Foliar Application of Chitosan and Cobalt Mitigates the Growth and Some Physiological Characteristics of Portulaca oleracea L. under Salinity Stress

Portulaca oleracea L. is an edible and medicinal herb in the Portulacaceae family. Purslane contains antimicrobial, antidiabetic, and anti-inflammatory properties. To investigate the effect of sodium chloride salinity stress (without salinity (0), 150, and 300 mM) and spraying of chitosan and cobalt nanoparticles (without spraying and 20 mg/L of nanoparticles) on Portulaca oleracea plant, a factorial experiment was conducted based on a completely randomized design. The results showed that the interaction effects of NaCl0 × foliar spraying with chitosan and cobalt nanoparticles enhanced chlorophyll a, calcium content, and K/Na ratio in plants. The top plant dry weight (6 g) was recorded in NaCl0 × chitosan spray. NaCl0 and 150 mM × foliar spraying with both nanoparticles increased zinc, magnesium, and iron content in the plant. 300 mM salinity stress in conditions without foliar spraying damaged the plant by enhancing malondialdehyde content. Foliar spray with both nanoparticles increased proline content at 150 and 300 mM salinity stress, and flavonoids content in all salinity levels to overcome the negative effects of salinity. With salinity rising, the elemental content was decreased in plants. Foliar spray with chitosan and cobalt increased nitrogen (41%), potassium (12.6%) and phosphorus (30%) content in plants compared to the control (without foliar spray). Overall, the results revealed that salinity stress harmed the growth and some physiological traits of plants. However, foliar sprayings helped improve plant yield and some physiological traits under stress conditions.