Seed structure and germination ecophysiology of Arenga wightii Griff., an endemic vulnerable palm of Southern Western Ghats.

BACKGROUND AND AIMS: Seed germination is the most vital yet challenging stage of tropical palms and the ecophysiology of this process remains undefined. Arenga wightii, an endemic palm of the Southern Western Ghats, is of key interest for toddy harvest and other value-added products. Under natural conditions, this palm regenerates from seeds with low germination. However, the reasons behind the decline in regeneration of this threatened species remain unexplored. We hypothesize that the localised distribution of the palm in the shady regions of the Southern Western Ghats is due to ecophysiological factors related to seed germination and dormancy type. METHODS: We investigated the imbibition time, and the optimum temperature for germination was determined using seed germinators. Dormancy was defined using treatment with dormancy breaking methods. Features of early seedlings were examined through anatomical and histochemical methods. KEY RESULTS: Mature seeds shed with a moisture content of 35%. The physiological, morphoanatomical and histochemical results indicate recalcitrant traits. The seeds exhibit non-deep simple morphophysiological dormancy. Germination of fresh seeds was below 35%; removal of the operculum increased germination to 97% and reduced the mean germination time (MGT) to 5 days. Germination was of a remote non-ligular type, and the seedlings exhibited adaptations to swampy habitats. CONCLUSION: Our findings indicate that slow seed germination, coexistence of dormancy, coupled with recalcitrant traits, indicate the critical nature of temperature requirement, and are an adaptation for survival in humid and shady areas of the Southern Western Ghats. Habitat protection and removal of the operculum from mature seeds are effective for generating seedlings for large scale restoration.