Effect of co-inoculation with arbuscular mycorrhizal fungi and phosphate solubilizing fungi on nutrient uptake and photosynthesis of beach palm under salt stress environment

Beach plum (Prunus maritima) is an ornamental plant, famous for its strong salt and drought stress tolerance. However, the poor growth rate of transplanted seedlings has seriously restricted its application in salinized soil. This study investigated the effects of inoculation with arbuscular mycorrhizal fungus (AMF), Funneliformis mosseae, and phosphate-solubilizing fungus (PSF), Apophysomyces spartima, on the growth, nutrient (N, P, and K) uptake, and photosynthesis of beach plum under saline (170 mM NaCl) and non-saline (0 mM NaCl) conditions. We aimed to find measures to increase the growth rate of beach plum in saline-alkali land and to understand the reasons for this increase. The results showed that salinization adversely affected colonization by AMF but positively increased PSF populations (increased by 33.9–93.3% over non-NaCl treatment). The dual application of AMF and PSF mitigated the effects of salt stress on all growth parameters and nutrient uptake, significantly for roots (dry weight and P and N contents increased by 91.0%, 68.9%, and 40%, respectively, over non-NaCl treatment). Salinization caused significant reductions in net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (E), and intercellular CO2 concentration (Ci) value, while inoculation with AMF and PSF inoculations significantly abated such reductions. The maximum efficiency of photosystem II (PSII) (Fv/Fm), the photochemical quenching coefficient (qP), and the nonphotochemical quenching (NPQ) values were affected little by inoculation with AMF, PSF, or both under non-NaCl treatments. However, plants inoculated with AMF and/or PSF had higher Fv/Fm, qP, and ФPSII values (increased by 72.5–188.1%) than the control under NaCl treatment, but not a higher NPQ value. We concluded that inoculation with AMF or PSF increased nutrient uptake and improved the gas-exchange and Chl fluorescence parameters of beach plum under salt stress environment. These effects could be strengthened by the combination of AMF and PSF, especially for nutrient uptake, root growth, and Pn, thereby alleviating the deleterious effects of NaCl stress on beach plum growth.

Arbuscular Mycorrhizal Fungi (AMF) on Growth and Nutrient Uptake of Beach Plum (Prunus maritima) under Salt Stress

The effects of an arbuscular mycorrhizal fungus (AMF), Glomus mosseae, Paraglomus occultum and Glomus etunicatum, on the growth and nutrient uptake of the Prunus maritima, cultured with or without NaCl, were evaluated. Plant biomass, AM colonization and spore density were also assessed. Salt stress adversely affected plant N, Ca, Mg, Cu, Zn and Mn nutrient acquisition, except for Fe, resulting in an important reduction in shoot dry biomass. Inoculation of the AM fungus strongly promoted AM colonization and spore density, plant dry biomass, root/shoot dry weight ratio and nutrient uptake by P. maritima, regardless of salinity level. Among the three Glomus species, the total dry biomass of beach plum plants associated with G. mosseae and G. etunicatum was significantly higher than that of the control plants (48 and 43%, respectively), and so is the total leaf area (34 and 33 %, respectively). These findings suggest that inoculation with specific AMF therefore constituted an alternative method to relieve stress of soil salinization on beach plum.