KYOUSEI Science Center for Life and Nature, Nara Women's University, Kita-uoya Higashimachi, Nara, Japan.
Tree Physiol. 2011 Feb;31(2):160-8. doi: 10.1093/treephys/tpq102. Epub 2011 Mar 7.
We investigated effects of heterogeneous stomatal behavior on diurnal patterns of leaf gas exchange in 10 tree species. Observations were made in middle and upper canopy layers of potted tropical rainforest trees in a nursery at the Forest Research Institute Malaysia. Measurements were taken from 29 January to 3 February 2010. We measured in situ diurnal changes in net photosynthetic rate and stomatal conductance in three leaves of each species under natural light. In both top-canopy and sub-canopy species, midday depression of net assimilation rate occurred in late morning. Numerical analysis showed that patchy bimodal stomatal behavior occurred only during midday depression, suggesting that the distribution pattern of stomatal apertures (either uniform or non-uniform stomatal behavior) varies flexibly within single days. Direct observation of stomatal aperture using Suzuki's Universal Micro-Printing (SUMP) method demonstrated midday patchy stomatal closure that fits a bimodal pattern in Shorea leprosula Miq., Shorea macrantha Brandis. and Dipterocarpus tempehes V.Sl. Inhibition of net assimilation rate and stomatal conductance appears to be a response to changes in vapor pressure deficit (VPD). Variable stomatal closure with increasing VPD is a mechanism used by a range of species to prevent excess water loss from leaves through evapotranspiration (viz., inhibition of midday leaf gas exchange). Bimodal stomatal closure may occur among adjacent stomata within a single patch, rather than among patches on a single leaf. Our results suggest the occurrence of patches at several scales within single leaves. Further analysis should consider variable spatial scales in heterogeneous stomatal behavior between and within patches and within single leaves.
我们研究了异质性气孔行为对 10 种树木叶片气体交换日变化模式的影响。观测在马来西亚森林研究所苗圃中盆栽热带雨林树木的中上层冠层进行。测量于 2010 年 1 月 29 日至 2 月 3 日进行。我们在自然光下测量了每个物种 3 片叶子的净光合速率和气孔导度的原位日变化。在顶冠层和下冠层物种中，净同化率的中午低谷出现在上午晚些时候。数值分析表明，仅在中午低谷期间出现点状双峰气孔行为，这表明气孔开度的分布模式（均匀或非均匀气孔行为）在单日内灵活变化。使用铃木通用微印刷（SUMP）方法直接观察气孔孔径，表明中午点状气孔关闭在 Shorea leprosula Miq.、Shorea macrantha Brandis. 和 Dipterocarpus tempehes V.Sl. 中呈双峰模式。净同化率和气孔导度的抑制似乎是对水汽压亏缺（VPD）变化的反应。随着 VPD 的增加而变化的可变气孔关闭是一系列物种用来防止通过蒸腾作用（即抑制中午叶片气体交换）从叶片中过度失水的机制。双峰气孔关闭可能发生在单个斑点内的相邻气孔之间，而不是在单个叶片上的斑点之间。我们的结果表明，单个叶片内存在多个尺度的斑块。进一步的分析应考虑异质气孔行为在斑块之间和斑块内以及单个叶片内的可变空间尺度。
