Abstract
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.
