| The trials were carried out in field experiment and artificial climate incubator. The sugar beet growth buds were treated at 1-3 pairs of true leaves with gibberellin(GA3) ,autix(IAA), naphthaleneacetic acid (NAA ) and kinetin (KT), and the plant growth regulating substances enhancing bolting of sugar beet in the first year and its doses were selected out. The sugar beet seedling induced by temperature and light were treated by abscisic acid (ABA) , maleic hydrazide(MH), uniconazole (S-3307) and paclobutrazol (PP333) ,and the plant growth regulating substances which make bolting reverse and their doses were screen out. The mechanisms of bolting and bolting reversing were discussed by examining the changes of endogenous hormones, activities of correlative enzyme to bolting, soluble protein, components of amino acid in the protein, components of fatty acid. The results were as follow:The best effective plant growth regulating substances of enhancing sugar beet bolting in the first year was GA3.The first pair of true leaves spread out completely was the optimum treating period; the optimum treating concentration of GA3 differed with the varieties: 40mg/kg for the Tianyan-7 and 45mg/kg for the Tianyan-8. ABA and MH could reverse the bolting which had been induced by temperature and light. The most optimum treating concentrations for ABA and MH were respectively 20mg/kg and 350mg/kg. S-3307 and PP333 could inhibit sugar beet bolting, the optimum treating concentrations were respectively 500mg/kg and 140mg/kg.The bolting or bolting reversing of sugar beet was regulated mainly by the content and proportion of endogenous hormones. During the bolting induced by GA3 or temperature and light, the content of endogenous hormones GA3 and ABA increased, which shows that a kind of balance was maintained between GA3 and ABA during bolting; during the bolting reversing treated by ABA and MH, the content of endogenous GA3 and ZRs decreased while endogenous ABA increased, which showed that the extraneous hormone controlled the bolting and bolting reversing through the changes of endogenous hormones.In the bolting induced by GA3, there were changes in peroxidase (POD) and catalase(CAT) activities and photosynthesis index: POD activities decreased before bolting and POD activities increased after bolting. This kind of change was in according to that of POD isoenzymes. CAT activities increased, both of stomatal conductance and rate of photosynthesis increased rapidly and rate of transpiration decreased during bolting; in the bolting reversing induced by ABA and MH, both of POD and CAT activities increased while rate of photosynthesis,stomatal conductance and rate of transpiration decreased. After the bolting reversing all of these index came near to the level of normal non-bolting.During bolting and bolting reversing, the content of soluble protein and components of the amino acid in protein changed. The content of protein increased during bolting, and the content of Glu, Gly, Ala, Met, Asp, Ser, Thr, Lys, Lue etc. in protein also increased. In the bolting reversing process the content of protein first increased and then, after the bolting reversing, came near to the same level of normal non- bolting. Met, Asp ,Ser, Thr ,Gly, Ala, Pro, Tyr,Lys,Phe, Arg and His in protein were very different with that in the bolting induced by temperature and light, and it displayed a correlation with the bolting reversing of sugar beet. It was not reported that the changes of the components of amino acid in the protein during bolting and bolting reversing.Changes of the components of fatty acid were explored at the first during bolting and bolting reversing on this study. The results showed that the content of saturated fatty acid(palmitic acid and stearic acid)increased rapidly during enhancing bolting while the content of unsaturated fatty acid(oil acid, linoleic acid and flaxic acid) decreased. On the contrary, the content of the fatty acid decreased during bolting reversing, lower than that in normal non-bolting, and the content of...
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