Ectomycorrhizal inoculation of Populus nigra modifies the response of absorptive root respiration and root surface enzyme activity to salinity stress

This study evaluated the effect of ectomycorrhiza on the tolerance of Populus nigra cuttings to salinity. Half of the cuttings were inoculated with Scleroderma sp. and treated with 50 mM NaCl. Ectomycorrhizal inoculation significantly stimulated plant growth under non-stressed and salt-stressed conditions. Exposure to NaCl decreased leaf chlorophyll concentrations, however the decrease was less in mycorrhizal cuttings. Salt treatment significantly increased root respiration in the non-inoculated plants compared to the control. The respiration of mycorrhizal roots was not increased by the exposure to salt. Exposure to salt also significantly increased the activity of the extracellular enzymes β-glucosidase, N-acetyl-glucosaminidase and leucine-amino-peptidase on the surface of both inoculated and non-inoculated root tips compared to the respective unexposed treatments. The results of this study show that inoculation of cuttings of Populus nigra with ectomycorrhiza increases tolerance to salinity stress, determined in terms of an alleviated decrease in chlorophyll content, and unaltered root respiration, but that this increased tolerance was not due to improved N nutrition.