The Effects of Inoculation with Three Glomus Species on Growth and Pb Uptake by Hemp (Cannabis Sativa) in a Pb-Contaminated Soil

Abstract

Increasing levels of hazardous heavy metals, which enter soil and water ecosystems have had a detrimental effect on global living organisms and needs special attention. The effect of inoculation with three Glomus mycorrhizal fungi (G. mosseae, G. etunicatum and G. constrictum) on hemp growth and some biological properties was evaluated in a soil contaminated with different levels of lead (0, 600, 1200 and 1800mg·kg^-1 Pb soil) in the form of Pb(NO₃)₂. The results show that shoot and root dry weights decreased with increasing Pb levels in soil. But Pb concentration in roots and shoots of hemp increased significantly with increasing Pb levels in soil. However the growth of mycorrhizal inoculated hemps was significantly higher than that of non-inoculated hemp. Mycorrhizal inoculation increased the concentration of Pb in the shoot and root of hemp. In this study, both translocation factor (TF) and enrichment factor (EF) were < 1 and decreased with increasing Pb concentration in soil. The TF was higher in non-inoculated hemp than inoculated hemps. It shows the inhibition effect of mycorrhiza in translocation of Pb from root to shoot. The EF of all inoculated hemps (0.18) was significantly greater than non-inoculated hemp (0.17), showing increased uptake of Pb due to inoculation with mycorrhiza. Simple linear regressions show that the diethylenetriaminepentaacetic acid (DTPA) extractable Pb is more suitable index for evaluating the toxicity effect of soil Pb than the total Pb content.