Study On The Changes Of Endogenous Hormones In Mulberry Fruit And Its Relationship With Fruit Development And Maturity

The interaction among plant hormones regulates the growth development and maturation of the fruits.Therefore,studying the regulation of hormones during plant fruit ripening plays an important role in improving fruit yield and quality.In this study,we collected the fruit of Da 10 and Hongguo 2 from the flowering stage to full ripe stage as the experimental materials.In addition,we systematically studied the changes of endogenous hormones and the relationship between these changes and fruit morphological indexes,cell wall metabolism-related enzymes,soluble sugar,titratable acid and anthocyanin of the fruit materials.This study aims to explore the changes of various endogenous hormones in different growth stages of mulberry fruits,and to determine the correlation between these changes and the growth and maturity of mulberry fruits,so as to find out the crucial hormones that may affect the growth development and maturation of mulberry and then provides a theoretical basis for artificial regulation of mulberry fruits.The results showed that:（1）The fruits of Da 10 and Hongguo 2 presented not obvious double S-shape curve.At the first fast growth stage,the content of Auxin（IAA）in both varieties and Gibberellin（GA₃）of Da 10 showed an upward trend,and the GA₃ content of Hongguo 2 was maintained at a high level;at early the second fast growth stage,the peaks of IAA and GA₃ appeared in both varieties,followed by a sharply decrease until ripening;at the second fast growth stage,Abscisic Acid（ABA）content of the two varieties remained at a high level,and Spermine（Spm）content increased quickly and maintained at a high level,the contents of ABA and Spm were significantly positively correlated with the morphological indexes,indicated that the high contents of ABA and Spm may positively regulate the growth and maturation of mulberry fruits.（2）In Da 10,the time of polygalacturonase（PG）activity peak was basically the same as the peak of IAA and GA₃ content,indicated that PG may cause cell wall relaxation and promote fruit softening by participating in cell expansion of mulberry fruits;the cellulase（Cx）activity in both varieties were at a low level at the first fast growth stage and increased sharply at the second fast growth stage,indicated that Cx activity was closely related to the softening and maturation of mulberry fruits.The contents of ABA and Spm were significantly positive correlation with Cx activity,further indicated that ABA and Spm were closely related to the softening of mulberry fruits.（3）At the second fast growth stage,the soluble sugar content in both varieties increased sharply,and reached the highest value when the mulberry was fully mature,which was94.1767 mg/g FW and 57.2166 mg/g FW respectively;The titratable acid content showed a rising-decreasing trend,and after reaching the peak at early the second fast growth stage,it decreased quickly as the fruit matured.ABA and Spm contents were positively correlated with soluble sugar content,indicated that ABA and Spm may positively regulate soluble sugar accumulation in mulberry.（4）The anthocyanin content in both varieties increased sharply after entering the second fast growth stage,the content of IAA and GA₃ decreased rapidly,the contents of IAA and GA₃ were negatively correlated with the content of anthocyanin,the contents of ABA and Spm were positively correlated with the anthocyanin content.It was further verified that in the later stage of fruit development,IAA and GA₃ may negatively regulated anthocyanin accumulation in mulberry fruit,ABA and Spm may positively regulated anthocyanin accumulation.In summary,higher levels of IAA and GA₃ promoted rapid fruits growth during the first fast growth stage and the second fast growth stage;ABA and Spm may positively regulate the accumulation of soluble sugar and anthocyanin,and closely relate to mulberry mature.