Biologia floral e reprodutiva de araçazeiros (Psidium sp.)

Abstract

Brazil is the country with the greatest plant genetic diversity in the world, with flora rich in edible fruit species. The knowledge about floral biology, such as pollination and reproduction is extremely important to domesticate this species. With it, this research aimed to elucidate floral aspects and reproductive biology of yellow and red araçá trees. For this trials were performed in the Laboratório de Fisiologia Vegetal and in the Unidade de Ensino e Pesquisa Viveiro de Produção de Mudas from the Experimental Station of UTFPR – Campus Dois Vizinhos, Paraná State. Phonological phases observations were made in the individuals and monitoring the evolution of reproductive structures until fruiting. The anatomical knowledge about floral parts structures, flower morphological characterization, number of anthers and pollen grains per anther were analyzed. The odoriferous structures were identified through colorimetric, luminescent and olfactory tests. Stigma receptivity was measured by colorimetric and hydrogen peroxide tests. The viability of the pollen was tested with dyes and germination in vitro, in addition to analyzing pollen tube kinetics. The reproductive strategy was evaluated. Floral visitors were observed and identified. It is concluded that the phenology differs between the morphotypes studied, but both were divided into 27 phases and followed the oscillation of abiotic factors. Their flowers last less than a day and are generalist, with large amounts of pollen, without nectar, with odor release in the anthers and without temporal separation of reproductive organs maturation. The pollen was recalcitrant, must be collected after anthesis and dehydrated for six hours in a refrigerated environment. The culture medium should be composed of 10% sucrose, boron 50 mg L-1 and 1% agar for red araçá or 2% for yellow araçá. Pollen tubes reached the ovary at 36 and 48 hours after pollination, for red and yellow araçá trees, respectively. They were self-compatible, without apomixes and preferably xenogamous. Pollinators were important for reproduction, with Apis mellifera being the effective pollinator of red araçá and native bees of the family Halictidae and Exomalopsis sp. of yellow araçá.