Physiological differences in response to soil salinity stress and salt spary stress of Catharanthus roseus

One-year-old cutting seedlings of Catharanthus roseus were used to compare the effects of soil salinity stress and salt spray stress at three salt concentrations (0, 8, and 16 g/L). Changes in growth and key physiological indicators were examined, and correlation analysis were performed to elucidate the relationships among these traits. The study aimed to identify how Catharanthus roseus responds to different types of salt stress and to reveal differences in salt tolerance.The results showed that salt spray stress had a much stronger inhibitory effect on plant growth than soil salinity stress. Under both stress treatments, plant biomass decreased as salt concentration increased. Under soil salinity stress, chlorophyll content first rose and then declined, whereas under salt spray stress, chlorophyll content decreased continuously and was more sensitive to increasing salt levels. Compared with salt spray stress, soil salinity stress led to significantly higher levels of MDA, osmotic adjustment substances (Pro, soluble sugars, soluble proteins), and SOD activity (P < 0.05). However, POD activity showed different patterns between the two stress types. Under soil salinity stress, chlorophyll content was negatively correlated with POD activity (P < 0.05), and MDA content was strongly positively correlated with soluble protein content (P < 0.01). Under salt spray stress, MDA content was positively correlated with POD activity (P < 0.05), while Pro content was strongly positively correlated with soluble protein content, SOD activity, and POD activity (P < 0.01).In summary, the sensitivity of Catharanthus roseus to salt spray stress was generallt higher than that to soil salinity stress. Differences exist in the response mechanisms of the osmotic regulation system and antioxidant enzyme system between the two. However, the specific mechanisms underlying the salt tolerance differences require further investigation. This study provides a theoretical basis for the cultivation management and salt-tolerant variety selection of Catharanthus roseus in coastal areas.