红树林植物气孔对环境因子的响应及其与水力功能的协调

Stomatal responses to environmental factors and its coordination with hydraulic functions in plants of mangrove forests

红树林植物长期生活在高盐、高光的环境中,其气孔对环境因子的响应行为及其气孔运动行为是否受自身水力功能的调控仍缺乏了解。本研究以9种红树林植物为研究对象,测定了它们的叶片气孔导度(G_s)对光照以及蒸汽压差(VPD)的响应曲线、G_s日变化、叶片的凌晨水势(Ψ_(pd))和中午最低水势(Ψ_(min))以及叶片导水率(K_(leaf))。结果显示:红树林植物的G_s均随光强的增加而线性增大,并且Ψ_(pd)越高的植物往往对光强有更强的响应。而随VPD的升高,9种红树林植物表现出3种不同的气孔响应模式:(1)G_s不断上升;(2)G_s先升后降;(3)G_s先降低然后维持在低值水平。这种不同的气孔响应行为可能与植物的叶片解剖特征以及不同的水分利用策略有关。叶片的Ψ_(pd)和Ψ_(min)均与一天中最大G_s呈显著线性相关,高的叶片水势有助于植物达到更高的G_s。此外,本研究还发现红树林植物K_(leaf)与一天中的最大气孔导度(G_(max))呈显著正相关,说明红树林植物的气孔行为与水力功能是相互协调的。

Plants of mangrove forests grow in circumstances with high salinity and high light density, and it is hardly understood the behavior of their stomatal response to the fluctuation of environmental factors and the relationship between their stomata movement and hydraulic function. In this study, nine species of mangrove forests were used to study the response curves of their stomatal conductance （Gs） to different transient light densities and vapor pressure deficit （VPD）, diurnal variation of stomatal conductance, predawn water potential （ψpd）, midday water potential （ψmin） and leaf hydraulic conductance （Kleaf）. The results showed that the stomatal conductance increased linearly with the increase in light intensity, and the sensitivity of stomatal response to light was correlated with ψpd. Moreover, with the increase in transient VPD, the nine species displayed three different modes of stomatal response： （1） continuously increasing Gs; （2） increasing Gs at rather low VPD and then decreasing Q; （3） decreasing Gs at low VPD and then remaining a low Gs with further increasing of VPD. These different stomatal response modes might be related to leaf anatomical structure and water use strategies. In addition, we also found that Gm,x was significantly linearly correlated with ψpd and ψzmin. This indicates that higher water potential status could help plants to achieve higher stomatal opening. Moreover, we also found that there was significant positive correlation between Kleaf and Gmax, indicating the coordination between stomatal behav- ior and hydraulic function in mangrove plants.