Effects Of Paclobutrazol Application On Biomass Accumulation And Grain Filling Of Castor Bean

Castor bean is an important oil and energy crop suitable for marginal land cultivation.Founding the rules of accumulation,transportation and distribution of photosynthetic products and the characteristics of grain filling in the process of growth and development is the basis for formulating the cultivation techniques for high yield of castor bean.The application of paclobutrazol(PBZ)can delay plant growth,inhibit stem growth enhance plant stress resistance and increase crop yield.In this paper,,three paclobutrazol concentrations(0,75 and 150 g hm-2)were applied twice,with the first application at the early budding stage of main spike and the second application at the leaf stage of first branch 1-2 of main spike.The growth and physiological parameters,biomass accumulations,grain filling and stress resistance of castor bean were measured.The main results were as follows:1.Effects of paclobutrazol on growth parameters of castor beanSetting different applied stages and dosage of paclobutrazol,the effects of growth parameters under paclobutrazol were studied.The change of plant height and branch number showed a rule of "slow-fast-slow".The application of paclobutrazol could significantly reduce plant height and increase branch number at the same time,which made the rule more obvious.In addition to the most significant increase in leaf area under the treatment of paclobutrazol at 75 g hm-2 concentration,other growth parameters such as plant height,branch number,capsule number and length and width of capsules changed most significantly at 150 g IUhm'2 concentration at the early budding stage of main spike.2.Effects of paaclobutrazol on physiological characters of castor beanThe effects of different paclobutrazol applied stage(the early budding stage of main spike and the leaf stage of first branch 1-2 of main spike)and dosage(0>75 and 150 g hm-2)on soluble sugar,sucrose and starch content in different parts of castor plant were studied.The results showed that the changes of sucrose and soluble sugar contents in different parts of castor bean were the same.Spraying 150 g hm-2 concentration of paclobutrazol at the early budding stage of main spike could significantly increase sucrose and soluble sugar contents.However,spraying paclobutrazol at the leaf stage of first branch 1-2 of main spike had a more significant effect on the improvement of starch content.3.Effects of paclobutrazol on biomass accumulation of castor beanIn two different applied stages:the early budding stage of main spike and the leaf stage of first branch 1-2 of main spike.The earlier spraying of paclobutrazol is more beneficial to the accumulation of biomass in castor bean.Spraying 150 g hm-2 concentration of paclobutrazol at the early budding stage of the main spike could better coordinate the temporal and spatial distribution of light,temperature and water on plant population,maintain a relatively moderate time of dry matter accumulation,accumulate quickly and spatially.The production could increase by 20.83%.Paclobutrazol can significantly increase the length and width of seeds,thereby increasing 100-grain weight and yield.4.Effects of paclobutrazol on grain filling of castor beanThe fresh weight of capsules was weighted at 3,6,9,15,21,27,33,39,45,51 and 57 days after flowering.The grain-filling curve of castor bean was drawn to study the effects of paclobutrazol on the grain filling of castor bean.The results showed that the fresh weight of capsule increased first,then decreased and finally stabilized during the filling period.From the 6th day to the 39th day after flowering,the fresh weight of capsule changed greatly.Compared with the control,the fresh weight of capsule was increased by the application of paclobutrazol,and the effects of 150 g·hm-2 concentration of paclobutrazol was the most significant.5.Effects of paclobutrazol on stress resistance of castor beanOxidation system is an important system to remove excess reactive oxygen species and protect itself from oxidative damage.Superoxide(SOD),catalase(CAT)and peroxidase(POD)play a major role.The effects of paclobutrazol on stress resistance of castor bean were studied by measuring SOD,CAT and POD activities of capsules at 3,6,9,15,21,27,33,39,45,51 and 57 days after flowering.The results showed that the activity of the same antioxidant enzyme in peels was higher than that in seeds.During the grain filling process,POD activity showed an upward trend,while CAT and SOD activity showed a downward trend.Paclobutrazol treatment had an enhanced effect on POD and SOD activity,but had a decreased effect on CAT activity.