The growth responses and antioxidant capabilities of melinjo (Gnetum gnemon L.) in different durations of drought stress

Melinjo (Gnetum gnemon L.) is a beneficial agroforestry plant that contains antioxidant compounds broadly studied as a natural source in pharmaceutical and nutraceutical uses. The antioxidant compounds benefit human health and plant to develop defense mechanisms under environmental stresses, such as drought stress. This study aims to evaluate the defense mechanism of melinjo under drought stress. Polyethylene glycol (PEG) was used to simulate drought stress to melinjo seedlings for 5, 10, 20, and 40 days compared to zero-day control without PEG. The inhibition and detoxification activities of 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl, superoxide radical, and superoxide dismutase (SOD) were determined to evaluate antioxidant capabilities during drought stress. Lipid peroxidation and hydrogen peroxide (H₂O₂) contents were also analyzed to evaluate the level of cellular damage during drought stress. The seedling's growth was significantly reduced as a response to the longer duration of drought stress treatment. On the contrary, the level of lipid peroxidation and H₂O₂ were increased, followed by the escalation of antioxidant activities. This result indicates that many antioxidant compounds act together to develop a defense mechanism in melinjo seedlings, and the different duration of drought stresses influences their capabilities.