Significance of leaf longevity in plants

The cost–benefit model of leaf life span is extended by incorporating the cost of construction and maintenance of supporting structures, such as shoots and roots. Published data on leaf longevities were reviewed, and they support qualitative predictions of optimal leaf life span based on the present model. In relation to life form, leaf life span increases in the following sequence, due to increasing costs of support structures: floating leaves of aquatic plants < annual herbs < perennial herbs < deciduous trees. Within species, leaf life span increases with plant size as support costs per unit of leaf increase. This prediction is supported by comparisons of seedlings and adults of temperate trees. These results suggest that the construction and maintenance costs of supporting structures significantly influence life span of individual leaves. Leaf longevity, in turn, connects the ecophysiology of the individual leaf to growth of the individual plant and energy and matter cycling at the ecosystem level.