A review of nitrogen allocation in leaves and factors in its effects

Nitrogen is an essential limiting resource for plant growth,and its effective utilization can increase the adaptability of plants.This is because nitrogen is required for the regulation of more than a hundred genes in plants and influences their physiological processes.Leaf nitrogen allocation is defined as the proportion of nitrogen distributed in every plant leaf cell and free compounds.Leaf nitrogen allocation not only determines the photosynthetic capacity of leaves but also affects their toughness and chemical defenses.Therefore,research on nitrogen allocation in leaves is of great importance.In this study,we evaluated the mode of leaf nitrogen allocation.Leaf nitrogen is generally distributed in the cell wall,cell membrane,nucleus,and organelles such as chloroplasts and mitochondria in the cytoplasm; leaf nitrogen is also found in free compounds.Usually more than half( up to 75%) of the leaf nitrogen is assigned to chloroplasts,which are involved in photosynthesis.An increase in the amount of nitrogen i