Effects of ambient temperature and defoliation on flower bud induction with chemicals in pineapple [Ananas comosus] plants

Effects of temperature and defoliation (mechanical wounding of leaves) on flower bud induction after treatment with various chemicals in pineapple plants were investigated. Pineapple plants showed high percentage of flower bud induction at relatively low temperatures (20 deg C) for 3 hours from 7 to 10 hours after ethephon treatment even after transfer to high temperature conditions (32 deg C). Flower bud induction was impeded by high temperature (32 deg C) for more than 10 hours and by defoliation within 10 hours after ethephon treatment. Defoliation of the leaves in the upper part of the plant impeded flower bud induction with ethephon treatment. Effects of fall of the leaves in the middle part of the plants on flower bud induction were more impediment than those of the fall of the leaves of lower part of the plants. Treatment with NAA induced flower bud induction. The strong effect of ethephon and NAA on flower bud induction in pineapple plants required two conditions as follows: the presence of healthy green leaves and a relatively low temperature (20 deg C) for 3 hours. It was considered that impediment of flower bud induction was directly affected by defoliation and indirectly by high temperature. It was found that the effect of chemical inducers on flower bud induction varied with the changes in the environmental conditions such as mechanical wounding of leaves due to heavy rain and wind by typhoon, and changes in the temperature.