Loss of desiccation tolerance and storage behavior in germinating seeds of Senna multijuga: implications for seed germination and conservation

Orthodox seeds lose desiccation tolerance (DT) and change their storage behavior with advancing germination and with different hydration conditions affect the extent of DT. The objectives of this study were to describe (1) the loss of DT in Senna multijuga seeds during hydration under different conditions and (2) the storage behavior of dry seeds and germinating seeds after desiccation. Seeds lose DT progressively as germination advances, and DT is totally lost before the radicle protrudes. Soaked seeds maintained DT for a longer period of time in comparison to imbibed seeds. Dry seeds tolerated storage even at sub-zero temperatures; however, when germinating seeds were dehydrated, the storability at sub-zero temperatures was reduced. Storage of dried germinating seeds at sub-zero temperature reduced germination and increased the proportion of abnormal seedlings. The hydration conditions changed seed response to desiccation, and this result may be related to differences in metabolism. Thus, the conditions in which seeds remain during hydration can affect the physiological response of seeds, and when studies are conducted to assess the DT, this fact should be taken into consideration. According to the results of this study, S. multijuga seeds can be classified as orthodox; however, storage at sub-zero temperatures is harmful to germinating seeds after drying. Thus, for successful long-term storage, although the current water content of the seeds is important, if the seeds are previously hydrated (and then dried), this will affect seed storability, with consequent implications for ex situ conservation.