Establishment and persistence characteristics in juvenile leaves and phyllodes of Acacia koa (Leguminosae) in Hawaii

Field measurements of gas exchange parameters, water relations, carbon isotope discrimination (Delta(13)C), and nitrogen content were used to test the hypothesis that juvenile leaves and phyllodes of Acacia koa possess characteristics that promote establishment (rapid growth) and persistence (stress tolerance), respectively. Juvenile leaves had higher conductance, higher photosynthetic rate by mass, lower water-use efficiency, higher photosynthetic nitrogen-use efficiency, higher nitrogen content, a lower ratio of carbon content to nitrogen content, lower average water potential, and higher Delta(13)C than phyllodes. As conductance and photosynthesis rates increased for both leaf types, rates in phyllodes were more limited than rates in juvenile leaves. Differences in leaf morphology, including the ratio of leaf mass to leaf area, inclination, and minimal leaf dimension, account for differences in leaf performance.