Modulation of sodium compartmentalization under excess sodium stress and morpho-physiological responses of cotton (Gossypium hirsutum L.) genotypes for their salt tolerance ability
摘要
Forty-day-old healthy seedlings of five cotton genotypes (Takfa 3, Takfa 6, Takfa 7, Takfa 84–4, and Takfa 86–5) were treated with 0 or 150 mmol L−1 NaCl for 14 days, and data on mRNA expression and morpho-physio-biochemical parameters were collected. At early salt treatment (48 h), upregulation of GhNHX1, GhVATPase, and GhVPPase in the vacuolar membrane of root tissues of Takfa 6 (> 3.6-fold over the control) was recorded in relation to the high amount of Na in the root. Takfa 6 exhibited a low Na concentration (72.5 mg g−1) and Na/K ratio (0.42) in its leaf tissues when subjected to salt stress, which played a crucial role in maintaining its photosynthetic capabilities and promoting overall growth. Takfa 3, on the other hand, exhibited a contrasting response to salt stress, where Na concentration in its root tissues was remarkably low (55.5 mg g−1), but its translocation level to the leaf tissues was relatively higher (142.3 mg g−1). This high translocation rate of Na from root to shoot exerted detrimental effects on the plant, resulting in the inhibition of net photosynthetic rate (26.53%), lower accumulation of sucrose (31.80%), and growth retardation. Based on the cluster analysis, Takfa 6 and Takfa 7 were identified as salt tolerant, whereas Takfa 3, Takfa 84–4, and Takfa 85–6 were classified as salt susceptible. In summary, Takfa 6 can be regarded as an elite genotype with high efficiency of Na compartmentalization, which could serve as a good candidate variety for cultivation in the mild salt-affected soil.