Study On The Characteristics And Formation Of Fleshy Fruit Stalk In Korla Pear

Being fleshy,fruits stalk of Korla pear(Pyrus sinkiangensis Yü)is vulnerable to wind during the fruit growth,especially in the picking period,it is common to appear 6-7 level wind resulting in sever fruit drop even loss of production.In addition,artificial fruit drop during picking is also serious because of the vulnerability of fleshy fruit stalk.Therefore,how to effectively improve the fleshy nature of fruit stalk has become a key problem to further improve the yield and quality of pear and to cultivate new varieties with strong resistance to mechanical damage.In this study Korla pear trees and Dangshansu pear(Pyrus brestschneideri Rehd)trees were taken as the plant material(there was no fleshing phenomenon in the stalk of Dangshansu pear).By comparing the differences in morphological structure,cell wall material,nutrients and mineral elements among normal fruit stalk(ZC)and fleshy fruit stalk(RZ)of Korla pear as well as fruit stalk of Dangshansu pear(DS)at different developmental stages.The value range of RZ and the key period of its formation were determined,meanwhile the relationship among cell wall material,nutrients and mineral elements and RZ were also explored.In addition,the effects of thinning(S)and girdling(H1,H2,H3)on the RZ were studied by comparing the nutrients and cell wall substances in the RZ,so as to provide a theoretical basis for how to effectively reduce the incidence of RZ.The main research results are as follows :(1)Field investigation results showed that the RZ formation mainly occurred after 60 days after flowering,and the incidence of RZ reached 84%.We found that in Korla pear,the fruit stalk development accorded with normal distribution,and according to the normal distribution curve,it was preliminary determined that the value range of RZ was ≥3.70,while value range of ZC was 2.38 mm ≤ZC≤ 3.70 mm.The stem diameter of Korla fragrant pear was positively correlated with the single fruit weight and negatively correlated with the fruit shape index.(2)By observing the anatomical structure of the three types of fruit stalk in the critical period,we found that there were differences in the number of vascular bundles between the two types of pear fruit stalk(10 in Dangshan pears and 9 in Xiang pears),while there was no difference in the number of vascular bundles between the ZC and RZ of Xiang pears.In DS vascular bundles arranged regularly with obvious inter-bundle formation layer.The distance between vascular bundles were short,and the phloem fiber around the vascular bundles were more developed than that of ZC and RZ.The vascular bundle area,phloem area and xylem proportion of RZ were significantly larger than those of ZC stalk.(3)The total amount of cellulose and hemicellulose in DS is significantly higher than that of ZC and RZ,and lignin in RZ is lower than that of ZC and DS.In addition,RZ contained higher level soluble sugar content,while starch and soluble protein contents were significantly higher in ZC and DS.33 mineral elements were detected both in normal fruit stalk and fleshy fruit stalk,of which 25 elements had significant differences between the two types of fruit stalk.(4)Thinning and girdling could reduce the fleshy stalk phenomenon in Korla pear.According to the above results,it is speculated that the formation of Korla fragrant pear RZ fruit stalk is mainly due to the increase of the xylem area in the vascular bundle of the fruit stalk during the summer growth period,the increase of the nutrient transport rate of the fruit stalk,the basic stagnation growth does not change after the fruit size reaches the limit,and the nutrient surplus phenomenon occurs when the fruit is not absorbing the nutrients transported by the fruit stalk,and the accumulation in the fruit stalk leads to the thickening of the pear fruit stalk.