Effects Of Dustfall On Reproduction And Physiology Of Juglans Regia

As one of the leading production areas of walnuts in China,southern Xinjiang Basin is adjacent to the Taklamakan Desert,where sandy and dusty weather is frequent.The frequent occurrence of sandy and dusty weather in spring is one of Xinjiang’s most serious ecological problems.As the main walnut growing areas in southern Xinjiang,Aksu,Kashgar,and Hotan have different geographical locations,sandy and dusty weather is different.However,there is no clear conclusion on the harm degree of different dustfall intensities to the reproductive process of walnut.Therefore,in this study,a simulation experiment was conducted with the dust-free bagging treatment as the control and the measured dustfall in Aksu(W1),Kashgar(W2),and Hotan(W3)as the control variables.By measuring the growth traits characteristics of walnut male and female flowers,physiological and biochemical indicators of male and female flowers,fruit set rate,fruit growth dynamics,and fruit quality,this study quantitative analysis of the effects of different dustfall stress on reproduction and physiology of walnut,which provides a theoretical basis for the evaluation of walnut dust hazard in southern Xinjiang.The main findings are as follows:(1)Walnut male inflorescence length decreased significantly(P < 0.05),the pollen amount bud and pollen viability extremely significant decreased with increasing dustfall(P < 0.01).Compared with the CK treatment,the length of male inflorescence,the pollen amount bud and the pollen viability of the W3 treatment decreased by 16.66%,58.83% and 48.84%.The physiological metabolism of male flowers was hindered by the increase of SOD and POD activities,malondialdehyde and proline contents in male walnut flowers due to dustfall stress,and the SOD and POD activities,malondialdehyde and proline contents of male flowers in the control treatment were significantly lower than with the dustfall treatment.The MDA content of male flowers increased with the increase of dustfall,which caused damage to male flowers.(2)The stigma length,width,area size,and stigma fertility of female walnut flowers tended to decrease with increasing dustfall.The stigma length,width,area size of female walnut flowers in W3 treatment were significantly lower than those in CK treatment(P<0.05),which were 44.39%,48.74% and55.67% smaller than that in CK treatment.The ultramicroscopic observation showed that dustfall caused water loss and crumpled stigma death of stigma cells tended to be severe with increasing dustfall.The SOD and POD activities,malondialdehyde and proline contents of female walnut flowers were significantly increased(P < 0.05)by dustfall stress.The malondialdehyde content of female flowers increased with the increase of dustfall.At the end of flowering stage,the malondialdehyde content of female flowers in W3 treatment increased by 80.78% compared with CK treatment,and the lipid peroxidation of female flowers increased with the increase of dustfall.(3)Dustfall significantly reduced the walnut fruit set rate(P < 0.05).and the fruit set rate of W3 treatment was 32.04% lower than that of CK treatment.During the fruit growth stage,the stress of dustfall during flowering period reduced the maximum relative growth rate of the three diameters of the fruit and prolonged the fast-growing period of the fruit.After the fruit matured,the three diameters,single fruit weight,kernel weight,and kernel yield of walnut fruit decreased to varying degrees due to dust stress,resulting in the decline of walnut quality.Using the principal component method,an evaluation model for the impact of dustfall on the reproductive process of walnut was constructed,and the analysis results showed that dustfall had an adverse effect on the reproductive process of walnut.