A comparative study of seed viability in Inga species: desiccation tolerance in relation to the physical characteristics and chemical composition of the embryo

Abstract

Seed (embryo) viability was investigated in seven species of the tropical legume genus Inga (I. calderoni, I. densiflora, I. insignis, I. leiocalycina, I. marginata, I. punctata and I. vera subsp. spuria) to determine the relationship between desiccation tolerance and the physical and/or chemical characteristics of the embryo. For all species, final germination (radicle emergence) percentage of isolated embryos was greatest in the temperature range 16-36°C. Lower levels of germination were observed at 11°C in a majority of species. The few seeds that germinated at temperatures below 11°C, did not produce epicotyls. Linear relations were observed between the dry weight of the embryonic axis and the cotyledons; in relation to the dry weight of the cotyledons, the axis dry weight was 0.8% on the average. Desiccation under up to three regimes (15, 26 and 36°C) reduced germination when the embryonic axis and cotyledon moisture content fell below 55-50% and 45 and 40%, respectively; little or no germination occurred after dehydration to 20 to 30% embryo moisture content. Desiccation sensitivity was relatively independent of drying rate as influenced by the physical characteristics of the embryo or the drying conditions used. Total lipid and soluble carbohydrate content were estimated at 0.6 to 3.8 and 1.6 to 4.5% of embryo dry weight, respectively. The results indicate that the frequently encountered desiccation intolerance in Inga embryos may be associated with critically-low levels of specific soluble carbohydrates in their tissues