岷江干旱河谷区典型灌木对干旱胁迫的生理生化响应

以岷江干旱河谷区6种典型山地灌木沙棘(Hippophae rhamnoides)、羊蹄甲(Bauhinia faberi)、白刺花(Sorphora davidii)、锦鸡儿(Caragana arborescens)、三颗针(Berberis sargentiana)、黄栌(Cotinus szechuanensis)]为试材,采用盆栽试验研究了土壤自然干旱胁迫对苗木叶片抗氧化保护酶活性、膜伤害程度以及渗透调节物质的影响,探讨植物应对土壤干旱逐渐加剧的生理生态适应机理。结果表明,植物不同抗氧化保护酶对干旱胁迫及随之而来的氧化胁迫的响应存在一定差异。各灌木的超氧化物歧化酶随着干旱胁迫的增强呈先上升后下降,过氧化物酶在整个胁迫期间表现为逐渐升高,过氧化氢酶的升高则主要发生在胁迫的中后期,表明不同胁迫时期对植物体起主导作用的保护酶不同,三者表现为相互协调的作用方式。随着干旱胁迫的增强,各灌木的丙二醛呈缓慢增加趋势,细胞的膜脂过氧化作用逐渐加强,植物开始遭受一定程度的毒害。沙棘和羊蹄甲叶片的质膜相对透性随胁迫的增强呈现先升后降最终回到初始水平的特点,表明植物可以通过干旱锻炼获得一定的抗旱能力。白刺花和黄栌叶片的质膜相对透性在胁迫的0—4 d保持不变,从8 d开始大幅上升并一直维持在较高水平,说明胁迫初期植物细胞膜的结构和功能还很完整,生理活动仍能正常进行,但从中期开始细胞膜遭受严重破坏。随着干旱胁迫的增强,各灌木叶片的脯氨酸总体均呈增加趋势,表明干旱胁迫下植物通过积累脯氨酸以提高细胞的渗透调节能力。主成分分析表明,6种灌木的抗旱能力由强到弱依次为:羊蹄甲、沙棘、锦鸡儿、黄栌、白刺花、三颗针。综合分析表明,干旱河谷区几种典型灌木可通过提高抗氧化酶活性并积累渗透调节物质对干旱胁迫进行积极的反馈,以减弱逆境胁迫下活性氧的危害,提高细胞的渗透调节能力,减轻细胞遭受的损伤。

Physiological and biochemical response of typical shrubs to drought stress in the Minjiang River dry valley

Physiological process is essential for plant growth, and is sensitive to environmental change. The Minjiang River dry valley in the upper reaches of the Yangtze River is increasing as it is affected by human activity, environmental changes, and their interactions under global climate change scenarios. Water deficit is a major limiting factor in vegetation recovery in this region. Therefore, evaluation of the physiological and biochemical levels is important to determine drought stress adaptations in plants and the selection of drought-tolerant plants. The aim of this study was to investigate the adaptation mechanisms of selected shrubs to drought stress in the Minjiang River dry valley, and to provide a reference for selecting drought-tolerant shrubs. We selected six mountain shrubs from this region, including Hippophae rhamnoides, Bauhinia faberi, Sorphora davidii, Caragana arborescens, Berberis sargentiana, and Cotinus szechuanensis. We evaluated changes of anti-oxidant protective enzyme activities, membrane injury indexes, and osmotic adjustment substances in leaves of these shrubs subjected to increasingly severe drought conditions, using pot experiments. The results showed that the responses of different anti-oxidant protective enzymes of these shrubs to drought stress and subsequent oxidative stress were different. In all six shrubs, superoxide dismutase (SOD) activities first increased and then decreased with prolonged drought stress, peroxidase (POD) activities increased gradually as drought stress continued, whereas catalase (CAT) activities increased in the middle and late stages of drought stress, indicating various protective enzymes could be playing inter-coordinating roles at different stress stages. Malondialdehyde (MDA) in all shrubs showed a slow increase with the prolonged drought stress, indicating that the membrane lipid peroxidation of cells gradually increased, and plants began to experience toxicity. With prolonged drought stress, the membrane permeability of H. rhamnoides and B. faberi initially increased, then decreased, and finally returned to the initial level at the end of the stress period, probably because these two shrubs obtained drought resistance by drought hardening. Membrane permeability of S. davidii and C. szechuanensis remained unchanged between 0 and 4 days when exposed to drought stress, and then sharply increased after 8 days, and then was maintained at a relatively high level. These findings implied that the membrane structure and function of these two plants was still intact and physiological activities could still proceed normally at early stages of drought stress; however, the cell membranes suffered serious damage during the middle stages of drought stress. In all six shrubs, proline contents increased with increased drought stress, indicating that drought stress resulted in proline accumulation and thus improved cell osmotic adjustment capabilities. Principal component analysis can provide a quantitative evaluation of the different physiological and biochemical indexes for the seedlings under drought, which indicated that the six shrubs could be ranked from the most to least drought resistant as follows:B. faberi, H. rhamnoides, C. arborescens, C. szechuanensis, S. davidii, B. sargentiana. The study revealed that all six shrubs positively responded to drought stress through improved antioxidant enzyme activity and the accumulation of osmotic adjustment substances, which could help to reduce reactive oxygen injury, improve osmotic adjustment capabilities, and reduce cell damage.