Irradiance heterogeneity within crown affects photosynthetic capacity and nitrogen distribution of leaves in Cedrela sinensis
Irradiance heterogeneity within crown affects photosynthetic capacity and nitrogen distribution of leaves in Cedrela sinensis
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DOI：
10.1111/j.1365-3040.2009.02100.x
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发表时间：
2010-05-01
影响因子：
7.3
通讯作者：
Yoshimura, Kenichi
中科院分区：
文献类型：
--
作者：
Yoshimura, Kenichi
由于森林林下的光照条件高度异质，树冠内空间变化辐照度的光合作用对于树冠水平的碳同化非常重要。研究了树冠内辐照度变化对先锋落叶树雪松幼树羽状复叶叶片氮含量和光合速率的影响。采用透光率25%的遮光伞进行人工重度遮光，设置叶片遮荫量为0%、25%、50%、75%和100%的5个遮光处理。尽管无论遮荫处理如何，叶片的氮含量都是恒定的，但部分遮荫树冠内遮荫叶子的核酮糖1中心点5-二磷酸羧化酶/加氧酶（Rubisco）含量和光饱和光合能力低于完全遮荫树冠内的核酮糖1中心点5-二磷酸羧化酶/加氧酶（Rubisco）含量和光饱和光合能力。部分遮荫树冠内的遮荫叶含有较高含量的氨基酸。大多数遮荫叶子在部分遮荫的树冠中死亡，而一半以上的遮荫叶子在完全遮荫的树冠中存活下来。对当地光照条件的光合作用适应的假设无法解释为什么遮荫叶子在部分和完全遮荫的树冠之间具有不同的光合能力和存活率。树冠内的辐照度异质性导致树冠内阳光和阴影叶子之间光合作用活动的明显变化。
Because light conditions in the forest understory are highly heterogeneous, photosynthetic acclimation to spatially variable irradiance within a crown is important for crown-level carbon assimilation. The effect of variation in irradiance within the crown on leaf nitrogen content and photosynthetic rate was examined for pinnate compound leaves in saplings of Cedrela sinensis, a pioneer deciduous tree. Five shading treatments, in which 0, 25, 50, 75 and 100% of leaves were shaded, were established by artificial heavy shading using shade screen umbrellas with 25% transmittance. Although the nitrogen content of leaves was constant regardless of shading treatment, ribulose 1 center dot 5-bisphosphate carboxylase/oxygenase (Rubisco) content and light-saturated photosynthetic capacity were lower in shade leaves within partially shaded crowns than within fully shaded crowns. Shade leaves within partially shaded crowns contained higher amount of amino acids. Most shade leaves died in partially shaded crowns, whereas more than half of shade leaves survived in totally shaded crowns. Assumptions on photosynthetic acclimation to local light conditions cannot explain why shade leaves have different photosynthetic capacities and survival rates in between partially and totally shaded crowns. Irradiance heterogeneity within the crown causes a distinct variation in photosynthetic activity between sun and shaded leaves within the crown.