effect of light conditions and controlled desiccation of sicyos deppei (cucurbitaceae) fruits on germination and seed hardness

Abstract

The variation of moisture content and germinability in response to light conditions and natural dry and controlled dry conditions was studied in Sicyos deppei G. Don (Cucurbitaceae) seeds and compared with germination of seeds from green and black fruits collected directly from field plants. The increase of germi nation by scarification defines hard seeds. The green and black scarified fruits were non-photoblastic. The non-scarified seeds from black fruits were indifferent to light but those from green fruits were positive photoblastic. This response may be due to the ratio Pfr/Pr in the seeds. Green fruits with 82% water content were tagged to follow natural desiccation for 5, 7 and 9 days at 75% RH and others were subjected to 8% RH controlled environment, over saturated urea solution, for the same number of days. Water content of seeds maintained under natural conditions decreased slowly, from 82% to 77% in 9 days, but no difference in germination percentage was found. In seeds stored under controlled conditions, the water content decreased from 79% to 11% in 9 days and germination increased from 34% to 46%. This was related to the induction of a state of tolerance by quick and drastic dry conditions.