Effects of arbuscular mycorrhizal fungi inoculation on growth and salt ion accumulation of sunflower under different saline-alkali stresses

Objective  To investigate the effects of arbuscular mycorrhizal (AM) fungi inoculation on sunflower (Helianthus annuus) growth and salt ion accumulation under different types of saline-alkali stress, and provide basic data and technical support for the utilization and bioremediation of different types of saline-alkali land.

Method  A greenhouse pot experiment was conducted to investigate the effects of AM fungi Funneliformis mosseae on mycorrhizal colonization rate, biomass, nutrient uptake, C∶N∶P stoichiometry, Na⁺ absorption, photosynthesis and membrane permeability of sunflower under different types of salt-alkali stress (CK, NaCl, NaCl+Na₂SO₄, NaCl+NaHCO₃).

Result  Three types of saline-alkali stress decreased the mycorrhizal infection rate of sunflower inoculated with F. mosseae by 29.53% to 47.31%. Three types of saline-alkali stress all inhibited the growth of sunflower to a certain extent, and the order of the inhibition effect was NaCl+Na₂SO₄＞NaCl+NaHCO₃＞NaCl. Inoculation with AM fungi increased the total dry weight of sunflower under salt-alkali stresses of NaCl, NaCl+Na₂SO₄ and NaCl+NaHCO₃ by 19.58%, 42.15% and 60.35% respectively. Inoculation of AM fungi increased the shoot P contents of CK, NaCl and NaCl+NaHCO₃ treatments by 82.50%, 71.11% and 74.47% respectively, and increased the root P contents of CK and NaCl+NaHCO₃ treatments by 61.54% and 88.37% respectively. Inoculation of AM fungi significantly decreased the C∶P and N∶P in shoots and roots of CK and NaCl+NaHCO₃ treatments and the C∶P and N∶P in shoots of NaCl treatment. The shoot and root Na⁺ accumulations of NaCl+NaHCO₃ treatment increased by 33.76% and 82.25% with AM fungi inoculation respectively, and the root Na⁺ accumulation of NaCl+Na₂SO₄ treatment increased by 74.20%. Inoculation of AM fungi increased transpiration rates (Tr) of NaCl and NaCl+NaHCO₃ treatments by 11.67% and 10.12% respectively, and increased stomatal conductance (Gs) of NaCl+NaHCO₃ treatment by 20.00%. The net photosynthetic rate (Pn) in shoots under three types of salt-alkali stress showed an increasing trend. The membrane permeability of NaCl+NaHCO₃ significantly decreased by 51.49% with AM fungi inoculation.

Conclusion  AM fungi can alleviate the toxic effect of saline-alkali stress on sunflower growth to a certain extent, but its inoculation effect is significantly different among different types of saline-alkali stress.