Specific leaf weight and nitrogen allocation responses to light exposure within walnut trees
1991
Klein, I. | DeJong, T.M. | Weinbaum, S.A. | Muraoka, T.T.
Exposure to photosynthetically active radiation and the consequent effect on leaf mass per unit leaf area (SLW) and nitrogen (percent dry weight and microgram.mm-2) allocation within tree canopies was investigated in walnut (Juglans regia 'Serr' and 'Hartley') trees. Percent contribution of discrete light flux densities below light saturation 100-700 micromoles.s-1.m-2) to the total light exposure of individual spurs, exposed up to 9 hour.day-1 to saturating light (>700 micromoles.s-1.m-2), was minimal (< 1 hour), indicating that individual spurs were either exposed or shaded most of the day. SLW and N content per unit leaf area of individual spurs were highly correlated (second-order polynomial curve fit) with light exposure within the tree canopy, indicating uneven allocation of available N for optimal utilization. Nitrogen expressed as percent dry weight was not correlated with light exposure and SLW. Leaf N content per leaf area was highly correlated (linear fit) with SLW.
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