"Estruturas subterrâneas gemíferas em Mimosa spp. como estratégia adaptativa ao alagamento e ao fogo no Pantanal. "

Abstract

Species of the genus Mimosa persist in the floodplains of the Pantanal, even after fire and flood. One of the largest genera in the Fabaceae family, some species propagate intensely during periods of drought in the Pantanal, with some of them known as hawthorns, among them, Mimosa pigra L., M. somnians Humb. & Bonpl. ex Willd, M. xanthocentra Mart. and M. weddelliana Benth. Here, we evaluate the regrowth capacity of Mimosa species in flooding and fire experiment. Furthermore, we examined the morphoanatomy of the underground organs of these species occurring in floodable fields in the Pantanal. We collect underground systems from 40 individuals of each species, and we carried out experiments in a greenhouse treatments: control, fire and flooded 30 and 120 days, with 10 individuals in each treatment. For all treatments we used soil collected in the Pantanal. For the fire treatment we plant the underground systems in a 1.5 x aluminum box 1 m and for the control and flooded treatments, we placed each individual in pots plastics. In the flooding test, the pots were submerged in a water tank of 500 l and, after periods of flooding, we transport the individuals to a greenhouse and we followed them for another 120 days, irrigated with a sprinkler for 10 minutes twice a day. day. We use leaf litter to carry out the burning in the fire treatment. We assess the temperature at and below ground level before and after burning, and we monitor the experiments for 120 days in a greenhouse under the same conditions. We observe the regrowth of underground buds up to 10cm deep in treatments control and fire. There was no regrowth in the flooded plants, except for one individual of M. pigra flooded for 30 days, with regrowth at 4.30cm above ground level. We observe structure stem in the underground system of these species, ranging from ground level up to 5.5 cm below it. We detected starch, phenolic compounds, lipids and gelatinous fibers in xylem and secondary phloem in all Mimosa sp. evaluated. Regrowth by underground buds is a functional trait shared by the studied species of Mimosa. Our experimental results demonstrated that the underground organs of tested individuals maintain their ability to resprout after exposure to fire, suggesting that soil is an important thermal insulator.