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.
Highlights
Soil salinization is a serious threat to crop productivity and predicted to increase in the face of global climate change (FAO, 2011)1
This suggests that severe salinity reduced growth progressively from roots along the vertical gradient of the maize plant, with the root found to be most sensitive (−40%), followed by L1,2 (−20%)
The Pro content slightly decreased in L1,2 leaves, but did not show significant changes in maize root and L3,4 leaves (Figure 4E) under exposure to salinity stress
Summary
Soil salinization is a serious threat to crop productivity and predicted to increase in the face of global climate change (FAO, 2011). Salinity stress induces a multitude of responses in plants including morphological, physiological, biochemical, and molecular changes (Ambede et al, 2012; Abreu et al, 2013). It causes ionic imbalance, which results in ionic toxicity, osmotic stress, and generation of reactive oxygen species (ROS; Chaparzadeh et al, 2004; Chawla et al, 2013). High concentrations of NaCl outside the roots reduce the water potential, making it more difficult for plants to extract water, and results in osmotic stress. To cope with osmotic stress, salt-stressed plants tend to accumulate compatible solutes such as proline (Pro) and glycine betaine (Holmström et al, 2000; Qureshi et al, 2013), that decrease the cytoplasmic osmotic potential, enabling water absorption (Pottosin et al, 2014; Puniran-Hartley et al, 2014)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
