RESPOSTAS MORFOFISIOLÓGICAS in vitro DE Alternanthera tenella Colla (Amaranthaceae) FRENTE AO ESTRESSE INDUZIDO PELO CÁDMIO E AÇÃO ATENUANTE DO SILÍCIO

Abstract

Among the techniques used to decrease the level of heavy metal contamination in the soil is the use of phytoremediation plant species. Although the ability to bioaccumulate heavy metals, such as Cd in the aerial part, is ensured, many plants have morphophysiological disorders that can reduce their use as phytoremediation due to changes in the accumulation of biomass. Thus, the understanding of the relationships between plant and heavy metals, as well as the interaction of these two factors with stress-mitigating elements such as silicon (Si), are fundamental for the recovery of ecosystems. Thus, this study aimed to analyze the anatomical and physiological modulations induced by the synergy between Cd and Si in A. tenella plants, in addition to elucidating whether Si can mitigate the deleterious effects induced by Cd. The environmental cultivation conditions chosen for this work was in vitro. Nodal segments of A. tenella were grown in MS medium supplemented with a gradient of Cd concentration (0, 50, 100 or 200 μM) combined with two levels of Si (0 and 40 μM), constituting eight treatments. After 34 days, leaf anatomy, pigment content, chlorophyll a fluorescence, growth characteristics and tolerance index were analyzed. The existence of interaction between Si and Cd during the in vitro cultivation of A. tenella was clearly proven. The addition of Si in the culture medium resulted in a better anatomical and photosynthetic joint, improving the growth rate and decreasing the level of physiological stress and successively increasing the Cd tolerance index, especially at the highest concentrations of this element. It is concluded that the synergy exists between these two elements, improving the capacity of bioaccumulation and, consequently, the remediation of this metal by this species.