水分胁迫下天然次生灌木山桃和山杏光合气体交换特征

以半干旱黄土丘陵区3年生天然次生灌木山桃(Prunus davidiana)和山杏(Prunus sibirica)为试验材料,采用充分供水、正常供水、轻度胁迫、中度胁迫和重度胁迫5种水分处理,比较了水分胁迫对山桃和山杏光合气体交换参数的影响.结果表明:山桃和山杏的净光合速率(Pn)、胞间CO2浓度(Ci)、蒸腾速率(Tr)、气孔导度(Gs)和水分利用效率(WUE)在不同水分处理之间差异显著.随着水分胁迫的缓解,山桃和山杏的Pn日变化曲线逐渐从单峰型转变成不明显的双峰型;重度水分胁迫下,Pn受到明显抑制,一直维持在较低水平;Pn在轻度或中度水分胁迫下出现最大值,且山桃的日均Pn要高于山杏;Pn降低的原因上午表现为气孔限制因素,而下午则以非气孔限制因素为主.山桃和山杏的Ci日变化规律与Pn基本相反,它们的Tr日变化在轻度和中度水分胁迫下为双峰曲线,并以正常供水条件下日均Tr最大;不同程度水分胁迫下,山桃、山杏的Gs日变化表现出相似的变化规律,且气孔都出现了过早关闭的现象.适度的水分胁迫能够提高山桃、山杏的水分利用效率,同时也降低了Pn和Tr.研究发现,山桃和山杏在水分胁迫下能通过较大幅度降低蒸腾速率来提高其水分利用效率,从而增强其适应干旱环境的能力,它们在黄土丘陵区具有较广阔的发展潜力.

Gas Exchange Characteristics of Natural Secondary Shrubs Prunus davidiana and Prunus sibirica under Different Water Stresses

We investigated the gas exchange characteristics of natural secondary shrubs Prunus davidiana and Prunus sibirica under different water stresses,with three-year old shrubs of the both tree species in semi-arid loess hilly-gully region as experimental materials.The five water stresses were designed for the experiment:sufficient water supply,normal water supply,light,medium and severe water stress.The results indicated that different water stress obviously affected photosynthetic rate(Pn),intercellular CO2 concentration(Ci),transpiration rate(Tr),stomatal conductance(Gs) and water use efficiency(WUE).Along with alleviation in water stress,the diurnal pattern of Pn shifted from single-peaked curve gradually to an unconspicuous double-peaked one.Under severe water stress,Pn was restrained obviously,and maintained inferior level continuously.Pn appeared maximum under light water stress or medium water stress.The average daily Pn of P.davidiana was higher than that of P.sibirica.On the whole,the diurnal change curve of Ci was opposite to Pn.According to the criteria suggested by Farquhar and Sharkey,the forenoon depression of Pn was caused by stomatal limitation,and non-stomatal limitation occured mainly in the afternoon.The curve of Tr was double-peaked curve under light and medium water stress,and the average daily Tr reached maximum under normal water supply.The diurnal changes of Gs in P.davidiana and P.sibirica exhibited similar style,and stoma seemed to close prematurely.Well-regulated water stress would improve water use efficiency of both experimental tree species,and debased their Pn and Tr at the same time.It was concluded that P.davidiana and P.sibirica increased WUE to improve drought resistance by decreasing Tr greatly under slight water stress for acclimation.They had a potential being applied use in the loess hilly-gully region.