2015 Volume 59 Issue 1 Pages 28-34
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 35ºC. 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 10–32ºC set fruit, whereas at 4–8ºC and 35ºC, the flowers often failed to set fruit. Fruit weight, symmetry, and number of seeds improved at 17–22ºC. Fruit set and number of seeds decreased below 8ºC: in these temperatures, pollen-tube penetration into embryo sac was significantly restricted. Below 6ºC, anthesis was often delayed, and embryo sacs hardly accepted pollen tubes. The limited fruit set below 8ºC 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 10ºC after pollination was found to be effective to prevent fruit set failure.