Physiological limits and adaptive responses of the Wetland species Acorus calamus (L.) to gradient drought stress: Insights from photosystem II dynamics and oxidative damage

Abstract

Wetland plants Acorus calamus (L.) face increasing drought pressure due to declining global rainfall. As a key wetland species contributing to ecosystem services such as water filtration, shoreline stabilization, and wildlife habitat provision, understanding its drought responses is essential for predicting wetland vulnerability and informing conservation strategies. This study investigated the physiological, morphological, and biochemical responses of A. calamus to varying levels of drought stress. Multiple drought-responsive parameters were assessed, revealing significant changes in photosynthetic pigments, morphological traits, and stress indicators, including malondialdehyde and proline. With increasing drought severity, leaf gas-exchange parameters such as net photosynthesis, transpiration rate, stomatal conductance, water use efficiency, and intrinsic water use efficiency declined significantly (p < 0.001). Functional traits, including leaf area, leaf area index, leaf area ratio, and specific leaf weight ratio, also showed significant reductions (p < 0.001). In contrast, root length, total phenolic content, soluble sugars, starch, proline, and malondialdehyde increased progressively with drought stress. These findings revealed that A. calamus undergoes pronounced physiological and biochemical limitations under drought conditions, highlighting the sensitivity of wetland plants to water shortage and underscoring the vulnerability of wetland ecosystems under ongoing climatic change.