Physiological and biochemical responses of Phragmites australis to wastewater for different time duration

Phragmites australis exhibits substantial tolerance for salt and heavy metals exposure in the environment. The purpose of this study was to evaluate some biochemical parameters of Phragmites australis irrigated with wastewater (containing nickel, zinc, copper, iron, cadmium, and lead) up to the vegetative (short term), flowering (average term), or reproductive (long term) stage. The plant samples were collected twice i.e., two days and four days after irrigation at each growth stage. The plants were irrigated with freshwater for control. The average-term application of wastewater causes to higher biomass than the control plants. Some physicochemical parameters (proline, electrical conductivity, total soluble protein, and potassium) were more strongly correlated with plant biomass. The chlorophyll a, chlorophyll b, total chlorophyll, and total soluble proteins were reduced at the reproductive stage. While, the proline, soluble sugars, and activities of antioxidant enzymes were increased. Long-term wastewater exposure led to a significant increase in sodium, potassium, and Na+/Ca2+ ratio of P. australis while magnesium contents were decreased by wastewater irrigation. The present findings suggest that P. australis possess several enzymatic and non-enzymatic defense processes that curtail oxidative stress caused by heavy metals toxicity from wastewater and protect photosynthetic pigments from damage in the flowering stage.