干旱胁迫对西藏半干旱河谷区典型灌木生理特性和解剖结构的影响

Physiological Characteristics and Anatomical Structure of Typical Shrubs in Semi-Arid Valley Areas of Tibet in Response to Drought Stress

以西藏干旱半干旱区5种典型灌木为研究对象,进行不同干旱下的盆栽试验,通过对比5种灌木叶片中的生理特性及解剖结构的变化,对其进行抗旱性能分析与评价。设充分供水(CK,土壤含水量为田间持水量的90%~95%),轻度干旱(LS,70%~75%),中度干旱(MS,50%~55%为),重度干旱(HS,30%~35%)。结果表明:①各树种生理特性对不同水分梯度的响应各异,其中各水分条件下砂生槐叶片过氧化物酶(POD)活性均显著高于其他树种(P<0.05),中度干旱时其分别是香柏、醉鱼草、江孜沙棘和细叶小红柳的3.1、5.3、6.0、10.5倍;细叶小红柳和香柏的叶绿素质量分数较另外3个树种较低,醉鱼草在中度干旱时叶绿素质量分数达到1.95 mg/g,显著高于其他处理(P<0.05);中、重度干旱会增加细叶小红柳、江孜沙棘、砂生槐及醉鱼草丙二醛质量摩尔浓度。②不同水分条件下各灌木树种气孔密度存在差异,细叶小红柳气孔密度在轻度干旱下最大;江孜沙棘气孔密度在充分供水、轻度干旱和中度干旱时较大,重度干旱时显著小于其余3个水分条件(P<0.05);香柏气孔密度在轻度干旱时最大;砂生槐气孔密度在轻度干旱和中度干旱时显著大于充分供水和重度干旱条件(P<0.05);醉鱼草气孔密度在充分供水和轻度干旱时较大。③随干旱加剧,细叶小红柳和醉鱼草叶片厚度和海绵组织厚度均逐渐减小,砂生槐栅栏组织厚度在各水分条件下均显著大于其他树种,且其在各水分梯度下差异不显著;组织紧密度砂生槐远大于其余树种,醉鱼草和江孜沙棘次之,香柏最小,组织疏松度香柏最大,其次为砂生槐,其余3个数种差异不显著。主成分分析结果表明5种灌木树种中砂生槐的抗旱性最强,香柏最弱,抗旱性由大到小表现为砂生槐、江孜沙棘、醉鱼草、细叶小红柳、香柏。

Five typical shrubs in the arid semi-arid valley region of Tibet were used to compare the response characteristics andadaptation mechanisms under different gradients of drought stress (CK (90%-95% soil moisture), LS (70%-75%),MS (50%-55%) and HS (30%-35%)) and to make a comprehensive evaluation of the drought resistance of eachseedling. The results showed that: (1) The physiological characteristics of various tree species respond differently todifferent water gradients, with the POD activity of Sophora moorcroftiana leaves significantly higher than other treespecies under different water conditions ( P <0.05). During moderate drought, the POD activity is 3.1, 5.3, 6.0, and10.5 times higher than that of Sabina pingii, Buddleja viciifolia, Hippophae gyantsensis and Salix microstachya ,respectively. The chlorophyll contents of Salix microstachya and Sabina pingiiare lower than those of the other threetree species, while the chlorophyll content of B. viciifolia reaches 1.95 mg/g during moderate drought, significantlyhigher than other treatments ( P <0.05). Moderate and heavydrought will increase the content of malondialdehyde inSalix microstachya, H. gyantsensis, Sophora moorcroftiana and B. viciifolia . (2) There were differences in stomataldensity among different shrub species under different water conditions, and the stomatal density of Salixmicrostachya was the highest under light drought. The stomatal density of H. gyantsensis was higher undersufficient water supply, light drought, and moderate drought, while it was significantly lower under heavy droughtthan the other three water conditions ( P <0.05). The stomatal density of Sabina pingii was highest during lightdrought. The stomatal density of Sophora moorcroftiana was significantly higher under light and moderate droughtconditions than under CK and heavy drought ( P <0.05). The stomatal density of B. viciifolia was higher under CKand light drought. (3) With the intensification of drought, the thickness of leaf blades and sponge tissue of Salixmicrostachya and B. viciifolia gradually decrease. The thickness of palisade tissue of Sophora moorcroftiana wassignificantly greater than that of other tree species under various water conditions, and its difference is notsignificant under different water gradients. The tissue density of Sophora moorcroftiana was much higher than thatof other tree species, followed by B. viciifolia and H. gyantsensis , and Sabina pingii was the smallest. The tissueporosity was the highest in Sabina pingii , followed by S. moorcroftiana , with no significant differences among theother three species. The results of principal component analysis showed that among the five shrub species, theSophora moorcroftiana had the strongest drought resistance, while the Sabina pingii was the weakest, as shown bythe descending order of Sophora moorcroftiana, H. gyantsensis, B. viciifolia, Salix microstachya and Sabina pingiivar. wilsonii .