PROMOTION OF OUT-OF-SEASON FLOWERING THROUGH PHYSICAL OR CHEMICAL STRESS APPLIED ON ORANGE TREES UNDER GREENHOUSE

Abstract

?Navelina? orange (Citrus sinensis L. Osbeck) plants were submitted to physical or chemical stress in order to increase flowering and to observe some nutritional compounds also. Five treatments were tested, each with ten plants: A single foliar spray with etephon, 500 mL L-1; ASA, 1.80 g L-1; foliar urea, 60 g L-1; drought stress for 50 days at -3 MPa; and cool temperatures (11-13/15-18 °C, 16 h dark period/8 h light period, during 42 days). The plants subjected to water stress had 720 % more mixed bud sprouting, 24 days after reinitiation of watering, and a concentration of arginine 354 % greater than the control. At that time, calcium/potassium ratio was 1.5 (control, 1.3). ASA promoted floral sprouting, while etephon and foliar urea did not. There were no differences in the content of total nitrogen (2.12 % on average of dry weight) in the leaves among treatments. It was concluded that water stress promoted the highest mixed sprouting, which was related to an increase in arginine concentrations, while ASA stimulated floral sprouting.