Biologia reprodutiva de Acacia mearnsii De Wild.: receptividade de estigmas

摘要

The purpose of this study was to evaluate the stigma receptivity of Acacia mearnsii De Wild. in 20 trees of the Seed Production Area on the Fazenda Locatelli of the company SETA S.A., in the county of Butiá, state of Rio Grande do Sul, and to compare the periods of stigma receptivity and pollen viability at different stages of flower opening. The colorimetry method of the Baker reagent was used to determine receptivity and viability. The analyses were evaluated in a completely randomized design and the χ2 statistics were used to verify the significance of the studied events. The receptivity increased from the beginning of flower opening (71%) to total receptivity (100%) at full anthesis. Pollen viability was detected in the beginning of anthesis (77%) and at total flower opening (88%). Receptive stigmas (50%) and viable polyads (23%) were observed in the senescence stage. The phases of male viability and female receptivity were superposed, which increases the chances of self-pollination. Full receptivity (100%) was observed in the sampled stigma of most evaluated trees (85%). In three trees (15%) receptive stigmas were in the mean below 95%. No significant difference was detected by the χ2 test in the stigma receptivity of the germplasm under study, indicating that the genotype does not interfere directly with stigma receptivity.