This study aimed to evaluate different types of drying and their effects on the physiological quality of physic nut seeds (Jatropha curcas L.). Seeds with 32% water content were dried in the shade to 9.9 %, in the sun to 8.8 %, in a forced circulation oven, at a temperature of 33 °C, to 8.5 % and at 43 °C to 8.3 % water content. The physiological seed quality was evaluated by germination, first count of germination, electrical conductivity and accelerated aging tests, as well as the seedling emergence index and emergence rate. A temperature of 43 °C dries seeds faster and lasts 42 hours. The drying period at 33 °C in the sun and shade lasted longer, at 54, 144 and 456 hours respectively. Shade drying caused an immediate reduction in physiological seed quality. Those seeds dried in the sun or at a temperature of 33 °C showed no differences regarding physiological status and were better than those dried in the shade. However, germination was lower than for seeds dried at 43 °C after 180 days storage. A drying temperature of 43 °C did not affect seed germination and only slightly reduced the vigor, even after 270 days storage. As the highest temperature used did not affect seed germination, it is suggested that seed drying time was crucial to its conservation. Physic nut seeds can be dried in the sun and in temperatures of 33 and 43 °C; a temperature of 43 °C results in a shorter drying time and a better germination and seed vigor of the physic nut whereas shade drying is detrimental to seed quality.
Jatropha curcas L.; germination; deterioration; physiological quality; conservation
