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Nitrogen Content and Expansion Rate of Young Leaves of Rain Forest Species: Implications for Herbivory
Thomas A. Kursar and Phyllis D. Coley
Vol. 23, No. 2 (Jun., 1991), pp. 141-150
Published by: Association for Tropical Biology and Conservation
Stable URL: http://www.jstor.org/stable/2388299
Page Count: 10
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We investigated variation in the nitrogen content of young leaves and the rate of leaf expansion in tropical shade tolerant species. Both these factors can influence rates of herbivory: low nitrogen content makes leaves less attractive to herbivores, while rapid expansion reduces the time that young leaves are vulnerable to herbivory. Among the 13 study species, nitrogen in young leaves (at 5% of full expansion) ranged from 20 to 71 mg/g DW Most species had higher nitrogen in young leaves compared to mature leaves, but one species showed no change with age. The ratio of nitrogen import relative to dry weight import was low (1-4%) and dropped during expansion. The amount of nitrogen imported daily into the leaf peaked at 70-75 percent of full expansion, though species varied in the percent of final nitrogen that was imported prior to full expansion (67%-93%). There was a significant positive correlation between nitrogen content of young leaves and the rate of leaf expansion. We suggest that the age-specific patterns of nitrogen can best be understood as a trade-off between high palatability to herbivores and escape through rapid expansion.
Biotropica © 1991 Association for Tropical Biology and Conservation