Analysis Of Tiller Characteristics And Influencing Factors Of Stipa Bieviflora Under Different Stocking Rates

Tillering is an important reproductive pattern for grasses,which is crucial for forage production.A long-term grazing platform with four stocking rate levels(including:control(CK),light grazing(LG),moderate grazing(MG),heavy grazing(HG))in the Stipa breviflora desert steppe was based to assess effects of stocking rate on the tillering of the dominant species S.breviflora.Tillering characteristics(Number of branches,clump diameter,height of branches,aboveground biomass and weight of branches)of S.breviflora under different stocking rates and their impact factors(storage of nutrients,endogenous hormones)were analyzed.The tillering gene(MOC1)was also cloned and analyzed its expression to explore the adaptive strategies of S.breviflora to different stocking rates and to provide a basis for rational utilization of this steppe.The main results are as follows:(1)The tiller amount of each individual,the number of vegetative branch,the basial diameter,the aboveground biomass and each single branch of each individual in HG was significantly lower than other treatments(P<0.05);The number of reproductive branch in MG was significantly higher than CK(P<0.05);With the increase of stocking rate,both the height of vegetative and reproductive branches decreased(P<0.05).(2)There was no significant difference in the contents of total sugar and soluble sugar stored in the stem base of S.breviflora among stocking rates.The content of reducing sugar in HG was significantly lower than other stocking rates(P<0.05),while the content of crude protein in HG was significantly higher than other stocking rates(P<0.05);The total sugar content which storage in 0-10 cm root in MG was significantly lower than CK(P<0.05),there was no significant difference in other contents;Leaf chlorophyll content and CTK/IAA ratio were significantly lower than other stocking rates under HG treatment(P<0.05);With the increase of stocking rate,the contents of endogenous auxin(IAA),cytokinin(CTK)and gibberellin(GA3)increased(P<0.05).(3)The homology between the fragment of MOC1 in S.breviflora and the tiller gene OsMOC1 was 86%;The expression level of MOC1 gene in HG was significantly lower than in other stocking rates(P<0.05).(4)There was a significant positive correlation between tiller number and the crude protein content in stem base(P<0.05),but no significant relationship with other stored nutrients were observed;The tiller number of S.breviflora was negatively correlated with their endogenous hormone contents,while the ratio of tiller number to CTK/IAA and MOC1 gene expression were positively correlated(P<0.05).(5)The expression of MOC1 gene in HG was inhibited(P<0.05),and the endogenous hormone content in HG was significantly increased(P<0.05),Therefore the tiller amount of each individual in HG was significantly lower than other stocking rates(P<0.05).To sum up,compared with other treatments,the number of tillers per plant and plant height of S.breviflora in HG were significantly reduced,which resulted in the decrease of above-ground biomass per plant(P<0.05).