EFFECTS OF ZINC (ZINC-SULFATE) ON RHIZOBIA-EARLEAF ACACIA (ACACIA AURICULAEFORMIS) SYMBIOTIC ASSOCIATION

This project was aimed at investigating the feasibility of using a leg ume woody plant Acacia auriculaeformis to reclaim Zn-contaminated area s. The effects of different concentrations of Zn, applied as zinc sulf ate, on nodulation (%) and nitrogen fixation activity of the A. auricu laeformis 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%, r espectively) for AA9108 were 373.6 mg l(-1) and 638.9 mg l(-1) respect ively. Nodule formation was inhibited by 10% and 50% at Zn levels of 6 2.9 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), respective ly. 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-toler ant varieties of the genus Acacia is therefore a prerequisite for usin g this genus in revegetation of Zn-contaminated areas. (C) 1998 Publis hed by Elsevier Science Ltd. All rights reserved.