水分胁迫对毛红椿幼苗生长和生物量分配的影响

以我国亚热带落叶阔叶优势树种毛红椿的1年生幼苗为试验材料,设置4个水分胁迫处理,模拟研究不同水分胁迫强度下毛红椿幼苗生长和生物量分配规律。结果表明:水分胁迫对毛红椿幼苗根系生长的限制作用明显大于对苗高生长的限制作用,对地径生长限制作用不明显;随着水分胁迫程度增加,根质量比表现出先增大后减小的趋势;叶质量比在处理初期和中期增大,在处理后期和末期降低;在整个处理阶段,茎质量比始终保持增加趋势;根系平均直径在处理中期和后期逐渐减小,处理末期则有所上升;细根/总根长比值则在处理中期和后期逐渐增大,处理末期则有所降低;不同水分胁迫程度导致根尖数量差异显著。在整个处理阶段,水分首先保证苗高和叶片生长,根系生长受到限制;随着水分胁迫程度增加,通过落叶和根系二次生长来保障根系的水分需求和提高水分吸收效率,以此来缓解水分胁迫对生存的胁迫。

Effects of Water Stress on Seedling Growth and Biomass Allocation of Toona ciliata var. pubescens

Toona ciliata var. pubescens is a native and widespread dominant deciduous broad-leaf tree in the subtropical region of China. An experiment was conducted to investigate the effect of water stress on the growth, biomass partition and root characteristic index of 1-year-old T. ciliata var. pubescens seedlings. The seedlings grew under well-watered and water stressed conditions which were imposed by controlling the water supply. The results showed that the water stress had a negative significant effect on the root growth, but no effect on the growth of ground diameter was found. The root mass ratio increased in the beginning, and then decreased. The leaf mass ratio increased at the early and medium water stress period, and decreased at later and terminal water stress period. The shoot mass ratio increased from beginning to end. The average root diameter decreased gradually from the medium to the later water stress period, and then increased at terminal water stress period. However, the ratio of fine root to total root length increased gradually from the medium to the later water stress period, and then decreased at terminal water stress period. The water stress has a significant effect on the root tip numbers. Therefore, the water supply is satisfied with the aboveground organ growth demand as the priority at the cost of limiting root growth under the water stress conditions. Defoliation and the secondary root growth were used to alleviate water stress pressure and improve water absorption efficiency.