西藏半干旱区3种柏树对干旱胁迫的生理响应特征

以巨柏、大果圆柏和香柏3年生盆栽苗为材料,采用自然干燥法控水,在4个土壤含水量梯度(T1、T2、T3、T4)下测定了3种柏树光合-光响应曲线、光合作用参数和保护酶的活性,以探讨它们对干旱胁迫的生理响应特征。结果显示:(1)3种柏树光合-光响应曲线随干旱胁迫加剧的变化趋势基本相同,当光量子通量密度(PFD)<200μmol.m-2.s-1,净光合速率随PFD的增强基本呈直线增长;当PFD达到1 200μmol.m-2.s-1左右时,净光合速率达到最大。(2)随着干旱胁迫的加剧,3种柏树的光饱和点下降而光补偿点升高,表观量子效率降低;水分利用效率在巨柏和大果圆柏中呈持续下降趋势,而香柏为先上升后下降,但水分利用效率平均值以香柏最大。(3)随着干旱胁迫的加剧,3种柏树SOD活性先升高后降低;巨柏和大果圆柏POD活性呈持续上升趋势,而香柏为先升高后降低;巨柏和大果圆柏的CAT活性先升高后降低,而香柏呈持续上升趋势;3种柏树的MDA含量均呈现逐渐升高趋势,但香柏的脂质过氧化程度远低于巨柏和大果圆柏。研究表明,香柏比巨柏和大果圆柏具有更强的抗旱适应性。

Physiological Response of Three Cypress Species to Drought Stress in Semi-arid Region of Tibet

Using Sabina pingii var.wilsonii,S.tibetica and Cupressus gigantea 3-year-old seedlings,we monitored the effects of drought simulated by natural drying method on the photosynthetic characteristics of three cypress species in a semi-arid region of Tibet by photosynthesis-light response curve and protective enzyme activities during four drought stress stages(T1,T2,T3,T4).The results showed that:(1)photosynthesis-light response curve of three cypress species were basically similar in the whole process of the drought stress.When photo flux density(PFD) was less than 200 μmol·m-2·s-1,net photosynthetic rate was increased in line with the increase of PFD;When PFD reached to about 1 200 μmol·m-2·s-1,net photosynthetic rate reached the maximum.(2)With the increase of drought intensity,light saturation point and apparent quantum yield(α) decreased,but light compensation point increased,and the mean value of water use efficiency of S.pingii var.wilsonii was higher than that of S.tibetica and C.gigantea.(3)With the increase of drought intensity,SOD activity of the three cypress species first increased and then turn to decrease.POD activities of C.gigantea and S.tibetica persistently increased,but that of S.pingii var.wilsonii first increased and then decreased.CAT activity of C.gigantea and S.tibetica first increased and then decreased,but that of S.pingii var.wilsonii was persistently increased.The MDA contents of the leaves in the three cypress species persistently increased,but that of S.pingii var.wilsonii was far less than that of C.gigantea and S.tibetica in the whole drought stress process.It was obvious that S.pingii var.wilsonii was more adaptable in the drought resistance than C.gigantea and S.tibetica.