Efeitos do cádmio na anatomia e na fotossíntese de duas macrófitas aquáticas

Abstract

RESUMO -(Efeitos do cádmio na anatomia e na fotossíntese de duas macrófitas aquáticas). As macrófitas aquáticas vêm sendo usadas no monitoramento de águas poluídas por metais pesados, dessa forma, avaliou-se a capacidade fitorremediadora de Alternanthera philoxeroides (Mart.) Palavras-chave: Alternanthera philoxeroides, fluorescência da clorofila, metal pesado, Polygonum ferrugineumABSTRACT -(Effects of cadmium on the anatomy and photosynthesis of two aquatic macrophytes). Aquatic macrophytes have been used to monitor waters polluted by heavy metals. The phytoremediation capacity of Alternanthera philoxeroides (Mart.) Griseb. (Amaranthaceae) and Polygonum ferrugineum Wedd. (Polygonaceae) was therefore evaluated. These two species were submitted to treatments of 0, 25 and 50 mg L -1 Cd in nutritive solution. Seven days after treatment application, leaf gas exchange and chlorophyll fluorescence were measured in mature and fully expanded leaves. Fragments of roots, shoots and leaves were fixed in FAA 70, embedded in historesin and cut with a rotating microtome, and the sections stained with 1% toluidine blue. The Cd content in plant biomass was determined using ICP-MS. In P. ferrugineum exposed to 25 and 50 mg L -1 Cd, an increase in the central leaf-vein-and root-aerenchyma lacunae was observed. Furthermore, in plants exposed to 50 mg L -1 Cd, an increase in leaf glandular trichomes and mesophyll compacting was observed. In the stem of A. philoxeroides exposed to 50 mg L -1 Cd, the nuclei of the cortex cells became elliptic, and at 25 and 50 mg L -1 Cd, the number of druses in the cells of the central leaf vein was reduced. Cd accumulation was higher in the roots, followed by the stem and leaves in A. philoxeroides. The net photosynthesis rate of P. ferrugineum was more affected by Cd than that of A. philoxeroides. There was no variation in photosystem II (Fv/Fm) activity between the two species and the Cd treatments. A. philoxeroides was more cadmium-tolerant than P. ferrugineum, which indicates its capacity for use in phytoremediation programs.

Cadmium tolerance of Typha domingensis Pers. (Typhaceae) as related to growth and leaf morphophysiology

“…In addition, this tissue is also important for the storage of O 2 and tissue respiration in wetlands (Drew et al, 2000). This tissue was increased by Cd in the Alternanthera philoxeroides and Polygonum ferrugineu, two aquatic macrophytes (Souza et al 2009). In addition, Eichhornia crassipes showed higher aerenchyma development under Cd contamination (Pereira et al, 2017).…”

“…Cadmium (Cd) is one of the most toxic heavy metals for plants and animals (Gratão et al, 2005). Cadmium can be found in soils and wetlands were it becomes available to plants (Souza et al, 2009). This metal is naturally found in soils due to the decomposition of rocks, but its level increases with anthropic activities such as industry and the application of fertilizers in large scale agriculture (Gratão et al, 2005).…”

The use of Salvinia auriculata as a bioindicator in aquatic ecosystems: biomass and structure dependent on the cadmium concentration

“…Aquatic plants exposed to heavy metals show typical symptoms, such as leaf and root necrosis (Vecchia et al, 2005;Souza et al, 2009), chlorosis, brownish-red coloration, reduced biomass and reduced yield (Oliveira et al, 2001;Guimarães et al, 2006). This pattern is associated with stomatal opening, a reduced rate of photosynthesis, a reduced nutrient absorption and transportation (Larsson et al, 1998).…”

Changes in protein profile detected in seedlings of Caesalpinia peltophoroides (Fabaceae) after exposure to high concentration of cadmium

“…Among the heavy metals, cadmium (Cd) is the most phytotoxic, even at low concentrations, because of its high water solubility (Das et al, 1997;Pinto et al, 2004;Zacchini et al, 2009). Therefore, it is easily taken up and translocated to different plant parts (Oliveira et al, 2001;Souza et al, 2009). Once accumulated in the plant, Cd promotes several physiological and biochemical changes, such as in photosynthesis and in several enzyme activities, affecting plant growth and development (Sanità di Toppi and Gabbrielli, 1999;Clemens, 2006;Pietrini et al, 2010).…”