Effects of Relative Soil Water Content on Antioxidant Enzyme System in Malus sieversii(Lebed.) Roem

By pot experiment under artificially simulated water stress conditions, soluble protein content, MDA content and SOD, POD, CAT and APX activities in Malus sieversfi leaves were determined to reveal the response mechanism of M. sieversii to changes of relative soil water content. According to the results, with the decrease of relative soil water content, MDA content in M. sieversii leaves increased by mem- brane lipid peroxidation. Cells resist water stress-induced membrane lipid peroxidation and clear the increased reactive oxygen species by improving soluble protein content and SOD, POD, CAT and APX activities. However, various enzymes were involved in the response to water stress under different moisture conditions. In addition, the results indicated that M. sieversii had a good adaptability to higher relative soil water contents.

QTL Analysis for Relative Water Content in Rice

Drought tolerance is complex in rice. Under drought stress, leaf water content trait can be used as a indicator for variety evaluation. In this study, ahybrid F2 population was constructed with drought-tolerant indica rice cultivar Luhan No.1 and japonica rice cultivar Nipponbare, to analyze QTLs related with relative water content in rice. According to the results, two QTLs were detected between markers 4-27M and 4-23M and between markers 6-3M and RM276 on chromosomes 4 and 6, with the contribution rate of 4.81% -6.43% to phenotypic variation.

Effect of Nitrogen on Water Content, Sap Flow, and Tolerance of Rice Plants to Brown Planthopper, Nilaparvata lugens

Water content (WC) and sap flow from leaf sheath of rice plants with varying nitrogen levels at different growth stages, and fluctuations in relative water content (RWC) of rice plants being damaged by brown planthoppcr (BPH), Nilaparvata lugens were determined in the laboratory, and the tolerance of rice plants to BPH at different nitrogen regimes was evaluated in the greenhouse at International Rice Research Institute (IRRI), the Philippines. The results indicated that both WC and RWC were increased significantly, as the amount of sap flow from rice plants was reduced statistically, with the increase of nitrogen content in rice plants. RWC in rice plants applied with high nitrogen fertilizer decreased drastically by the injury of BPH nymphs, while the reduced survival duration of rice plants with the increase of nitrogen content was recorded. These may be considered to be one of the important factors in increasing the susceptibility to BPH damage on rice plants applied with nitrogen fertilizer.

Using attributes of electromagnetic waves to determine the water content and frost table in a permafrost area

The thawing-melting of the permafrost damages the subground of highways on the Qinghai-Tibet Plateau.With the application of ground-penetrating-radar(GPR)technology,the maximum permafrost melting interface can be effectively distinctly differentiated and imaged.A hierarchical feature of the permafrost region is shown clearly on the imaging profile of GPR data.The complete ablation zone or part of it is displayed distinctly.In addition,the details of subsurface layers can be effectively characterized by GPR attribute-analysis technology.With the attribute calculation and filter,the instantaneous amplitude,instantaneous frequency,and relative wave impedance can be applied in a more efficient way to divide the complete ablation zone,part of the ablation and non-ablation interface.The relative distribution of water content in a seasonally thawing permafrost region can be obtained through a comprehensive GPR attribute analysis.

Biomass and water partitioning in two age-related Caragana korshinskii plantations in desert steppe,northern China

Understanding of biomass and water allocation in plant populations will provide useful information on their growth pattern and resource allocation dynamics. By direct measurement, the biomass and water content partitioning were compared at the aboveground, belowground and whole-plant levels for artificial Caragana korshinskii populations between 6- and 25-year-old sites in desert steppe, northern China. The biomass was mainly allocated to third-srade branches at the aboveground level, and to firstand second-grade roots at the belowground level, and to aboveground parts at the whole-plant vegetative level. Those plant parts mentioned above became the major component of biomass pool of these shrub populations. Biomass pattern changed significantly at aboveground and/or whole-plant levels （P 〈0.05）, but not at belowground level （P 〉0.05） at 25-year-old site in comparison to 6-year-old site. Also, the water relations between dif- ferent plant parts changed considerably at all three levels from 6- to 25-year-old sites. These results imply that biomass pattern and relative water content of plant parts are correlated with the process of plantation development. The ratio of belowground to aboveground, though below 1, increased from 6- to 25-year-old site. These results suggest that these shrub populations can adjust biomass partition and relative water content of different compartments to alter their ecological adaptive strategies during stand development in desertified regions.

Leaf Water Status and Its Relationship with Reproductive Responses of Common Bean (<i>Phaseolus vulgaris</i>L.) Genotypes under Water Stress

Two tolerant (BB24 and BB43) and two susceptible (BARI busbean-2 and BB04) genotypes of common bean (Phaseolus vulgaris L.) were evaluated for their water status and its relationship with reproductive responses under continuous water stress (50% field capacity) and control (80% field capacity) conditions in a net house covered with polyethylene sheet at the Bangabandhu Sheikh Mujibur Rahman Agricultural University, Bangladesh. Under water stress condition, the susceptible genotype namely BB04 exhibited more negative leaf water potential (LWP) which was followed by that of BARI bushbean-2 in all the time of the day except at noon. The tolerant genotype namely BB24 exhibited less negative LWP at noon. The tolerant genotypes maintained higher relative water content (WRC) than the susceptible ones from dawn to dusk. The relationship between RWC and LWP was examined separately for four genotypes under water stress condition. The genotype BB24 showed a smaller decrease in RWC with more negative LWP than BB04. Water stress reduced pod setting ratio. The relationship between the leaf water status and reproductive responses showed that the genotype with a little reduction in mid-day drop of RWC or with high mid-day RWC displayed a high pod setting ratio.

Effects of Water Stress on Leaf Water and Chlorophyll Fluorescence Parameters of Sugarcane Seedling

[Objective] The aim was to explore the effects of water stress on leaf water and chlorophyll fluorescence parameters of sugarcane seedling,as well as to provide basis for the study on sugarcane production and evaluation. [Method] Seven different sugarcane varieties were studied at the seedling stage under drought stress,and the changes of leaf water and chlorophyll fluorescence parameters under stress conditions were detected. [Result] leaf water potential,leaf relative water content and soil relative water content showed a certain amount of internal relationship,the sugarcane varieties that had more tolerant to drought had higher utilization rate of soil water; the correlation analysis and factor analysis suggested that the survival rate at seedling stage under drought stress,Fv/Fm,leaf water potential and relative water content could be used as drought resistance evaluation indicators. [Conclusion] As a relatively independent influencing factor,water potential had dominating effect on drought resistance,and the reliability of Fv/Fm as drought resistance evaluation indicator had been verified.

Growth and Physiological Performance of Aerobic and Lowland Rice as Affected by Water Stress at Selected Growth Stages

Aerobic rice technology is still new in Malaysia, and information regarding MARDI Aerob 1(MA1), the first local aerobic rice variety, is still lacking. Therefore, comparative studies were carried out to determine the physiological performance of aerobic rice variety MA1 and lowland rice variety MR253 under water stress given at the panicle initiation, flowering and ripening stages. This experiment was arranged in a randomized complete block design. Stomatal conductance(g_s), chlorophyll a fluorescence(F_v/F_m), leaf relative water content(leaf RWC), and soil moisture content(SMC) as well as yield component parameters such as panicle number, grain yield and 100-grain weight were measured. Results revealed that gs and leaf RWC for both varieties decreased with depletion of SMC. The correlation study between the physiological parameters and SMC indicated that F_v/F_m was not affected by water stress, regardless of varieties. The yield components(panicle number, grain yield and 100-grain weight) for both varieties greatly decreased when water stress was imposed at the panicle initiation stage. This study showed that the panicle initiation period was the most sensitive stage to water stress that contributed to a substantial reduction in yield for both varieties. Under the aerobic condition(control), MR253 produced higher panicle number, 100-grain weight and yield than MA1. Although MR253 is bred for lowland, it is well adapted to aerobic condition.

Responses in gas exchange and water status between drought-tolerant and-susceptible soybean genotypes with ABA application

The purpose of this study was to investigate the physiological responses of drought-tolerant and drought-susceptible soybean genotypes to exogenous abscisic acid(ABA) application during progressive soil drying at seedling stages. Five-day old soybean seedlings were transplanted into PVC tubes filled with soil mixture. Seedlings were watered daily with similar water volumes until second trifoliate leaves emerged, and thereafter soil drying with or without exogenous ABA application was imposed. Half of the seedlings of each genotype were left for regular watering as control plants. Soil water status declined significantly over seven days of withholding water supply for both genotypes. Leaf expansion rate, stomatal conductance(g_s), leaf water potential(ψ_w), and relative water content of leaves(%RWC) declined significantly under soil drying as well as soil drying with ABA application, compared to their values for well-watered soybean genotypes. However, a drought-tolerant genotype(C12) responded more rapidly than a drought-susceptible genotype(C08) after imposition of soil drying and soil drying with exogenous ABA. In addition, application of exogenous ABA to water-restricted soybeans resulted in higher %RWC and ψwin the drought-tolerant than in the drought-susceptible genotype. Compared to the drought-susceptible genotype, the drought-tolerant genotype was more responsive to exogenous ABA application, resulting in a higher root-to-shoot ratio.

Potassium-Induced Regulation of Cellular Antioxidant Defense and Improvement of Physiological Processes in Wheat under Water Deficit Condition

Drought is the most common form of abiotic stress that reduces plant growth and productivity.It causes plant injuries through elevated production of reactive oxygen species(ROS).Potassium(K)is a vital plant nutrient that notably ameliorates the detrimental effect of drought stress in the plant.A pot experiment was conducted at the Laboratory of Plant Stress Responses,Faculty of Agriculture,Kagawa University,Japan,under controlled environment of green house to explore the role of K in mitigating drought severity in wheat(Triticum asevitum L.)seedlings.Three days after germination,seedlings were exposed to three water regimes viz.,100,50,and 20%field capacity(FC)for 21 days.Potassium was adjusted in Hoagland nutrient solution at 0,6 and 12 mM concentration and applied to pot instead of normal water.Results show that,water deficit stress notably reduced plant growth,biomass accumulation,leaf relative water content(RWC)along with reduced photosynthetic pigments.Increased amount of biochemical stress markers viz.,malondialdehyde(MDA),hydrogen peroxide(H_(2)O_(2)),methylglyoxal(MG),proline(Pro)as well as an impaired antioxidant defense system were observed in drought affected wheat plants.On the contrary,K supplementation resulted in improvement of biochemical and physiological parameters that worked behind in improving growth and development of the wheat plants.In addition,enzymes of ascorbateglutathione(AsA-GSH)cycle were also enhanced by supplemented K that accelerated the ROS detoxification process in plant.Although glyoxalse system did not performed well till MG was detoxified might following another short stepped pathways.Our results revealed that drought stressed plants showed better performances in terms of biochemical and physiological attributes,antioxidant defense and glyoxalase system,as well as ROS detoxification due to K supplementation with better performance at 12 mM K added in 50%FC growing condition.

Relationship Between Physiological-biochemical Changes Under Drought Stress and Drought Resistance in Ramie

A study on the physiological-biochemical changes of different ramie(Boehmeria Jacq. ) varieties under drought stress was carried out, the results showed that relative water contents(RWC) decreased and RPP increased with the increase of drought stress. Compared with drought sensitive varieties, drought resistant varieties had higher RWC in leaves but lower RPP. Peroxidase activity of drought-resistance varieties changed from low to high whereas sensitive ones changed in opposite direction. Proline contents of drought sensitive varieties was higher than those of drought resistant ones under a certain degree drought stress. Proline accumulation in drought resistant varieties was faster than that in drought sensitive ones under serious drought stress.MDA contents in leaf was increased under drought stress. MDA contents increased slowly in resistant varieties while that increased rapidly in sensitive ones.

Evaluation of Tomato Genetic Resources for Response to Water Deficit

Water deficit strongly affects plant yield and quality. However, plants can minimize drought injury by adaptation mechanisms that have evolved to escape harmful conditions. The response to water deprivation is a complex trait controlled by several genes. In order to gain a deeper understanding of drought response mechanisms in tomato, a collection of 27 genotypes was studied under different water deficit conditions. Since developmental stages might be differently influenced by drought, analyses were carried out on young plantlets during fruit setting. The only genotype that showed good performances both as water retention and fruit production was the ecotype Siccagno. All the genotypes were analyzed at molecular level with the aim of detecting structural polymorphisms in selected stress-responsive genes. In addition, the expression level of a number of these genes was measured in the genotypes more tolerant to water deficit. Many polymorphisms were detected in six stress-responsive genes, and some could imply significant modifications in the protein structure. Furthermore, the expression analysis by RT-qPCR of three stress-responsive genes allowed arguing that a higher level of expression of the gene erd15 might be related to the better response to water deficit exhibited by Siccagno. Similarly, the lower expression of eight genes in the same genotype analysed through a microarray experiment confirmed the involvement of these stress-related genes in the tomato response to drought. Further investigations are required for a better comprehension of the mechanisms underlying response to water deficit in tomato by exploiting the genetic resource identified as more tolerant. The use of new technologies able to globally analyze structural polymorphism and expression level of genes will succeed to identify crucial genes involved in stress response in the ecotype Siccagno grown under different water regimes.

Screening of tall fescue genotypes for relative water content and osmotic potential under drought stress

Background:Tall fescue(Festuca arundinacea Schreb.)is an important coolseason perennial grass.Its persistence and forage yield can be severely affected by drought stresses during the hot,dry summers of the southern USA.Methods:One thousand tall fescue genotypes were evaluated in the greenhouse for high relative water content(RWC)and low cell sap osmotic potential(OP).Fifty contrasting genotypes for the two traits were identified and used in further greenhouse and field studies.These genotypes were also screened with 30%PEG8000.Root and shoot characteristics were studied in 10 genotypes.Results:The genotypes differed for RWC(33.7%–97.3%,mean:79.7%)and had an almost fivefold difference in OP(−0.5 to−2.4 MPa,mean:−1.2 MPa).Significant variation(p<0.001)for the main effects of environment and genotypes was found for RWC and OP.Apart from the greenhouse trial,no correlation was found between RWC and OP,indicating that differences in RWC might have been due to factors other than osmotic adjustment.Genotypes with either long roots or high root weights,and high root/shoot ratios demonstrated high RWC and low OP.Conclusions:Genotypes with consistently high RWC and low OP were identified and used for the development of mapping populations and transcriptome studies.

干旱胁迫对小麦染色体代换系旗叶相对含水量和离体失水速率的影响

以中国春-Synthetic 6x小麦染色体代换系及其亲本为材料,对其旗叶相对含水量(RWC)、离体叶片失水速率(RWL)进行测定。结果表明,在干旱胁迫下,1A,2D和3D代换系叶片的相对含水量及其干旱/对照值显著或极显著高于中国春,3A,3B,4B,5B,6B,1D,2D和4D代换系叶片离体失水速率及其干旱/对照值显著或极显著低于中国春。由此表明,Synthetic 6x的1A,2D和3D染色体上可能存在干旱胁迫下调控相对含水量的基因,Synthetic 6x的3A,3B,4B,5B,6B,1D,2D和4D染色体上可能存在干旱胁迫下调控离体失水速率的基因。

辽西地区黄土的强度与本构特性

采用应变控制式三轴仪对取自辽宁西部地区阜新—朝阳段黄土的力学性质进行了试验,获得了黄土的应力-应变关系和抗剪强度的变化规律;采用人工制备不同含水率试样的方法,测试并分析了含水率对黄土本构和强度特征的影响。结果表明:(1)试样的应力-应变关系在不排水剪条件下呈强软化型,表现为脆性破坏;在固结不排水剪条件下随初始含水率的增加由弱软化型向硬化型转变;而在排水剪条件下低含水率时呈软化型,随含水率增加,呈弱硬化型和硬化型。(2)饱水后试样的抗剪强度有很显著的降低:cUU为13.7～363.3kPa时,φUU为18.6°～40.2°;而cUU为0.2～29.6kPa时,φCU则为4°～23.4°。(3)土的有效抗剪强度指标均随含水率增加呈非线性减小的关系,粘聚力与含水率呈半对数函数关系,内摩擦角则与含水率呈幂函数关系。给出了黄土本构的数学模型和黄土抗剪强度指标的取值方法。

膨胀土弹塑性本构关系数值建模方法研究

按照数值建模理论,建立了不同含水率条件下膨胀土的应力-应变关系。通过可视化绘出了在整个应力场(p,q)中的三维应力-应变关系曲面和屈服轨迹。经过对比可见含水率的变化对膨胀土本构关系的影响是明显的。未使用传统的塑性势理论,而是采用数值建模方法,既克服了寻找塑性势解析表达式的困难,又可以任意选择含水率等初始条件,从而使建立的本构数值模型能够真实地反映膨胀土的变形过程。

基于灰度关联分析的冬小麦叶片含水量高光谱估测

尝试应用灰色关联分析方法(GRA)分析典型的水分植被指数(WVI)和水分含量(LWC)间的关联度,然后选择对冬小麦叶片水含量敏感的指数,比较SRM-PLS(逐步回归-偏最小二乘)方法和PLS方法估算LWC的精度。首先,对冬小麦WVI与LWC进行灰色关联分析,筛选出对冬小麦LWC敏感的WVI;其次,利用筛选出的敏感WVI,分别用PLS-SRM方法和PLS两种方式估算冬小麦LWC;然后对两种方式进行比较,选择最高决定系数(R2)和最小均方根误差(RMSE)的LWC估算模型来估算冬小麦LWC。结果表明:在整个生育期用PLS和PLS-SRM方法估算LWC,R2和RMSE分别为0.605和0.575,4.75%和7.35%。研究表明:先使用GRA对WVI和LWC进行关联度分析,再用PLS或PLS-SRM方法可以提高冬小麦的LWC估算精度。

介质含水量与介电常数模型参数试验研究

介质含水量与介电常数之间的关系研究奠定了利用电磁波理论测定含水量的重要理论基础,探索一种快速、无损、精确地测量包气带中水分变化过程的方法,为利用地质雷达等技术快速、精确测定上覆风积沙地区包气带水分提供理论支持。以鄂尔多斯盆地风沙滩地区风积沙为试验介质,通过试验测定介质含水量与介电常数,结合试验结果对Topp模型、Roth模型、Herkelrath模型进行讨论,并确定模型中的参数。研究结果表明,Herkelrath模型和拟合多项式优于Topp模型和Roth模型,更适合于本地区。

不同水分条件下小麦生理性状与产量的灰色关联度分析

为了解干旱胁迫条件下小麦冠层温度、旗叶光合性状的变化特点及其对产量的影响,以小麦回交导入系(IL)群体[(鲁麦14×晋麦47)×鲁麦14]BC3F5代的160个株系及其亲本为材料,分析了雨养和灌溉条件下,开花期和灌浆期冠层温度、冠气温差、旗叶叶绿素含量和叶绿素荧光动力学参数等性状的相关性以及不同性状与产量的灰色关联度。结果表明,在两种水分条件下IL群体多数性状表现超双亲,性状变异系数为1.19%～48.30%,性状均值偏向轮回亲本鲁麦14;雨养条件下抗旱亲本晋麦47的冠层温度及叶绿素荧光动力学参数比水地品种鲁麦14表现稳定,IL群体的性状稳定性(D值)超过轮回亲本。两种水分条件下,荧光动力学参数之间相关性表现复杂,Fv与Fm、Fo/Fm与Fv/Fm之间相关性最高,相关系数大于0.991。灰色关联度分析结果表明,两个发育时期的Fv/Fm和灌浆期的冠层温度对产量的影响较大,可以作为选择抗旱高光效小麦的重要评价指标。

水分亏缺时氮磷营养对春小麦幼苗抗逆性的影响

在盆栽条件下研究了水分亏缺时 ,氮、磷营养对春小麦幼苗渗透物质及相关保护酶活性的影响 .结果表明 :水分胁迫使春小麦幼苗叶片游离脯氨酸、可溶性糖含量增加 ,RWC降低 ,POD、CAT活性增强 .随着水分亏缺加剧 ,氮营养相应地提高了幼苗叶片脯氨酸、可溶性糖含量以及POD、CAT活性 ;磷营养仅能提高叶片脯氨酸含量以及POD活性 ,但使其可溶性糖含量以及CAT活性维持在较低水平上 .施肥使叶片RWC降低 .春小麦的抗逆性指标之间存在相关性 ,特别是小麦幼苗叶片POD活性与游离脯氨酸累积量之间有极显著正相关关系 ,其决定系数r2 为 0 .74 72 .图 1表 2参