Differences in Physiological Responses of Two Oat (Avena nuda L.) Lines to Sodic-Alkalinity in the Vegetative Stage

Abstract

Sodic-alkalinity is a more seriously limiting factor in agricultural productivity than salinity. Oat (Avena nuda) is a salt-tolerant crop species and is therefore useful in studying the physiological responses of cereals to alkalinity. We evaluated the differential effects of sodic-alkalinity on two naked oat lines, Caoyou1 and Yanke1. Seedlings of the two lines were exposed to 50 mM alkaline salt mixture of NaHCO3 and Na2CO3 (18:1 molar ratio; pH 8.5) for 2 weeks in a soil environment. Sodic-alkalinity exposure led the assimilation of abundant Na+ at similar concentrations in the organs of both lines. However, Caoyou1 showed much stronger growth than Yanke1, exhibiting a higher dry weight, total leaf area, and shoot height under sodic-alkalinity. Further analysis showed that Caoyou1 was more sodic-alkalinity tolerance than Yanke1. This was firstly because of differences in the oxidative stress defense mechanisms in leaves of the two lines. Antioxidant enzyme activities were either slightly elevated (catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GP), glutathione reductase (GR)) or unaltered (superoxide dismutase (SOD)) in Caoyou1 leaves, but some enzyme (SOD, GPOX, GR) activities were significantly reduced in Yanke1. AnAPX1 transcript levels significantly increased in Caoyou1 under sodic-alkalinity conditions compared with Yanke1, indicating its better antioxidant capacity. Secondly, the related parameters of Mg2+ concentration, phosphoenolpyruvate carboxylase (PEPC) activity, and AnPEPC transcript levels in the leaves showed significantly higher values in Caoyou1 compared with Yanke1. This demonstrated the effective utilization by Caoyou1 of accumulated HCO3− in the irreversible reaction from phosphoenolpyruvate to oxaloacetate to produce inorganic phosphorus, which was elevated in Caoyou1 leaves under alkalinity stress. Overall, the results demonstrated that the greater sodic-alkalinity tolerance of Caoyou1 is the result of: (1) maintained antioxidant enzyme activities; and (2) a higher capacity for the phosphoenolpyruvate to oxaloacetate reactions, as shown by the higher PEPC activity, Mg2+ concentration, and total phosphorus concentration in its leaves, despite the lower soil pH.

Metabolic and Physiological Changes in the Roots of Two Oat Cultivars in Response to Complex Saline-Alkali Stress

“…Under saline-alkali stress, the rapid and excessive accumulation of ROS, including H 2 O 2 and O 2 – can cause damage to cell membranes through lipid peroxidation and can even cause cell death ( Gill and Tuteja, 2010 ; Liu et al, 2020 ). Among the antioxidant enzymes, CAT is sensitive to saline-alkali reaction, and, APX and POD play important roles in H 2 O 2 clearance ( Liu et al, 2016 ).…”

“…To cope with oxidative stress, the plant has two enzymatic and non-enzymatic active oxygen scavenging systems to avoid injury, which metabolizes reactive oxygen species (ROS) and their reaction products to avert oxidative stress conditions ( Gill and Tuteja, 2010 ). Antioxidant enzymes mainly include superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GP), ascorbate peroxidase (APX), and glutathione reductase (GR) ( Liu et al, 2020 ). Non-enzymatic antioxidants such as ascorbic acid, cysteine, carotenoids, alkaloids, α-tocopherol, flavonoids, and reduced glutathione can effectively help resist the damage caused by stress ( Luo et al, 2009 ).…”

Effect of NaCl on physiological, biochemical, and ionic parameters of naked oat (Avena nuda L.) line Bayou1

“…Due to an imbalance in ionic homeostasis in its leaves, the growth of a 34 days-old Mengnongda1 seedling is inhibited when exposed to 100 mM NaCl (Liu et al, 2020a). The application of 50 mM sodic-alkalinity caused a reduction in the activities of antioxidant enzymes in a 20 days-old Yanke1 seedling, which affected its growth (Liu et al, 2020b). The study of salinity-tolerant naked oat lines and their mechanisms can be beneficial for crop breeding in salt-affected areas due to increasing agricultural difficulties.…”

Effect of Chemical Reclamation on the Physiological and Chemical Response of Rice Grown in Varying Salinity and Sodicity Conditions

“…The deleterious effects of soil salinity/ sodicity are dependent upon the type and period of salt-affected soil. Moreover, plant species and their genetic makeup also play a remarkable role (Ata- Ul-Karim et al 2016;Liu et al 2020;Riaz et al 2020).…”

“…Plant growth mechanisms such as photosynthesis, stomatal conductance, nutrient balance and metabolic functions are all affected by salinity and sodicity (Nam et al 2018;Zahra et al 2018). The high concentration of NaHCO 3 / Na 2 CO 3 under sodic conditions results in increased pH (> 8.5) that negatively influences nutrient uptake in plants (Liu et al 2020). The imbalance of nutrients (excess of Na + ) in plants deteriorates the normal growth process and ultimately leads to abnormal cell functioning and plant death (Quintero et al 2007).…”