Physiological Mechanisms of Grain Yield Loss Under Combined Drought and Shading Stress at the Post-silking Stage in Maize

Decreased light conditions due to cloud cover and smog pollution severely limit crop cultivation and production. Reduced light interception coupled with irregular rainfall caused damage to major crops' yield at their critical growth stages, especially at the post-silking stage in maize (Zea mays L.). This study was conducted in underground soil columns containing a moveable shed (to apply shade and avoid rainfall) to investigate the combined effect of drought and shading stress at the post-silking stage of maize. Plants were exposed to five shading treatments (a control without shading (SD0), shading for 3 (SD3), 6 (SD6), 9 (SD9), and 12 days (SD12)) and four drought levels (100, 75, 50, and 25% of irrigation) after silking in maize. A split-plot design was used. The combined stresses caused oxidative damage to maize leaves, which caused a significant reduction in the photosynthetic efficacy, grain yield, and grain quality. The combination of SD12 and 25% irrigation caused a 24% reduction in photosynthetic activity and grain yield compared with the respective control. Under interactive drought and shading conditions, SD12 combined with 25, 50, and 75% irrigation caused an upsurge in grain protein by 3.94, 8.06, and 6.70%, respectively. The combined drought and shading stress during the post-silking stage in maize caused a significant reduction in rain yield by altering antioxidant potential and photosynthetic efficiency. An increase in antioxidant defense was observed under combined stresses; however, this increase was insufficient to combat the oxidative damage caused by stress.