Ziziphora clinopodioides is a perennial plant native to Iran that has gained significant attention due to its uses in food and medicine. Given the complexity of yield trait heritability, understanding how this plant manages water deficit through its morpho-physiological traits is essential.
A split-plot design based on randomized complete block design was employed with three replications in this research. The irrigation treatments included full irrigation (the control), transient drought stress (irrigation cut-off at the flowering stage), and prolonged drought stress (irrigation cut-off at the vegetative growth stage). Different ecotypes from various regions were cultivated and evaluated for morphological traits, pigment content, enzymatic antioxidant activities, soluble carbohydrates, and proline accumulation across two harvests.
The results indicated that drought stress had a significant impact on both morphological and physiological traits. Under transient drought stress, the effects on plant morphological traits were less compared to prolonged drought stress; however, there was a considerable reduction in pigments and soluble protein levels, along with an increase in both enzymatic and non-enzymatic antioxidant activities. In contrast, during prolonged drought stress, pigment and soluble protein levels increased, but the activities of enzymatic and non-enzymatic antioxidant declined. Notable morphological and physiological differences between the ecotypes in response to drought stress were observed in both harvests.
Overall, this study demonstrated that Z. clinopodioides adopts a tolerance strategy under transient drought stress, whereas under prolonged drought stress, it both maintains tolerance and utilizes avoidance and escape strategies. These findings can be applied in breeding and domestication programs for this plant.