Study On The Distribution Of Sugar In Bearing Shoots Of Cabernet Sauvignon Under Water Stress

In order to understand the effects of different water stress on the distribution of sugar components in bearing shoot of grapevine.In this study.The 9-year-old Cabernet Sauvignon was used as research material.The water potential value of grapevine leaves predawn was used to reflect the degree of water stress.Firstly,Three treatments on grapevine were carried out from setting to veraison,which were mild(-0.2 MPa??b?-0.4 MPa),moderate(-0.4 MPa??b?-0.6 MPa)and severe(-0.6 MPa??b)water stress,respectively.Then each treatment was treated with mild,medium and severe water stress from after veraison to harvest.Nine treatments were set up,which were named T1 to T8,respectively.The treatment of mild stress from setting to harvest was used as control.Sugar content in phloem,leaves and berries of bearing shoots at different developmental stages was determined.The main results are as follows:(1)The effects of different water stress on sugar content in grape fruits,but did not change their accumulation pattern.At harvest,fructose and glucose were the main components of berries,and sucrose content was very low.T4,T5,T6 and T7 all increased the contents of total soluble sugar,fructose,glucose and sucrose in fruits.T4 was the largest,204.78 mg·g-1?90.88 mg-g·g-1?103.03 mg·g-1 and 10.15 mg·g-1,respectively.(2)The effects of different water stress on sucrose metabolism-related enzymes activities in grape fruits.The activities of AI,NI and SPS were increased in all treatments,and the activities of AI were higher than those of NT and SPS.All treatments reduced the activity of SS before veraison,but increased after veraison.The correlation analysis showed that AI and SPS were the key enzymes affecting fructose and glucose accumulation in grape fruits under water stress,and SS-s were the key enzymes affecting sucrose accumulation in grape fruits under water stress.(3)The effects of different treatments on total soluble sugar content in leaves at the same node of bearing shoot were increased first and then decreased at different stages.From setting to veraison,The total soluble sugar content in leaves of moderate and severe stress treatments was higher than CK,which indicated that moderate and severe stress increased the total soluble sugar content in leaves.T3,T4,T6,T7 and T8 increased rapidly from after veraison to initial ripening stage.At the late stage of maturation,the total soluble sugar content in leaves of T3,T4,T5 and T7 decreased rapidly.The total soluble sugar content in leaves at different nodes of bearing shoot increased first,then tended to be flat,and then decreased.The content of total soluble sugar in leaves of different nodes could be increased by moderate and severe treatment before veraison.Severe water stress can change the direction of sugar transport,hinder sugar transport to fruits.(4)The effects of different water stress on total soluble sugar content in phloem at the same node of bearing shoot showed a "U" trend at different stages.From setting to veraison,moderate and severe treatments were lower than CK on the whole,indicating that moderate and severe treatments promoted the transport of soluble total sugar in phloem.T4,T5 and T8 were higher than CK,and T1 was always lower than CK from after veraison to initial ripening stage.There was a minimum value in this period,indicating that sugar was mainly transported to the storage and accumulation of berries during this period.At maturity stage,the total soluble sugar content reaching a peak at maturity,and the sugar mainly transported to the branches.The total soluble sugar content in phloem at different nodes of bearing shoots decreased first and then increased.At maturity,sugars of T2,T3 and T8 were transported to the top and middle-upper parts,while sugars of T4,T5,T6 and T7 were transported to the base,and sugars might be transported to the root.(5)The effects of different water stress on grape fruit components.Water stress can make grape berries turn color earlier,moderate and severe water stress can enter the turn color earlier than CK.During berry growth and development 100-grain quality of fruit decreased with the increase of water stress.At harvest,T3,T4,T5 and T7 all decreased the titratable acid content of grape berries.T4,T5,T6 and T7 all increased the soluble solids,tannins and total anthocyanins content of grape berries,while T8 had the lowest content of all effective components.