Effects Of Different Organic Fertilizers On Sugar Metobolism In Pear Fruit And Leaves

Pear is one of the important fruits in China, and its culitivated area was only less than those of apples and oranges. Sugar, an important component of pear fruit, is a significant factor in the assesment of fruit quality. There were a lot of researches showed that applying organic fertilizers could improve fruit quality. However, few studies focus on the effects of organic fertilizer on development, sugar metabolism of fruit and leaf in pear. In this paper, the effect of different organic fertilizer (BF1, BF2, ABL, MH, CF, CM) on the development and quality of three pear cultivars (’Huangguang’,’barlett’,’Dangshansuli’) in three regions (Xinji, Penglai, Dangshan) by a two-years continuous experiment. Moreover,’Huangguang’pear was used to investigate the effect of organic fertilizers on the dynamic changes of the sugar concentration and activities of related enzymes involved in sugar metabolism in leaf and fruit during pear fruit development, and the relationship between these enzymes and concentration of N, P, K in leaf and fruit were also studied to investigate the regulation of organic fertilizer on sugar metabolism in pear. The results are as follows:The optima condition of HPLC for measure sugars component was CAPCELL PAK NH2(4.6mm X250mm) column, constant temperature of50℃, and CH3CN and H2O with a volume ratio of70:30as mobile phase. The sugar components could be precisely separated in12minutes at a flow rate of1.0mL·min-1by an ELSD detector (the temperature of drift tube80℃, nitrogen flow2.0mL·min-1). The recovery of sugar was96.4%-103%. As shown in the results of four pear cultivars,’Barlett’,’Huangguan’,’Houshui’,’Dangshansuli’, glucose, fructose, sucrose and sorbitol were the major soluble-sugar in fruit. And among all sugar fractions determined in pear fruit, fructose predominated firstly (43%-66%of total sugar), then came sorbitol and glucose (about13%-28%and14%-18%of total sugar, respectively), and sucrose were at the least level which was4%-12%of total sugar.The single fruit weight of’Dangshansuli’was significantly increased by the organic fertilizer treatments (BF1, BF2, ABL, MH), and BF1, BF2could also increase the single weight of’Huangguang’ pear, while the yield was only increased by BF1for these two cultivars, and there was no significant difference for’Barlett’ caused by organic fertilization. Except a significant effect on fruit shape index for ’Dangshansuli’, there was no significant difference on firmness and fruit shape index by organic fertilization in other cultivars. BF1, MH and LY could significantly improve the fruit soluble solids, soluble sugar concentration and sugar to acid ratio of ’Huangguang’,’Dangshansuli’and’Barlett’fruit, respectively. Moreover, LY could decrease the titratable acid concentration in’Barlett’. In addition, compared with Control and CV, BF1and CF could significantly increase the fructose concentration and decrease the malic acid concentration in’Huangguang’pear fruit, and LY could significantly increase the fructose and sorbitol contration and decrease citrate content in’Barlett’fruit, furthermore, BF1and MH could significantly increase the fructose and sucrose content and decrease the malic acid in’Dangshansuli’fruit, leading to a higher total sugar content and sweetness but lower acid content of each cultivar fruit.BF1could improve the leaf net photosynthetic activitity and transpiration rate compared to the unfertilized control, while other index was not significantly influenced by BF1treatment. Generally, sorbitol and sucrose were mainly accumulated in pear leaf, oppositely, the glucose and fructose content was only a little. Furthermore, fructose, sorbitol, glucose in leaves all decreased from the early stage, coming to the minimum level at maturation, while sucrose were nearly in the same level throughout the development. BF1led to the higher activities of leaf S6PDH in40,70DAB and NAD-SDH throughout the fruit development than that of CK. In addition, it resulted in the corresponding higher contents of fructose, sorbitol and total sugar in BOF. Otherwise there was no significant influence of organic fertilization on the sucrose concentration and the activity of SS and SPS in leaf, except a higher SPS activity in120DAB in fertilized treatments. In addition, there was a significant positive correlation between SPS, SP6DH and the concentration of N in leaf.Single weight of fruit was significantly increased by BF1in70and120DAB. During the fruit development. Fructose, sorbitol and glucose concentrations first showed an increasing trend and then declined until maturation, except sucrose, which was in a consistent increase throughout the development. Compared to CK, the levels of total sugar contents in fruit were significantly increased by organic fertilizers during fruit development. To the sugar components, fructose, sorbitol and sucrose were enhanced by organic fertilizations by7%-9%,12%-20%and30%-40%in the mature fruit, respectively. Compared with Control, BF1could increase the activity of NAD-SDH in fruit from40DAB to100DAB, and BF1, CF could increase the activity of SPS in fruit over whole development but only increase the activity of SS in40DAB. In addition, there was a significant positive correlation between SS, NAD-SDH and the concentration of N, P, K in fruit, but a significant negative correlation between SPS and the concentration of N, P, K in fruit.