Environmental effects on seed development and hardseededness in Stylosanthes hamata cv. Verano. III. Storage humidity and seed characteristics

Abstract

Seed pods (upper articulation) from Stylosanthes hamata cv. Verano plants grown at 27,24 and 21¦C from flowering onwards were suspended above saturated salt solutions which provided 77, 32, 15 or 6% relative humidity. The seed moisture content which developed after storage in 77 and 32% relative humidity was negatively related, and the degree of hardseededness positively related, to temperature of seed provenance. Seeds formed under high temperature had more lignin (which was concentrated in the counterpalisade cells) and hemicellulose, less cellulose, and shorter palisade cells than seeds formed under cooler temperature. Cutin content was independent of temperature, but the testa of hard seeds exhibited under the scanning electron microscope a more regular, evenly reticulate surface than that of soft seeds. Seed colour changed from dark to light as temperature of seed formation decreased from 27 to 21¦C, but hardseededness within each temperature treatment was not consistently associated with seed colour.