1. Direct oxidation of photo respiratory peroxides in plants is carried out by-
(1) Superoxide Dismutase
(2) Glutathione Synthase
(3) Catalase
(4) Glutathione reductase

Introduction

Plants produce reactive oxygen species (ROS) such as hydrogen peroxide during photorespiration, which are potentially harmful. To protect cells, plants employ antioxidant enzymes to detoxify these peroxides. Catalase is the key enzyme responsible for the direct oxidation and breakdown of hydrogen peroxide formed during photorespiration.

Explanation of Each Option

(1) Superoxide Dismutase (SOD)

• This enzyme converts superoxide radicals (O2- −) into hydrogen peroxide (H2O2) and oxygen, acting upstream in the ROS detoxification pathway, but does not directly oxidize photorespiratory peroxides.

(2) Glutathione Synthase

• Glutathione synthase is involved in the synthesis of glutathione, a key antioxidant molecule, rather than direct oxidation of peroxides.

(3) Catalase

• Correct. Catalase directly converts hydrogen peroxide into water and oxygen, efficiently removing peroxides produced during photorespiration and other metabolic processes.

(4) Glutathione Reductase

• This enzyme regenerates reduced glutathione from its oxidized form but does not directly oxidize peroxides.

Why Catalase is the Correct Enzyme

Catalase directly neutralizes hydrogen peroxide, a main photorespiratory peroxide, thereby preventing oxidative damage to cellular components. It works predominantly in peroxisomes and is crucial in maintaining cellular redox balance under photorespiratory stress.

Understanding this detoxification pathway is vital for studies on plant stress physiology, ROS management, and overall plant health.