Effects Of 6-BA And PP₃₃₃ Application On Grain Yield, Starch Synthesis And Its Quality Of Winter Wheat (Triticum Aestivum L.)

Field experiments were carried out in growth-seasons of 2003-2004 and 2004-2005 to evaluate the effects of 6-BA(6-benzyladenine) and PP₃₃₃(paclobutrazol) on grain yield and starch quality of wheat cultivars differing in gluten strength(strong-, medium- and weak-gluten wheat cultivars). The optimal spaying concentration and time for these regulators would be confirmed. Especially, Yumai 49, a medium-strong gluten cultivar, was used to evaluate the sucrose metabolism, key enzymes involved in starch synthesis, changes of endogenous contents and dynamic of the endosperm cells number. The main results were as follows:1. Among the 72 treatments (three cultivars, two regulators with four spaying concentrations and three spraying stages), 4.5 mg/L of 6-BA sprayed 1d before anthesis (DBA) and 1.0 mg/L PP₃₃₃ sprayed 14 days after anthesis(DAA) improved grain yield and starch quality obviously. In addition, effects of PP₃₃₃ on grain yield and starch quality were different among cultivars with different gluten-strength. Positive interactions between PP₃₃₃ and 6-BA on grain yield and starch quality were also found in the experiment. The regulation mechanism of these regulators on grain yield and starch quality was further investigated.2. Both treatments of 4.5 mg/L 6-BA application 1 DBA and 1 mg/L PP₃₃₃ application 14 DAA promoted sucrose synthesis in flag leaves and enhanced sucrose supply and its degradation capacity in grains of Yumai49. In the treatments total starch accumulation was increased and grain yield was improved. Comparing between the two treatments, effect of PP₃₃₃ on activity of sucrose metabolism was larger than 6-BA, which resulted in a significant increase of grain weight. Obvious interactions between PP₃₃₃ and 6-BA were found on increase of total starch content.3. From the results of changes of key enzyme activities and starch accumulation rate of Yumai49 in grain filling stage, it was concluded that 6-BA and PP₃₃₃ increased activities of AGPP, SSS, GBSS, SBE and DBE , and accelerated accumulation of total starch, amylopectin and amylose, which was favorable to the increase of grain yield...