Seedling morphology of three mangrove species and its taxonomic implications

Abstract

Seedling establishment is an important part of the life cycle of mangroves. Very early in the juvenile stage, they face adverse situations such as a variable and unstable substrate as well as a high-saline environment Therefore, the propagules should have some ability to float in saline water. Seedlings differ morphologically from the adult plants. Here, I examined the seedling growth stages in three species of mangrove:Aegialitis rotundifolia Roxb.,Aegiceras corniculatum (L) Blanco, andAvicennia marina (Forsk.) Vierh. that grow in the Sundarbans swamps of West Bengal. In all cases, fruits were the propagating units; seeds were inseparable from those fruits. Germination was rapid and required no dormancy period. The hypocotyi pierced the seed coat rather than emerging from the pericarp — a variation on the traditional viviparous type of germination. Seedlings then became exposed prior to abscission from parent plants. Based on germination patterns and differences in seedling morphology observed here, these species should be classified in a more relevant taxonomic group than was done previously.