园艺植物水分胁迫生理及耐旱机制研究进展

概述了园艺植物在水分胁迫下的生理生化,分子反应及耐旱机制研究进展,并指出尚需进一步研究的问题。     

植物耐旱与基因工程

占我国国土面积50％以上的西部和北部地区,降水量少,且季节分配不均,受到严重缺水 威胁,这是造成西部经济滞后的一个重要原因。近20年来全球荒漠化面积已占陆地面积的25％。我国西部荒漠化的土地以每年300万亩的速度扩大。据估计每年因风沙危害导致直接经济损失高达45亿元。年复一年的陷入干旱的生态危机,严重威胁到人类社会的可持续发展。 河流断流、土地沙化、沙尘暴频发、湖泊湿地萎缩、草地退化、森林锐减、生物量和生物多 样性急剧下降已引起全社会的关注。目前,我国西部面临着实施大开发的历史机遇,但同时 又是挑战。西部开发…     

耐旱玉米

1干旱和玉米:问题涉及的范围 玉米是世界上继小麦和水稻之后的第三大重要谷物.玉米的产量在温带的发达地区平均可以达到8.2吨/公顷,在热带欠发达国家为3.5吨/公顷.无论在哪一类产区,干旱都作为最重要的非生物因素制约着玉米的产量,并且使其非常不稳定,同时这也是热带和温带地区的平均产量产生差别的原因之一.这两类地区在耕作季节的水资源缺乏是不可预期的.农田中土壤质地和深度的差别表明植物可利用的水量不同,这会导致在干旱年份中产量相差10倍以上.此外,由于农民通常只在其所有土地上耕种一种作物,这就要求种植于雨养条件下的农作物具有较高水平的耐旱能力.     

4种灌木地被植物耐旱指标探讨

对城市绿化中4种灌木类地被植物的抗旱性进行研究。结果表明,4种植物抗旱性强弱依次为:小叶蚊母树、火棘、红花檵木、水桅子。其中,小叶蚊母树适应性强,干旱条件下成活率高,可成为当今园林绿化中重点选择的色块植物之一。     

植物防御的新发现: 植物-植物相互交流

 植物和昆虫在长期的相互作用过程中形成了复杂的防御体系。近年来, 人们发现植物在受到外界伤害后, 它们邻近的健康植物能够感受到威胁来临, 并积极表达抗性基因和产生防御物质。这种现象被称为“植物-植物相互交流”。一系列的相关研究表明: 绿叶挥发物和萜烯类物质是受伤害植物对邻近健康植物发送的主要信号, 邻近的健康植物在接收到这些挥发性有机化合物信号后, 直接防御和间接防御能力都能够迅速提升。人们猜测植物挥发性有机化合物“启动”了邻近健康植物的多种防御反应, 使它们在面临真正威胁时迅速做出防御反应。然而, 植物-植物交流的分子机制至今尚不清楚。我们运用拟南芥(Arabidopsis thaliana)全基因组芯片技术和突变体材料, 对植物-植物交流的分子机理进行了探讨。结果发现: 有效的挥发性有机化合物并不限于绿叶挥发物和萜烯类物质, 且挥发性有机化合物的种类和节律能够相互配合, 从而达到最佳效果; 邻近健康植物的乙烯信号途径在植物-植物交流过程中是不可或缺的, 茉莉酸信号起到了辅助和信号放大的作用。     

植物的色香味与植物液泡

植物的色香味与植物液泡植物细胞具有酸甜苦涩等味道,植物的花果叶也具有红橙黄绿等颜色,有些植物还具有特殊的香气,这都与植物的液泡有关系。植物液泡中的液体是细胞代谢活动的产物,其中主要成分是水和溶于水的糖、丹宁、有机酸、植物碱、色素和盐类。由于植物的种类...     

苔藓植物耐旱机制研究进展

耐旱藓类快速脱水并存活的能力可由快速建立起来的对环境变化的耐受机制来反映,保护细胞完整性的组成型机制与修复细胞损伤的诱导机制协同作用使苔藓植物渡过干旱胁迫.再水化时光合系统原初恢复非常迅速;ABA处理可显著改变PSⅡ的生理特征;基因表达的变化主要由翻译调控引起;脱水组织中贮存mRNPs既保护了mRNAs,又加快了再水化修复速度.山墙藓(Tortula ruralis)是耐旱研究较多的一个种,已建立了表达序列文库(EST),将会成为耐旱研究的重要模式植物.     

苔藓植物耐旱机制研究进展

耐旱藓类快速脱水并存活的能力可由快速建立起来的对环境变化的耐受机制来反映,保护细胞完整性的组成型机制与修复细胞损伤的诱导机制协同作用使苔藓植物渡过干旱胁迫。再水化时光合系统原初恢复非常迅速;ABA处理可显著改变PSⅡ的生理特征;基因表达的变化主要由翻译调控引起;脱水组织中贮存mRNPs既保护了mRNAs, 又加快了再水化修复速度。山墙藓(Tortula ruralis)是耐旱研究较多的一个种,已建立了表达序列文库(EST),将会成为耐旱研究的重要模式植物。     

高等植物调渗蛋白与耐旱耐盐基因工程

高等植物调渗蛋白与耐旱耐盐基因工程艾万东（中国科学院遗传研究所植物生物技术实验室）土壤中盐的积累是一个全球性的问题,了解植物耐盐机制,对于耐盐作物多样性的开发与应用是一个关键因素。植物为了消除由盐胁迫而造成的不平衡,通常在细胞中积累两类性质不同的渗透保护剂（Ｏｓｍｏｐｒｏｔｅｃｔａｎｔ）,一类是小分子的有机化合物,如甜菜碱和脯氨酸,另一类是蛋白质。     

三个耐旱树种木质部栓塞化的脆弱性及其恢复能力

植物在长期适应赖以生存的自然环境中 ,形成了一套最适宜自身生长发育的生理生态行为 ,采取各种方式来抵御或忍耐水分胁迫的影响。如通过具有深广而茂密的根系格局来保持水分吸收 ,通过气孔调节、角质层障碍作用和小的叶蒸发表面来减少水分散失 ,通过渗透调节和增加组织弹性来保持膨压 ,通过增强原生质耐脱水能力来免受伤害或少受伤害等等。植物遭受干旱危害时 ,首先出现表型反应的多是植物的叶片 ,因此 ,研究植物的耐旱机理多从叶入手 ,对根系类型、分布及根茎比在植物耐旱性方面也有不少报道[1,2 ],而对木质部在干旱适应性反应方面的研究…     

Additive and non-additive responses of seedlings to simulated herbivory and drought

Drought is a global threat, increasing in severity and frequency throughout tropical ecosystems. Although plants often face drought in conjunction with biotic stressors, such as herbivory or disease, experimental studies infrequently test the simultaneous effects of drought and biotic stress. Because multiple simultaneous stressors may have non-additive and complex effects on plant performance, it is difficult to predict plant responses to multiple threats from research examining one stress at a time. Using an experimental approach in the greenhouse, we investigated potential non-additivity in seedling growth and survival to simulated drought and herbivory across a phylogenetically diverse pool of ten Hawaiian plant species. Overall, seedlings showed limited tolerance, defined as similar growth and survival in stressed compared with control (non-stressed) plants, to simulated herbivory and drought, with the combined effects of both stressors to be generally additive and negative across species. Significant variation in stress tolerance was detected among species, and species variation was explained, at least in part, by functional traits such that species with larger root/shoot ratios and smaller seeds, tended to demonstrate greater herbivory and drought tolerance. Future research incorporating additional trait analysis and different stressors could shed light on mechanisms underlying seedling stress tolerance and clarify whether additivity, as detected in this study, extends across other combinations of stressors. Such work will provide needed insights into the regeneration of seedlings in tropical forests under threats of herbivory and climate change.     

When is breeding for drought tolerance optimal if drought is random?

* Increasing climatic unpredictability associated with characteristics of some species makes plant drought-tolerance an important drought-adaptation strategy. Using norm-of-reaction functions, or empirically determined functions that enable us to predict the state of a trait given the state of an environmental variable, allows modelling of plant performance when water availability varies randomly. * A mathematical model is proposed to evaluate drought-tolerance and growth strategies given a set of environmental parameters: the frequency of rainy days, the soil water-storage capacity, plant water use and plant growth rates. This model compares the performance of genotypes that differ in drought tolerance expressed as the ability to grow in drier soils, and assumes a general trade-off function between drought tolerance and maximum plant growth rate. * It is worth selecting plants with a greater degree of drought tolerance, expressed by the ability to grow in drier soils whenever the frequency of rains is smaller than the rate of soil water depletion. Otherwise, maximizing growth rate at the expense of drought tolerance is the best strategy. The nature of the trade-off between drought tolerance and plant growth rate also constrains the selection for optimal drought-adapted genotypes. * Breeders will have to consider these aspects of plant-environment interactions before establishing selection programs for drought adaptation.     

Evaluation of breeding strategies for drought tolerance in potato by means of crop growth simulation

Breeding strategies for drought tolerance in potato were evaluated by means of a crop growth model, in which seasonal courses of crop dry matter accumulation and soil moisture availability were simulated in dependence of plant characteristics and weather and soil data.Several plant characteristics substantially influenced the simulated instantaneous water consumption of the genotype. However, effects of genotypic differences on final tuber yield were much smaller because of the close relationship between transpiration and growth. Hence, a lower water consumption not only saved water for later use, but was also at the expense of the actual growth rate. Selection for low-transpiration types, at unchanged water use efficiency, would result in lower yields under optimum conditions.Short periods of drought, in general, reduced tuber yield of late genotypes less than that of early genotypes. Late genotypes had a surplus of leaf area for full light interception giving a lower impact of leaf area reduction. Late drought affected early genotypes less because of escape.The simulation results emphasized the complexity of selection for drought tranrance caused by the many plant processes involved, the contrast between instantaneous and cumulative reactions and the strong genotype × environment interaction for drought tolerance.     

Role of plant growth-promoting rhizobacteria and their exopolysaccharide in drought tolerance of maize

The present study deals with the isolation and characterization of exopolysaccharides (EPS) produced by the plant growth-promoting rhizobacteria (PGPR) from arid and semiarid regions of Pakistan, and to investigate the drought tolerance potential of these PGPR on maize when used as bioinoculant alone and in combination with their respective EPS. Three bacterial strains Proteus penneri (Pp1), Pseudomonas aeruginosa (Pa2), and Alcaligenes faecalis (AF3) were selected as EPS-producing bacteria on the basis of mucoid colony formation. All these strains were gram negative, motile, and positive for catalase. Strain Pp1 was positive for oxidase test and was phosphate solubilizing, while Pa2 and AF3 were negative. The isolated strains were sequenced using 16SrRNA. Total soluble sugar, protein, uronic acid, emulsification activity, and Fourier-transformed infrared spectroscopy of EPS were determined. Drought stress had significant adverse effects on growth of maize seedlings. Seed bacterization of maize with EPS-producing bacterial strains in combination with their respective EPS improved soil moisture contents, plant biomass, root and shoot length, and leaf area. Under drought stress, the inoculated plants showed increase in relative water content, protein, and sugar though the proline content and the activities of antioxidant enzymes were decreased. The Pa2 strain isolated from semiarid region was most potent PGPR under drought stress. Consortia of inocula and their respective EPS showed greater potential to drought tolerance compared to PGPR inocula used alone.     

褪黑素对玉米幼苗根系发育和抗旱性的影响

褪黑素是一种在生物体内广泛存在的吲哚胺类化合物,参与植物的多种生理和生化过程。近年来研究认为褪黑素可以不同程度地增强植物的抗逆性,但对其作用机理仍知之甚少。通过两种褪黑素的施用方法,详细研究了褪黑素对于玉米根系发育和抗旱性的影响。首先,采用水培根灌褪黑素的方法对玉米幼苗的根系和生长状况进行分析,结果表明施加褪黑素显著提高多种玉米幼苗根系参数,包括根长、根表面积、根体积和侧根数目等。其次,采用盆栽浸种褪黑素的方法,对叶片相对含水量、光合作用、抗氧化酶活性、地上部分生物量等进行测定,结果表明在干旱胁迫条件下,褪黑素浸泡种子的处理方式能够提高植株的光合速率、气孔导度和蒸腾速率,增强抗氧化酶活性以及降低活性氧和丙二醛含量,证明褪黑素促进植物根系发育,减轻氧化损伤,缓解光合抑制,改善植物水分状况,从而提高植物抗旱性。     

Changes in Germination and Seedling Traits of Sesame under Simulated Drought

Drought is considered one of the leading abiotic constraints to agricultural crop production globally. Present study was conducted to assess the effects of different drought treatments (viz. Control, 10% PEG, and 20% PEG) on seed germination, germination indices, seedling traits, and drought tolerance indices of sesame. Our results showed that maximum reduction in the studied parameters was observed at higher PEG concentration (i.e., 20% PEG). As compared to control, the drought treatments viz. 10% and 20% PEG decreased the values for germination indices, such as germination percentage, coefficient of variation of germination time, germination index, and seedling vigor index. Similarly, for seedling traits, the values were decreased for root length, shoot length, root shoot ratio, root fresh weight, shoot fresh weight, root dry weight and shoot dry weight under 10% and 20% PEG treatments significantly in comparison with control. Furthermore, relative to control, the values for drought tolerance indices, such as germination drought tolerance index, root length drought tolerance index, shoot length drought tolerance index, total seedling length drought tolerance index, root fresh weight drought tolerance index, shoot fresh weight drought tolerance index, total fresh weight drought tolerance index, root dry weight drought tolerance index, shoot dry weight drought tolerance index and total dry weight drought tolerance index were also reduced under 10% and 20% PEG treatments, respectively. Our results confirms that drought impact on seed germination and seedling traits could be quantified by using different indices which can further help to design drought adaptation and mitigation strategies. Based on these results it can be concluded that germination indices, seedling traits, and drought tolerance indices have great potential to simulate drought stress impacts on different crop traits thus they should be used in all kinds of stress related studies.     

Impact of drought stress on growth and quality of miscanthus for biofuel production

Miscanthus has a high potential as a biomass feedstock for biofuel production. Drought tolerance is an important breeding goal in miscanthus as water deficit is a common abiotic stress and crop irrigation is in most cases uneconomical. Drought may not only severely reduce biomass yields, but also affect biomass quality for biofuel production as cell wall remodeling is a common plant response to abiotic stresses. The quality and plant weight of 50 diverse miscanthus genotypes were evaluated under control and drought conditions (28 days no water) in a glasshouse experiment. Overall, drought treatment decreased plant weight by 45%. Drought tolerance – as defined by maintenance of plant weight – varied extensively among the tested miscanthus genotypes and ranged from 30% to 110%. Biomass composition was drastically altered due to drought stress, with large reductions in cell wall and cellulose content and a substantial increase in hemicellulosic polysaccharides. Stress had only a small effect on lignin content. Cell wall structural rigidity was also affected by drought conditions; substantially higher cellulose conversion rates were observed upon enzymatic saccharification of drought‐treated samples with respect to controls. Both cell wall composition and the extent of cell wall plasticity under drought varied extensively among all genotypes, but only weak correlations were found with the level of drought tolerance, suggesting their independent genetic control. High drought tolerance and biomass quality can thus potentially be advanced simultaneously. The extensive genotypic variation found for most traits in the evaluated miscanthus germplasm provides ample scope for breeding of drought‐tolerant varieties that are able to produce substantial yields of high‐quality biomass under water deficit conditions. The higher degradability of drought‐treated samples makes miscanthus an interesting crop for the production of second‐generation biofuels in marginal soils.     

PIP Aquaporin Gene Expression in Arbuscular Mycorrhizal Glycine max and Lactuca sativa Plants in Relation to Drought Stress Tolerance

Although the discovery of aquaporins in plants has resulted in a paradigm shift in the understanding of plant water relations, the relationship between aquaporins and plant responses to drought still remains elusive. Moreover, the contribution of aquaporin genes to the enhanced tolerance to drought in arbuscular mycorrhisal (AM) plants has never been investigated. Therefore, we studied, at a molecular level, whether the expression of aquaporin-encoding genes in roots is altered by the AM symbiosis as a mechanism to enhance host plant tolerance to water deficit. In this study, genes encoding plasma membrane aquaporins (PIPs) from soybean and lettuce were cloned and their expression pattern studied in AM and nonAM plants cultivated under well-watered or drought stressed conditions. Results showed that AM plants responded to drought stress by down-regulating the expression of the PIP genes studied and anticipating its down-regulation as compared to nonAM plants. The possible physiological implications of this down-regulation of PIP genes as a mechanism to decrease membrane water permeability and to allow cellular water conservation is further discussed.