Nutrient Uptake and Distribution in Mycorrhizal Cuttings of Populus × canadensis ‘Neva’ Under Drought Stress

Abstract

Arbuscular mycorrhizal fungi (AMF) have been reported to improve the resistance to drought stress in some plant species. The aim of this study was to evaluate the effects of Rhizophagus irregularis inoculation on the growth, photosynthetic capacity, nutrient uptake, and nutrient distribution of poplar cuttings under drought stress. The experiment was performed with a randomized block design with two factors: (i) AMF treatment, inoculated with R. irregularis (AM) or not (NM); (ii) drought treatment, well-watered (WW, 70–75% of field capacity), mild stressed (MS, 50–55% of field capacity), or severe stressed (SS, 30–35% of field capacity). The results showed that R. irregularis colonized more than 70% of the roots of poplar cuttings. Drought stress limited the plant growth and photosynthetic capacity of poplar, while inoculation increased the plant height, stem diameter, stem dry weight, root dry weight, net photosynthetic rate (PN), stomatal conductance (gs), and intrinsic water use efficiency (WUEi) regardless of the drought stress treatment. Drought stress decreased the absorption of nutrients and affected their distribution in plant tissues. Regardless of drought stress treatment, inoculation increased the concentrations of Ca and Mn in leaves and the concentration of Cu in roots. Under mild drought stress conditions, the contents of P, Ca, Cu, Fe, and Zn increased significantly in the leaves of inoculated plants, while the contents of P, Ca, Fe, and Mn increased significantly in the roots. Under severe drought stress, inoculation decreased the distribution of N, P, K, and Mg in the leaves; the distribution of K, Ca, Mn, and Zn in roots; and the distribution of Cu in roots. Moreover, a principal components analysis showed that under well-watered and severe drought stress conditions, the inoculation of poplars with R. irregularis could significantly increase the absorption of nutrients. The results of a correlation analysis indicated that the growth parameters and gas exchange parameters positively correlated with the concentrations of leaf P, K, Ca, Fe, Mn, Cu, and Zn. Photosynthetic capacity, nutrient absorption, and a change in nutrient distribution were enhanced in the mycorrhizal poplar cuttings, which resulted in enhanced growth and a limited loss of biomass during drought stress compared with the non-mycorrhizal cuttings.