Cadmium Accumulation and Tolerance of Two Salix Genotypes Hydroponically Grown in Presence of Cadmium

Abstract

In general, according to previous studies, pioneer species do not require arbuscular mycorrhizal fungi (AMF) to increase their growth and survival in tropical systems. The aim of this study was to determine the dependence response to AMF of Heliocarpus appendiculatus, a pioneer species, at different phosphorus (P) levels. In a greenhouse experiment, H. appendiculatus seedlings were grown in pots with a sterile vermiculite-sand mixture (1:1). Two sets of pots were set up: One set was inoculated (150 spores per pot) with indigenous AMF from a tropical rain forest at “Los Tuxtlas” (Veracruz, Mexico); the other set was not inoculated. To each set, 0, 0.02, 0.2, and 2 g L^?1P was added. All pots were watered with 250 mL of nutrient solution. Mycorrhizal plants showed a higher total dry weight and relative growth rate in 0.02 g L^?1P concentration, while nonmycorrhizal plants responded positively at 0.2 g L^?1P; a decrease in plant responses at higher P levels was observed in both treatments. H. appendiculatus showed to have higher relative dependence at lower P concentration (≈50%). As levels of P increased, mycorrhizal colonization decreased. Successful growth of pioneer species during succession process may be improved if there is AMF content in soils, prior to disturbance.     

Tolerance of Two Hydroponically Grown Salix Genotypes to Excess Zinc

Woody cuttings from two Salix genotypes (genotype I—clone LUC-31, Salix alba and genotype II- clone STOTT, Salix viminalis) were grown hydroponically for 14 days at increasing concentrations of Zn: control, 50, 100 or 150 μ M Zn. Genotype tolerance to excess zinc (Zn) was evaluated using a root elongation test. The changes in growth, Zn, iron (Fe), copper (Cu) and manganese (Mn) concentrations as well as photosynthetic performance were used as additional evaluation criteria. Photosynthetic pigments concentrations in Zn-exposed cuttings of genotype II decreased as compared with genotype I, which corresponded well with the higher leaf Zn accumulation, decreased Fe concentrations as well as lowered photosynthetic rate. Based on the indicators used, genotype I (Salix alba) was classified as more tolerant to excess Zn than genotype II (Salix viminalis).