期刊
NEW PHYTOLOGIST
卷 183, 期 4, 页码 1114-1123出版社
WILEY
DOI: 10.1111/j.1469-8137.2009.02893.x
关键词
leaf life-span; nitrogen resorption; nitrogen resorption efficiency; N-15 labelling; soil nitrogen availability; sink-source interactions
How the balance between exogenous and endogenous nitrogen for shoot growth varies with soil nitrogen availability, and its consequences on leaf life-span, have rarely been studied within a single species in the field. In this study, we investigated two Rhododendron ferrugineum populations with contrasting leaf life-span. Soil nitrogen availability and nitrogen resorption of different leaf age classes were assessed, as were the interactions between plant compartments, using N-15 labelling and sink organ suppression. The population growing on poorer soil had a shorter leaf life-span (17.9 vs 21.5 months) and a higher net contribution of leaf reserves to shoot growth (32% vs 15%), achieved by faster nitrogen resorption and greater shedding of young nitrogen-rich leaves. For both populations, wood contributed to over 40% of shoot nitrogen demand. Both the negative relationship between current-year shoot mass and the percentage of 1-yr-old attached leaves and the delay of leaf shedding after bud removal suggest that shoot development has a strong effect on leaf life-span. Our results suggest that, contrary to the evolutionary response, plastic response to low soil nitrogen could reduce leaf life-span in evergreen plants. In addition, leaf life-span seems to be strongly influenced by the discrepancy between shoot nitrogen demand and soil nitrogen uptake rather than nitrogen demand alone.
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