Why does needle photosynthesis decline with tree height in Norway spruce?
Why does needle photosynthesis decline with tree height in Norway spruce?
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为什么挪威云杉的针叶光合作用随着树高的增加而下降？
DOI：
10.1111/j.1438-8677.2011.00503.x
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发表时间：
2012
期刊：
影响因子：
3.9
通讯作者：
E. Merilo
中科院分区：
文献类型：
--
作者：
O. Räim;E. Kaurilind;L. Hallik;E. Merilo
以爱沙尼亚耶尔夫塞利亚实验林为研究对象，对挪威云杉针叶的形态、化学和生理特性进行了研究。当年的枝条从5个林分的树冠上部取样，高度从1.8到33.0米不等（相应的年龄范围是10-85年）。测定A/C（i）曲线以获得最大羧化速率（V（cmax））和最大电子传递速率（J（max））。根据V（cmax）、J（max）和叶片叶绿素浓度计算了针叶氮（N）在光合功能中的分配。针叶的长度、宽度、厚度、体积、叶肉和木质部的截面积均随树高的增加而显著增加。较高的树木针叶有较低的质量为基础的N和叶绿素浓度（21%和43%之间的差异最短和最高的立场，分别），但较高的单位面积干质量（35%），单位体积干质量（18%），细胞数每叶肉横截面积（40%）和分配到非光合功能的N（12%）。光饱和净同化率、V（cmax）、J（max）和气孔导度随树龄的增加而降低（分别相差35%、16%、12%和29%）。一个路径分析模型描述树的年龄相关的减少光合能力作为一个结果库限制提供了最适合我们的数据。然而，由于路径模型对应的源限制，光合作用减少来自针叶结构和化学的变化没有被拒绝，我们得出结论，光合作用随着树龄的下降，结果从几个机制（有限的库强度，气孔和N限制）同时和顺序操作。
Needle morphological, chemical and physiological characteristics of Norway spruce were studied in a forest chronosequence in Järvselja Experimental Forest, Estonia. Current-year shoots were sampled from upper canopy positions in five stands, ranging in height from 1.8 to 33.0 m (corresponding age range was 10-85 years). A/C(i) curves were determined to obtain maximum carboxylation rates (V(cmax)) and maximum rates of electron transport (J(max)). Needle nitrogen (N) partitioning into photosynthetic functions was calculated from the values of V(cmax), J(max) and leaf chlorophyll concentration. All needle size parameters (length, width, thickness, volume and cross-sectional areas of mesophyll and xylem) increased significantly with tree height. The needles of taller trees had lower mass-based N and chlorophyll concentrations (21% and 43% difference between shortest and tallest stands, respectively), but higher dry mass per area (35%), dry mass per volume (18%), number of cells per mesophyll cross-section area (40%) and partitioning of N into non-photosynthetic functions (12%). Light saturated net assimilation rate, V(cmax), J(max) and stomatal conductance decreased with tree age (35%, 16%, 12% and 29% difference, respectively). A path analysis model describing tree age-related reduction of photosynthetic capacity as a result of sink limitation provided the best fit to our data. However, since the path model corresponding to source limitation, where photosynthetic reduction derives from changes in needle structure and chemistry was not rejected, we conclude that the decline in photosynthesis with tree age results from several mechanisms (limited sink strength, stomatal and N limitation) operating simultaneously and sequentially.