Growth and physiological response of Arundo donax L. to controlled drought stress and recovery

Soil water deficit constrains crop growth more than any other abiotic stress, both per se and in combination with other factors, making drought resistance a key element for the successful exploitation of marginal areas. Arundo donax (Poaceae), is a mesophyte that can adapt to a wide variety of ecological conditions, although its growth can be retarded by a shortage of water. The objective of the present research is to draw a comprehensive picture of the integrated response mechanisms of A. donax to controlled drought conditions, and characterize its ability to recover upon rewatering in terms of photochemical efficiency. Plants were subjected to a gradually applied drought stress for a period of three weeks, after which they were returned to fully hydrated soil conditions for one week. Overall, plant dry weight and key growth parameters were not significantly affected. However, detrimental effects were visible in the form of impaired leaf gas exchange, which influences the performance of photosynthesis, and pre-dawn leaf water potential (pdΨW), −92.1% of net CO2 assimilation rate and −0.36 MPa, respectively at the cessation of stress. Nonetheless, a rapid restoration of A. donax physiological functions was observed upon rewatering, testifying to the environmental plasticity of this species.