Leaf Ecology of Pre-reproductive Ontogenetic Stages of the Palm TreeEuterpe edulisMart. (Arecaceae)

Abstract

We studied leaves of 208 seedlings (S), infants (I) and juveniles (J) ofEuterpe edulis,randomly selected from plants in 1 ha of swampy forest in SE Brazil. Each new leaf began extending after the complete development of the preceding leaf. The sequence steps of leaf growth were emergence, linear growth while closed, opening of segments and logarithmic growth of the petiole. Average leaf production rate (2.21 leaves per plant year−1) did not vary among ontogenetic stages, conforming to a plastochronic rhythm. Average linear growth rate of the closed leaf was directly related to average area of the open lamina. Herbivores attacked 33.0% of all leaves giving rise to up to 10% loss of area and included damping-off-inducing suckers (7.1%), ordinary suckers (9.8%), chewers (5.4%), miners (2.7%) and multiple attacks (8.0%). These attacks varied among stages (S=22.4%, I=38.1%, J=33.3%), as did leaf mortality rates (S=26.5%, I=14.3% and J=0.0%). Unknown factors were the main cause of leaf mortality (S=14.3%, I=7.1%). Not losing a leaf while a seedling and attaining a minimum leaf area in the infant stage were critical events for survival. Plants gained leaf area by not losing leaves while a seedling, by producing larger leaves with greater growth rates, and by accumulating leaves with longer lifespans. The petiole can simulate an energetically cheaper branch, delimit a vital space around the stem, favourably position the leaf lamina and substitute provisionally for stem growth in height.