| Chinese cabbage-pak-choi {Brassica campestris L. ssp. chinensis Makino) is an important vegetable of Brassica. The main methods of obtaining better quality cultivars depend on heterosis. As far as the maintenance and propagation of parents is concerned, there are some problems. In our studies receptacle with ovary and pedicel, receptacle with ovary, pedicel and rhachis were used as explants to construct regeneration system. At the same time, some phenomena were observed. The characteristics of vernalization were studied with adventitious shoots. In addition, the relationships between vernalization and antioxidant enzymes, soluble protein content were probed into. The ESTs related to vernalization were screened by the means of cDNA-AFLP. The main results as followers:(1) There was a difference of regeneration frequency between fertile and sterile resulting from fertility, as the receptacle with ovary and pedicel was used as explants. As BAP concentration was 2 mg·L-1, the better concentration for fertile was 0.1 mg·L-1, but for sterile is 0.2 mg·L-1. Under this condition the shoot induction rate were 72.6%, 77.1%, respectively. Fertile explants required for a strict BAP concentration, but the sterile didn't. Receptacle with ovary and pedicel, receptacle with ovary, pedicel and the cuttings of rhachis all could regenerate adventitious shoots, but among of them, the receptacle with ovary and pedicel was the best. On the whole, the regeneration of fertile explants was better than that of the sterile.(2) The endogenous hormones are different in the explants of the fertile and sterile. It was found that IAA, GA3, ZT contents in fertile were all higher than that of in sterile.(3) The vernalized state was transfered to the adventitious shoots through the cell mitosis, which maybe the main reason of high frequency flowering in vitro. However, the regenerative tendency declined with the increasing of subculture. It was many factors, such as the component of the medium, exogenous hormones, and so on, that resulted in this change.(4) Vegetative shoots were vernalized again at 5°C for more than 14 days (the critical period of vernalization). It can't be devernalize completely at 5°C for 21 days, subsequently 33 °C for 5 days.(5) GA3 partly substituted for the role of low temperature to induce to flower. However, to some extent, it repressed the origination of roots. The flowering speed and the length of rachides were not a patch on vernalization.(6) It was observed there was no difference for microsporegenesis between regeneration plants andtheir parents.(7) After vernalization with an over long time, the adventitious initiated flower differentiation, and formed floral primordial.(8) After vernalization, the soluble content increased in all the tissue (shoot apical meristem, young leafs, callus) tested. At 5℃ for 7 days, except for SOD increase, the activities of APX, CAT and POD declined significantly; for 14 days. The activities of the three enzymes had an increasing process. The activity of SOD and POD in SAM showed the tendency of increase with the treating duration increasing. Devernalization treatment decreased all the enzymes tested in all tissues. Theses results seemed to suggest that changes of antioxidant enzymes, especially SOD and POD, probably play a vital role in SAM vernalization regulation in vitro of B. campestris ssp. chinensis. After cold treatment, the product of lipid peroxidation MDA decreased at the start, and then increased gradually in all tissues tested. Furthermore, under the treating period of inducing vernalization the content of soluble protein increased significantly in all parts researched, and it was 28 d > 21 d > 14 d. The increase of the soluble protein possibly offers the base of the transition of flowering induced by vernalization.(9) After vernalization treatment the expressions of some genes are repressed, but of some are induced. Genes repressed are possible the enzymes involved in the disassimilation, in which including genes probably encoding hydrolytic enzyme associated with...
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