Receptiveness of the stigma and in vitro germination of orange pollen, submitted to different temperatures

Abstract

The study was carried out in order to evaluate the effect of temperature and in vitor stigma receptivity on regeneration of orange cultivar (Valência, Pêra and Natal) pollen. Two experiments were carried out, in the first the ideal temperature of germination was assessed. Pollen was obtained from flowers at the balloon stage and inoculated in culture medium with 10 g L-1 agar, 200 mg L-1 boric acid, 100 g L-1 sucrose, 800 mg L-1 calcium nitrate, pH adjusted to 6,5 and incubated in a BOD chamber at temperatures of 23, 24, 25, 26 and 27ºC during a 24-hour photoperiod. After 12 hours of incubation, the best temperature for pollen grain germination was 25ºC for all varieties. In a second experiment, in order to test the receptivity of the stigma, flowers were collected at different flowering stages: small bud, balloon and open flower. The stigmas were by immersion exposed to hydrogen peroxide (perioxidase reaction), 3% for 3 minutes. Through the technique of Zeisler (1938), better results were detected at the balloon stage with 80 to 100% receptivity, while for the open flower the receptivity presented maximum indexes.