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The compensation effect of re-watering after drought has been widely reported in various crops during different growth stages. It is considered as an important self-regulation mechanism for plants to resist abiotic stresses and also an efficient utilization of limited water resource. In this study, two rounds of re-watering after drought treatments were carried out during tuber expansion period of potato, to investigate the drought threshold of potato and explore the potential mechanisms of compensation effect with source-sink aspect. We used virus-free plantlets of "Atlantic" potato as experimental materials. Four treatments were included: sufficient water supply (W), re-watering after mild drought (D旱后复水的补偿效应在多种作物的不同生育时期都存在,是植物抵抗逆境胁迫和伤害的重要自我调节机制,也是对有限水分高效利用的体现.本研究在马铃薯块茎膨大期进行两轮干旱后复水处理,明确马铃薯补偿效应产生的干旱胁迫阈值,并从源-库角度探索马铃薯旱后复水补偿效应产生的缘由.试验选取‘大西洋’马铃薯脱毒组培苗为材料,设置充分供水(W)、轻度干旱后复水(D

A better understanding of the mechanisms of water uptake by plant roots should be vital for improving drought resistance and water use efficiency (WUE). In the present study, we have demonstrated correlations between root system hydraulic conductivity and root characteristics during evolution using six wheat evolution genotypes (solution culture) with different ploidy chromosome sets (Triticum boeoticum Bioss., T. monococcum L.: 2n=2x=14; T. dicoccides Koern., T. dicoccon (Schrank) Schuebl.: 2n = 4x = 28; T. vulgare Vill., T. aestivum L. cv. Xiaoyan No. 6: 2n = 6x = 42). The experimental results showed that significant correlations were found between root system hydraulic conductivity and root characteristics of the materials with the increase in ploidy chromosomes (2x6x) during wheat evolution. Hydraulic conductivity of the wheat root system at the whole-plant level was increased with chromosome ploidy during evolution, which was positively correlated with hydraulic conductivity of single roots, whole plant biomass, root average diameter, and root growth (length, area), whereas the root/shoot ratio had an inverse correlation with the hydraulic conductivity of root system with increasing chromosome ploidy during wheat evolution. Therefore, it is concluded that that the water uptake ability of wheat roots was strengthened from wild to modern cultivated species during evolution, which will provide scientific evidence for genetic breeding to improve the WUE of wheat by genetic engineering. (Managing editor: Ya-Qin HAN)

Achieving greater crop yield per unit of rainfall is one of the most important challenges for wheat production in dryland environments. Efficient use of limited water resources may be one means of achieving this goal. This chapter reviews the physiological adaptation to water deficit under variable environmental conditions in wheat. In addition, it reveals the compensatory effect of limited irrigation and fertilizer supplementation on wheat water-use efficiency (WUE) and highlights the breeding of new varieties for high WUE that could improve wheat productivity under water-limited environments. Considerable potential for further improvement in wheat productivity in semiarid areas seems to depend on effective conservation of moisture and efficient use of limited water. Different crops, soil and water management strategies should be adjusted according to the conditions that prevail in the various semiarid areas. Wheat productivity can be significantly improved by integrating the soil and water conservation approach and the regulated cropping system with cultivating drought-tolerance and water-saving cultivars.

With drought-resistant wheat (Triticum aestivum) cultivar Changwu 134 and drought-sensitive cultivar Zhengyin 1 as test materials, and by using -1.2 MPa PEG 6000 to treat their seeds, this paper studied the protein expression and physiological properties of the sprouts under different soil moisture conditions. SDS-PAGE analysis showed that water stress induced the production of two new proteins with molecular weights of 39.5 kDa and 23.0 kDa in Changwu 134 but not in Zhengyin 1 sprouts. Under normal water supply, the expression of the protein with molecular weight of 48.5 kDa in the sprouts of both Changwu 134 and Zhengyin 1 increased with sprout growth. This protein was preliminarily named as water-sensitive protein, due to its water-sensitivity and of newly discovered protein. The determinations of physiological properties showed that under water stress, the sprouts of drought-resistant Changwu 134 had higher root/shoot ratio and higher relative water content, but lower relative membrane permeability and lower malondlaldehyde content than those of drought-sensitive Zhengyin 1.

To investigate the role of ZmPIP1-1 and ZmPIP1-2 in water uptake of roots and drought resistance of crops, semi-quantitative PCR was used to examine the expression of ZmPIP1-1 and ZmPIP1-2 in root systems of different maize genotypes under water deficit. These genotypes showed different resistance to water shortage under field conditions. The reference gene to target genes was tubulin. Maize seedlings were grown by hydroponics in a growth chamber. Water deficit was imposed on the seedlings with PEG-6000. The result showed that ZmPIP1-1 was up-regulated under water deficit in root systems of plants of the filial generation 'Hudan 4' and the mother line 'Tiansi', which were resistant to water shortage, but there was no noticeable up-regulation of ZmPIP1-1 in the root systems of the father line '803', which was sensitive to water deprivation. The result also showed that the extent of up-regulation was positively correlated with drought resistance of maize (Fig.3). On the other hand, the expression of ZmPIP1-1 showed different degrees of tendency after different duration of water stress in the root systems of the maize seedlings of different genotypes. The result showed that ZmPIP1-2 was identically expressed in three different species of maize and under different water conditions. The results support the theory that the intercellular water transport contributes to increased water uptake in root systems under water deficit by up-regulating the number of some kinds of aquaporins. The increases amount of transcripts of aquaporins is positively correlated to drought resistance of plant varieties. But not all kinds of number of aquaporins is up-regulated during water shortage, some kinds of aquaporins are identically expressed under water deficit conditions and well watered conditions.