Changes of Sugar,pH and ABA around the Onset of Grape Berry Ripening

The changes of berry length,diameter,pH value,soluble sugar,total acid and ABA contents in Muscat Hamburg grape(vitis vinifera L.) around the onset of grapeberry fruit ripening were observed.The main results showed that the soluble sugar,including more glucose and fructose,as well as less sucrose,increased rapidly before veraison,and having similar trend.The average daily increment of glucose,fructose and sucrose varied from 0.29mg/g,0.23mg/g,0.01mg/g before veraison to 1.35mg/g,1.67mg/g,0.12mg/g after veraison,respectively.The ratio of glucose/fructose before veraison was 12∶1,and both increased rapidly at veraison.The rate of increment of fructose was higher than that of glucose,finally the ratio of glucose/fructose was 1∶1 at 77 days after flowering.At and after veraison,pH value increases rapidly,having opposite changing trend with total acid content.Similarly,ABA content increased rapidly coupling with veraison,and having a peak at two weeks after veraison,then declined during complete ripening.Conclusively,soluble sugar content 1,pH value and ABA levels all began to increase rapidly at 56 days after flowering(namely at veraison).The grapeberry ripening was coindent with the appearance of ABA peak,while the fruit post-ripening was not dependent on the accumulation of ABA.The physiologically regulated mechanisms of the parallel relationship for soluble sugar content,pH value and ABA level,namely the core question about the physiological mechanism of the accumulation of ABA at veraison,was an important research field in future.