Tolerance of different varieties of Salix integra to high zinc stress

The effect of high Zn stress on Zn uptake, accumulation and the growth of three varieties of Salix integra were analyzed through nutrient solution culture. The results show that the influence of Zn treatment on growth parameters is related to plant variety, plant part and Zn concentration. Growth parameters of the three varieties are retarded at Zn concentration of 100 mmol·L^-1(low) and 1 000 μmol·L^-1(high). Root length of ‘Weishanhu’ and ‘Dahongtou’, and root biomass of ‘Dahongtou’ significantly drop in low Zn concentration. Stem height, root length and biomass markedly reduce in high Zn concentration. Zn uptake and accumulation vary with plant variety and shoot Zn content decreases with increasing Zn concentration. However, root Zn content increases with elevated Zn concentration. Root Zn concentration is generally higher than that of shoot. For the different plant varieties, shoot Zn concentration ranges from 1 477.58 to 1 583.19 μg·g^-1 in low concentration Zn with an average of 1 530.29 μg·g^-1. Translocation factor (TF) decreases with Zn concentration increasing with TF for ‘Weishanhu’ and ‘Yizhibi’ higher than that for ‘Dahongtou’. Shoot total Zn content decreases with increasing Zn concentration. Shoot total Zn amount from 2 332.58 to 3 871.41 μg with an average of 3 266.27 μg. Shoot/root total Zn ratio is in excess of 1 for three varieties. Tolerance index (TI) decreases with increasing Zn concentration, which is above 0.5 for the three varieties in low Zn concentration. This study suggests that high Zn concentration severely inhibits growth of S. integra. The three varieties have strong tolerance and high accumulation capacity in low Zn concentration. This shows that S. integra has a high potential for phytoextraction of Zn, whose concentration is not higher than 100 μmol·L^-1.