Fisiologia e anatomia em matrizes e clones de Typha domingensis Pers. (Typhaceae) submetidos ao cádmio

Abstract

Little is known about differentiated effect that heavy metal can promote in matrix and clone plants, produced by vegetative growth, and the reflexes of this effect to phytoremediation systems or natural populations of these plants. Therefore, the aim of work was to evaluate cadmium effects in ecophysiology and anatomy of Typha domingensis in matrix and clone plants. Growth, gas exchange and anatomy characteristics of matrix plants and its clones produced during exposition to cadmium were evaluated. Plants were collected from Univesity Federal of Lavras water reservoirs, disinfected and cultivated under nutritive solution in a greenhouse to acclimatization. After this step, healthy plants were selected and cultivated in nutritive solution containing three cadmium nitrate concentrations (0, 10 and 50 μM) for 60 days. The experiment were conducted in 2x3 factorial scheme with ten replications (n=60). Obtained data were submitted to ANOVA test and Scott-Knott test (P<0,05). In relation to leaf growth, only a reduction in the final length was observed associated with a higher cadmium concentration. However, significant differences were noted between matrix plants and clones, with higher rates of elongation in the clone plants in relation to the matrices. However, these matrix plants showed greater leaf length and area in relation to the clones. Regarding the growth indexes, reductions were observed in the relative growth rate and net assimilation rate in the highest concentration of Cd. In this sense, the greatest differences were noted when comparing the matrix plants and clones. No changes were observed in gas exchange in relation to Cd, only between the matrix plants and clones. There was a higher photosynthetic rate in the matrix plants compared to the clones, however, they showed greater transpiration. There was no effect of Cd or plant for the indirect evaluation chlorophyll. The stomatal index showed differences only for Cd concentrations, with higher values in the treatment with 10 μM of Cd for the adaxial face and in the concentrations of 0 and 10 μM for the abaxial face. Stomatal density showed an interaction between cadmium concentration and plants. For leaf anatomical characteristics in cross section, the most notable changes were seen on the abaxial surface, comprising vascular, supporting and photosynthetic tissues. In addition, in general, higher values were also observed in the evaluated leaf characteristics associated with the matrix plants compared to the clones. Regarding the anatomical root characteristics, increments were observed for the endoderm thickness, metaxylem vessels diameter and vascular cylinder proportion along the Cd concentrations. Other characteristics, such as phloem area and cortex thickness, showed a reduction in the presence of the metal. Although the results have shown responses with different intensities for the matrix and clones plants, associated with the maturity of these plants, the work reveals tolerance of the species in both types of plants for this pollutant, which may reflect on its colonization capacity and use for phytoremediation.