干旱胁迫对润楠幼苗生长和生理生化指标的影响

Effects of drought stress on growth and physiological parameters of Machilus pingii seedlings

以2年生润楠(Machilus pingii)幼苗为试验材料,采用盆栽和持续停水的干旱处理方法,模拟研究不同干旱胁迫时段对润楠幼苗生长及抗性生理的影响,旨在为润楠幼苗的栽培和水分管理提供理论依据及技术参考.结果显示:(1)随着干旱胁迫时间延长和胁迫程度增加,土壤体积含水量(SWC)、叶片组织中相对含水量(LRWC)、苗高和地径生长量均下降,叶绿素a、叶绿素b、类胡萝卜素Car以及叶绿素a/b均呈先增加后降低的趋势;(2)主要渗透调节物质可溶性糖(SS)含量、可溶性蛋白(SP)含量随着干旱时间延长表现为先升后降,脯氨酸(Pro)含量逐渐升高;(3)丙二醛(MDA)、过氧化氢(H2O2)含量在轻度(SWC为10%-15%)和中度(SWC为6%-10%)胁迫下缓慢增加,重度胁迫(SWC<6%)下大幅度增加,说明膜脂过氧化作用加剧,膜透性增加;(4)在整个干旱过程中,超氧化物歧化酶(SOD)活性、抗坏血酸(As A)逐渐下降,而过氧化物酶(POD)活性在轻度和中度干旱过程中逐渐加强,重度胁迫下急剧下降,但胁迫结束时仍高于对照25.5%.本研究表明,在轻度和中度干旱条件下(SWC>7.6%),润楠幼苗能通过调节自身的抗氧化系统和渗透调节物质含量来减轻干旱伤害,维持植物体的生长及正常生理代谢,从而表现出一定的耐旱抗旱潜力;但在土壤水分亏缺较严重的条件下,润楠幼苗会受到严重伤害.

This paper is aimed to determine the drought-resistant characteristics of Machilus pingii seedlings in order to provide theoretical foundation and technical reference for the cultivation and water management of M. pingii seedlings. The study was a pot trial in greenhouse. The continuous drought stress in different duration was classified as different soil water levels： well-watered （CK）, mildly stressed （water soil content （SWC）： 10-15%）, moderately stressed （SWC： 6-10%） and severely stressed （SWC： 〈 6%）. The results indicated that： （1） with longer duration of drought stress, the SWC, relative leaf water content （LRWC）, and the height and basal diameter increment of seedling decreased significantly. Chlorophyll a （Chla）, Chlorophyll b （Chlb）, carotenoids （Car） contents and Chla/b increased at the beginning and then decreased. （2） Main osmotic adjustment substances including soluble sugar （SS） and soluble protein （SP） contents increased at first, reached the maximum values under moderate drought stress, and declined under severe drought, while proline （Pro） content increased continuously. （3） With higher drought stress intensity, the contents of mlonaldehyde （MDA） and hydrogen peroxide （H2O2） increased slowly under moderate drought stress, and then rose sharply under severe drought stress, which led to aggravation of membrane lipid peroxidation and increase of membrane permeability. （4） The superoxide dismutase （SOD） activity and ascorbic acid （AsA） content in leaves were significantly lower in drought-stressed plants compared with well-watered plants, whereas peroxidase （POD） activity initially increased but then declined. By the end of drought stress, POD activity was still 25.5% higher than that of CK. We concluded that under the condition of mild and moderate drought stress （SWC 〉 7.6%） M.. pingii seedlings can adjust the protective enzyme system and osmotic adjustment substances to reduce the damage of drought stress and maintain growth of the seedlings and normal physiological metabolism. But under the condition of serious soil water deficit, M. pingii seedlings will be severely hurt.