Seed anatomy, moisture content and scarification influence on imbibition in wild banana (Musa acuminata Colla) ecotypes
Low and erratic germination in wild banana seed is caused by dormancy due to physical, anatomical or physiological reasons. Imbibition activates germination process and the rate of water uptake during imbibition is influenced by seed molecular composition and internal and external morphological structures. The present study aimed at examining the effect of seed anatomy and seed moisture content on water uptake by wild banana seeds. Matured fresh and dry, intact or scarified seeds of three wild banana ecotypes (Musa acuminata Colla) viz. Krau White, Serdang Red and Serdang Yellow were imbibed for up to 96 h. Percentage increase in seed mass was recorded at different intervals. Internal morphological structures of fresh and dry seeds were viewed using scanning electron microscopy (SEM). Seed mass increased rapidly within first hour and the rate of increase was always higher in dry seed than the fresh seed in all the ecotypes. The SEM observation revealed that the rapid increase of seed mass is likely due to the shrinking of the operculum and the surrounding tissues in the hilum area which resulted in the formation and widening of a water channel in dry seed. This study indicates that operculum does not impede water uptake in mature banana seed during imbibition, suggesting that seed dormancy in these three ecotypes is not due to physical dormancy but may be physiological in nature.
Key words: Musa acuminata, imbibition, seed coat, scarification, physical dormancy.