Study On The Physiological Mechanism And Preventive Measures Of Fruit Cracking Of Pomelo (Citrus Grandis (L.) Osbeck.cv.Duweiwendan)

Duweiwendan pomelo (Citrus grandis(L.) Osbeck.cv. Duweiwendan) was used in the experiment. The effect of pollinations on fruit cracking rate, fruit quality, endogenous hormones contents, enzyme activity, structure of fruit pericarp, RNase activity and total soluble sugars was studied. The results showed:1. Guanxi-pollinated and 'Duyou VI'-pollinated treatment both decreased fruit cracking rate, but Guanxi-pollinated treatments produced large numbers of seeds and Duyou VI-pollinated only produced a small quantity of seed.2. Cuanxi-pollinated and Duyou VI-pollinated treatment increased the contents of ABA during 30～60 d after anthesis period, and the contents of GA₃ during 60～130 d after anthesis period. The ZR contents of both treatments reduced during 40～90 d after anthesis period and reached to a higher level compared to control during the 90～140 d after anthesis period. Pollinations decreased the contents of IAA during the whole fruit development period. The pollination treatments increased the balance of endogenous hormones (IAA+ZR+GA₃)/ABA during the fruit development period especially the period 90～140 d after anthesis.3. There were no obviouse change of PG activity was detected in the pollination treatments. However, Guanxi-pollinated and Duyou VI-pollinated treatments increased the CX activity and decreased the PAL activity at the late stage of fruit development.4. The fruit cracking was a combination process of cracking and concrescence. Duweiwendan pomelo because of relative thiner cutin around the fruit navel, the primary crack was likely to occured in this area and finally developed to cracking. Benefit from the besieging effect around the primary cracks in early development period there was less cracking shown on Duyou VI-pollinated treatment.5. Duyou VI-pollinated had shown to have a positive effect to the fruit setting rate of Duweiwendan pomelo, but not much change been observed to the fruit weight in the early period. The endogenous hormones balance (IAA+ZR+GA₃)/ABA in ovary, RNase activity and the total souble sugars of ovary were also been rised by Duyou VI-pollinated treatment during early fruit development period.From what had been discussed above, effects of pollination with Duyou VI on the physiological indexes of endogenous hormones, RNase activity and total soluble sugar in ovary (immature fruit) of Duweiwendan pomelo induced the changes of contents of endogenous hormones in pericarp, corresponding enzyme activities and cell structure during fruit development, preventing the occurrence of fruit cracking.