Changes of endogenous hormone and polyamine contents during in vitro adventitious shoot regeneration from hypocotyI explants of Chinese cabbage

Dynamic changes of endogenous hormone and polyamine contents were investigated during in vitro shoot regeneration from hypocotyl explants of Chinese cabbage [Brassica campestris ssp.pekinensis (L.) Olsson].The results were as follows.Before shoot primordia occurred (0 to 8 days after inoculation), endogenous zeatin ribosides (ZRs) and abseisic acid (ABA) contents increased, while indole-3-acetic acid (IAA) content decreased.After shoot promordia occurred (on the 8th day of inoculation), the contrary changing patterns of ZRs, ABA and IAA contents were observed.At the early stage of culture (0 to 8 days after inoculation), ABA/IAA and ZRs/IAA ratios increased, then gradually decreased after adventitious shoots occurred.Endogenous putreseine (Put), spermine (Spm) and spermidine (Spd) contents increased at the early stage and then gradually declined during the culture course, these indexes reached their peaks on the 8th day of culture.Similar changing patterns were also observed in the ratios of Spm/Put and Spd/Put.The results indicated that endogenous hormone and polyamine contents and their balance were closely associated with the in vitro adventitious shoots regeneration from hypocotyl explants of Chinese cabbage.