Changes in physiological and antioxidant activity of indica rice seedlings in response to mannitol-induced osmotic stress

Abstract

Morphological, physiological, and biochemical plant responses were studied in unstressed and stressed seedlings of indica rice (Oryza sativa L.) genotypes. The effect of NB medium supplemented with a 100 mM mannitol treatment, which induced drought stress conditions, was measured for relative growth rate, cell membrane stability, antioxidant enzyme activity (superoxide dismutase [SOD], catalase [CAT], and peroxidase [POD]), and total antioxidant capacity by DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2′-azinobis[3-ethylbenzothiazoline-6-sulfonic acid] diammonium salt) assays. Results of morphological and physiological factors showed two contrasting rice groups, drought-sensitive and drought-tolerant genotypes. After drought stress, the increased rate of SOD activity was lower in drought-tolerant than in drought-sensitive genotypes, but the increased rate of CAT and POD activity and total antioxidant capacity was higher in drought-tolerant than in drought-sensitive genotypes. Increasing changes in activity levels of antioxidant enzymes and total antioxidant capacity indicated more rapid free radical scavenging compared with relative growth and cell membrane stability in drought-tolerant genotypes under shortterm treatment. The trend toward change in CAT and POD antioxidant enzyme activity and total antioxidant capacity of stressed seedlings, as well as the correlation between these changes, and the morphological and physiological responses (0.96 correlation coefficient [R 2 ] between relative growth rate and CAT; 0.93 R 2 between relative growth rate and POD enzyme activity; 0.96 R 2 between relative growth rate and Trolox equivalent antioxidant capacity values) coincided with the degree of drought tolerance.

Influence of drought hardening on the resistance physiology of potato seedlings under drought stress

“…When plants are grown under adverse stress, free radicals or reactive oxygen species (ROS), such as H 2 O 2 , O 2 -• and HO• may accumulate. Under drought stress, plants have a limited capacity for C fixation, stomatal closure restricts the assimilation of CO 2 and leads to surplus electron flux to O 2 and overproduction of ROS (Chutipaijit 2016). When a certain threshold value is reached, ROS are toxic and capable of causing lipid peroxidation, oxidative damage to the DNA and cellular proteins and the leakage of intracellular electrolytes, ultimately damaging the structure and function of the cell membrane (Henricks and Nijkamp 2001;Siedlinski et al 2009;Gill and Tuteja 2010).…”

Role of Reactive Oxygen Species and Contribution of New Players in Defense Mechanism under Drought Stress in Rice

“…Production of radical ions under drought stress not only induces lipid peroxidation but also causes injury to membrane. Decrease in cell membrane stability in susceptible genotypes under drought is reported in contrast to tolerant genotypes (Chutipaijit, 2016).…”

“…00,No. 0,201x Furthermore, it was revealed that the small increase in POD and CAT activity in drought-susceptible genotypes could decrease efficiency of rice plant cell to scavenge ROS (Chutipaijit, 2016). Drought tolerance in rice can be achieved by scavenging ROS using dehydrin proteins.…”

“…The enzymes SOD, CAT and POD are vital antioxidant enzymes in rice cell (Chutipaijit, 2016). Among enzymatic antioxidants, ROS scavenging mechanism consists of two steps.…”

“…Oryza sativa (Rice) serves as a staple food in different countries of the world (Bishwajit et al, 2013;Chutipaijit, 2016) and ranks second among cultivated cereals (Madabula et al, 2016). Asia is on the top in terms of production and consumption of rice.…”