High Salinity Induces Different Oxidative Stress and Antioxidant Responses in Maize Seedlings Organs

Abstract

Salinity negatively affects plant growth and causes significant crop yield losses world-wide. Maize is an economically important cereal crop affected by high salinity. In this study, maize seedlings were subjected to 75 mM and 150 mM NaCl, to emulate high soil salinity. Roots, mature leaves (basal leaf-pair 1,2) and young leaves (distal leaf-pair 3,4) were harvested after 3 weeks of sowing. Roots showed the highest reduction in biomass, followed by mature and young leaves in the salt-stressed plants. Concomitant with the pattern of growth reduction, roots accumulated the highest levels of Na+ followed by mature and young leaves. High salinity induced oxidative stress in the roots and mature leaves, but to a lesser extent in younger leaves. The younger leaves showed increased electrolyte leakage (EL), malondialdehyde (MDA), and hydrogen peroxide (H2O2) concentrations only at 150 mM NaCl. Total antioxidant capacity (TAC) and polyphenol content increased with the increase in salinity levels in roots and mature leaves, but showed no changes in the young leaves. Under salinity stress, reduced ascorbate (ASC) and glutathione (GSH) content increased in roots, while total tocopherol levels increased specifically in the shoot tissues. Similarly, redox changes estimated by the ratio of redox couples (ASC/total ascorbate and GSH/total glutathione) showed significant decreases in the roots. Activities of enzymatic antioxidants, catalase (CAT, EC 1.11.1.6) and dehydroascorbate reductase (DHAR, EC 1.8.5.1), increased in all organs of salt-treated plants, while superoxide dismutase (SOD, EC 1.15.1.1), ascorbate peroxidase (APX, EC 1.11.1.11), glutathione-s-transferase (GST, EC 2.5.1.18) and glutathione reductase (GR, EC 1.6.4.2) increased specifically in the roots. Overall, these results suggest that Na+ is retained and detoxified mainly in roots, and less stress impact is observed in mature and younger leaves. This study also indicates a possible role of ROS in the systemic signaling from roots to leaves, allowing leaves to activate their defense mechanisms for better protection against salt stress.

Evaluation of Alfalfa (Medicago sativa L.) Populations’ Response to Salinity Stress

“…In studies with other crops, researchers have also observed decreased shoot-root ratios with increasing salinity (Pearen et al, 1997;Bayuelo-Jiménez et al, 2003;Acosta-Motos et al, 2015). However, there are some reports of increased shoot-root ratios (Bernstein et al, 2004;AbdElgawad et al, 2016). The observation that salinity has less of an adverse effect on root growth compared with shoot growth is consistent with other observations related to stress, such as P deficiency (Fredeen et al, 1989), N deficiency (Sattelmacher et al, 1990), and drought stress (Sharp et al, 1988;Buwalda and Lenz, 1992).…”

“…However, shoot growth has been found to be more adversely affected by salinity than root growth (Munns and Termaat, 1986). However, there are some reports of increased shoot-root ratios (Bernstein et al, 2004;AbdElgawad et al, 2016). The root biomass per plant was reduced by 18 and 49%, respectively, while the shoot biomass was reduced by 50 and 73%, respectively.…”

Influence of exogenously applied nitric oxide on strawberry (Fragaria × ananassa) plants grown under iron deficiency and/or saline stress

“…Photosynthetic activity of most plants decreases under saline conditions because PSII activity is disturbed and thylakoid membrane along with its pigments is damaged due to formation of ROS under salinity stress (Dombrowski , Naeem et al , Shaheen et al , Wu et al , Deinlein et al , AbdElgawad et al , Askary et al , Gomes et al ). Like many other stresses, the deficiency of iron can also generate ROS and disturb the electron transport chain in the chloroplast because iron plays an important role in it (Graziano and Lamattina ).…”

Response of ROS-Scavenging Systems to Salinity Stress in Two Different Wheat (Triticum aestivum L.) Cultivars

“…Salinity same as water stress, leads to oxidative stress in plant cells due to increased production of reactive oxygen species (ROS) such as superoxide radicals (O2 .-), hydrogen peroxide (H2O2) and hydroxyl radical (HO . ) (Yadava et al, 2013;AbdElgawad et al, 2016;Asadi Karam and Keramat, 2017 ). ROS's are partially reduced forms of atmospheric oxygen, which are produced in vital processes such as photorespiration, photosynthesis and respiration.…”