Strong effect of recovery period between hypoxia events on roots of chickpea (Cicer arietinum L)

Abstract

Hypoxia as an environmental stress affects the physiological, metabolic, and anatomical parameters in plants. This experiment was conducted in order to evaluate the changes of these parameters in chickpea roots in response to hypoxia followed by recovery. With this aim, two periods of hypoxia (two and four days) and recovery subsequent (one and three days) were applied on chickpea roots in a hydroponic condition. Hypoxic condition significantly decreased the root dry weight of plants. However, the contents of anthocyanins, flavonoids, malondialdehyde (MDA), hydrogen peroxide (H2O2), as well as the activities of antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX)) were increased by hypoxia. In addition, anatomical changes were observed in the chickpea roots under the hypoxia and recovery treatments. Under the hypoxic condition, root's aerenchyma began to form and the thickness of the Casparian strip was decreased. Interestingly, the one-day recovery following two or four days of hypoxia could not reduce the hypoxia effects on the chickpea roots. In contrast, the three-day recovery period partly reduced the adverse effect of hypoxia. The pattern of physiological, metabolic, and anatomical changes during the recovery period following the four-day hypoxia was similar to the recovery period following the two-day hypoxia. These findings display a negative effect of hypoxia and one-day recovery following hypoxia on different parameters of chickpea roots. Nevertheless, prolonging the period of recovery (three-day recovery) has a positive effect on the chickpea roots after exposure to hypoxia.