干旱胁迫对青海杨不同种群的影响

通过对青海杨的两个分别来自极端干旱和湿润地区的种群进行不同水分处理,研究其在生物量的积累与分配、气体交换、脱落酸积累以及水分利用效率上的种群差异.结果表明:①不同种群在各种生长和形态指标上均表现出了显著性差异,例如株高(Ht)、基径(Bd)、总生物量(Tb)、总叶面积(La)和细根比(Ft).②不同种群在各种生理指标上也表现出了显著性差异,例如净光合速率(A)、蒸腾速率(E)、气孔导度(g)、水分利用效率(WUEi)和脱落酸(ABA)积累.③与来自湿润地区的种群相比,来自干旱地区的种群表现出了较小的生长和形态指标值以及较大的生理指标值.这些对水分可利用性的形态和生理适应性表明,不同种群在其幼苗早期生长和建立方面采用了不同的生存策略,来自湿润地区的杨树种群采用耗水策略从而抗旱性低,而来自干旱地区的杨树采用节水策略从而抗旱性高.这些对干旱的不同反应可以为不同气候地区选择相应的生态型提供一定的参考标准.表4参26

Population Differences in Adaptive Responses to Drought Stress in Populus przewalskii Maxim

Population differences in dry matter accumulation and allocation, gas exchange, abscisic acid content and water use efficiency of Populus przewalskii Maxim. cuttings were measured after exposure to well-watered and drought-stressed treatments. Two contrasting populations from dry and wet climate regions were used for this study. Significant differences in height (Ht), basal diameter (Bd), total biomass (Tb), total leaf area (La), fine root/total root ratio (Ft), net photosynthesis (A), transpiration (E), stomatal conductance (g) and instantaneous water use efficiency (WUEi), as well as abscisic acid content (ABA) between the two populations were detected under two watering regimes; as affected by drought stress, the dry climate population had smaller Ht, Bd, Tb, La, Ft and higher A, E, g, WUEi and ABA than the wet climate population. These morphological and physiological adaptations to water availability showed that the different populations might employ different survival strategies under drought stress at the initial phase of seedling growth and establishment. The wet climate population possessed a prodigal water use strategy with lower drought tolerance, while the dry climate population exhibited a conservative water use strategies with higher drought tolerance. These differences in drought responses may be used as criteria for genotype selection in different climate regions. Tab 4, Ref 26