ABSTRACT
Enhancing salt tolerance in maize using co-application of exogenously applied lipoic acid or silicon with soil-based vermicompost tea by reinforcing antioxidant defense mechanisms and regulating plant performance

Khadiga Alharbi1*, El-Sayed M. Desoky2, Mostafa M. Rady3, Eman Selem4, and Ahmed Elrys5, 6
 
Maize (Zea mays L.) is highly sensitive to salt stress, which poses a threat to its production, especially with predicted increases in salinity due to climate change. Enhancing salt tolerance in maize is critical to mitigating these adverse effects, sustaining its production, and ensuring global food security. This study aimed to evaluate the effects of exogenously applied lipoic acid or Si, alone or in integration with soil application of vermicompost-tea on physio-biochemical components, antioxidant defense systems, growth, and yield of maize plants exposed to salt stress. The application of vermicompost-tea was carried out as a soil treatment incorporated into irrigation water at a concentration of 200 L ha-1, and administered in three equal doses in irrigation water within the last 10 min of drip irrigation. Silicon was applied at a rate of 6 mM using potassium silicate and lipoic acid was applied at 0.1 mM. Silicon and lipoic acid were applied three times at 25, 40, and 55 d after planting. The results indicated that the integrative application of soil-based vermicompost-tea with exogenously applied Si or lipoic acid significantly enhanced all studied parameters. Specifically, the combination of Si with vermicompost-tea exhibited the highest improvement percentage compared to untreated control in chlorophyll a (60.3%), chlorophyll b (72.7%), carotenoids (69.9%), net photosynthetic rate (111%), transpiration rate (134%), stomatal conductance (129.5%), relative water content (28.4%), membrane stability index (44.3%), N (33.4%), P (71.9%), K (39.7%), Ca (89.9%), K/Na (81.2%), total soluble sugars (63.7%), proline (60.1%), ascorbate (44.4%), glutathione (83.5%), and α-tocopherol (72.1%). These positive effects were reflected in enhancing yield traits under salt-affected soil conditions by enhancing plant height (25.1%), number of grains per row (43.3%), number of rows per ear (26.7%), 1000-grain weight (25.9%), grain yield (45.4%), and biological yield (42.8%) compared to untreated control.
Keywords: Agronomic performance, heatmap and hierarchical clustering, Mediterranean environment, physio-biochemical parameters, Zea mays.
1Princess Nourah bint Abdulrahman University, College of Science, Riyadh 11671, Saudi Arabia.
2Zagazig University, Faculty of Agriculture, Zagazig 44519, Egypt.
3Fayoum University, Faculty of Agriculture, Fayoum, 63514, Egypt.
4Zagazig University, Faculty of Science, Zagazig 44519, Egypt.
5Hainan University, School of Tropical Agriculture and Forestry, Haikou 570228, China.
6Justus Liebig University, Liebig Centre of Agroecology and Climate Impact Research, 35392 Giessen, Germany.
*Corresponding author (kralharbi@pnu.edu.sa).