Contrasting seed biology of two ornamental palms: Pygmy Date Palm (Phoenix roebelenii O’Brien) and Fishtail Palm (Caryota urens L.) and implications for their long-term conservation

Abstract

The Arecaceae family includes palm trees of economic importance both as a source of agricultural produce and as ornamental components in landscaping projects. Pygmy date palm (Phoenix roebelenii) and solitary fishtail palm (Caryota urens) are well known landscaping plants today. Both species have their origin in Southeast Asia and, especially C. urens is widespread in peninsular India and Sri Lanka. They are multipurpose species with a variety of applications and thus very heavily utilized. Knowledge of palm seed storage biology will improve their conservation prospects. In present studies, fresh seed moisture content in P. roebelenii was recorded to be 30% with germinability of 98%. After desiccation to 8% moisture germinability was reduced to 90% and the seeds survived cryo-exposure. Fresh seeds of C. urens, with initial moisture content of 34% and 95% germinability could be desiccated to lowest level of only 29% moisture content, with complete loss of germinability. Fresh as well as desiccated seeds of this species did not survive cryo-exposure. While the seeds of C. urens stored at room temperature lost their germinability by 110 days, seeds of P. roebelenii could germinate even after 9 months of storage. P. roebelenii is proven to exhibit orthodox seed storage behaviour while C. urens is found to exhibit recalcitrant seed storage behaviour. Long-term ex situ cryo-conservation in the form of seed gene banks would be suitable for seed propagated orthodox palm species and a few germplasm centres may be established for recalcitrant Indian palms in suitable bio-geographic regions as a complimentary ex situ conservation.