黄龙山林区不同演替时期典型树种光诱导的气孔动力学研究

Light-induced Stomatal Dynamics in Typical Trees of Different Succession Stages in Huanglong Mountain Forest Region

光诱导的气孔动力学响应快慢是影响植物叶水分利用效率的重要因素,为探索黄土高原不同演替阶段树种水分利用效率差异的生理机制,该研究以黄龙山林区典型树种(演替早期种山杨和白桦、演替后期种辽东栎)的幼龄实生苗为材料,采用盆栽试验,研究了叶片光诱导的气孔导度动力学参数差异及其与气孔特征、叶长期水分利用效率的关系。结果表明:(1)山杨和白桦气孔开放过程中气孔导度(g_(s))增加的时间常数(K_(i))小于辽东栎,但气孔关闭过程中气孔导度降低的时间常数(K_(d))则大于辽东栎,表明山杨和白桦气孔开放更快,而辽东栎的气孔关闭更快。同时,气孔开放过程中山杨和白桦的g_(s)响应幅度均大于辽东栎,气孔关闭过程中山杨的g_(s)响应幅度亦大于辽东栎。(2)3种树种中,辽东栎的气孔密度最大,气孔最小,气孔指数最大,辽东栎气孔特征无法解释其慢速的气孔开放过程。(3)山杨和白桦具有高的光合速率、最大羧化效率和最大电子传递速率,3种树种碳同位素比率(δ^(13)C)表征的长期水分利用效率表现为山杨>白桦>辽东栎。研究认为,演替早期种山杨和白桦的高水分利用效率与其快速的气孔开放有关,而演替后期种辽东栎快速的气孔关闭并未增加其水分利用效率,且长期水分利用效率低于山杨和白桦,可能与辽东栎慢速的气孔开放限制了其光合速率有关。

The rapidity of stomatal response to dynamic irradiance is one of important factors affecting leaf water use efficiency.In order to explore the physiological mechanism of water use efficiency variation in trees from different succession stages,we studied the light-induced stomatal conductance(gs)dynamics and their relation with stomatal traits and leaf long-term water use efficiency in seed-planted seedlings of three species(early succession stage species:Populus davidiana and Betula platyphylla,and late succession species Quercus liaotungensis)native to Huanglong Mountain forest region using a pot experiment.Results showed that,(1)time constant during stomatal opening(Ki)in P.davidiana and B.platyphylla was shorter than that in Q.liaotungensis,but time constant during stomatal closing(Kd)in P.davidiana and B.platyphylla was longer than that in Q.liaotungensis,reflecting that stomata open faster in P.davidiana and B.platyphylla,and close faster in Q.liaotungensis.P.davidiana and B.platyphylla had larger gs response amplitude than Q.liaotungensis during stomatal opening,and P.davidiana had larger gs response amplitude than Q.liaotungensis during stomatal closing.(2)Q.liaotungensis had the largest stomatal density,smallest stomatal size and biggest stomatal index among three species,stomatal traits in Q.liaotungensis could not explain its slower stomatal opening response.(3)P.davidiana and B.platyphylla had higher photosynthetic rate,maximum carboxylation velocity,maximum electron transport rate,long-term water use efficiency indicated by leafδ13C exhibited as P.davidiana>B.platyphylla>Q.liaotungensis.The results show that higher water use efficiency in P.davidiana and B.platyphylla was partly attributed to their rapid stomatal opening,while rapid stomatal closing in the late succession species Q.liaotungensis did not enhance its water use efficiency,and the long-term water use efficiency is lower than that of P.davidiana and B.platyphylla,which may be related to the slow stomatal opening of Q.liaotungensis limiting its photosynthetic rate.