Wikberg Jenny, Ogren Erling
Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-90183 Umeå, Sweden.
Tree Physiol. 2007 Sep;27(9):1339-46. doi: 10.1093/treephys/27.9.1339.
Growth and water-use parameters of four willow (Salix spp.) clones grown in a moderate drought regime or with ample water supply were determined to characterize their water-use efficiency, drought resistance and capacity for drought acclimation. At the end of the 10-week, outdoor pot experiment, clonal differences were observed in: (1) water-use efficiency of aboveground biomass production (WUE); (2) resistance to xylem cavitation; and (3) stomatal conductance to leaf-specific, whole-plant hydraulic conductance ratio (g(st)/K(P); an indicator of water balance). Across clones and regimes, WUE was positively correlated with the assimilation rate to stomatal conductance ratio (A/g(st)), a measure of instantaneous water-use efficiency. Both of these water-use efficiency indicators were generally higher in drought-treated trees compared with well-watered trees. However, the between-treatment differences in (shoot-based) WUE were smaller than expected, considering the differences in A/g(st) for two of the clones, possibly because plants reallocated dry mass from shoots to roots when subject to drought. Higher root hydraulic conductance to shoot hydraulic conductance ratios (K(R)/K(S)) during drought supports this hypothesis. The same clones were also the most sensitive to xylem cavitation and, accordingly, showed the strongest reduction in g(st)/K(P) in response to drought. Drought acclimation was manifested in decreased g(st), g(st)/K(P), osmotic potential and leaf area to vessel internal cross-sectional area ratio, and increased K(R), K(P) and WUE. Increased resistance to stem xylem cavitation in response to drought was observed in only one clone. It is concluded that WUE and drought resistance traits are inter-linked and that both may be enhanced by selection and breeding.
测定了在中度干旱条件或充足供水条件下生长的四个柳树（柳属）无性系的生长和水分利用参数，以表征它们的水分利用效率、抗旱性和干旱适应能力。在为期10周的室外盆栽试验结束时，观察到无性系在以下方面存在差异：（1）地上生物量生产的水分利用效率（WUE）；（2）对木质部空化的抗性；（3）气孔导度与叶特定、全株水力导度比（g(st)/K(P)；水分平衡指标）。在各个无性系和处理条件下，WUE与同化率与气孔导度比（A/g(st)）呈正相关，A/g(st)是瞬时水分利用效率的指标。与充分浇水的树木相比，干旱处理的树木中这两个水分利用效率指标通常更高。然而，考虑到两个无性系的A/g(st)差异，基于枝条的WUE处理间差异小于预期，这可能是因为植物在干旱时将干物质从枝条重新分配到根部。干旱期间较高的根水力导度与枝条水力导度比（K(R)/K(S)）支持了这一假设。相同的无性系对木质部空化也最敏感，因此，响应干旱时g(st)/K(P)降低最强。干旱适应表现为g(st)、g(st)/K(P)、渗透势和叶面积与导管内部横截面积比降低，以及K(R)、K(P)和WUE增加。仅在一个无性系中观察到干旱导致茎木质部空化抗性增加。得出的结论是，WUE和抗旱性状相互关联，并且两者都可以通过选择和育种得到增强。
