Sectional Temperature Control and Anatomical Study for Critical Post-pollination Night Temperatures to Prevent Fruit Set Failure in Cherimoya (Annona cherimola Mill.)

摘要

The critical post-pollination temperature that negatively affects cherimoya fertilization and subsequent fruit set was determined by regulating nighttime (1800-0900 h) temperatures from 4 to 35°C. Fruit set, weight, symmetry, number of seeds, and total soluble solid contents were recorded, and anatomical observations were performed for pollen-tube growth and fertilized embryos. All flowers at 10-32°C set fruit, whereas at 4-8"C and 35°C, the flowers often failed to set fruit. Fruit weight, symmetry, and number of seeds improved at 17-22°C. Fruit set and number of seeds decreased below 8°C: in these temperatures, pollen-tube penetration into embryo sac was significantly restricted. Below 6°C, anthesis was often delayed, and embryo sacs hardly accepted pollen tubes. The limited fruit set below 8°C may be caused by inhibition of pollen-tube growth and of embryonic development after fertilization due to the direct effect of low night temperatures. Overall, heating to maintain minimum night temperatures of 10°C after pollination was found to be effective to prevent fruit set failure.