Unaroj Boonprakob

Adverse effects of high temperature on the development of reproductive organs in ‘Hakuho’ peach trees

Summary To examine the effect of the temperature on the development of reproductive organs, potted plants of five year old ‘Hakuho’ peach were exposed to constant temperatures of 15°C, 20°C, 25°C, 30°C, and natural conditions. The rate of flower and leaf bud burst, and flowering were recorded every day. The characteristics of reproductive organs in each treatment were examined by measuring flower size, pollen germinabitily, pollen tube elongation, development of embryo sacs, and fruit set. Percentage of flower bud bursting at 30°C was about 80% within 3 d after the onset of the treatment, while it took 18 d to reach the same percentage in the control. Flower bud break preceded leaf bud break in all treatments. Flowering was earliest at 30°C, and the period from bud burst to flowering was as short as 3–4 d. Flower sizes were significantly decreased with increasing temperature. The pollen germination was negatively affected by higher temperature, but the pollen tube elongation in the pistils was faster at higher temperatures. On the other hand, the development of the embryo sac at high temperature was considerably less satisfactory than that at lower temperature and under field conditions. High temperatures also significantly reduced the percentages of fruit set. The results suggested that the high temperature above 25°C interferes with the normal development of reproductive organs especially embryo sac, and causes poor fruit set in ‘Hakuho’ peach.