A review of light interception in plant stands from leaf to canopy in different plant functional types and in species with varying shade tolerance
A review of light interception in plant stands from leaf to canopy in different plant functional types and in species with varying shade tolerance
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DOI：
10.1007/s11284-010-0712-4
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发表时间：
2010-07-01
影响因子：
2
通讯作者：
Niinemets, Uelo
中科院分区：
文献类型：
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作者：
Niinemets, Uelo
沿着植物冠层顶部到底部的光梯度，光拦截效率和光收集成本的变化是生态系统实现高效光收集的主要手段。在当前的综述分析中，分析了植物光收集的叶、芽和冠层水平决定因素，改变光收集的关键性状的光驱动可塑性，以及不同植物功能类型之间和不同耐荫性物种之间的差异。此外，还检查了光收集效率的植物年龄和大小依赖性变化。在叶子水平上，光收集的变化是由叶子叶绿素含量的变化驱动的，叶子叶绿素含量改变了给定叶面积收集的入射光的比例，而单位面积的叶子干质量 (M (A)) 决定了叶子中一定比例的植物生物量形成的叶面积量。在具有复杂叶子横截面的针叶物种中，叶子表面暴露的程度还取决于叶子总表面积与投影表面积的比率。在枝条尺度上，叶子倾斜角度分布和叶子空间聚集是光收集的主要决定因素，而在冠层尺度上，分枝频率、叶子分布和叶子的生物量分配（F（L））显着改变光收集。 F (L) 随着植物尺寸的增加（从草本植物到灌木再到树木）而减小，因为高度较高的植物功能类型的支持成本逐渐增大。在树木中，F (L) 和林分叶面积指数与叶子寿命成正比。改变光收集的植物性状具有很大的潜力来适应光的可用性。随着光可用性的降低，单位质量的叶绿素增加，而 M (A)、叶子水平倾斜度和空间聚集程度则降低。此外，在弱光下，分枝频率降低，树冠变得更平坦。所有这些塑料改性都极大地增强了弱光下的光收集。具有较高耐荫性的物种通常通过在落叶物种中具有较低的 M (A) 和在常绿植物中具有更长的叶子寿命来形成更广泛的冠层。此外，耐荫植物的幼苗通常具有不太强烈的聚集叶子和较平坦的冠层，而在部分暴露于强光的成年植物中，较高的叶子耐荫性使耐荫植物能够保持更多的叶层，从而导致树冠延长。在给定的植物功能类型中，植物年龄和大小的增加会导致 M (A) 增加、F (L) 减少和叶子聚集增加，从而降低植物叶面积指数和光收集效率。植物光收集的这种动态变化在林分发育和生产力中发挥着关键作用。总体而言，当前的综述分析表明，不同尺度的一系列化学和结构特征及其可塑性驱动植物光收集效率。增强的光收集可以通过各种性状组合来实现，并且这些性状组合在植物个体发育过程中会发生变化。
Changes in the efficiency of light interception and in the costs for light harvesting along the light gradients from the top of the plant canopy to the bottom are the major means by which efficient light harvesting is achieved in ecosystems. In the current review analysis, leaf, shoot and canopy level determinants of plant light harvesting, the light-driven plasticity in key traits altering light harvesting, and variations among different plant functional types and between species of different shade tolerance are analyzed. In addition, plant age- and size-dependent alterations in light harvesting efficiency are also examined. At the leaf level, the variations in light harvesting are driven by alterations in leaf chlorophyll content modifies the fraction of incident light harvested by given leaf area, and in leaf dry mass per unit area (M (A)) that determines the amount of leaf area formed with certain fraction of plant biomass in the leaves. In needle-leaved species with complex foliage cross-section, the degree of foliage surface exposure also depends on the leaf total-to-projected surface area ratio. At the shoot scale, foliage inclination angle distribution and foliage spatial aggregation are the major determinants of light harvesting, while at the canopy scale, branching frequency, foliage distribution and biomass allocation to leaves (F (L)) modify light harvesting significantly. F (L) decreases with increasing plant size from herbs to shrubs to trees due to progressively larger support costs in plant functional types with greater stature. Among trees, F (L) and stand leaf area index scale positively with foliage longevity. Plant traits altering light harvesting have a large potential to adjust to light availability. Chlorophyll per mass increases, while M (A), foliage inclination from the horizontal and degree of spatial aggregation decrease with decreasing light availability. In addition, branching frequency decreases and canopies become flatter in lower light. All these plastic modifications greatly enhance light harvesting in low light. Species with greater shade tolerance typically form a more extensive canopy by having lower M (A) in deciduous species and enhanced leaf longevity in evergreens. In addition, young plants of shade tolerators commonly have less strongly aggregated foliage and flatter canopies, while in adult plants partly exposed to high light, higher shade tolerance of foliage allows the shade tolerators to maintain more leaf layers, resulting in extended crowns. Within a given plant functional type, increases in plant age and size result in increases in M (A), reductions in F (L) and increases in foliage aggregation, thereby reducing plant leaf area index and the efficiency of light harvesting. Such dynamic modifications in plant light harvesting play a key role in stand development and productivity. Overall, the current review analysis demonstrates that a suite of chemical and architectural traits at various scales and their plasticity drive plant light harvesting efficiency. Enhanced light harvesting can be achieved by various combinations of traits, and these suites of traits vary during plant ontogeny.