Although cowpea (Vigna unguiculata (L.) Walp.) is known as one of the drought-tolerate crops with various strategies coping with water deficit, it is very sensitive to the drought stress in the flower bud developing stage. In this study, we planned to explore how these flower bud abscission in cowpea under drought stress is regulated through the ABA and ethylene. Drought stress enhanced the rate of flower bud abscission and ethylene functions to promote it vice versa ABA. Gene expression of ABA responsible element binding factor 1, AREB1 was induced at 6 days after drought treatment and ethylene responsive factor 1 (ERF1) was induced at 9 days after drought treatment. Drought stress enhanced both endogenous ABA and ethylene productions, and especially endogenous ABA content was enhanced by ethylene inhibitor treatment. In addition, ABA treatment suppressed endogenous ethylene production in both the well-watered flower bud and the drought stressed one. These results indicate that ABA and ethylene interaction regulates responses in intact flower buds to drought stress.
