Interrelationships among light, photosynthesis and nitrogen in the crown of mature Pinus contorta ssp. latifolia.
Interrelationships among light, photosynthesis and nitrogen in the crown of mature Pinus contorta ssp. latifolia.
复制标题
成熟松树冠部光照、光合作用和氮素之间的相互关系。
DOI：
10.1093/treephys/19.1.13
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发表时间：
1999
期刊：
影响因子：
4
通讯作者：
W. Smith
中科院分区：
文献类型：
--
作者：
A. Schoettle;W. Smith
为了估计整个叶冠或树冠的碳增益，需要对树冠内的光合作用能力和相应的光微环境的分布进行测量。比较了斑节松光合光响应和单位叶面积氮素含量的变化。SSP。[医]麻叶属(樟子松)树叶与树龄和光照微环境的关系。从树冠上部到树冠下部的日积分光量子通量密度(PPFD)的垂直梯度与从幼叶到老叶的PPFD的水平梯度在大小上相似。无论是幼叶还是老叶，光饱和净光合作用(A(Max))与日PPFD的关系都是显著的。然而，在相似的日照度条件下，老叶的A(Max)低于年轻叶。对于不同树龄的树冠，A(Max)与叶片在自然PPFD环境下的估计日净碳增量(估计的A(Day))呈线性相关(r(2)=0.84，P<；0.001，n=39)，表明估计的A(Day)可能主要由叶片处于光饱和时的固定碳主导，并在A(Max)下运行。达到A(Max)所需的PPFD与叶片可用的PPFD的比较表明，所有测量的叶片(n=39)，无论它们在树冠上的位置或树龄，都处于光环境中，可以在一天中相似比例的时间内进行光饱和光合作用。在所有汇集的数据中，叶片N与每日PPFD的相关性较弱。对各叶龄的分析表明，叶片N与幼叶的PPFD、A(Max)和估计的Ad(D)显著相关，而与中叶和老叶的相关不显著。因此，在本研究中，仅对幼叶(1-4岁)支持叶面氮素根据每日总光能分配到树冠内的一般理论。
Scaling leaf-level measurements to estimate carbon gain of entire leaf crowns or canopies requires an understanding of the distribution of photosynthetic capacity and corresponding light microenvironments within a crown. We have compared changes in the photosynthetic light response and nitrogen (N) content (per unit leaf area) of Pinus contorta Dougl. ssp. latifolia Engelm. (lodgepole pine) leaves in relation to their age and light microenvironment. The vertical gradient in integrated daily photosynthetic photon flux density (PPFD) from the upper to the lower crown of lodgepole pine was similar in magnitude to the horizontal gradient in daily PPFD along shoots from young to old leaves. The relationship between light-saturated net photosynthesis (A(max)) and daily PPFD was significant for both young and old leaves. However, old leaves had a lower A(max) than young leaves in a similar daily irradiance regime. For leaves of all ages from throughout the crown, A(max) was linearly related to the estimated daily net carbon gain that leaves could achieve in their natural PPFD environment (estimated A(day)) (r(2) = 0.84, P < 0.001, n = 39), indicating that estimated A(day) may be dominated by carbon fixed when leaves are light-saturated and operating at A(max). Comparison of the PPFD required to achieve A(max) and the PPFD available to the leaves showed that all of the measured leaves (n = 39), regardless of their position in the crown or age, were in light environments that could light-saturate photosynthesis for a similar proportion of the day. For all data pooled, foliar N was weakly correlated with daily PPFD. Analyzing each leaf age class separately showed that foliar N was significantly related to daily PPFD, A(max), and estimated A(day) for the youngest leaves but not for middle-aged or old leaves. Therefore, the general theory that foliar N is allocated within a crown according to total daily light availability was supported only for young (1-4 years old) leaves in this study.