Barley yield in water-stress conditions.: The influence of precocity,osmotic adjustment and stomatal conductance

The behavior of eight cultivated barley (Hordeum vulgare L.) genotypes consisting of three breeding lines and five cultivars varieties was studied in a rain shelter to determine the influence of osmotic adjustment and stomatal conductance on drought tolerance and yield under terminal water stress. When the crop reached the flag leaf stage, half of the experimental plots were submitted to a water-stress treatment and the remainder maintained in optimal water conditions. Variation was observed in osmotic adjustment (OA) and stomatal conductance among the genotypes under stress. Two of the breeding lines exhibited the highest OA capacity. These lines also showed the least differences in stomatal conductance and maintained the highest stomatal conductance as water stress increased. Correlations between yield and OA and conductance in the water-stress treatment were positive and significant. In the irrigated control the correlation coefficients were smaller. Osmotic adjustment and stomatal conductance were linearly related, indicating that OA favors higher conductance when there is water stress. Under conditions of terminal drought yield was negatively correlated with time to ear emergence and maturity. Earliness to flower and OA contributed to greater yields under terminal water stress.     

Tuber age as a contributory factor in the water relations of potato (solanum tuberosum L.)

Seed tuber age effects on the response of potato plants (cv Alpha) to different drought stress regimes during the pre-tuberization period were evaluated. During a slow drying cycle of approximately 2 weeks’ duration, young expanding leaves on plants grown from young or old seed tubers showed no evidence of osmotic adjustment and pre-stressing the plants did not affect this situation. Pre-stressed plants from young and old tubers possessed a higher relative water content at a zero turgor potential than unstressed plants. However, tuber age did not affect significantly the relative water content at zero turgor potential. Plants derived from young seed tubers exhibited improved drought resistance such as reduced water loss from mature leaves, a larger root/shoot dry weight ratio and possible effects on root distribution in soil.     

Divergent selection for osmotic adjustment results in improved drought tolerance in maize (Zea mays L.) in both early growth and flowering phases

The value of the capacity for osmotic adjustment (OA) as a trait, which can contribute effectively to yield maintenance under drought, has not yet been established for maize (Zea mays L.) using cultivars of similar genetic background. Here we report results obtained using crops of two S4 populations derived from a cross between inbred lines exhibiting the highest and lowest capacities for osmotic adjustment in a screening applied to 20 inbred lines. The mean values of OA for the two S4 populations were 0.47 MPa for the high OA population (HOA) and 0.06 MPa for the low (LOA). Crops of these populations were grown under a rain-out shelter and subjected to 30-day droughts either before or during flowering. In both experiments, exposure to drought evoked a significant (p < 0.05) decrease in osmotic potential measured at full turgor in the HOA population, no change was found in the LOA population. This induced response became evident in plants of the HOA population in measurements effected 16–18 days after suspension of irrigation. Irrespective of the timing of drought, the HOA crops extracted significantly more water from deeper in the soil profile during the stress period, exhibited higher leaf area duration and attained greater grain yields and, in the crop droughted at flowering, greater harvest index than the LOA crops. The components of yield and their determinants (i.e., floret number per ear, grain set, grain number and weight per grain) exhibited differential responses with timing of the drought and in response to level of OA. Under irrigation, there were no differences between populations in either experiment in terms of yield and its components, or in harvest index, leaf area duration, or soil water extraction. We conclude that OA can contribute to drought tolerance in maize crops exposed to water deficit both before and during flowering, and that the trait carries no yield penalty under irrigation.     

Studies on Mechanisms of Dehydration Postponement in Cassava Leaves under Short-term Soil Water Deficits

Abstract

Cassava (Manihot esculenta Crantz) can produce a high crop yield even in an environment with irregular rains. This is mainly attributed to its abilities to maintain leaf area under drought conditions and rapidly regrow after rain. In this study, we investigated the mechanism of leaf maintenance under water deficits through measurement of photosynthetic rate and water potential changes in leaves. The cassava plants were grown in pots and exposed to water deficits, and the diurnal changes in water potentials, rates of photosynthesis and transpiration and stomatal conductance were measured. The relationship between leaf water potential (ψW) and photosynthetic rate with decreasing soil water, and osmotic adjustment were also investigated. With respect to water supply in leaves, the movement of water in plants was measured using stem heat balance. Under water deficits, photosynthesis occurred only in the early morning. The water loss was reduced by stomatal closure in the mid-day. This was attributed to the complete closure of the stornata during the decrease in ψW to a range between –1.0 and –1.4 MPa. Furthermore, the firm stomatal closure is caused by the consistency of osmotic potential under decreases in soil water, i.e., to a lack of osmotic adjustment. Water stored in the pith parenchyma of stem flowed into leaves in the morning. From these results, we conclude that cassava can consistently maintain an adequate water level in leaves via water storage and the sensitivity of stornata to water deficits, thereby avoiding leaf dehydration.     

抽穗期干旱复水对不同产量早稻品种结实及一些生理指标的影响

 为了探明生育后期干旱复水对双季早稻产量补偿效应及其生理机制,选择淦鑫203和淦鑫206为材料,于抽穗期干旱7 d,然后复水处理,分析了其结实和产量、剑叶渗透调节物质、丙二醛（MDA）和内源激素含量及保护酶活性等。结果表明,干旱复水处理后供试品种的结实率、千粒重及单株产量均表现出不同程度下降,其中,结实率和单株产量降幅均达显著水平;抽穗期干旱7 d复水不存在产量补偿效应;两个品种剑叶可溶性糖（SS）、游离脯氨酸（Pro）、MDA含量以及超氧化物歧化酶（SOD）和过氧化氢酶（CAT）活性均表现为干旱处理显著高于CK,以复水0 d后相差最大,复水后上述指标均明显下降,但处理与CK之间至复水12 d后仍然存在一定差距;总体上,淹水条件下抽穗期两个品种剑叶IAA、GA3含量随生育进程呈现上升趋势,而ABA、ZR含量呈现下降趋势;干旱复水处理下两个品种剑叶ABA、IAA及ZR含量呈持续上升趋势,GA3含量则表现出先降后升趋势。抽穗期干旱处理将启动稻株体内抗衰老机制,复水后将在一定程度上激活稻株体内生长促进因子并抑制生长抑制因子,但其效果十分有限,且与品种产量相关不显著。     

Evaluation of physiological traits as indirect selection criteria for drought tolerance in sugar beet

Drought is the most important limitation to sugar beet (Beta vulgaris L.) production in the UK and other areas dependent on usually insufficient summer rainfall. As increased irrigation is not a viable answer to the problem, an economically and environmentally desirable solution is new varieties with decreased sensitivity to water deficits. However, there is little genotypic information on drought tolerance in sugar beet, and breeders are not equipped to make these selections. The objectives of this study were to assess the degree of genotypic diversity for drought-related morpho-physiological traits and to measure the strength of association between these traits and indicators of crop performance. 46 sugar beet genotypes with diverse genetic backgrounds were tested in three field experiments from 1999 to 2001. Drought was imposed by covering plots with large polythene tunnels, allowing the crop to grow solely on stored soil moisture. Agronomic characters and drought tolerance indices are described in a companion paper [Ober et al., Assessing the genetic resources to improve drought tolerance in sugar beet. Agronomic traits of diverse genotypes under droughted and irrigated conditions. Field Crops Res., in press]. In this report, we show that there were significant genotypic differences for stomatal conductance, succulence index, specific leaf weight, and osmotic adjustment, but not for photosynthetic rate, relative water content or total water use. Patterns of water use within the soil profile differed between genotypes; some extracted more water from deep soil layers. The maintenance of green foliage cover during drought was positively correlated with drought tolerance index, which was negatively correlated with succulence index and scores for wilting and leaf senescence. Droughted sugar yield was positively correlated with soil water extraction and negatively correlated with relative leaf expansion rate measured in late summer. Under irrigated conditions, there was high positive correlation between transpiration rate and sugar yield. Genotype × trait biplots showed superior genotypes with relatively greater expression of combinations of favourable traits. The results suggest that succulence index and wilting score could be used to cull inferior plants in early stages of breeding programs, and green foliage cover and patterns of water use could help identify superior genotypes in elite germplasm. These data should enable tools to be developed for indirect selection of genotypes suited to drought-prone environments.     

干旱胁迫对不同肥水类型小麦旗叶光合特性及产量的影响

为给小麦抗旱育种和节水高产栽培提供理论和技术支持,在防雨旱棚池栽条件下研究了干旱胁迫对6个不同肥水类型小麦品种旗叶光合特性和产量的影响。结果表明,干旱胁迫条件下,小麦开花后旗叶的净光合速率、气孔导度、蒸腾速率、气孔限制值和单叶水分利用效率均呈下降趋势,而胞间CO₂浓度有所升高。其中,水浇地品种烟农21、烟农24和济麦22净光合速率、气孔导度、蒸腾速率、气孔限制值和单叶水分利用效率较低且下降幅度大,而旱地品种青麦6号、济旱5034和鲁麦21的净光合速率、气孔导度、蒸腾速率、气孔限制值和单叶水分利用效率较高且下降较为缓慢,而胞间CO₂浓度较低。青麦6号具有较高的抗旱指数,在干旱胁迫条件下能够保持较好的叶片结构和功能状况,是其获得高产的重要原因。     

水分胁迫对春小麦光合和渗透调节物质的影响

为进一步了解春小麦的抗旱生理机制,以春小麦品种陇春26号为材料,采用盆栽法研究了中度和重度水分胁迫下春小麦旗叶光合参数和渗透调节物质含量的变化.结果表明,随土壤水分的减少,春小麦旗叶的叶绿素含量、光合速率、气孔导度、胞间CO2浓度、蒸腾速率逐渐降低,可溶性糖和可溶性蛋白含量及酸性转化酶活性呈先增后减趋势,脯氨酸和丙二醛含量及过氧化物酶活性逐渐增强.中度水分胁迫的可溶性糖含量和酸性转化酶活性显著高于重度水分胁迫和正常供水对照;重度水分胁迫的可溶性蛋白含量显著低于中度水分胁迫和正常供水对照,而脯氨酸和丙二醛含量显著高于中度水分胁迫和正常供水对照.说明中度或重度干旱胁迫下春小麦旗叶光合速率降低是叶绿素含量降低和光合原料缺乏所致,脯氨酸含量和过氧化物酶活性升高有助于春小麦抵御干旱胁迫.     

灌水对不同小麦品种旗叶渗透调节、光合速率及产量的影响

为了解灌水对不同小麦品种旗叶水分生理特性和产量的影响,于2009-2010年度在田间栽培条件下,以2个小麦品种济麦22和洲元9369为材料,采用测墒补灌的方法研究了不灌水(W0)、拔节期0～140cm土层土壤相对含水量补灌至75%+开花期补灌至70%(W1)、拔节后8d补灌至75%+开花后8d补灌至70%(W2)、拔节后8d补灌至75%+开花后8d补灌至75%(W3)4个不同灌水处理下小麦旗叶渗透调节、光合速率和籽粒产量的差异。结果表明:(1)W3处理的小麦旗叶相对含水量、水势、渗透调节能力和光合速率高于W1和W2处理;济麦22旗叶相对含水量低于洲元9369,旗叶水势、渗透调节能力和光合速率高于洲元9369。(2)W3处理下穗数和千粒重显著增加,但穗粒数显著低于W1处理,以高的灌水量和耗水量获得最高籽粒产量,水分利用效率无显著变化。济麦22籽粒产量、穗数、千粒重、耗水量和水分利用效率均显著高于洲元9369,穗粒数低于洲元9369。本试验条件下,在拔节后8d和开花后8d0～140cm土层平均土壤相对含水量补灌至75%,是兼顾节水和高产的最优处理。     

Growth and water relations of simulated swards of Lolium perenne L. selection lines with contrasting leaf osmotic potentials

Two selection lines of Lolium perenne , which had different leaf lamina osmotic potential (Ψ_s) when droughted in controlled environments, were grown as vegetative simulated swards in containers of soil 1·0 × 1·3 × 0·9 m deep in the glasshouse. Water was withheld during July, August and September.
Under irrigation the low-ψ_s line had leaf lamina and leaf base ψ^s 0·06 MPa lower than the high-ψ_s line. Under drought, the two lines did not differ significantly in lamina ψ_s but leaf base ψ_s was 0·16 MPa lower in the low line than in the high line. Upon rewatering, most of the osmotic adjustment in the leaf bases was lost within 2 d, but that in the laminae was more stable.
Herbage growth under irrigation was similar in the two lines until September, when it was greater in the highψ_s line. Drought reduced herbage growth, and also regrowth rates following rewatering, but the two lines did not differ in their sensitivity to drought.
Selection for low ψ^s also increased leaf extension rates, and reduced tillering and leaf water conductance of irrigated plants.
The results are discussed in relation to selecting for improved drought resistance on the basis of physiological characters.     

Faba bean breeding for drought-affected environments: A physiological and agronomic perspective

The faba bean (Vicia faba L.) crop often experiences drought during its growth and development such that soil moisture deficits constrain its production. As droughts are predicted to increase in both frequency and intensity due to climate change, a better understanding of drought response patterns and associated traits is essential for obtaining yield stability in water-limited environments. This review deals with adaptation mechanisms associated with drought avoidance, escape and tolerance, with an emphasis on physiological traits such as stomatal conductance, carbon isotope discrimination and leaf temperature. Leaf temperature is considered an effective surrogate measure for other measures of stomatal characteristics. Drought tolerance through osmotic adjustment has not yet been demonstrated in faba bean although it is found in many other legumes including chickpea and pea. Deeper root growth, leading to uptake of otherwise unavailable water, helps the plant to avoid drought by delaying dehydration, but genetic variation and heritability of the trait are essentially unknown for faba bean. Crop management strategies, such as early planting, and appropriate phenology, are particularly important for drought escape in regions where terminal drought is common. Disease resistance is especially important in drought-prone areas to reduce the need for expensive control measures when yields are uncertain. The relevance of soil fertility status and nutrient availability are also covered. Drought escape and ascochyta blight resistance are important breeding objectives for terminal drought regions. Some form of drought resistance is necessary for the transient droughts experienced in most regions, and drought avoidance can be screened by a combination of leaf temperature or other rapid test of stomatal characteristics followed by carbon isotope discrimination in the most valuable materials. No single trait is adequate to improve yield in drought-prone environments, rather, a combination of characteristics is needed.     

The potential use of plant physiological responses to water stress as an indication of varietal sensitivity to drought in four potato (Solanum tuberosum L.) varieties

Four potato varieties were subjected to water stress under controlled conditions. Leaf relative water content, leaf diffusive resistance, and photosynthesis were measured on stressed and unstressed plants during a stress period and during the recovery period following stress relief. Subsequent to the stress, plants were grown to maturity with optimal water supply. Mature plants were harvested and tuber yield and haulm production measured. Stressed plants of all varieties exhibited an increase in leaf diffusive resistance and a decrease in relative water content, transpiration, and photosynthesis as soil moisture decreased. Significant varietal differences in leaf diffusive resistance of stressed plants are apparent and offer promise for development of a screening technique for varietal sensitivity to drought based on stomatal response to water deficits.     

Genotypic Variation in Response of Rainfed Lowland Rice to Prolonged Drought and Rewatering

Abstract

Duration of the drought period is important for plant response during drought and after rewatering. We hypothesized that, if drought duration is extended, (1) high seedling vigor and rapid development of a deep root system will not be advantageous, and (2) osmotic adjustment will be more important. Six diverse rice (Oryza sativa L.) genotypes were selected from rainfed lowland germplasms to examine the development of a deep root system and osmotic adjustment, and their relationship with biomass production during drought and after rewatering, under two different drought durations (shorter and prolonged) in the greenhouse. NSG19 and KDML105 had greater seedling vigor (larger seedling biomass), developed a deep root system earlier in response to drought, extracted soil water more quickly, and their pre-dawn leaf water potential declined more rapidly during the prolonged drought period. These two genotypes showed superior drought recovery even after a prolonged drought period in which they suffered a greater reduction in transpiration, water use efficiency, and biomass production. The superior recovery ability was associated with larger plant size by the end of the drought period rather than with plant water status during drought, such as osmotic adjustment or leaf water potential. Osmotic adjustment was greater during prolonged drought periods (ca. 0.7 MPa) than during shorter drought periods (ca. 0.5 MPa), and lower osmotic adjustment was mostly associated with a higher leaf water potential. Genotypic variation in osmotic adjustment was observed, but there was no clear relationship between osmotic adjustment and biomass production during drought periods. These patterns of response of rice seedlings to drought and rewatering in the greenhouse should help to explain the patterns of adaptation of rainfed lowland rice in the field. Selection for drought recovery ability should be an advantageous strategy for early season drought.     

The influence of mist irrigation on the potato I. Micro-environment and leaf water relations

The influence of low gallonage “mist” irrigation on the following parameters were measured: leaf, air and soil temperature; and soil moisture, relative turgor and stomatal aperature. Misted canopies had lower leaf, air and soil temperature and higher soil moisture than the non-irrigated plants. Stomata of misted plants did not close as rapidly as those of non-irrigated plants.     

栽培稻抗旱性研究的现状与策略

 水资源短缺正成为制约我国农业发展的重要因素。培育抗旱的栽培稻品种并实现水稻旱作，不但可在很大程度上节约水资源，而且有利于增产稳产，节约能源和减少环境污染。抗旱性包括逃旱性、避旱性、耐旱性和复原抗旱性。形态生理学的研究揭示出大量的与栽培稻抗旱性有关的形态特征和生理特性，如根系和叶片性状、生育期、渗透调节、脱落酸含量与栽培稻抗旱性密切相关，且已利用分子标记对上述性状进行了基因定位（QTL）研究。旱稻品种改良也已取得重大进展。在进行抗旱品种改良的基础上，通过引进相应的栽培技术，节水种植，实现水稻旱作，并达到稳产与增产的目的，是抗旱性研究的战略目标。在增产、稳产和优质的前提下，以培育耐旱性极强的水稻（或旱稻）为中心，建立有代表性的抗旱性研究基地, 进一步加强稻属抗旱基因资源的发掘和创新、抗旱生理学和遗传学的研究、利用现代生物技术实现不同物种间抗旱基因的转移、建立节水种植栽培技术新体系是目前抗旱性研究的主要内容。     

苗期外源脱落酸和茉莉酸缓减小麦花后干旱胁迫的效应及其生理机制

为探究生育前期喷施脱落酸（ABA）和茉莉酸（JA）对小麦花后干旱胁迫的缓减效应,在盆栽试验条件下,测定和分析了苗期喷施ABA和JA后花后干旱胁迫下小麦籽粒产量及部分生理指标的变化。结果表明,花后干旱胁迫显著降低小麦穗粒数、千粒重和产量。干旱胁迫下,喷施ABA和JA可显著提高植株内源ABA和JA含量、旗叶光合速率和PSⅡ的最大光化学效率、渗透调节物质（可溶性糖、游离氨基酸和脯氨酸）含量以及抗氧化酶（SOD、CAT、APX和GR）活性,降低丙二醛含量,增加穗粒数、千粒重和产量。说明生育前期喷施外源ABA和JA可缓解花后干旱胁迫对小麦光合的抑制作用,增强干旱胁迫下植株的渗透调节和抗氧能力,促进产量形成。     

干旱胁迫对燕麦叶片气孔和叶肉细胞超微结构的影响

为了解干旱后燕麦解剖结构的变化,以燕麦品种白燕2号为材料,通过盆栽控水试验,设置正常供水、轻度干旱和重度干旱三个不同水分处理(土壤含水量分别为田间持水量的75%、60%和45%),研究了干旱胁迫对燕麦叶片渗透调节物质含量、气孔和叶肉细胞超微结构的影响。结果表明,正常水分条件(对照)下,燕麦叶片脯氨酸和可溶性糖含量较低,表皮细胞皱褶,气孔关闭或微张,叶肉细胞内细胞器形状规则,结构清晰。与对照相比,轻度干旱胁迫下,燕麦叶片脯氨酸和可溶性糖含量增加,叶片表皮细胞饱满,气孔开启度较大,叶绿体形状变圆,近球状,线粒体外被膜膨胀,但结构未见明显损伤;重度干旱胁迫下,叶片脯氨酸和可溶性糖含量极显著增加,表皮细胞干瘪,气孔保卫细胞膨胀,气孔关闭,气孔器下陷。重度干旱胁迫下,燕麦叶绿体和线粒体受到的损伤较大,叶绿体内基粒、基质类囊体降解,出现较大的空腔;线粒体外被膜断裂,内含物流失;细胞核染色质凝聚,叶绿体之间出现嵌合现象。因此,干旱胁迫能诱导燕麦叶片渗透调节物质的积累和细胞超微结构的改变,渗透调节物质增幅和细胞超微结构的破坏程度随着土壤有效水分含量的降低而上升,但在细胞超微结构上也出现抗性反应,表明燕麦具有较强的抗旱性。     

玉米对水分亏缺的响应

对玉米不同生育时期的水分亏缺指标进行分析,从玉米对水分亏缺的生态响应、激素响应、抗氧化系统的响应、渗透调节物质的响应、蛋白质的响应、呼吸作用的响应、氮代谢的响应、光合作用的响应、核酸的响应等方面研究结果进行综述。玉米吐丝期遭受水分亏缺时,对产量影响最大;在玉米受到水分亏缺时,首先细胞膨压进行改变,然后诱导信号物质（ABA）大量产生来调节气孔的开闭,达到减少水分散失的目的,进一步影响光合作用,抑制物质生产,最终产物分配受到约束,收获指数降低,产量下降。对玉米进行适度水分亏缺可以提高玉米抗旱性和水分利用效率。     

甜菜碱对玉米幼苗抗旱性的诱导效应

以旱玉5号和太单32为材料,在20%PEG模拟干旱条件下,研究外源甜菜碱对玉米幼苗抗旱性的诱导效应。结果表明,水分胁迫显著降低了玉米幼苗的生物量和叶片相对含水量,提高了幼苗的根冠比和渗透调节物质、抗氧化酶活性、ABA含量。喷施0.5mmol/L的甜菜碱溶液能缓解玉米幼苗的水分胁迫,提高幼苗的生物量、叶片相对含水量、根冠比及渗透调节物质、抗氧化酶活性、ABA含量。     

花生部分根系干燥对干旱胁迫的缓解效应

本研究基于植物旱生原理,对花生植株进行部分根系干燥（PRD）刺激,以期调节花生旱生反应,增强植 株后期对干旱胁迫的防御能力。采用隔板（P1）、分容器（P2）和凡士林（P3）3种分根方法,将根系分为两侧根区并进 行4轮根区交替灌溉,一侧根区保持40%田间持水量,另一侧根区正常浇水（75%田间持水量）,研究PRD诱导的花 生旱生反应相关生理指标的变化。结果表明：与对照相比,3种PRD处理根冠比均增加,叶片细胞溶质浓度值CFT增 加,ΔCFT分别为43.1（P1）、65.1（P2）和49.6（P3）osmol∙m-3,水势和渗透势降低,膨压显著增大;O2·-含量增加2~3倍, 超氧化物歧化酶（SOD）活性显著增加并在复水后保持较高的活性;PRD缩短离体叶片气孔关闭时间,延长水分蒸发 时间,复水后光合势能增强,叶片和根系中Gdi-15 基因表达增强2~7倍。为进一步研究PRD预处理对干旱胁迫的 缓解作用,以凡士林分根法进行PRD预处理的干旱试验,设3个处理：正常浇水（Control,75%田间持水量）、干旱胁 迫（D,35%田间持水量）和PRD预处理的干旱胁迫（DP）,分析比较各处理间生理指标的变化。结果表明：与D处理 相比,DP处理叶片相对含水量由51.68%增加到61.07%,脯氨酸含量由4328.72μg g-1FW减少到2104.50 μg∙g-1FW, MDA和O2·-含量均降低,POD活性由592.46降低到217.68 U∙g-1FW。3种PRD处理方式都能诱导花生植株产生旱生 反应,以凡士林法效果最佳。PRD预处理可对植株进行干旱驯化,使植株再次感知干旱胁迫时表现迅速的生理防 御和快速的生理恢复能力。