DORMANCY RELEASING MECHANISMS IN SOIL SEED BANKS OF Desmanthus GENOTYPES

Abstract

Desmanthus is a genus of forage legumes with potential to improve pastures and livestock produc-tion on clay soils of dry tropical and subtropical regions such as the existing in Brazil and Australia. Despite this patterns of natural or enforced after-ripening of Desmanthus seeds have not been well established. Four year old seed banks of nine Desmanthus genotypes at James Cook University were accessed for their patterns of seed softe-ning in response to a range of temperatures. Persistent seed banks were found to exist under all of the studied ge-notypes. The largest seeds banks were found in the genotypes CPI 78373 and CPI 78382 and the smallest in the genotypes CPI’s 37143, 67643, and 83563. An increase in the percentage of softened seeds was correlated with higher temperatures, in two patterns of response: in some accessions seeds were not significantly affected by tempe-ratures below 80º C; and in others, seeds become soft when temperature rose to as little as 60 ºC. At 80 °C the heat started to depress germination. High seed production of Desmanthus associated with dependence of seeds on eleva-ted temperatures to softening can be a very important strategy for plants to survive in dry tropical regions.