Study On The Regulation And Coloration Effect Of Exogenous ALA On The Metabolic Physiology Of Grape Anthocyanins

In this experiment,Crimson and Flame were used as experimental materials to study the effects of The objective of this experiment was to determine effects of exogenous 5-aminolevulinic acid(ALA)on(i)the growth and coloring of grape berries,(ii)berry quality(i.e.,sugar content,acidity,soluble solid content,chlorophyll content,carotenoid content,and anthocyanin content),and(iii)the activities of enzymes associated with anthocyanidin and anthocyanin biosynthesis in grape berry skin.The study included two grape cultivars: ‘Crimson Seedless' and ‘Flame Seedless.' The results are as follows:1.Effects of exogenous ALA on the growth and coloring of grape berries: Exogenous ALA application significantly increased the growth and development of berries of both cultivars compared with the control.The ALA also significantly increased the fruit coloring index(CIRG).In contrast,exogenous ALA reduced fruit surface color brightness(L *),color components(a *,b *),color saturation(C *)and color angle(h °).Fruit surface brightness was deeper in the ALA treatments than in the control.Overall,ALA significantly promoted berry growth and improved fruit coloring.2.Effects of exogenous ALA on the intrinsic quality of grape berries: Total sugar concentrations and soluble solid concentrations were greater in the ALA treatments than in the control treatment on all sample dates and in both cultivars.Total sugar concentrations were significantly greater in the 100 mg·L-1 ALA treatment than in the control,50 mg·L-1 and 150 mg·L-1 ALA treatments on d 15 to 25.The soluble solid content of Crimson Seedless berries was significantly greater in the 50 and 100 mg·L-1 ALA treatments than in the control.In contrast,there was no significant difference in soluble solid content between the 150 mg·L-1ALA treatment and the control.In Flame Seedless berries,the soluble solid content in the 100 mg·L-1 ALA treatment was significantly greater than in the control.The soluble solid content in the 50 and 150 mg·L-1ALA treatments was significantly greater than that in the control on d 20 but not on the other sampling dates.The titratable acid content in the berries of both cultivars decreased gradually across time.All three ALA treatments significantly reduced titratable acid contents.The 100 mg·L-1 ALA treatment reduced titratable acid contents more than the 50 and 150 mg·L-1 ALA treatments.Chlorophyll and carotenoid contents decreased gradually as the berries of both cultivars matured.Exogenous ALA application significantly reduced chlorophyll degradation rates in the grape berries,thus alleviating the effect of chlorophyll degradation on anthocyanin synthesis.3.Effects of exogenous ALA on the activities of enzymes associated with anthocyanidin and anthocyanin biosynthesis in grape berry skin: In the ALA treatments,anthocyanin concentrations in the skin of Crimson Seedless berries gradually increased as the berries matured.In comparison,anthocyanin concentrations in the skin of Flame Seedless berries increased gradually and then decreased as the berries matured.All three ALA treatments significantly increased anthocyanin concentrations in the grape berries.The largest increases were in the 100 mg·L-1 ALA treatment.The activities of two enzymes related to anthocyanin biosynthesis,PAL and CHI,increased gradually and then decreased as the berries matured.All three ALA treatments significantly reduced PAL activity in the skin of Flame Seedless berries.In Crimson Seedless,ALA increased PAL activity in the berry skin between 5 and 15 d after ALA application.The 100 mg·L-1ALA treatment significantly increased CHI activity in the skin of Crimson Seedless berries from 10 to 20 days after treatment.In contrast,there was no significant difference in CHI activity between the 50 and 150 mg · L-1 ALA treatments and the control.In the skin of Flame Seedless berries,CHI activity was significantly greater in the 100 mg·L-1ALA treatment than in the control on all sample dates.The 50 and150 mg·L-1 treatments significantly increased CHI activities on d 10 and 25 but not on the other sampling dates.The 100 mg·L-1 ALA treatment significantly increased DFR activities in the berry skin of both cultivars on all sample dates.The DFR activities in the 50 and 150 mg·L-1 ALA treatments were sometimes higher and sometimes lower than those in the control.The UFGT activity in the berry skin of both cultivars fluctuated as the berries matured.The UFGT activities increased in the skins of Crimson Seedless berries from 15 to 25 d after treatment.In comparison,UFGT activities in the skin of Flame Seedless berries increased significantly from 15 to 25 d in the 50 and 100 mg·L-1 ALA treatments compared with the control.There was no significant difference between the 50 and 100 mg·L-1 ALA treatments and the control on the other sampling dates.The 100 mg·L-1 ALA treatment increased UFGT activities more than the 50 and 100mg· L-1 ALA treatments.Correlation analysis was conducted between anthocyanin and the activities of enzymes related to its synthesis.The results showed significant positive correlation between anthocyanin concentration and the activities of PAL,CHI and UFGT in the exogenous ALA treatments.There was no significant correlation between anthocyanin concentration and DFR activity.Exogenous ALA can promote anthocyanin synthesis by increasing CHI activity.The results showed that the accumulation of anthocyanin in berry skin was related to increases in the activities of PAL,CHI,and UFGT.There was no significant correlation between DFR activity and the accumulation of anthocyanin.