A influência da morfologia e da biologia floral no sucesso reprodutivo do adubo verde Crotalaria juncea L. (Leguminosae, Papilionoideae)

Abstract

The pollination is a fundamental ecosystem function for the plants development, including the reproductive success. In Crotalaria juncea L., it is verified that the flowers have distinct anthers morphs and fillets length, which in turn can influence in their reproduction. In this context, the aim of this manuscript was to study the pollination and reproductive system of C. juncea. The aim of the chapter I were to verify if floral morphology and biology influence the behavior of floral visitors. The aim of the chapter II were to compare the efficacy of floral visitors in the fruits and seeds set in different treatments; and to evaluate the fertility components. The study was carried out in a planting area in a green area, in Santa Bárbara d'Oeste (22°44'21.9"S; 47°21'22.6"W), São Paulo, with 120 individuals. Floral visitors were observed between February and March 2016. Determination of floral opening and floral anthesis were obtained through field observation, during flowering. The stigmatic receptivity was verified by the 3% hydrogen peroxide submersion test. The estimate of pollen production was given by counting the number of pollen grains produced by anther. The number of viable pollen grains was quantified through cytoplasmic staining, using the acetic carmine technique. To verify the effectiveness of flowering visitors in the formation of fruits and seeds of C. juncea, controlled tests of pollinator visits were carried out on floral buds previously bagged with tulle. In order to verify the effects of the fertility components, developed fruits were counted in 30 individuals, as well as the number of developed and aborted seeds in 684 fruits. The fruits were counted by position (basal, median and apical), in the inflorescences. The same method was used for the development and abortion of the seeds in the fruits. Variance analyzes were performed to detect differences between developed and aborted seeds masses in efficacy tests. In the analysis of the fecundity components, differences in fruit development and seed abortion were observed between the inflorescence and fruit positions, respectively. Through analysis of floral morphometry, there was a difference between male reproductive structures, characterizing floral heterantry. The observations indicated only the presence of large bees (X. frontalis) as floral visitors. When comparing the values obtained between the small anthers and the large anthers, for the total amount of pollen grains, no variation was obtained (p=0,5079). In the stigmatic receptivity test it was seen that the stigmas are receptive in all phases of floral anthesis. In the test of staining of the pollen grains, with acetic carmine, pollen viability was verified above 90%, in both morphs of anthers. There was a significant difference in the number and mass of the fruits developed, only between treatments of 1 and 3 visits of X. frontalis. There was a significant difference when comparing the distribution of the aborted and developed seeds between the fruit positions. It is concluded that the specific behavior of the bees is important in order to be able to contact the floral resources, and a greater number of visits of the pollinators can increase the productivity of the C. juncea crop, resulting in an increase in the number and mass of the fruits. In addition, maternal resources are necessary for the development of the fruit, but for the seed it is more advantageous to be near to the stigma.