P effects on N uptake and remobilization during regrowth of Italian ryegrass (Lolium multiflorum)
2003
Kim, Tae-Hwan | Jung, Woo-Jin | Lee, Bok-Rye | Yoneyama, Tadakatsu | Kim, Hak-Yoon | Kim, Kil-Yong
The influence of P deficiency on the utilization of two sources of N, mineral N (exogenous N) and reserved N (endogenous N), for regrowth of Italian ryegrass (Lolium multiflorum) was studied. P-sufficient (+P) or P-free (-P) nutrition solution was applied from 7 days before defoliation to 24 days of regrowth and the N flows derived from two different N sources within the plant were quantified by 15N pulse-chase labeling. Shoot regrowth significantly reduced by 12 days of regrowth, while root growth was more in -P plants. Inorganic P (Pi) concentration was highly reduced by P deprivation more in the stubble and regrowing shoots and less in the roots. At defoliation, P deprivation had induced a higher accumulation for all N compounds in the stubble and for amino acids in the roots. The previously incorporated 15N in stubble and roots as nitrate and amino acids was much decreased in -P plants especially for the first 6 days of regrowth. Total N content in the regrowing leaves was not significantly different between +P and -P plants, but percentage contribution of remobilized N for total leaf N formation was significantly higher in -P plants (78%) than in +P plants (69%) at 6 days of regrowth. From day 12, the utilization of both endogenous and exogenous N was apparently inhibited in -P plants.
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