Study On The Bolting Characteristics And The Change Of Hormone Of Flowering Chinese Cabbageunder Low Temperature Treatment

Flowering Chinese cabbage(Brassica campestris L. ssp. chinesis var. utilis Tsen et Lee),possesses the large cultivated area in the south of China, is a variant of early bolting flowering Chinese cabbage by selecting and domesticating for a long time. Because of flowering Chinese cabbage is a kind of Brassica campestris vegetables, flower stalk is the product of organ of flowering Chinese cabbage. The formation and development of flower stalk determines the yield of flowering Chinese cabbage. Based on the above reasons, the study is significant to probe into the mechanism of bolting and development, it has also very useful to theoretical and applied value. In this paper, studying on the different maturity of low temperature sensitivity based on the early bolting “youlv 501”, medium bolting “youlv 701” and late bolting “cuilv 80”, it further studied the low temperature impact on the process of bolting,growth and development, the changing regularities of cell structure and endogenous hormones based on the early bolting and late bolting. At the same time, endogenous hormones function on the low temperature induced flowering Chinese cabbage bolting and flowering were analyzed of the early bolting, according to investigate into the effects of on the key enzymes in the synthesis of GA. The results were as follows:(1) Effect of low temperature on bolting of flowering Chinese cabbage. The bolting and flower bud of different bolting flowering Chinese cabbage could be promoted by different low temperature. The results show that the effect and low temperature treatment time were significantly positive correlation, with the longer treatment time, the earlier bolting and flower bud. But there were differences among the different treatments and early bolting “youlv 501” was more sensitive to low temperature treatment.(2) Effect of low temperature on growth and development of flowering Chinese cabbage. The elongation of bolting and reduction of stem diameter of the early bolting “youlv 501” and late bolting “cuilv 80” were significantly effected by low temperature. The results showed that Compared with normal temperature treatment, low temperature treatment could increase the flowering Chinese cabbage shoot tip endogenous hormones GA, IAA and CTK content at five different stages(seedling, bolting stage, bud stage, rapid bolting stage and flowering stage), restrained the flowering Chinese cabbage shoot tip pith cell longitudinal elongation in seedling, bolting stage, bud stage and rapid bolting.(3) Effect ofgibberellin and uniconazole on bolting, growth and endogenous hormones of flowering Chinese cabbage. Exogenous gibberellin could promote the early bolting “youlv 501” and late bolting “cuilv 80” bolting, flower bud and flowering, it is also beneficial for increasing endogenous hormones content. Low temperature treatment significantly promoted stem elongation. Compared with the room temperature treatment, the low temperature treatment was useful to increasing GA content at the whole flowering Chinese cabbage growing period. At the same time, after low temperature treatment, spraying exogenous gibberellin had the performance of the flowering Chinese cabbage bolting out positive additive effects. On the contrary, spraying uniconazole seriously inhibited flowering Chinese cabbage bolting and stem elongation. In addition, at the whole flowering Chinese cabbage growing period, GA content was rapid declined compare with sprayingdeionized water. What is more, uniconazole inhibited the low temperature useful effects on flowering Chinese cabbage bolting.(4) Effect of low temperature on the expression of the GA key synthetase gene in flowering Chinese cabbage shoot tip. The results showed that the low temperature treatment promoted the expression of the early Bruc CPS, midium Bruc KAO1(Bruc KAO1、Bruc KAO2)and late Bruc GA20ox(Bruc GA20ox2) in the gibberellin synthesis pathway at seedling and bolting stage compare with room temperature treatment.In summary, the low temperature treatment promoted the expression of the GA key synthase gene, further increased flowering Chinese cabbage shoot tip GA, IAA and CTK content and increased stem elongation and flower bud differentiation promote the early bolting and flowering of flowering Chinese cabbage.