Physiological and Biochemical Responses of Chrysanthemum × morifolium to Salinity Stress under In-Vitro Conditions

Salinity is a critical abiotic stress that significantly limits plant growth and productivity by disrupting physiological and biochemical processes. This study investigated the effects of NaCl-induced salinity on the in vitro culture of Chrysanthemum × morifolium Ramat. Explants were cultured under varying concentrations of NaCl (0–300 mmol/L) to assess its impact on callus formation, shoot regeneration, physiological attributes, and biochemical responses. Results showed that increasing NaCl concentrations reduced callus formation percentages, shoot regeneration frequency, and shoot length, with the highest reduction observed at 300 mmol/L NaCl. The number of shoots per explant decreased from 13.03 under non-saline conditions to 0.90 at 300 mmol/L. Chlorophyll content, carotenoids, and protein levels declined significantly with increasing salinity, whereas the proline content increased, indicating its role in osmotic adjustment and stress tolerance. Antioxidant enzyme activities, including catalase and superoxide dismutase, were enhanced under salt stress, with maximum activity recorded at 300 mmol/L NaCl, suggesting their involvement in mitigating oxidative damage. Lipid peroxidation and protein oxidative damage also increased, further indicating the detrimental effects of salinity. During the hardening phase, optimal survival was achieved using a potting mixture of coco peat, sand, vermicompost, and garden soil (2:1:1:1 ratio). Plants grown under in vivo saline conditions exhibited reduced biomass, root growth, and shoot development, with severe effects at 400 mmol/L NaCl. These findings provide insights into the physiological and biochemical responses of C. morifolium under salt stress, contributing to the development of salt-tolerant varieties and improving in vitro propagation techniques.