摘要
以西双版纳地区石灰山季节雨林三种优势常绿树种油朴(Celtis wightii)、尖叶闭花木(Cleistanthus sumatranus)和轮叶戟(Lasiococca comberi var. pseudoverticillata)为材料,研究了季节性干旱对树木枝条水分传导、最大光合速率(Amax)和渗透调节相关的叶片的生理生态特征等的影响。结果表明,与雨季相比三种植物的叶片凌晨水势在旱季都有显著的降低,说明该生境的植物在旱季遭受较为严重的土壤干旱胁迫。除油朴的枝条边材比导率(Ks)在旱季和雨季没有显著性差异外,尖叶闭花木和轮叶戟的Ks在旱季都有显著的降低;而枝条的叶比导率(Kl)三树种在两个季节间均无显著变化。Kl在旱季没有显著性降低,可能是常绿树种在旱季通过脱落部分叶片以调整其水力结构来保持较高的单位叶面积的水分供应。在旱季三树种Amax都有显著减小。Ks和Kl都和Amax呈正相关关系,说明了枝条木质部的水分传导对叶片光合作用有较直接的影响。三树种叶片膨压丧失点的水势和饱和渗透势在旱季也均显著降低,表明三树种都通过较强的渗透调节来适应季节性的干旱。与同一生境中两种常见落叶树种相比较,三树种木质部导管抵抗空穴化的能力较强,能在较低的木质部水势下保持其水分传导,以在旱季仍能维持叶片较为正常的生理功能。这些结果初步揭示了石灰山常绿优势树种通过水力结构的调整和渗透调节等来适应季节性干旱的策略。
To investigate the adaptive mechanisms of evergreen species to seasonal drought, we studied seasonal changes of plant hydraulics, photosynthesis and leaf osmotic related traits in three dominant evergreen species （ Celtis wightii, Cleistanthus sumatranus and Lasiococca combed var. pseudoverticillata ） of a limestone mountain area of Xishuangbanna, SW China. Compared to the wet season, the predawn leaf water potential in the dry season is significantly lower in all the three species, indicating a relatively strong soil drought stress. During the dry season, sapwood specific hydraulic conductivity （ Ka ） was significantly lower compared to that of the wet season in Cleistanthus sumatranus and Lasiococca comberi var. pseudoverticillata, but there was no significant change in Celtis wightii. There was no significant change in leaf area specific hydraulic conductivity （Ki） between the two seasons in all the three species, which may caused by the adjustment in hydraulic architecture through partial loss of leaves during the dry season. In the dry season, maximum carbon assimilate rate （ Amax ） was significantly lower than that of the wet season in all the three species. There were strong correlations between Amax and both of the two hydraulic traits （ i.e. Ka and K1 ）, especially during the wet season, indicating a relatively strong independence of photosynthesis to water transport in stems. Leaf turgor loss point osmotic potential and saturation osmotic potential during the dry season were both significanfly lower in all the three species, indicating a strong osmotic adjustment in adaptive to seasonal drought. Compared to the two co-occurring deciduous species, the ability to tolerate drought-induced cavitation in stem xylems were substantially higher in the three evergreen species. These results indicated that the adaptation of these three evergreen species to seasonal drought mainly involves an adjustment in hydraulic architecture and a strong osmotic regulation in leaves.
出处
《云南植物研究》
CSCD
北大核心
2008年第3期325-332,共8页
Acta Botanica Yunnanica
基金
国家重点基础研究发展计划973项目(2006CB403207)
关键词
石灰山季节雨林
干旱胁迫
水分传导
光合作用
Limestone seasonal rainforest
Seasonal drought
Hydraulic conductivity
Photosynthesis
