Effects Of Flower Thinning On The Early Development Of 'Okubo' Peach (Prunus Persica L. Batsch) Fruit

The peach fruit (Primus persica (L.) Batsch. cv. Okubo) was used as material to study the effects of flower thinning on the early fruit development at cell, hermone, nutrition, protein and gene levels. The mechanism of early development of peach fruit was discussed primarily. The results are showed as follows:The Intensive cell division of "Okubo" peach fruit did not cease until 42 days after anthesis. Flower-thinning promoted the cell division of the fruit mesocarp and increased the thickness of the mesocarp within 3 weeks after anthesis, leading to the increase in the fruit size and fresh weight at harvest.The changes in soluble sugar and protein contents in fruit mesocarp were similar to those of fruit resh weight and volume. This suggested that the levels of soluble sugar and protein in fruit mesocarp might closely related to the fruit development. The important sugars were fructose and sucrose. The contribution of the soluble sugars in fruit mesocarp to the increase of mesocarp total DNA content was larger than that to the increase of fruit volume. The levels of the carbohydrate had a close relationship with fruit cell division, though its effect might not be direct.The contents of DHZR, iPA and ZRs in fruit mesocarp and seed were determined by ELASA during early fruit development.The DHZR content was higher than that of iPA and ZRs content was the lowest. The ZRs content was higher than that of DHZR and iPA content was the lowest in the seed. The ratio of DHZR were correlated with the ratio of total DNA content between flower thinning and control in mesocarp. It suggested that DHZR might play an important role in mesocarp cell division and its effect might be direct. Flower thinning increased the levels of DHZR in mesocarp and ZRs in seed. The results showed that the cytokinin levels in mesocarp may regulate the rate of mesocarp cell division. High cytokinin contents resulted in the increase of cell division activity, leading to a large fruit. Low cytokinin contents reduced the cell division rate, leading to a small fruit.The cyclin gene cycD3 of tomato fruit was used as a probe to study the expression of cyclin in mesocarp of "Okubo" peach fruit by Northern blotting. The expression of cycD3 reached the maximum level at the stage of intensive cell division. DHZR level of mesocarp correlated with the expression of cycD3. This suggested that DHZR wao important cytokinin further and it promoted mesocarp cell division perhaps through regulating the expression of cycD3.