Pollen fertility of Satsuma orange could be increased about 14 to 23% by the temperature treatments (at 15°C and 20°C) as compared with the outdoor control. At 25°C temperature treatment, the increase of pollen fertility was a little higher than the outdoor control, but the flowers were comparatively smaller in size and feeble which dropped off within 2 or 3 weeks after anthesis. Therefore, it may be considered that the favorable minimum temperature during the growth and development of flower buds is 15-20°C, deliberating on the increase of pollen fertility and the development of flower buds.
The increase of pollen fertility caused by the temperature treatment would be attributed to the recovery of some of the vacuous starveling microspores at the vacuole enlarging stage and the starch accumulation in microspore at the vacuole disappearing stage.
These phenomena indicate the following: 1) Enzyme activities, such as hexokinase, invertase, amylase and maltase in anther and activity of starch synthesizing enzyme system in microspore were increased by the high temperature treatments. 2) These high activities of the enzyme might decompose much more starch which reserved in anther walls and supplied rich nutrient to microspore. Furthermore, it might also release much more energy through the glycolytic pathway in anther. 3) The vacuous starveling microspores might have utilized the rich energy and absorbed the nutrient from periphery of the anther sac and excluded the large vacuole from the cytoplasm in microspore. 4) As a result, a great number of microspores recovered from the critical vacuole enlarging stage during the pollen develoment and deposited starch in the cytoplasm at the vacuole disappearing stage. 5) Consequently, those recovering microspores proceeded to the next growth cycle, became viable pollen grains and increased the pollen fertility at anthesis.