Roberto Núñez-Elisea

Flowering of mango trees in containers as influenced by seasonal temperature and water stress

Abstract Experiments were conducted in Homestead, FL, during July (mean minimum temperatures about 20°C, non-floral-inductive), and October and November (mean minimum temperatures about 15°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 ( Ψ 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 Atkins’ trees for 35 days resulted in Ψ 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°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°C), water stress delayed shoot extension, but did not induce floral morphogenesis. In cool temperatures (mean minimum temperatures about 15°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.

Effect of leaf age, duration of cool temperature treatment, and photoperiod on bud dormancy release and floral initiation in mango

Abstract Floral induction in apical buds of container-grown ‘Tommy Atkins’ mango trees occurred after a cool temperature regime of 18 °C day/10 °C night, 12-h photoperiod, was imposed for a minimum period of 3 weeks on trees bearing leaves at least 7 weeks old. Growth of induced buds during exposure to the cool temperature regime appeared to be necessary for floral initiation, since buds resuming growth in warm temperatures (about 28 °C day/22 °C night) immediately after receiving an inductive, cool temperature treatment produced a vegetative flush. Trees bearing younger leaves or chemically forced (thidiazuron or ammonium nitrate application) to resume growth prior to completing 3 weeks of cool temperature treatment also produced vegetative growth instead of inflorescences. Cool temperatures of 18 °C day/10 °C night with either 11-, 12-, 13-, or 24-h photoperiods resulted in floral initiation, whereas only vegetative growth occurred with warm temperatures of 30 °C day/25 °C night using 11- or 13-h photoperiods. Results of this study suggest that floral induction of ‘Tommy Atkins’ mango occurred during bud dormancy in cool temperatures around 15 °C, and that warm temperatures near 30°C prevented floral initiation of induced buds. Cool temperatures rather than a short photoperiod caused floral induction, whereas warm temperatures rather than a long photoperiod inhibited flowering.

Selective pruning and crop removal increase early-season fruit production of carambola (Averrhoa carambola L.)

Carambola (Averrhoa carambola L.) trees grow and bear fruit year-round in their native, tropical environment. Fruits of this species are borne mainly on the canopy periphery, and the delicate skin is easily damaged during windy conditions (wind-scar). Pruning, as well as fruit drop caused by strong winds, stimulates re-bloom of carambola trees. In subtropical southern Florida, cool temperatures and dry winds during the winter inhibit tree growth and shorten the production season to July‐February. Crop value is greatest during the early part of the season. We evaluated manual, selective pruning and crop removal as techniques for increasing production of early-season fruit in ‘Arkin’ carambola. Pruning 3‐4-year old branches to their main axes in early March (late winter in the Northern Hemisphere) resulted in flowering during mid-April (mid-spring) and a crop by the end of June (early summer), whereas harvest of intact, non-pruned trees began 4‐5 weeks later. Pruned branches produced 15 kg (November pruning) to 24 kg of fruit (July pruning). Selectively pruned branches deep within the tree canopy did not appear to be moved by wind as much as branches along the canopy periphery. Thus, fruit from pruned branches were nearly 100% free of wind-scar and had excellent appearance. In comparison, more than 58% of fruit harvested from the canopy periphery had wind-scar, with only ca. 20% free from such damage. Crop removal in November or December (mid‐late-autumn) increased early bloom and the amount of early fruit produced in the summer. De-fruited trees produced an average of 48 kg per tree of early fruit, harvested July 7, whereas non-de-fruited trees produced an average of only 5 kg per tree. # 2000 Elsevier Science B.V. All rights reserved.