不同西瓜基因型对干旱胁迫的生理响应及其抗旱性评价

以来源于不同地区的12个西瓜基因型为试材,采用盆栽控水的方式进行持续干旱处理,研究干旱胁迫对西瓜幼苗株高、根长、鲜质量及干物质积累等生长状况的影响,比较不同基因型材料对干旱胁迫的生理响应差异,同时依据旱害指数对其抗旱性进行直接评价,并采用隶属函数法进一步验证和综合评价.结果表明: 干旱处理下,12个西瓜基因型对干旱胁迫的耐受能力存在明显差异,各基因型开始出现旱害症状的时间和发生旱害的程度各不相同.干旱胁迫降低了西瓜幼苗的株高、地上、地下鲜质量和地上干物质积累量,普遍提高了根冠比,而对根长和地下干质量存在正向和负向两种不同的影响.干旱处理后,西瓜叶片的相对含水量和叶绿素含量均不同程度降低,丙二醛、过氧化氢和超氧阴离子含量增加,脯氨酸大量积累,而可溶性蛋白含量以及抗氧化酶活性则因基因型的不同而表现出不同的结果.分析认为,3个野生型材料M20、KY-3和Y-2为抗旱性强的西瓜种质,Y34、金美人和04-1-2为敏感种质,而其余基因型为中抗种质.     

Physiological and growth responses of two dogwoods to short-term drought stress and re-watering

Cornus florida and its cultivars have attracted many attentions by its colorful ornamental features. Suitable moisture condition is a major factor in the success of introduction. However, little is known about dogwoods drought adaptation to seasonal water deficit, and recovery potential from the following rainfall. In this paper, treatment of continuous drought lasted 19 days, followed by re-watering for 7 days was performed on 10-month-old seedlings of C. florida, comparing with native C. kousa. Meantime, well-watered seedlings of two species were regarded as controls. Soil relative water content (SRWC) in stressed seedlings of both dogwoods decreased significantly with drought stress prolonged, and recovered to the normal level after re-watering. As the response to drought stress, significant decline in internal carbon dioxide concentration (C_i), remarkable increment in intrinsic water use efficiency (WUE_i) in C. florida, significant increment in chlorophyll content in C. kousa, and notable decline in leaf relative water content (LRWC), maximum quantum efficiency of PSII photochemistry (F_v/F_m), photochemical quenching (qP), as well as significant increment in malondialdehyde (MDA) content, superoxide dismutase (SOD) activity, soluble sugar content (SSC) in both dogwoods were observed. However, most of physiological variables recovered to the level of control after re-watering. Furthermore, drought stress promoted root volume, root area, root biomass, whereas inhibited seedling height, basal diameter, aboveground biomass, resulting in increase of root/shoot ratio. Our findings indicate that, although C. florida has a weaker performance than C. kousa under drought stress, it can recover to the normal level after re-watering. These results suggest that C. florida and its cultivars possess drought adaptive potential for introducing to southern China.     

干旱胁迫和复水对浙江楠光合与根系生长的影响

为探索珍贵树种斑块化混交造林的可行性, 以浙江楠为研究对象, 通过干旱胁迫和复水试验, 分析其光合生理特征、根系生长和抗氧化系统的响应。结果表明, 对照条件下浙江楠的光合生理最优, 重度干旱严重影响浙江楠的生理进程, 具体表现为光合能力、光适应特征、瞬间气体交换参数和叶绿素荧光参数的显著下降, 其光合速率的下降是由气孔因素导致; 中度干旱条件下的浙江楠植株水分利用率最高, 重度干旱条件下的水分利用率与对照、中度干旱相比较, 分别下降了29.6%和46.4%; 中度干旱条件下根半径下降, 但SOD、POD和CAT未显著下降, CAT均值略有上升, 重度干旱条件下的3种保护酶均表现出显著下降, 抗氧化酶已不能有效清除掉活性氧物质。因此, 浙江楠具备一定的抗旱能力, 中度干旱并不影响浙江楠的正常生长, 在实际斑块化造林过程中, 可适度控制土壤含水量, 有利于在不同树种斑块化混交配置应用中提升浙江楠造林的成活率和保存率。     

Comparative physiological and proteomic analysis of cultivated and wild safflower response to drought stress and re-watering

Drought is one of the major environmental stress that adversely affect the growth and development of oil seed plant, safflower. There is a limited knowledge on proteomic responses to support physiological, biochemical changes in how safflowers can regulate growth and metabolism under drought conditions and followed by re-watering. The changes in morphological, physiological, biochemical and proteomics of safflower genotypes (Carthamus tinctorius L.; Remzibey-05 and Linas, tolerant and sensitive cultivars, respectively, and C. oxyacantha M. Bieb., wild type) after exposure to drought and followed by re-watering have been examined. Drought negatively affected the shoot weight, water content, chlorophyll fluorescence, and biochemical parameters, including photosynthetic pigment, proline, MDA, and H₂O₂ contents and antioxidant enzyme activities in all genotypes, while the re-watering period allowed Remzibey-05 to recover, and it even provided the wild type completely recovered (approximately 100%). A total of 72 protein spots were observed as differently accumulated under treatments. The identified proteins were mainly involved in photosynthesis and carbohydrate, protein, defense, and energy metabolisms. Protein accumulation related to these metabolisms in Remzibey-05 were decreased under drought, while increased following re-watering. However, sensitive cultivar, Linas, could not exhibit an effective performance under drought and recovery when compared with other safflower genotypes. Supplementary InformationThe online version contains supplementary material available at (10.1007/s12298-021-00934-2).     

花生幼苗对重复干旱胁迫的生理响应

防雨棚内设盆栽试验,设置对照(Control,75%田间持水量)、干旱胁迫(D,35%)、重复干旱胁迫(D_D,35%)3个处理,探讨花生幼苗对预干旱胁迫的适应和记忆响应,分析预干旱对缓解重复干旱胁迫危害的生理作用。结果表明,与干旱胁迫处理相比,重复干旱胁迫提高了叶片的相对含水量,减少脯氨酸的积累,降低MDA和O·_2~-含量;抗氧化酶SOD、CAT活性降低,其中POD活性降低最为明显,并在复水后恢复到与对照相同水平或低于对照。与正常水分的对照相比,干旱胁迫显著降低叶片光合速率(P_N)、最大光合势能(P_C)、最大光量子产量(Y_Q),但重复干旱处理在重复干旱胁迫时期和复水后P_N、P_C和Y_Q均高于干旱处理。预干旱胁迫导致光合和气孔导度滞后面积、滞后率(H_P和H_g)增加,经过预干旱胁迫后,重复干旱显著降低光合和气孔导度滞后面积和滞后率。预干旱胁迫提高植株在重复干旱胁迫下叶片含水量,减轻重复干旱对植株造成的生理伤害,在光合作用上提高对重复干旱的抵御能力,并在复水后快速恢复到正常水分条件下植株生长水平,减少干旱对植株的不利影响。因此,预干旱胁迫促使花生幼苗具备适应或可记忆初始胁迫的能力,重复干旱胁迫时表现更为迅速和强烈的生理防御和快速的生理恢复机制。     

The responses of Briza media and Koeleria macrantha to drought and re-watering

1. To test whether differences in response to drought can help to explain the differing distributions of Briza media and Koeleria macrantha , changes in their leaf growth and water relations during soil drying were measured. After droughting, plants were re-watered and recovery recorded.
2. Leaf growth of the two species showed a similar sensitivity to drought with respect to duration of soil drying and soil moisture content.
3. In both species tiller base relative water content (RWC) was maintained at similar levels to controls until soil moisture content had fallen to less than 9%. This may aid survival in habitats subject to periodic droughting by preventing damage to the meristems.
4. Briza media did not respond to re-watering. However, plants of K. macrantha re-grew after periods of over 20 days of drought, when tiller base RWCs had fallen as low as 13%. This ability to resurrect may explain the occurrence of K. macrantha in xeric calcicolous grasslands subject to episodes of severe droughting, from which B. media is absent.     

Differential responses of sorghum genotypes to drought stress revealed by physio-chemical and transcriptional analysis

Molecular Biology Reports - Sorghum is an essential food crop for millions of people in the semi-arid regions of the world, where its production is severely limited by drought stress. Drought in...     

Recovery responses of photosynthesis,transpiration, and stomatal conductance in kidney bean following drought stress

Photosynthesis, transpiration, stomatal conductance and chlorophyll fluorescence characteristics were examined in kidney bean plants, with developing gradually water stress for several days after watering and then permitted to recover by re-watering. The photosynthetic rate, transpiration rate, and stomatal conductance decreased rapidly by withholding water for 2 days. The F_v/F_m of chlorophyll fluorescence characteristics slightly decreased when the water was withheld for 7 days. After re-watering the rate of recovery of photosynthesis, transpiration, and stomatal conductance decreased gradually as the days without watering became longer. The differences existed in rates of recovery of photosynthesis, transpiration, and stomatal conductance following drought stress. Among the fractional recoveries the highest was photosynthesis, and the lowest was stomatal conductance. Photosynthesis rate following drought stress was rapidly recovered until 2 days after re-watering, then recovered slowly. The critical time for the recovery of photosynthesis was recognized. The results show clearly a close correlation between the leaf water potential and the recovery level and speed of photosynthesis, transpiration, and stomatal conductance.     

Morpho-physiological responses of sugar beet (Beta vulgaris L.) genotypes to drought stress

The identification of morpho-physiological traits related to drought tolerance and high yield potential is a challenge when selecting sugar beet genotypes with greater tolerance to water stress. In this paper, root morphological parameters, antioxidant systems, leaf relative water content (RWC) and H⁺-ATPase activity as key morpho-physiological traits involved in drought tolerance/susceptibility of sugar beet were studied. Genotypes showing a different drought tolerance index (DTI) but a similar yield potential, under moderate (?0.6 Mpa) and severe (?1.2 MPa) water stress, were selected and their morpho-physiological traits were investigated. The results showed a wide genetic variation in morpho-physiological parameters which demonstrated the different adaptive strategies under moderate and severe drought conditions in sugar beet. In particular, an efficient antioxidant system and redox signalling made some sugar beet genotypes more tolerant to drought stress. The alternative strategy of other genotypes was the reduction of root tissue density, which produced a less dense root system improving the axial hydraulic conductivity. These results could be considered as interesting challenge for a better understanding of the drought tolerance mechanisms in sugar beet.     

Growth,stress, and acclimation responses to fluctuating temperatures in field and domesticated populations of Manduca sexta

Diurnal fluctuations in temperature are ubiquitous in terrestrial environments, and insects and other ectotherms have evolved to tolerate or acclimate to such fluctuations. Few studies have examined whether ectotherms acclimate to diurnal temperature fluctuations, or how natural and domesticated populations differ in their responses to diurnal fluctuations. We examine how diurnally fluctuating temperatures during development affect growth, acclimation, and stress responses for two populations of Manduca sexta: a field population that typically experiences wide variation in mean and fluctuations in temperature, and a laboratory population that has been domesticated in nearly constant temperatures for more than 300 generations. Laboratory experiments showed that diurnal fluctuations throughout larval development reduced pupal mass for the laboratory but not the field population. The differing effects of diurnal fluctuations were greatest at higher mean temperature (30°C): Here diurnal fluctuations reduced pupal mass and increased pupal development time for the laboratory population, but had little effect for the field population. We also evaluated how mean and fluctuations in temperature during early larval development affected growth rate during the final larval instar as a function of test temperature. At an intermediate (25°C) mean temperature, both the laboratory and field population showed a positive acclimation response to diurnal fluctuations, in which subsequent growth rate was significantly higher at most test temperatures. In contrast at higher mean temperature (30°C), diurnal fluctuations significantly reduced subsequent growth rate at most test temperatures for the laboratory population, but not for the field population. These results suggest that during domestication in constant temperatures, the laboratory population has lost the capacity to tolerate or acclimate to high and fluctuating temperatures. Population differences in acclimation capacity in response to temperature fluctuations have not been previously demonstrated, but they may be important for understanding the evolution of reaction norms and performance curves.     

Establishment of a transgenic hairy root system in wild and domesticated watermelon (Citrullus lanatus) for studying root vigor under drought

Root vigor is an important trait for the growth of terrestrial plants, especially in water-deficit environments. Although deserts plants are known for their highly developed root architecture, the molecular mechanism responsible for this trait has not been determined. Here we established an efficient protocol for the genetic manipulation of two varieties of watermelon plants: a desert-grown wild watermelon that shows vigorous root growth under drought, and a domesticated cultivar showing retardation of root growth under drought stress. Agrobacterium rhizogenes-mediated transgenic hairy roots were efficiently induced and selected from the hypocotyls of these plants. Transgenic GUS expression was detected in the roots by RT-PCR and histochemical GUS staining. Moreover, a liquid culture system for evaluating their root growth was also established. Interestingly, growth of the hairy roots derived from domesticated variety of watermelon strongly inhibited under high osmotic condition, whereas the hairy roots derived from wild variety of watermelon retained substantial growth rates under the stress condition. The new protocol presented here offers a powerful tool for the comparative study of the molecular mechanism underlying drought-induced root growth in desert plants.     

Physiological responses of different olive genotypes to drought conditions

Gas exchange rates, chlorophyll fluorescence, pressure–volume relationships, photosynthetic pigments, total soluble sugars, starch, soluble proteins and proline concentrations were investigated in five Olea europaea L. cultivars with different geographical origins (Arbequina, Blanqueta, Cobran?osa, Manzanilla and Negrinha) grown under Mediterranean field conditions. We found considerable genotypic differences among the cultivars. Comparing the diurnal gas exchange rates, we observed that Cobran?osa, Manzanilla and Negrinha had high photosynthetic rate than Arbequina and Blanqueta. The first group reveals to be better acclimated to drought conditions, and appears to employ a prodigal water-use strategy, whereas Blanqueta and Arbequina, with high water-use efficiency, appear to employ a conservative water-use strategy. The degree of midday depression in photosynthesis was genotype dependent, with a maximum in Arbequina and a minimum in Negrinha. The reductions in the photosynthetic rate were dependent from both stomatal and non-stomatal limitations. Elastic adjustment plays an important role as drought tolerance mechanism. The group of cultivars that employ a prodigal water-use strategy revealed high tissue elasticity, whereas Arbequina and Blanqueta revealed high tissue rigidity. We also identified the existence of drought tolerance mechanisms associated with soluble proteins accumulation in the foliage. The high levels of soluble proteins in Arbequina may represent an increased activity of oxidative stress defence enzymes and may also represent a reserve for post stress recovery. In all cultivars, especially in Manzanilla, free proline was accumulated in the foliage. The discussed aspects of drought stress metabolism may have an adaptative meaning, supporting the hypothesis that olive cultivars native to dry regions, such as Cobran?osa, Manzanilla and Negrinha, have more capability to acclimate to drought conditions than cultivars originated in regions with a more temperate climate, like Arbequina and Blanqueta.     

Responses of wild watermelon to drought stress: accumulation of an ArgE homologue and citrulline in leaves during water deficits

Wild watermelon from the Botswana desert had an ability to survive under severe drought conditions by maintaining its water status (water content and water potential). In the analysis by two-dimensional electrophoresis of leaf proteins, seven spots were newly induced after watering stopped. One with the molecular mass of 40 kilodaltons of the spots was accumulated abundantly. The cDNA encoding for the protein was cloned based on its amino-terminal sequence and the amino acid sequence deduced from the determined nucleotide sequences of the cDNA exhibited homology to the enzymes belong to the ArgE/DapE/Acy1/Cpg2/YscS protein family (including acetylornithine deacetylase, carboxypeptidase and aminoacylase-1). This suggests that the protein is involved in the release of free amino acid by hydrolyzing a peptidic bond. As the drought stress progressed, citrulline became one of the major components in the total free amino acids. Eight days after withholding watering, although the lower leaves wilted significantly, the upper leaves still maintained their water status and the content of citrulline reached about 50% in the total free amino acids. The accumulation of citrulline during the drought stress in wild watermelon is an unique phenomenon in C3-plants. These results suggest that the drought tolerance of wild watermelon is related to (1) the maintenance of the water status and (2) a metabolic change to accumulate citrulline.     

Physiological responses to drought stress in wild relatives of wheat: implications for wheat improvement

Wild progenitors of common wheat are a potential source of tolerance to biotic and abiotic stresses. We conducted a glasshouse pot experiment to study genotypic differences in response to drought stress in a collection of 180 accessions of Aegilops and Triticum along with one tolerant and one sensitive control variety. Several physiological traits and chlorophyll fluorescence parameters were evaluated. Our findings indicated that drought significantly reduced shoot fresh (59.45%) and dry (50.83%) weights, stomatal conductance (41.52%) and maximum photosynthetic capacity (41.06%), but increased initial fluorescence (28.10%). Drought stress also decreased the chlorophyll content, relative water content and maximum quantum efficiency by 14.90, 12.13 and 11.42%, respectively. Principal component analysis of the 182 individuals identified three components that explained 57.61 and 61.68% of the total variation in physiological and photosynthetic traits under control and stress conditions, respectively. When grouped into the 12 species tested, the three top components explained 78.22% of the total variation under drought. The means comparison, stress tolerance index and biplot analysis identified five accessions with superior tolerance to drought. Remarkably, four species of wild relatives—Ae. cylindrica (DC genome), Ae. crassa (DM genome), Ae. caudata (C genome) and T. urartu (A^u genome)—responded well to drought stress with a lower percentage decline for most traits and high values for the first two components. The potential of these species offers further opportunities for analysis at the molecular and cellular levels to confront with drought stress through a physiological mechanism.     

Drought stimulation by hypocotyl exposure altered physiological responses to subsequent drought stress in peanut seedlings

Drought stress occurring at the seedling stage of peanut (Arachis hypogaea L.) plants is a limiting factor resulting in considerable reductions in production. Plants can improve their resistance to subsequent stresses after experiencing an initial stress. The aim of this study was to explore the possible role of drought priming by hypocotyl exposure in alleviating subsequent severe drought stress in peanut. Hypocotyl exposure in peanut seedlings as a drought stimulus induced xerophytophysiological regulation, shown by induced osmotic adjustment, activated antioxidant enzymes, anthocyanin accumulation, up-regulation of Gdi-15 and fewer amyloplasts. The seedlings primed by hypocotyl exposure showed improved leaf water retention and reduced proline content when exposed to subsequent drought stress. The alleviated oxidative damage and lower antioxidant enzyme activities indicated rapid acclimation following past hypocotyl exposure and further defenses against subsequent drought stress by retaining ‘memories’ to enable more rapid or stronger physiological responses. The improved leaf photosynthesis and low photosynthetic hysteresis as drought ended indicated a positive effect of drought priming in peanut seedlings. The peanut seedlings ‘remembered’ the xerophytophysiological responses caused by the prior drought stimulation from hypocotyl exposure and displayed quicker and more potent physiological responses to following drought stress. The results showed that hypocotyl exposure could help peanut seedlings survive the severe environments that occurred in the later growth stages.     

Differential inhibition of photosynthesis during pre-flowering drought stress in Sorghum bicolor genotypes with different senescence traits

Young (16-day-old) Sorghum bicolor plants of a late- and slow-senescing Texas A&M line (B 35) and of an early- and fast-senescing descendant of an Ethiopian landrace (E 36-1) were subjected to drought stress by decreasing the soil water content to 30% field capacity over 6 days. Plant water potentials decreased from − 2 bar (controls) to − 10 to − 18 bar, and this drought stress resulted in: (1) differential phenotypic reactions and (2) differential decreases in photosynthesis rates in the two cultivars. While E 36-1 tended to lose viable leaf area from the leaf tips downwards, B 35 showed a gradual overall drying of the leaf. At the same time, photosynthesis rates decreased from 31.5 ± 1.6 to 12.3 ± 5.0 µmol CO₂ m⁻² s⁻¹ (E 36-1) and from 30.5 ± 1.6 to 3.3 ± 2.6 µmol CO₂ m⁻² s⁻¹ (B 35), respectively. In vitro enzyme activities of phosphoenolpyruvate carboxylase (PEPCase), malate dehydrogenase (MDH) and malic enzyme (ME) on a leaf area basis exceeded the photosynthesis rates. Pyruvate phosphate dikinase (PPDK) activity was close to the photosynthesis rates in control plants and higher than the photosynthesis rates in drought-stressed plants. Thus, none of the enzymes appeared to limit photosynthesis under drought stress, and likely bottleneck enzyme activities of the C3 pathway in the bundle-sheath cells, i.e. ribulose-1,5-bisphosphate carboxylase (RubisCO) and stromal fructose-1,5-bisphosphatase (sFBPase), also showed sufficient activities to sustain higher photosynthesis rates than those observed in the stressed plants. However, under drought stress, total leaf malate concentrations were higher in B 35 (up to 33.1 µmol g⁻¹ FW) than in E 36-1 (up to 22.4 µmol g⁻¹ FW). In particular, at the presumed cytosolic pH of 7.0–7.3, S. bicolor PEPCase was strongly inhibited by malate. In contrast with the in vitro PEPCase enzyme activities, the A/C_i curves suggested a stronger decrease in the in vivo activity of the enzyme in B 35 under drought stress than in E 36-1. It is therefore suggested that photosynthesis under drought stress may be inhibited differentially through feedback malate inhibition of PEPCase in S. bicolor.     

The genetics of adaptive responses to drought stress: abscisic acid-dependent and abscisic acid-independent signalling components

Drought stress is the major limitation to crop productivity. However, crops are genetically complex with many loci contributing quantitatively to a given physiological trait. Nonetheless, significant in-roads into the molecular mechanisms of drought-adaptive responses have been made from the use of Arabidopsis thaliana . In this special review, we will discuss results gleaned from reverse and forward genetic studies that revealed the involvement of both ABA-dependent and ABA-independent components. In particular, mutant analyses have highlighted the surprising prevalence of RNA metabolism in many key steps. We will also discuss our recent use of infrared thermography to visualize stomatal closure in response to dehydration as a means to identify novel regulatory genes. This has allowed us to recover mutations belonging to at least eight complementation groups. Analysis of six of these loci revealed that all of their corresponding mutations affect either abscisic acid (ABA) biosynthesis or perception. Hence, in contrast to molecular studies on gene networks which pointed to the clear existence of multiple ABA-independent pathways in the control of dehydration tolerance, our results reinforce ABA-based signalling pathways as the predominant factor in primary or rapid responses. Finally, we will provide some details learned from the molecular analysis of OPEN STOMATA1 ( OST1 ), a gene that encodes an ABA-activated kinase issued from this targeted genetic approach.     

Growth, photosynthesis, active oxygen species and antioxidants responses of paddy field cyanobacterium Plectonema boryanum to endosulfan stress

The present paper deals with the insecticide endosulfan (5, 10 and 20 microg/ml)-induced changes in physiological and biochemical parameters related to photosynthesis and defense systems in paddy field cyanobacterium Plectonema boryanum grown under laboratory conditions. Growth and photosynthetic pigments, i.e., chlorophyll a, carotenoids and phycocyanin, were adversely affected by endosulfan treatment and the inhibition was found to be dose dependent. The toxic effect of endosulfan was more pronounced on phycocyanin; however, a considerable reduction in chlorophyll a and carotenoids was also noticed. 14C-fixation appeared to be more sensitive to insecticide than whole cell oxygen evolution. Spheroplasts treated with endosulfan exhibited a severe effect on PSII activity which was mainly due to blocking of the electron flow at the water oxidation side. In contrast to this, similar doses of endosulfan caused the least effect on PSI activity (DCPIP/ASC-->MV). Furthermore, endosulfan with increasing doses accelerated the formation of active oxygen species, i.e., O2- and H2O2, in cells progressively, whereby an enhanced peroxidation of lipid and leakage of cell membrane were noticed. As a consequence of active oxygen species (AOS) generation in endosulfan-treated cells, the activity of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) was enhanced considerably. Besides the accelerated action of enzymatic defense systems, chemical antioxidant ascorbate showed a decreasing trend with the rising concentration of endosulfan (5, 10 and 20 microg/ml).