Effect of water cadmium concentration and water level on the growth performance of Salix triandroides cuttings.

Abstract

The growth performance of Salix triandroides cuttings at three water cadmium (Cd) concentrations (0, 20, and 40mgL-1) and three water levels (- 40cm, water level 40cm below the soil surface; 0cm, water level even with the soil surface; and 40cm, water level 40cm above soil surface) was investigated to evaluate its potential in phytoextraction strategies. Compared to cuttings in the - 40 or 0cm water levels, cuttings in the 40cm water level showed significantly lower biomass, height, and adventitious root length and significantly fewer leaves and adventitious roots. However, these growth and morphological parameters were not different among the three water Cd concentrations. Water level decreased stomatal conduction and transpiration rate but showed no significant effects on chlorophyll concentration or photosynthetic rate. Chlorophyll concentration and stomatal conductance were higher at 40mgL-1 Cd treatment than at 0 or 20mgL-1 Cd treatment; yet, photosynthetic rate and transpiration rate were not different. Cd concentration in the leaves and stems increased as the water level increased, but the highest Cd concentration in the roots occurred in the 0cm water level. As water Cd concentration increased, Cd concentration in the leaves, stems, and roots increased in all three water levels, except in stems in the - 40cm water level. Under Cd stress, cuttings in the - 40 or 0cm water levels were characterized by a higher bioaccumulation coefficient, but a lower translocation factor, than those in the 40cm water level. However, the bioaccumulation coefficient increased with increasing water Cd concentration in all three water levels, as did the translocation factor in the 40cm water level. The tolerance index for the cuttings was the same among all water levels and water Cd concentrations. The results clearly indicated that the low water level increased plant growth and Cd accumulation in underground parts, while the high water level decreased plant growth but increased Cd accumulation in aboveground parts.