Slow drying outperforms rapid drying in augmenting the desiccation tolerance of Genipa americana seeds

Seeds of Genipa americana (Rubiaceae) are tolerant to partial desiccation but lose viability rapidly when stored at low temperatures without prior desiccation. The aim of the present study was to test the hypothesis that rapid drying would be more effective at preserving seed viability than slow drying. Fresh seeds (approximately 46.9% water content, fresh weight basis) were subjected to rapid drying at 20 degrees C over silica gel, while slow drying was performed at the same temperature by exposure to various relative humidity gradients for different periods. For both methods, samples were removed as drying progressed in order to obtain seeds with average water contents of 30, 20, 15, 10 and 5%. The germination rate of fresh seeds was 98%, and a similar proportion of the seedlings displayed normal growth. Rapid drying resulted in a marked loss of viability for seeds containing less than 20% water. In contrast, slow drying preserved both seed viability and normal seedling growth even when the water content was reduced to 10%. It is suggested that the slow drying method outperformed the rapid drying of G. americana seeds because the mechanisms involved in desiccation-tolerance were activated under the slow drying conditions.