干旱胁迫对蚬木幼苗表型可塑性的影响

Effect of drought stress on phenotypic plasticity of Excentrodendron hsienmu seedlings

以3年生蚬木Excentrodendron hsienmu幼苗为试验材料,采用盆栽控水法,设置4个水分处理梯度,模拟研究不同强度干旱胁迫下蚬木幼苗生长和形态的表型可塑性。结果表明:干旱胁迫对蚬木幼苗地上部分的抑制作用明显大于地下部分;随着干旱胁迫程度的增加,蚬木幼苗地上部分形态指标均呈下降的趋势,而地下部分根系先升高后降低,在中度胁迫处理条件下达到峰值;各组分生物量积累显著降低,其中,叶生物量对干旱胁迫的反应更为敏感,变化的幅度最大,茎次之,根最小;干旱胁迫下,植株将更多的同化物分配到根系,根生物量比增加,根冠比增大,增强了植株抵御干旱胁迫的能力;综合分析表明,土壤含水量11.23%~14.44%是蚬木幼苗生长、生物量积累受到明显抑制的阈值,在育苗和造林实践中可将该值作为土壤水分含量的下限。

An experiment was conducted to explore effect of drought stress on biomass allocation and phenotypic plasticity of 3-year- old potted E. hsienmu seedlings. The seedlings grown under four soil water stressed conditions, of field moisture capacity, which were imposed by controlling the water supply. Results showed that inhibitory effect of drought stress on above-ground orE. hsienmu seedlings was stronger than that on under-ground. All above-ground morphological indexes of E. hsienmu seedlings decreased as the soil drought stress increasing, while the under-ground ascended firstly then descended, with the greatest under MS condition. Biomass of each group significantly decreased. Among them, response of leaf biomass to drought stress was more sensitive. Variation range of leaf biomass was the highest, that of stem biomass the second, and root was the least. Under drought stress conditions, plants allocated more assimilates to the root, and root mass ratio and root-shoot ratio increased as the soil drought stress increasing, which enhanced the capacity of E. hsienmu seedlings to resist drought stress. Comprehensive analysis showed that soil water content of 11.23%-14.44% was the threshold to the growth and biomass accumulation orE. hsienmu seedlings be significantly inhibited by drought stress, which can be as the limit of soil water content for E. hsienmu seedling cultivation and afforestation.