Evaluation of some mangrove species on the nature of their reproduction along the coastal belt of the Indian Sunderbans

Abstract

Reproductive biology of three dominating mangrove species Rhizophora mucronata, Ceriops decandra and Avicennia marina from the Indian Sunderbans were studied. A comparative account on all floral parts revealed that as the bud progresses to completely open, the length of androecium surpassed the length of gynoecium and the anther matured first thus showing protandrous nature and favouring cross-fertilization. A study of pollen grain viability revealed that all of them produces fairly good amounts of viable pollen grains in their natural condition. The pollens showed their maximum viability late in the morning till early noon. The stigma showed peak receptivity after three days of flower opening in C. decandra and four days of flower opening in R. mucronata and A. marina. All the species showed out-breeding mechanism of pollination. The fruit setting percentage obtained by xenogamy was the highest and autogamy failed to show any result in all the three genera. Although Ceriops decandra and Avicennia marina showed very limited fruit set with geitonogamy, these two species can be called facultative out-crossers, while Rhizophora was obligate outcrosser in nature. The study on floral structure, pollen viability along with stigma receptivity of the investigated taxa guided to maximum exploitation of reproductive behavior for rising artificial and natural plant population in addition to build up a future research strategy in ecosystem conservation.