Mediavilla Sonia, Escudero Alfonso
Departamento de Ecología, Facultad de Biología, Universidad de Salamanca, 37071 Salamanca, Spain.
New Phytol. 2003 Jul;159(1):203-211. doi: 10.1046/j.1469-8137.2003.00798.x.
• The relationships between leaf longevity and the average photosynthetic capacity of the different leaf age-classes present in the crown were studied in several tree species to understand the effects of the differences in leaf longevity on the final C budget of the leaves. • Photosynthetic capacity per unit leaf mass (A/mass) was measured in leaves of all age classes present in the crown. Demographic analyses were conducted to establish the age structure of the leaf populations. With these data we estimated the average A/mass of the whole leaf population, weighted by the mass of leaves present in each age class. • A/mass decreased in all the evergreen species as the leaves aged. As a result, the assimilation rates averaged over all leaf age classes in species with greater leaf longevity were much lower than assimilation rates of young foliage, and the average rate of assimilation decreased with the increase in leaf life span of the different species. • The reduction in the average assimilation rates with the increase in leaf life span was proportional to the increase in leaf longevity. With these results it may be predicted that CO assimilation integrated over the lifetime of the leaf should be independent of leaf longevity.
• 研究了几种树种树冠中叶片寿命与不同叶龄级别的平均光合能力之间的关系，以了解叶片寿命差异对叶片最终碳收支的影响。• 测量了树冠中所有叶龄级别的单位叶质量光合能力（A/质量）。进行了种群统计学分析以确定叶片种群的年龄结构。利用这些数据，我们根据每个叶龄级别中叶片的质量加权，估算了整个叶片种群的平均A/质量。• 在所有常绿树种中，随着叶片变老，A/质量下降。因此，叶片寿命较长的物种中，所有叶龄级别平均的同化率远低于幼叶的同化率，并且不同物种的平均同化率随着叶片寿命的增加而降低。• 随着叶片寿命增加，平均同化率的降低与叶片寿命的增加成正比。根据这些结果，可以预测叶片一生中累积的CO同化量应与叶片寿命无关。
