The Effects Of Plant Growth Regulators On The Ability Of Lodging-Resistance, Yield And Quality In Wheat And Its Physiological Mechanism

Lodging is one of limiting factors for obtaining high yield and quality in wheat. Crop lodging could cause yield loss, reduce grain quality, and increase harvesting cost. In this paper, effects of PGRs treatment applied at different growth periods on the ability of lodging-resistance, yield and quality in wheat and its physiological mechanism were studied. The difference in the effects of PGRs treatment applied at different growth periods on the ability of lodging-resistance in wheat was confirmed. The effect of PGRs on the accumulation and transportation of nitrogen and carbon, and synthesis and accumulation of dry matter in vegetative organs of wheat was discussed. The physiological mechanism of PGRs on the formation of yield and quality in wheat was analyzed. The main results of the study are listed below:1. Effects of PGRs treatment applied at different growth periods on the traits and ability of lodging-resistance in wheat stem.The result indicated:Jingfeng(JF) and Ethephon(ETH) decreased the plant height significantly at both jointing stage and full heading stage of wheat. The basal internode length was decreased by JF and ETH treatment at jointing stage, while the length of the1st and2nd upper internodes were reduced at full heading stage, compared with the control. The effect of ACC treatment was not significant at two stages. Gibberellin(GA3) and cobalt nitrate increased the internode length and plant height at both two stages. When applied at jointing stage, GA3and cobalt nitrate increased the lower internode length, while GA3and cobalt nitrate increased the length of the1st and2nd upper internodes if used at full-heading stage.JF, ETH and ACC treatment also increased the stem diameter and wall thickness of the3rd and4th upper internodes, cellulose content and the ratio of C/N in stem, improved the plumpness of basal internode, increased the anti-fracture force and lodging-resistance of wheat stem at both two stages. However, GA3and cobalt nitrate decreased the stem diameter and wall thickness of the3rd and4th upper internodes, reduced the plumpness of basal internode, cellulose content and the ratio of C/N in stem at both two stages, thus decreased the anti-fracture force of internode, which was not good for the lodging-resistance in wheat stem. Furthermore, the plant height, clum wall thickness and cellulose content were important factors which influenced the ability of lodging-resistance in wheat stem.2. Effects of PGRs treatment applied at different growth periods on yield and its components of wheat and its physiological mechanismThe result indicated:JingFeng (JF) increased chlorophyll content and grain filling rate, prolonged the functional period of leaf and its grain filling time, and improved dry weight of grain, compared with control. However, when applied at jointing stage, JF decreased the grain number per spike and thousand kernel weight, and caused yield loss. In contrast, JF applied at full-heading stage increased the grain number per spike and thousand kernel weight, improved yield and HI significantly. Ethephon(ETH) treatment increased chlorophyll content and grain filling rate, but also promoted the degradation of chlorophyll, shortened grain filling time and caused early maturity. Furthermore, ETH decreased the grain number per spike and thousand kernel weight and caused yield reduction if applied at jointing stage. When applied at full-heading stage, ETH increased thousand kernel weight, but reduced the grain number per spike, yield and HI. Treatment with GA3, ACC and cobalt nitrate increased the synthesis of chlorophyll and its content. In addition, GA3and cobalt nitrate prolonged the function period of leaf. The effect of GA3and ACC on grain filling rate was not significant, while cobalt nitrate significantly increased grain filling rate when applied at jointing stage. GA3treatment decreased spike number and grain number per spike, but increased thousand kernel weight. when applied at jointing stage, GA3reduced yield and HI. However, when applied at full-heading stage, GA3increased yield and HI. ACC treatment decreased grain number per spike and thousand kernel weight, hence caused a significant yield loss and HI reduction when used at jointing stage of wheat. However, ACC could increase grain yield and HI significantly when applied at full-heading stage due to the improvement of grain number per spike and thousand kernel weight, compared with the control. Cobalt nitrate treatment increased grain number per spike and thousand kernel weight, promoted yield and HI when applied at both jointing and full-heading stage of wheat. Furthermore, when used at jointing stage, JF, ETH and ACC treatment improved the remobilization of pre-anthesis stored assimilates and its contribution to grain of wheat. However, when applied at full-heading stage, PGRs increased the contribution of post-anthesis stored assimilates to grain of wheat.3. Effects of PGRs treatment applied at different growth periods on quality of wheatThe result indicated:each PGRs treatment had a significant effect on the protain content in grain. JF, ETH and ACC treatment could enhance the protain content in grain significantly at both jointing stage and full-heading stage of wheat. Furthermore, every PGRs treatment increased the content of total starch, amylose and amylopectin in wheat grain with different extent at both stages. There was a significant difference in the content of total starch, amylose and amylopectin in wheat grain with JF and ETH treatment. When applied at jointing stage, PGRs decreased the proportion of amylopectin/amylose. ACC treatment reduced the proportion of amylopectin/amylose with a significant difference of13.7%. However, when applied at full-heading stage, only JF increased the proportion of amylopectin/amylose, while other PGRs reduced it. GA3treatment significantly decreased the proportion with6.1%. The effect of PGRs on the pasting properties of wheat flour was different. JF and ETH treatment significantly improved the peak viscosity of wheat flour at jointing stage. However, GA3decreased peak viscosity, through viscosity and final viscosity significantly. When applied at full-heading stage of wheat, JF and cobalt nitrate reduced the peak viscosity, through viscosity and final viscosity with a significant difference. ETH and ACC treatment reduced the breakdown value, while the effect of GA3on each pasting index was not significant.