Effects of water deficit on flower opening in coffee (Coffea arabica L.)

The response of coffee (Cofsea arabica L.) floral buds to different water deficits followed by re-irrigation was investigated. Flower opening was stimulated by irrigation after one period of water deficit if predawn leaf water potential declined below-0.8 MPa. Similar stimulation of flowering was observed when less severe but more prolonged water deficits (ca.-0.3 to-0.5 MPa for two weeks) were imposed, even if water deficit was relieved by re-irrigation several times during this period. Consistent results were obtained in the field and in two greenhouse locations. Stimulation of flower opening by water deficit followed by re-irrigation was restricted to buds at the “open white cluster ” stage of development (Stage 4). Only buds at this stage exhibited development of secondary xylem. Split-root experiments indicated that a root signal stimulated flower opening, independently of predawn or midday leaf water status. Frequent irrigation to prevent flowering, followed by a controlled water deficit and re-irrigation to stimulate flowering, may represent apractical method to synchronize flowering and shorten the harvest period in leeward coffee production areas in Hawaii