EFFECT OF ENVIRONMENT AND GIBBERELLINS ON THE EARLY GROWTH AND DEVELOPMENT OF THE RED MANGROVE, RHIZOPHORA-MANGLE L

Seedlings of the red mangrove, Rhizophora mangle L., were subjected to a variety of salinity, light, and plant growth regulator treatments t o examine the influence of these factors on early development. Stem, l eaf, and root growth were significantly enhanced in both low salinity seawater and under reduced intensities of solar radiation. Semi-quanti tative analyses of GAs by enzyme-linked immunoabsorbant assays (ELISA) suggest that under these conditions the early 3/13 hydroxylation GA(1 ) biosynthetic pathway is predominant in R. mangle. Concentrations of GA(1) and GA(19)-like substances were highest in propagules exhibiting enhanced development. Attempts to identify the endogenous GAs by CC-M S were unsuccessful, most likely due to undetermined impurities presen t in mangroves. Exogenous applications of GA(3) to R. mangle were mode rately successful in alleviating shoot, growth inhibitions observed at higher salinities and light levels. The role of gibberellins is discu ssed in terms of metabolic responses to the external environment and p ossible impacts upon the distribution of this species.