Physiological and Molecular Responses to Salinity in Two Tobacco (<i>Nicotiana tabacum</i> L.) Varieties

ABSTRACT This study compared the salt tolerance of two tobacco varieties with different salt tolerances during the germination period—Basma (Oriental tobacco) and K326 (flue‐cured tobacco)—under NaCl stress. Basma exhibited higher antioxidant enzyme activity (1.16–3.58 times that of K326), reduced levels by 16.5% during the peak accumulation of reactive oxygen species (ROS) and effectively regulated ion homeostasis by upregulating NtSOS1 , reducing Na+ accumulation in aboveground tissues by 21.01–22.90 times and in underground tissues by 12.84–14.15 times compared to K326. Additionally, Basma increased the indole‐3‐acetic acid (IAA) content in underground tissues by 1.5 times after 72 h of saline stress, a change supported by increased expression of NtPIN4 . In summary, Basma demonstrated greater salt tolerance than K326 by increasing antioxidant enzyme activity, regulating ion homeostasis and maintaining IAA balance. These findings suggest that enhancing ROS scavenging, modifying root structure and applying IAA can effectively enhance salt tolerance in tobacco cultivation.