Abstract:

To investigate the relationship between the tolerance to dehydration and superoxide dismutases(SOD) in Pachira macrocarpa, fresh mature seeds were pretreated with a 12 h DDTC and subjected to 3～20 h desiccation silica gel at 25 °C. The results showed that 20 mmol·L^-1 diethyldithiocarbamate(DDTC) treatment inhibited efficiently SOD and SOD activity in seeds and reduced tolerance of seeds to water deficit, which was evidenced with increases in electrical conductivities and malondialchehy of the seeds, and a rapid decrease of the seed vigor during desiccation. There were 2 isoforms of MnSOD, 4 isoforms of FeSOD and 2 isoforms of Cu/ZnSOD in seeds of P. macrocarpa. Their mobility in electrophoresis was Cu/ZnSOD＞FeSOD＞MnSOD, and bands intensity was in the descending order of FeSOD＞Cu/ZnSOD＞MnSOD. During the dehydration, the band intensity of all SOD isoforms was reduced differentially. The most significant reduction was for the band of MnSOD, followed by Cu/ZnSOD. After 20 h, all bands disappeared except for FeSOD2 and Cu/ZnSOD1.When the seeds were pretreated with 20 mmol·L^-1 DDTC for 12 h, the band intensity of all SOD isoforms reduced significantly. All bands in the seeds disappeared after 20 h desiccation. It suggested that the tolerance to dehydration would be highly related to SOD activity.

Key words: Pachira macrocarpa, seed, tolerance to dehydration, SOD isoenzymes, diethyldithiocarbamate(DDTC)