Mecanismo de tolerância em plantas jovens de ucuúba (Virola surinamensis (Rol. ex Rottb.) Warb) expostas ao cádmio e potencial para fitoestabilização: Respostas fisiológicas, bioquímicas, nutricional e de crescimento.

Abstract

Virola surinamensis (Ucuúba), is a Neotropical tree occurring naturally in the floodplain of the lowland forests, igapó and estuaries. Cadmium (Cd) is one of the most toxic and persistent heavy metais in the environment, and can he incorporated and bioaccumulated into the components of the food chain. The objective of the study was to evaluate the physiological and biochemical responses, vegetative growth, nutrient distribution, phytoextraction capacity and tolerance of young plants of V. surinamensis submitted to five concentrations of Cd (0, 15, 30, 45 and 60 mg L"1) for 60 days. The predawn water potential (Tfim), stomatal conductance (gs), transpiration (£), the liquid assimilation rate of CO2 (A), the concentration of intercellular CO2 (C/), the relation of liquid photosynthesis and intercelular CO2 concentration (A/Ci), the instantaneous efficiency ofwater use (EWU), the chlorophyll total content (Chi), the maximum photochemical efficiency of PSII (Fv/Fm), the photochemical extinction coefficient (c/P), the non-photochemical extinction coefficient (NPQ), electrons transport rate (ETR), bioconcentration factor (BCF), translocation factor (TF), the tolerance index (77), the nitrate concentration, nitrate reductase (NR), free ammonium, total soluble aminoacids (ISA), total soluble proteins (TSP), starch, proline, sucrose and total soluble carbohydrates (7SP), reducing sugars, plant height, stem diameter, number of leaves, dry matter of aerial part (DMAP), dry matter of root (DMR), total dry mass (TDM), root aerial part reason (RJAP) were evaluated. The Tam, gs, E, A, A/Ci and EWUwere lower than the control, but Chi increased at the dose of 15 and 30 mg L"1 and Ci was higher than the control. Fv/Fm, qP, ETR reduced in plants with Cd, but NPQ increased. Cd concentrations increased in different plant tissues (root > stem > leaf). The highest BCF value was 30 and 45 mg L'1 Cd and FT at 45 mg L"1 Cd, whereas IT was higher at 15 mg L"1 Cd dose. Cd did not affect the nitrate concentration in the root, but had a positive effect on the leaves. The NR, ammonia, TSA and TSP decreased in plants with Cd. TSC, proline, sucrose and reducing sugars increased in plants with Cd. Cd affected height, stem diameter, number of leaves and biomass production. The Cd negatively influenced Fe, Mg, Ca, N, P and K, especially in the root. Zn increased in the roots and leaves, while the Mn reduced in the root and increased in the leaves of the plants with Cd. Ali the plants survived until the end of the experiment. The results demonstrate tolerance and low plant capacity in the phytoextraction of Cd, indicating that V. surinamensis may be promising for Cd phytostabilization.