 microM Fe3+ added cells however, 20 microM Fe3+ (the Fe3+ concentration generally used for routine culturing of cyanobacterial cell in Chu 10 medium) incubation resulted in lower growth. Fe3+ starvation on the other hand showed very poor growth up to 4th day but once the growth started it reached at significant level on 7th day. Higher Fe3+ concentration reflected reduced growth with lethality at 500 microM Fe3+. Chlorophyll a fluorescence under Fe3+ stress reflected almost the similar results as in case of growth. However, the pigment was found to be more sensitive as compared to protein under Fe3+ stress. Similar results have been observed in case of NO3-uptake with only 80% reduction in nutrient uptake in 500 microM Fe3+ incubated cells. Nitrate reductase activity was lower in Fe3+ starved cells as compared to significant enzyme activity in 20 and 50 microM Fe3+ incubated cells. Similar to nitrate reductase, glutamine synthetase also showed maximum level in 50 microM Fe3+ added cells, however, higher Fe3+ concentration (300-500 microM ) resulted in reduced enzymatic activity. Glutamine synthetase activity was less sensitivity as compared to nitrate reductase activity under Fe3+ stress. ATPase (Mg2+ and Ca2+ dependent) always showed higher level with increasing Fe3+ concentration.     

Photosynthetic parameters and leaf water potential of five common bean genotypes under mild water deficit

The leaf water potential, gas exchange and chlorophyll fluorescence were evaluated in five common bean (Phaseolus vulgaris) genotypes A222, A320, BAT477, Carioca and Ouro Negro subjected to moderate water deficit. At the maximum water deficit (10 d of water withholding), the leaf water potential of genotypes A320 and A222 was higher (−0.35 and −0.50 MPa) when compared to the other genotypes (−0.67 to −0.77 MPa). The stomatal conductance and net photosynthetic rate were significantly reduced in all genotypes due to the water deficit. The greater reduction in stomatal conductance of A320 under drought resulted in high intrinsic water use efficiency. Mild water deficit affected the photochemical apparatus in bean genotypes probably by down-regulation since plants did not show photoinhibition. The photochemical apparatus of A222 and A320 genotypes was more sensitive to drought stress, showing reduced apparent electron transport even after the recovery of plant water status. On the other hand, even after 10 d of water withholding, the maximum efficiency of photosystem 2 was not affected, what suggest efficiency of the photoprotection mechanisms.     

镉胁迫下红树植物木榄幼苗的生理生化特性

用含CdCl2的Hoagland营养液处理了沙培中的木榄(Bruguiera gymnorrhiza)幼苗.2个月后对幼苗丙二醛(MDA)、叶绿素含量、过氧化物酶(POD)、超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性及其同工酶进行分析.结果表明,镉引起幼苗膜质过氧化,导致总叶绿素含量显著下降.镉主要影响迁移率大的阴离子型POD同工酶的活性.1 mmol·L-1镉显著抑制根中2条CAT同工酶RC-1和RC-2的活性.木榄根CAT和叶POD同工酶分析可作为红树林镉污染的监测手段之一.     

Effect of drought stress on leaf optical properties in drought-resistant and drought-sensitive maize and triticale genotypes

The effect of a short (7 d), prolonged (14 d) soil drought (D) and (7 d) recovery (DR) on the leaf optical properties — reflectance (R), transmittance (T) and absorptance (A) in photosynthetically active radiation (PAR) and near infrared radiation (NIR) range of irradiation (750–1100 nm) was studied for maize and triticale genotypes differing in drought tolerance. The drought stress caused the changes in leaf optical properties parameters in comparison with non-drought plants. The observed harmful influence of drought was more visible for maize than triticale.     

Physiological and biochemical responses of Phoebe bournei seedlings to water stress and recovery

Phoebe bournei commonly called nanmu is an important and endemic wood species in China, and its planting, nursing, and preserving are often affected by drought stress. Two-year-old P. bournei seedlings were subjected to water stress and recovery treatment to study their physiological and biochemical responses. Physiological and biochemical indices did not change when seedlings were subjected to mild water stress (<15 days of water withholding). As drought stress intensified (>20 days of water withholding), malondialdehyde and electrolyte leakage increased, and chlorophyll and soluble protein decreased, indicating an increased oxidative stress induced by water deficit. Enhanced activities of superoxide dismutase (SOD) and peroxidase (POX), accumulation of free proline and total soluble sugar contribute to plant protection against the oxidative stress. However, SOD and POX decreased when seedlings were subjected to an extended drought. After 5 days of recovery, physiological and biochemical indices were not restored to the control level values except for leaf relative water content when the seedlings were subjected to more than 20 days water stress. These results demonstrate that P. bournei could enhance their ability to mitigate water stress effects by up-regulating antioxidant system and osmotic adjustment, but these two protective mechanisms were limited when seedlings were subjected to moderate and severe water stress. The threshold of water deficit to P. bournei seedlings is 15–20 days, and permanent damage will be induced if water status is not improved before this threshold. The results will provide some theoretical and practical guidance for nanmu afforestation and production.     

Salicylic acid induces physiological and biochemical changes in three Red bayberry (Myric rubra) genotypes under water stress

Water stress is one of the main environmental stresses that affect plant growth and development. Salicylic acid (SA) induces water stress tolerance in plants. In this study, the effect of exogenous SA on physiological and biochemical process in Red bayberry (Myric rubra) seedlings, of three different genotypes, that were grown under water stress (soil ranging from 20 to 50 % of field capacity) was evaluated. Results showed that water stress severely affected the relative water content (RWC), photosynthesis, stomatal conductance and enzymes activities. Genotypes differed in RWC, Chlorophyll content, gas exchange parameter, antioxidant enzymes activities and proline, and the genotype Biqi had the RWC, photosynthesis, stomatal conductance and enzymes activities greater than the other two genotypes Wangdao and Shenhong. SA treated plants showed, in general, a higher RWC, chlorophyll content, photosynthetic rate, stomatal conductance, superoxide dismutase activity and proline content, and a lower relative electrolyte conductivity, methane dicarboxylic aldehyde content and catalase activity compared to those of untreated seedlings. These results signified the role of SA in diminishing the negative effects of drought on Red bayberry plants and suggest that SA could be used as a potential growth regulator, for improving plant growth under water stress.     

Structural-functional state of thylakoid membranes of wheat genotypes under water stress

Plants were grown in field conditions in the wide area under normal water supply and severe water deficit. Two wheat (Triticum aestivum L.) genotypes contrasting by architectonics and differing in drought-resistance were used: Giymatli-2/17, short stature, with broad and drooping leaves, drought-sensitive, and Azamatli-95, short stature, with vertically oriented small leaves, drought-tolerant). It was found out that Giymatli-2/17 was characterized by relatively low content of Chl a-protein of PS I (CP I) and β-subunit of ATP-synthase complex, the high content of proteins in the 33-30.5 kDa region and LHC polypeptides (28-24.5 kDa), the intensive fluorescence at 740 nm and more high photochemical activity of PS II under normal irrigation compared with Azamatli-95. However, the content of CP I (M_r 115 kDa) and apoprotein of P700 with M_r 63 kDa insignificantly increases in the drought-resistant genotype Azamatli-95 under extreme water supply condition while their content decreases in drought-sensitive cv Giymatli-2/17. Intensity of synthesis α- and β-subunits of CF₁ (55 and 53.5 kDa) also decreases in Giymatli-2/17. The levels of the core antenna polypeptides of FS II with M_r 46 and 44.5 kDa (CP47 and CP43) remains stable both in normal, and stressful conditions. At the same time the significant reduction is observed in the content of polypeptides in the 33-30.5 kDa region in the more sensitive genotype Giymatli-2/17. There is an increase in the LHC II polypeptides level in tolerant genotype Azamatli-95 in contrast to Giymatli-2/17 (where the content of these subunits is observed decreasing). The intensity of short wavelength peaks at 687 and 695 nm sharply increases in the fluorescence spectra (77 K) of chloroplasts from sensitive genotype Giymatli-2/17 under water deficiency and there is a stimulation of the ratio of fluorescence band intensity F687/F740. After exposure to drought, cv Giymatli-2/17 shows a larger reduction in the actual PS II photochemical efficiency of chloroplasts than cv Azamatli-95.     

Structural-functional state of thylakoid membranes of wheat genotypes under water stress

Plants were grown in field conditions in the wide area under normal water supply and severe water deficit. Two wheat (Triticum aestivum L.) genotypes contrasting by architectonics and differing in drought-resistance were used: Giymatli-2/17, short stature, with broad and drooping leaves, drought-sensitive, and Azamatli-95, short stature, with vertically oriented small leaves, drought-tolerant). It was found out that Giymatli-2/17 was characterized by relatively low content of Chl a-protein of PS I (CP I) and beta-subunit of ATP-synthase complex, the high content of proteins in the 33-30.5 kDa region and LHC polypeptides (28-24.5 kDa), the intensive fluorescence at 740 nm and more high photochemical activity of PS II under normal irrigation compared with Azamatli-95. However, the content of CP I (M(r) 115 kDa) and apoprotein of P700 with M(r) 63 kDa insignificantly increases in the drought-resistant genotype Azamatli-95 under extreme water supply condition while their content decreases in drought-sensitive cv Giymatli-2/17. Intensity of synthesis alpha- and beta-subunits of CF(1) (55 and 53.5 kDa) also decreases in Giymatli-2/17. The levels of the core antenna polypeptides of FS II with M(r) 46 and 44.5 kDa (CP47 and CP43) remains stable both in normal, and stressful conditions. At the same time the significant reduction is observed in the content of polypeptides in the 33-30.5 kDa region in the more sensitive genotype Giymatli-2/17. There is an increase in the LHC II polypeptides level in tolerant genotype Azamatli-95 in contrast to Giymatli-2/17 (where the content of these subunits is observed decreasing). The intensity of short wavelength peaks at 687 and 695 nm sharply increases in the fluorescence spectra (77 K) of chloroplasts from sensitive genotype Giymatli-2/17 under water deficiency and there is a stimulation of the ratio of fluorescence band intensity F687/F740. After exposure to drought, cv Giymatli-2/17 shows a larger reduction in the actual PS II photochemical efficiency of chloroplasts than cv Azamatli-95.     

Physiological,biochemical, and metabolic responses of a Taxus baccata L. callus culture under drought stress

In Vitro Cellular & Developmental Biology - Plant - The metabolic stimulation induced by abiotic stress is an efficient strategy for the production of secondary metabolites in sterile and...     

Physiological performance of two contrasting rice varieties under water stress

Two rice varieties PR-115 and Super-7 were imposed to water stress and different physiological traits were monitored to evaluate the performance of these varieties under drought. Under water stress condition although the relative water content, osmotic potential, chlorophyll content, photosynthesis rate, carbon discrimination and biomass decreased in both the varieties however, the reduction was more pronounced in Super-7 variety. Oryzanol a trans-ester of ferulic acid functions as antioxidant and it increased along with total phenolic and anthocyanin content in both the varieties under drought stress. However, gallic acid, 4 hydroxy benzoic acid, syringic acid and chlorogenic acid showed differential pattern in both of the varieties under water limiting conditions. Under drought, grain yield was penalized by 17 and 54% in PR-115 and Super-7 varieties, respectively in comparison to watered plants. Super-7 variety showed pronounced electrolyte leakage and MDA enhancement under water stress condition. High non photochemical quenching and reduction in Y(NO) and Y(II) indicated balanced energy management in tolerant PR-115 variety. The studies showed that PR-115 is a drought tolerant variety while Super-7 is drought sensitive in nature.     

Differential accumulation of mRNAs in drought-tolerant and susceptible common bean cultivars in response to water deficit

The physiological response to drought was measured in two common bean varieties with contrastive susceptibility to drought stress. A subtractive cDNA library was constructed from the two cultivars, Phaseolus vulgaris'Pinto Villa' (tolerant) and 'Carioca' (susceptible). 18 cDNAs displayed protein-coding genes associated with drought, cold and oxidative stress, signal transduction, plant defense, chloroplast function and unknown function. A cDNA coding for an aquaporin (AQP) was selected for further analyses. The open reading frames (ORFs) of AQPs from 'Pinto Villa' and 'Carioca' were compared and despite their similarity, accumulated differentially in the plant organs, as demonstrated by Northern blot and in situ hybridization. A phylogenetic analysis of the deduced amino acid sequence with other AQPs suggested a tonoplast-located protein. Under drought conditions, the levels of AQP mRNA from the susceptible cultivar decreased to undetectable levels; by contrast, 'Pinto Villa' mRNA was present and restricted the phloem tissue. This would allow 'Pinto Villa' to maintain vascular tissue functions under drought stress.