Departamento de Biología de Organismos, Universidad Simón Bolívar, Apartado 89.000, Caracas 1080-A, Venezuela.
J Exp Bot. 2010 Mar;61(3):843-55. doi: 10.1093/jxb/erp351. Epub 2010 Jan 15.
The adaptive significance of leaf longevity has been established in relation to restrictive nutrients that can be retranslocated within the plant. However, the effect of deficiencies in 'non-mobile' nutrients on leaf lifespan and photosynthetic carbon gain is uncertain. Calcium is frequently given as an example of an essential nutrient with low phloem mobility that may alter the leaf senescence process. This study has been designed to estimate leaf lifespan, leaf production (L(p)) and leaf death (L(d)) rates, the age structure of leaves, and the decline in maximum photosynthetic rate (A(max)) with age in plants of Ipomoea pes-caprae growing with a full supply of nutrients and with a low Ca supply. The Ca deficiency produced reductions in L(p) and leaf lifespan compared with control plants. In spite of the differences in the demographic parameters between treatments in control and low-Ca plants, the percentage of leaves of a given leaf age class is maintained in such a way that the number of leaves per plant continues to increase. No relationship was found between Ca supply and A(max). However, the decline in A(max) with leaf senescence was rather sudden in control plants compared with plants growing with a low Ca supply. The importance of simultaneously using the total leaf demographic census and the assimilation rate along with leaf lifespan data in order to understand the performance of whole plants under constrained conditions is discussed.
叶片寿命的适应意义已经在与可在植物体内再转移的限制营养物质有关的方面得到确立。然而，“不可移动”营养物质缺乏对叶片寿命和光合碳增益的影响尚不确定。钙经常被作为一个例子，说明它是一种必需的营养物质，在韧皮部中的移动性较低，可能会改变叶片衰老过程。本研究旨在估计叶片寿命、叶片生产（L(p)）和叶片死亡（L(d)）速率、叶片的年龄结构以及在养分充足和低钙供应条件下生长的Ipomoea pes-caprae 植物中最大光合速率（A(max)）随年龄的下降。与对照植物相比，缺钙会降低 L(p)和叶片寿命。尽管对照和低钙植物处理之间在人口统计参数上存在差异，但特定叶片年龄类别的叶片百分比得以维持，使得植物的叶片数量继续增加。在钙供应和 A(max)之间没有发现关系。然而，与低钙供应植物相比，对照植物中 A(max)随叶片衰老的下降相当突然。讨论了同时使用总叶片人口普查和同化率以及叶片寿命数据来理解受限制条件下整个植物性能的重要性。
