Moisture sorption characteristics of seeds of five ornamental species

Abstract

Genetic resources conservation of ornamental crops and their relatives is a challenging task because of limited available information. In seed genebanks, seed moisture content and temperature play an important role in stored seed longevity. In this study, the moisture sorption characteristics of four priority genera and one minor genus of the Ornamental Plant Germplasm Center were evaluated. Moisture sorption isotherms were conducted on seeds of Aster ptarmicoides, Impatiens walleriana, Lupinus texensis, Salvia splendens and Tagetes patula using seven different salt solutions with relative humidities (RH) ranging from 7 to 96%. Seeds were stored at 5, 15, 25 and 35oC until they achieved equilibrium with the ambient RH and the seed moisture contents (MC) were determined by the air-oven method. Constructed moisture sorption isotherm curves showed that seed MC increased with increasing RH in all temperature regimes. Rate of water loss in each species was studied on imbibed seeds stored in an ultra-dry RH-controlled cabinet set at 10% RH. Seed weight loss during desorption was continuously recorded until the seeds achieved equilibrium MC. The initial MC (in parentheses) of imbibed A. ptarmicoides (37%), I. walleriana (37%), L. texensis (13%), S. splendens (44%) and T. patula (26%) equilibrated during storage to 4, 3, 5, 4 and 4%, respectively. Weight loss during desorption accounted for 9 to 40% of the original seed weight until equilibrium was achieved during storage. Rapid weight loss occurred between 4-12 h of storage in the cabinet with weight loss ranging between 5-37%. This study showed that seed MC of five ornamental species is influenced by RH and temperature of the storage environment