SALINITY RESPONSES IN 2 POPULATIONS OF VIVIPAROUS RHIZOPHORA-ANGLE L SEEDLINGS

Viviparous seedlings of the red mangrove, Rbizophora mangle L., were c ollected from adult trees growing in areas of low (5 parts per thousan d) and high (36 parts per thousand) surface water salinities, and plan ted as groups in large rectangular pots and treated with seawater corr esponding to the two natural concentrations. Among individuals collect ed from the same site, growth was significantly enhanced in the low (5 parts per thousand) versus high (36 parts per thousand) salinity trea tment. Stem and leaf development exhibited larger differences between high and low salinities than did root growth. Propagules showed no inc reased capacity for growth when treated with salinities similar to the parent tree environments. Seedlings from the high salinity site exhib ited faster growth than those from the low salinity site when treated with low salinity water. However, differences between sites were insig nificant in the high salinity treatment. Results are discussed in the context of vivipary as a preconditioning mechanism for sale-tolerance and the general effects of salinity on physiological and possible gene ric aspects of early development.