Floral Development and Synchronizing Flowering of Robusta Coffee

Abstract

Floral development of robusta coffee can be classified into 6 stages.  The fourth stage is the most important in relation to synchronized cherry ripening.  At this stage the floral bud is mature and enters dormancy phase, which can be broken by a required drought period followed by rain.  The floral bud then develops into full bloom and is pollinated. Synchronizing flowering of potted robusta trees, at fully mature floral bud stage, was carried out outdoor.  Plastic sheets were used to prevent water reaching to the soil in the pots and constant water stress, of -2.0 to -2.5 MPa y _l, was imposed for 1-4 weeks.  Flowering occurred 7+2 days after rainfall or mist, irrespective of soil water content or water withholding period.  The result indicates that rainfall or high ambient humidity may be the most crucial factor for triggering synchronized flowering in coffee.  Therefore, leaves, not roots, could be the first receptors of high ambient humidity that trigger dormancy release.