Stress Resistence And Inducible Regulation Of Allelopathic Potential Characteric Of Weed Suppression In Different Wheat Varieties Under Prohydrojasmon (PDJ) Treatment

Effect of prophydrojasmon (PDJ) on germination, growth, gas exchange parameters and allelopathic potential characteristic of weed suppression by different wheat varieties were studied under water stress and low temperature pressure conditions using hydroponics cultivation, soil cultivation and allelopathy study methods we studied. Following research results were gained:Wheat varieties of Xiaoyan 22, Jinchun No.1 and 1608 displayed drought and cold resistances on germination potential, coleoptiles length, average root length and the longest root under the treatment of prophydrojasmon (PDJ). PDJ promoted the wheat germination although osmotic press and low temperature have a restricted affect PDJ have certain adaptability to repellence of wheat to drought stress and low temperature. This response has a better sensitivity under some degree stress, but the response would be slow under ascendant circumstance.PDJ had an inducible action to wheat metabolization under four different concentrations. While osmotic stress of PEG6000 and low temperature increased to a certain degree, the inducible action of PDJ is feebler than the resistance action. As the osmotic and temperature stress changes, the three wheat varieties, Xiaoyan22, Jinchun No.1 and 1608, their root vigor order have different order, which indicated that the three wheat varieties have their own endurance difference to water deficit with increasing stress degree.To the three wheat varieties, Xiaoyan22, Jinchun No.1 and 1608, their net photosynthesis rate (Pn) were all larger than that of control when concentration of PDJ reached a certain degree(10 mg/L), while leaf transpiration rate (T) and stomatal conductance (Cond) were lower than control under the same concentration. Unexpectedly, their water use efficiency (WUE) and stomata limiting value (Ls) will be enhanced when PDJ concentration reach a enough high degree, meanwhile, leaf transpiration rate (T) showed significant differences. Two spring wheat varieties, which WUE and stomata limiting value (Ls) were all rising after treated by 1 mg/L and10 mg/L concentrations. In addition, when the concentration of PDJ were very high (reached 100 mg/L), WUE and stomatal limiting value (Ls) were all decreasing, even it was lower than control. This displayed that these two parameters were restrained by hormone. With same method it was found that the winter wheat, Xiaoyan 22, had a different behavior. After treated by PDJ with concentrations of 1 mg/L and 10 mg/L, its WUE and stomatal limiting value (Ls) were all lower than control significantly, but only when concentration of PDJ reached 100 mg/L , values of the two parameters would increase.Soil water and PDJ treatment have different effects on wheat physiological characteristics for the different wheat varieties and the measuring parameters. Water deficit decreased plant biomass significantly and changed phenotypic characteristics like plant height and leaf area of all wheat materials, whereas, combining with PDJ pretreatment, the inhibitive effect by water stress would become weak and PDJ was found to stimulate wheat root growth and development so as to enhance pressure resistance, although with its non-drastic effect on the aerial part. Soil drought and PDJ was verified to stimulate overall allelopathic inhibition and weed resistance of wheat in pot trial by inducing and increasing its roots allelopathic potential, according with pot observation of low weed biomass.Water deficit and PDJ treatments could enhance physiological response in var. Lankao 95-25, like the leaf net photosynthesis rate and WUE, meanwhile, reducing stomata limitation. There was no evidence in significant effect of soil water and PDJ on gas exchange and water use of the rest varieties, which possibly depended on wheat cultivar, water stress intensity and PDJ concentrations. Based on Canonical Correspondence Analysis (CVA) water deficit and PDJ would lead to plant phenotype and photosynthesis physiology change, consequently, influenced allelopathic variation and weed suppression of wheat. It was hypothesized that to stimulate allelopathic potential and defense against weed would cost limited resources to grow fast enough to compete and/or invest these resources in secondary metabolites to maintain defense, which was possibly bilateral interaction of active and passive transport in wheat. Water deficit would induce the production and accumulation of more allelochemicals in wheat by passive transport of energy cost. Differing the regulation mechanism of water stress, PDJ showed active transport of energy supply in allelopathic stimulation, which implied that PDJ mainly exhibited its hormone effect to regulate and control wheat growth and development such as improving phenotypic features on competition at the basis of increasing growth cost. It was interesting that PDJ showed both effects of similar hormone and certain allelopathic potential.