Introduction: Ginger (Zingiber officinale Roscoe) is a medicinal crop indigenous to China. As for conservation, propagation, and enhanced crop growth rate under a protected environment, understanding the mechanisms of abiotic stress tolerance plays an integral role in enhancing medicinal properties in the herb's subsequent growth stages.

Methods: The effects of three different light durations (15, 30, and 45 days) represented by 50% shade levels in 3 times harvesting (every 15, 30 and 45 days shading in each harvesting time durations combined with three water levels in greenhouse condition on plant growth parameters, including the level of peroxidase activity and proline content in the root and shoot of 2 month-old seedling plants, were investigated. The two-factor experiment was laid out in a split-plot design based on RCBD with three replications. The proline concentration was measured spectrophotometrically employing the method of Bates et al. (1973). Peroxidase (POX) activity was measured according to the method of Herzog and Fahimi (1973).

Results: Both peroxidase activity and proline content were increased in the inappropriate light duration condition. Peroxidase (POX) in roots increased sharply, reaching 68.3% and 50% in 15 and full-time shading days, respectively, at each harvest after months of treatment, compared to the 30-day shaded condition. Meanwhile, lower proline levels were recorded after 30 days of shading in each harvest; while the height ratio in root and shoot (58% and 40%, respectively) was higher after 15 days of shading compared to 30 days of shading.

Conclusion: In the case of POX and proline, there were increasing trends in terms of shortened shading duration compared with the other two shade durations. Peroxidase plays an essential role in plant growth and development. Proline content of under- and above-ground plant organs augmented upon exposure to the shortest and longest shade durations.