Alleviative Effects Of Triadimefon(Tdm)on The Growth And Antioxidant In Oilrape Under Drought At The Bolting-Stage

The Yangtze River Basin is the main distribution area of Winter Oilrape in China,where the distribution of annual rainfall is uneven,and the seasonal drought is frequent,while the rainfall is abundant,which is causing huge losses of the Oilrape production.Bolting-stage of Oilrape is importantperiod when vegetative growth is exuberant,and reproductive growth is from weak to strong,but also when is a relatively sensitive period of water,directly related to the growth and yield formationof oilrape.Triadimefon(TDM)is a kind of plant growth regulator.Practical application proved triazole bactericidal agent can alleviate adverse effects on plant normal growth and metabolism caused by the abiotic stresses such as salt stress,high temperature stress,freezing stress,drought stress,which has been widely used in wheat and grains and fruits and vegetables,but less to oilrape under drought resistance.The experiment studied the effect of bolting-stage oilrape under drought on growth morphological indexes,antioxidant system,photosynthesis,sugar metabolism and yield by pot experiment with oilrape variety(B.napus cv.)Nannong 4,which researched the mitigative effect of Triadimefon(TDM)on drought stress to provide theoretical basis and technical support.Test results show that:1.TDM reduced the adverse effects of drought on the growth and development of rape and increased yield:Drought significantly inhibited the growth of oilrape,so that the plant was short,root growth was inhibition,the number of branches was significantly reduced,and the leaves were still relatively thin while leaf surface waxes increased a little.Drought stress significantly decreased rape inflorescence pods,seeds per pod and 1000 grain weight,at last serious reduction.In a certain extent,TDM can alleviate influence of oilrape growth on drought,which increasedleaf epicuticular wax and leaf thickness significantly to effectively enhance the water holding capacity of oilrape under drought stress.TDM increased branches and root length in the same time,when dry mass of root and shoot increased significantly.During the mature stage,the plant height was obviously restored,the stem was thicker,the number of pod and grain weight increase significantly,and actual yield per plant increased significantly.After re-water,the oilrape could recover to the normal level more quickly after TDM,the plant dry matter accumulation and plant morphology were restored.2.TDM significantly decreased the membrane lipid peroxidation degree of rape leaves and increased the oxidation resistance.:With the prolonging of drought stress time,the chlorophyll content in the leaves of rape reduced,H2O2 and O2-generated rate increased,MDA content increased and the degree of membrane lipid peroxidation enhanced,which decreased the activity of SOD and CAT,POD,APX,GPX,MDHAR and GR when ASA,GSH content increased at first and then reduced.TDM treatment can significantly reduce the production rate of O2-,the content of H2O2and MDA,significantly increase the activity of SOD,CAT and POD,also effectively slow down the change of APX、GPX、MDHAR and GR activity in the later period of drought whenthe content of AsA and GSH was significantly higher than that of drought treatment.So that TDMcan alleviate the oxidative damage to the leaves of oilrape,in order to better protect the structure of chloroplast and cell membrane.After re-water,the antioxidant enzyme activity and the aantioxidant substances of TD were basically recovered to normal level.3.TDM can relieve the stomatal limitation,regulate and improve the non-stomatal limitation,and improve the photosynthesis:Drought resulted in a significant reduction in the number of stomata per unit area,stomatal closure,Chloroplast swelling and disordered whose grana lamellae arranged irregularly and dilated,where osmiophilic particles were more and larger.With severe degradation of chlorophyll a and b content,fv/fm,ΦPSⅡ,qp was significantly decreased,RUBPCase activity decreased significantly,Ci,Gs,Tr,Pn decreased significantly,which decreased photosynthetic performance.TDM can relieve the stomatal limitation,regulate and improve the non stomatal limitation,improve the photosynthesis:TDM promoted stomatal opening,and increased significantly the number of open pores on the leaves,which improved the content of chlorophyll,and protected chloroplast structure where grana lamellae arranged orderly,and osmiophilic particles were smaller.TDM can improve fv/fm,ΦOPS Ⅱ,qpto improve the utilization rate of light energy.By the light energy in the form of heat energy dissipation,TDM can delay the decline late of NPQ,improve the actual photochemical quantum yield,and improve the electron transfer between the PSⅡ complex,while improving the RUBPCase enzyme activity,which then improved the net photosynthetic rate of leaves.After re-water,photosynthetic fluorescence characteristics of TDM treatment can return to normal levels.4.TDM can maintain the synthesis and transport of assimilate and improve the activity of glucose metabolism.:In the early stage of drought,drought increased the content of total soluble sugar,sucrose,glucose,fructose,while enzyme activity of SPS,SS,Ni,FBP and starch decomposing and the osmotic adjustment ability was increased significantly.With the extension of drought time,the contents of starch and sugar decreased significantly,and the related enzyme activities decreased significantly,and the balance of glucose metabolism was destroyed.The content of sucrose and soluble sugar in oilrape leaves by TDM treatment was significantly higher than that in drought treatment,and can delay the decrease of soluble sugars in the later period of drought.TDM increased starch accumulation,retarded starch decomposition rate,which can significantly improve the activity of sucrose synthase and sucrose hydrolase activity and FBP.So TDM can maintain synthesis and transport of assimilates,maintained higher leaf osmotic adjustment ability,reduce the damage of rape leaf,and promote plant growth and development process.After re-water,glucose metabolism of TDM treatment can return to normal levels.Drought damaged to the growth and development of oilrape,and damage to the antioxidant properties of leaves,photosynthetic fluorescence characteristics and sugar metabolism,severely cut production.TDM can alleviate adverse effects of drought on oilrape growth and development,by improving the oxidation resistance of the leaf,photosynthetic fluorescence characteristics and glucose metabolism,which promotes the growth and physiological metabolism of oilrape to return to normal level,and increased the yield significantlyafter rewatering.