Guo Xuchen, Shi Peijian, Niinemets Ülo, Hölscher Dirk, Wang Rong, Liu Mengdi, Li Yirong, Dong Lina, Niklas Karl J
Bamboo Research Institute, College of Biology and the Environment, Nanjing Forestry University, 159 Longpan Rd., Nanjing, 210037, China.
Tropical Silviculture and Forest Ecology, University of Göttingen, Büsgenweg 1, 37077, Göttingen, Germany.
Am J Bot. 2021 Sep;108(9):1662-1672. doi: 10.1002/ajb2.1738. Epub 2021 Sep 27.
Leaf mass (M) and lamina surface area (A) are important functional traits reported to obey a scaling relationship called "diminishing returns" (i.e., M ∝ A ). Previous studies have focused primarily on eudicots and ignored whether the age of leaves affects the numerical value of the scaling exponent (i.e., α).
The effect of age was examined using 1623 Phyllostachys edulis leaves from culms differing in age collected in Nanjing, China. The scaling relationships among leaf A, fresh mass (FM), and dry mass (DM) were evaluated using reduced major axis protocols. The bootstrap percentile method was used to test the significance of differences in α-values.
Overall, the numerical values of α exceeded 1.0. The scaling relationship between FM and A was statistically more robust than that between DM and A. The scaling exponents of FM vs. A exhibited a "high-low-high-low-high" numerical trend from the oldest to the youngest age-group. FM increased linearly as culm age decreased; the leaf DM per unit area (LMA) exhibited a parabolic trend across the age-groups.
"Diminishing returns" is confirmed for all but one age-group of an important monocot species. The relationship between FM and A was statistically more robust than that between DM and A for each age-group. The FM per unit A decreased with increasing age-groups, whereas the middle age-groups had a greater LMA than the oldest and youngest age-groups. These data are the first to show that the age of shoots affects the scaling relationship between leaf mass and area.
叶质量（M）和叶片表面积（A）是重要的功能性状，据报道它们遵循一种称为“收益递减”的比例关系（即M ∝ A ）。以往的研究主要集中在双子叶植物上，而忽略了叶片年龄是否会影响比例指数（即α）的数值。
在中国南京采集了1623片来自不同年龄茎秆的毛竹叶片，研究年龄的影响。使用主轴缩减法评估叶片A、鲜质量（FM）和干质量（DM）之间的比例关系。采用自助百分位数法检验α值差异的显著性。
总体而言，α的数值超过1.0。FM与A之间的比例关系在统计学上比DM与A之间的关系更稳健。从最老到最年轻的年龄组，FM与A的比例指数呈现出“高-低-高-低-高”的数值趋势。随着茎秆年龄的降低，FM呈线性增加；单位面积叶片干质量（LMA）在各年龄组中呈现出抛物线趋势。
除一个年龄组外，一个重要单子叶植物物种的所有年龄组均证实了“收益递减”。对于每个年龄组，FM与A之间的关系在统计学上比DM与A之间的关系更稳健。单位A的FM随年龄组增加而降低，而中年组的LMA比最老和最年轻年龄组更大。这些数据首次表明，嫩枝年龄会影响叶质量与面积之间的比例关系。
