title: Calcium Supplementation Improves Na(+)/K(+) Ratio, Antioxidant Defense and Glyoxalase Systems in Salt-Stressed Rice Seedlings.
abstract: The present study investigates the regulatory role of exogenous calcium (Ca) in developing salt stress tolerance in rice seedlings. Hydroponically grown 13-day-old rice (Oryza sativa L. cv. BRRI dhan47) seedlings were exposed to 200 mM NaCl alone and combined with 2 mM CaCl2 and 2 mM ethylene glycol tetraacetic acid (EGTA, a Ca scavenger) for 3 days. The salt stress caused growth inhibition, chlorosis and water shortage in the rice seedlings. The salt-induced stress disrupted ion homeostasis through Na(+) influx and K(+) efflux, and decreased other mineral nutrient uptake. Salt stress caused oxidative stress in seedlings through lipid peroxidation, loss of plasma membrane integrity, higher reactive oxygen species (ROS) production and methylglyoxal (MG) formation. The salt-stressed seedlings supplemented with exogenous Ca recovered from water loss, chlorosis and growth inhibition. Calcium supplementation in the salt-stressed rice seedlings improved ion homeostasis by inhibition of Na(+) influx and K(+) leakage. Exogenous Ca also improved ROS and MG detoxification by improving the antioxidant defense and glyoxalase systems, respectively. On the other hand, applying EGTA along with salt and Ca again negatively affected the seedlings as EGTA negated Ca activity. It confirms that, the positive responses in salt-stressed rice seedlings to exogenous Ca were for Ca mediated improvement of ion homeostasis, antioxidant defense and glyoxalase system.
authors.affiliation: Laboratory of Plant Stress Responses, Department of Applied Biological Science, Faculty of Agriculture, Kagawa UniversityKagawa, Japan; Department of Agronomy, Faculty of Agriculture, Sher-e-Bangla Agricultural UniversityDhaka, Bangladesh.
authors.forename: Anisur
authors.initials: A
authors.lastname: Rahman
authors.affiliation: Laboratory of Plant Stress Responses, Department of Applied Biological Science, Faculty of Agriculture, Kagawa UniversityKagawa, Japan; Department of Agricultural Botany, Faculty of Agriculture, Sher-e-Bangla Agricultural UniversityDhaka, Bangladesh.
authors.forename: Kamrun
authors.initials: K
authors.lastname: Nahar
authors.affiliation: Department of Agronomy, Faculty of Agriculture, Sher-e-Bangla Agricultural University Dhaka, Bangladesh.
authors.forename: Mirza
authors.initials: M
authors.lastname: Hasanuzzaman
authors.affiliation: Laboratory of Plant Stress Responses, Department of Applied Biological Science, Faculty of Agriculture, Kagawa University Kagawa, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Fujita
keywords: calcium; methylglyoxal; nutrient homeostasis; osmotic stress; oxidative stress; salinity