Effects of neutral salt mixture on growth, photosynthesis, and physiological characteristics of Gerbera jamesonii ‘Yunnan Red’

To investigate the physiological mechanism of salt tolerance in the cut flower Gerbera jamesonii ‘Yunnan Red’ seedlings, the present experiment was conducted to simulate saline soil with different concentrations (0, 50, 100, 150, 200 mmol·L⁻¹) of neutral mixed salt solution (NaCl and Na₂SO₄ molar ratio of 9 ꞉ 1) and investigate their effects on growth, photosynthesis, and physiological characteristics of Gerbera seedlings. The experiment showed that when the mixed neutral salt concentration was ≤100 mmol·L⁻¹, the low salt stress stimulated the leaves of Gerbera seedlings to scavenge accumulated reactive oxygen species by increasing the activities of protective enzymes, such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), to maintain the stability of plasma membrane. In addition, the amount of the net photosynthesis rate (P_n), stomatal conductance (G_s), and transpiration rate (T_r) increased, promoting the increase of fresh weight of aboveground and belowground parts of Gerbera. When the neutral mixed salt concentration was ≥150 mmol·L⁻¹, the high salt stress led to excessive accumulation of reactive oxygen species, significant increase in MDA content, intensified plasma membrane permeability, and a sharp decrease in P_n, T_r, and G_s of Gerbera leaves. This may be due to the addition of non-stomatal limiting factors, which seriously affected their growth. This study indicates that ‘Yunnan Red’ Gerbera seedlings are salt tolerant, and they can tolerate a neutral mixture of salt stress with a molar ratio of 50～100 mmol·L⁻¹ NaCl and Na₂SO₄ of 9 ꞉ 1.