Coupled response of stomatal and mesophyll conductance to light enhances photosynthesis of shade leaves under sunflecks
Coupled response of stomatal and mesophyll conductance to light enhances photosynthesis of shade leaves under sunflecks
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DOI：
10.1111/pce.12841
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发表时间：
2016-12-01
影响因子：
7.3
通讯作者：
Duursma, Remko A.
中科院分区：
文献类型：
--
作者：
Campany, Courtney E.;Tjoelker, Mark G.;Duursma, Remko A.
树冠内的光梯度在植物资源的分布中起着重要作用，植物资源决定了阳光和遮荫叶子的光合作用能力。然而，阳光和遮荫叶子响应光的气体交换的生化和扩散限制仍然缺乏量化，但对于预测冠层碳和水交换至关重要。为了研究阳光和遮荫叶子的二氧化碳扩散途径，将叶子气体交换与碳同位素辨别的同时测量相结合，以测量在气候控制的全树室中生长的细角桉树的净叶光合作用（A（n））、气孔导度（g（s））和叶肉导度（g（m））。与向阳叶相比，遮荫叶的A(n)、g(m)、叶氮和光合能力(A(max))较低，但g(s)相似。当暂时增加遮荫叶的光照强度以匹配向阳叶的光照强度时，g(s)和g(m)均增加，并且A(n)增加至大于向阳叶的值。我们表明，遮荫叶子对改变的光环境的动态生理反应对于扩大叶子水平测量和预测整个冠层碳增益具有影响。尽管表现出光合能力降低，但随着光照的增加，g(m) 的快速上调使遮荫叶子能够对阳光斑点做出快速反应。
Light gradients within tree canopies play a major role in the distribution of plant resources that define the photosynthetic capacity of sun and shade leaves. However, the biochemical and diffusional constraints on gas exchange in sun and shade leaves in response to light remain poorly quantified, but critical for predicting canopy carbon and water exchange. To investigate the CO2 diffusion pathway of sun and shade leaves, leaf gas exchange was coupled with concurrent measurements of carbon isotope discrimination to measure net leaf photosynthesis (A(n)), stomatal conductance (g(s)) and mesophyll conductance (g(m)) in Eucalyptus tereticornis trees grown in climate controlled whole-tree chambers. Compared to sun leaves, shade leaves had lower A(n), g(m), leaf nitrogen and photosynthetic capacity (A(max)) but g(s) was similar. When light intensity was temporarily increased for shade leaves to match that of sun leaves, both g(s) and g(m) increased, and A(n) increased to values greater than sun leaves. We show that dynamic physiological responses of shade leaves to altered light environments have implications for up-scaling leaf level measurements and predicting whole canopy carbon gain. Despite exhibiting reduced photosynthetic capacity, the rapid up-regulation of g(m) with increased light enables shade leaves to respond quickly to sunflecks.