Leaf longevity is controlled by the light gradient in the canopy and also by the nitrogen (N) sink strength in the plant. Stand density may influence leaf dynamics through its effects on light gradient and on plant growth and reproduction.
Ogawa et al. grow plants of Xanthium canadense at two stand densities and record emergence, growth and death of every leaf on the main stem and branches from germination to full senescence of the plants. They demonstrate that in the vegetative phase the light gradient strongly controls leaf longevity, whereas later the effects of branching and reproductive activities become stronger and overrule the effect of the light environment. As leaf N supports photosynthesis and also works as a N source for plant development, N use is pivotal in linking leaf dynamics with plant growth and reproduction.