Abstract
Storage nitrogen (N) is a buffer pool for maintaining leaf growth and synthesizing photosynthetic proteins, but the dynamics of its forms within the life cycle of a single leaf and how it is influenced by N supply remain poorly understood. A field experiment was conducted to estimate the influence of N supply on leaf growth, photosynthetic characteristics, and N partitioning inthe sixth leaf of winter oilseed rape (Brassica napus L.) from emergence through senescence. Storage N content (Nstore) decreased gradually along with leaf expansion. The relative growth rate based on leaf area (RGRa) was positively correlated with Nstore during leaf expansion. The water-soluble protein form of storage N was the main N source for leaf expansion. After the leaves fully expanded, the net photosynthetic rate (An) followed a linear-plateau response to Nstore, with An stabilizing at the highest value above a threshold and declining below the threshold. Non-protein and SDS (detergent)-soluble protein forms of storage N were the main N sources for maintaining photosynthesis. For the leaf N economy, storage N is used for co-ordinating leaf expansion and photosynthetic capacity. N supply can improve Nstore, thereby promoting leaf growth and biomass.
Highlights
As a major mineral nutrient that limits the growth of plants, nitrogen (N) absorption by plants is always faster than is required for their current growth, resulting in nitrogen content of sodium dodecyl sulfate (SDS)-soluble protein (Ns) accumulation in the tissue and the formation of nitrogen content of SDS-soluble protein (Ns) reserves (Millard, 1988)
The relative growth rate based on leaf area (RGRa) was positively correlated with storage nitrogen content (Nstore) during leaf expansion
For the leaf N economy, storage N is used for co-ordinating leaf expansion and photosynthetic capacity
Summary
As a major mineral nutrient that limits the growth of plants, nitrogen (N) absorption by plants is always faster than is required for their current growth, resulting in N accumulation in the tissue and the formation of N reserves (Millard, 1988). Storage N is a buffer pool for maintaining leaf expansion and synthesizing photosynthetic proteins in early leaf growth (Chapin et al, 1990; Lehmeier et al, 2013). In the initial growth stage of leaves, both the formation of the photosynthetic apparatus and the expansion of leaves require a large. Increasing the N supply could maintain the photosynthetic protein content in leaves, delaying the onset of senescence (Osaki, 1995). It is essential to clarify the relationships between storage N and leaf expansion/ photosynthesis to understand functionally the mechanisms of storage N for balancing leaf expansion and photosynthetic capacity
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