FLOWERING OF MANGO TREES IN CONTAINERS AS INFLUENCED BY SEASONAL TEMPERATURE AND WATER-STRESS

Experiments were conducted in Homestead, FL, during July (mean minimum temperatures about 20-degrees-C, non-floral-inductive), and October and November (mean minimum temperatures about 15-degrees-C, floral-inductive), to determine if water stress induces floral morphogenesis in mango (Mangifera indica L.). Suspending irrigation of container-grown cultivar 'Tommy Atkins' trees for 25 or 36 days in July caused water stress (PHI(L) of -3.55 MPa and -3.78 MPa, respectively), while irrigated trees remained non-stressed (-0.30 MPa). No flowering occurred, and all apical buds produced a vegetative flush which emerged later in water-stressed trees than in controls. In October, suspending irrigation of 'Tommy Atkine trees for 35 days resulted in PHI(L) values similar to those obtained during July. However, all apical buds, including those of irrigated trees, initiated flowers. Water stress advanced floral budbreak by nearly 2 weeks in nearly 40% of buds. In November, trees of four mango cultivars were or were not water-stressed in a glasshouse under warm conditions (mean minimum temperatures about 20-degrees-C), and were lightly pruned to stimulate growth of dormant axillary buds. Axillary buds produced vegetative growth only. Lightly pruned trees growing outdoors in cool temperatures initiated axillary floral buds. In warm temperatures (mean minimum temperatures about 20-degrees-C), water stress delayed shoot extension, but did not induce floral morphogenesis. In cool temperatures (mean minimum temperatures about 15-degrees-C), floral buds were initiated regardless of water stress. Thus, floral morphogenesis was induced by chilling temperatures. In contrast to water stress delaying the development of vegetative buds, the growth of floral buds was stimulated by water stress. Low temperatures thus promoted floral induction of mango, whereas water stress promoted growth of florally induced buds.