Effects of zinc (zinc sulfate) on rhizobia-earleaf acacia (Acacia auriculaeformis) symbiotic association

This project was aimed at investigating the feasibility of using a legume woody plant Acacia auriculaeformis to reclaim Zn-contaminated areas. The effects of different concentrations of Zn, applied as zinc sulfate, on nodulation (%) and nitrogen fixation activity of the A. auriculaeformis symbiont Rhizobium strain (AA9108) and on growth of the host plant in solution culture conditions were studied. The EC10 and EC50 values (effective concentration to reduce the growth by 10% and 50%, respectively) for AA9108 were 373.6 mg l(-1) and 638.9 mg l(-1) respectively. Nodule formation was inhibited by 10% and 50% at Zn levels of 62.9 mg l(-1) and 115.6 mg l(-1) respectively. EC10 and EC50 values for N-2-fixation activity were 4.7 mg l(-1) and 38.6 mg l(-1), respectively. Growth of host plant was the most sensitive (EC10 and EC50 values were 0.6 mg l(-1) and 18.3 mg l(-1), respectively). Screening Zn-tolerant varieties of the genus Acacia is therefore a prerequisite for using this genus in revegetation of Zn-contaminated areas. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.