Study on physiological characteristics of Passiflora edulis Sims with different ploidy under drought stress.

Passiflora edulis Sims, an economically important fruit crop known as the “king of juices,” is severely affected by drought, which significantly constrains its growth and yield. To investigate whether polyploidy enhances drought resistance, we compared the physiological responses of diploid and triploid tissue-cultured seedlings of the P. edulis ‘Mantianxing’ cultivar subjected to Polyethylene Glycol 6000 (PEG-6000) for 7 days. Physiological parameters were analyzed in mixed samples of mid-shoot segments (mixed stem and leaf segments or leaves) from three biological replicates, with the data subjected to one-way ANOVA and Duncan’s test (p < 0.05). The experimental results confirmed that: (1) The optimal rooting medium for sterile seedlings of diploid and triploid is 0.1 mg/l NAA + 0.2 g AC + 1/2 MS. (2) Under drought stress, particularly at 40% and 50% PEG-6000 concentrations, triploids exhibited significantly higher activities of peroxidase (POD) and catalase (CAT), higher proline (Pro) and soluble sugar contents, and lower malondialdehyde (MDA) content than diploids. Superoxide dismutase (SOD) activity did not differ significantly by ploidy. Under severe drought (50% PEG-6000), triploids maintained higher soluble sugar but lower soluble protein content. These results demonstrate that triploid ‘Mantianxing’ possesses superior drought adaptability, mediated by enhanced osmotic adjustment and a more robust antioxidant system, providing a physiological basis for polyploid breeding in P. edulis.