The Response of Hydrated Recalcitrant Seeds to Long-Term Storage

Abstract

Recalcitrant seeds will ultimately die if stored in the hydrated state. This could be because newly-shed recalcitrant seeds are metabolically active and undergo germinative metabolism in storage. This in turn could generate a requirement for additional water, which could impose a long-term water stress if water is not supplied. Increases in hydrated storage lifespan might be achieved by reducing metabolic rate and thus the rate of post-shedding development. This paper presents some data from storage experiments with seeds of Avicennia marina designed to test this hypothesis. To reduce germinative metabolism naked seeds were coated with alginate in which ABA had been incorporated. Coating the seeds with alginate or alginate with ABA extended the lifespan by up to a factor of three to four. Germination rate, respiration, consumption of storage reserves and ultra-structural data indicated that a reduction of the rate of post-shedding development may have contributed to, but could not fully explain the enhanced storage lifespan of coated seeds. No evidence of water stress in bulk tissue could be detected. It was concluded that dehydration of root primordia might have contributed to the early viability loss of uncoated seeds. Alginate coating may have reduced the rate of dehydration of the primordia, contributing to the extended storage lifespan of coated seeds.