Effect of Varying Light Intensity on Physiological and Yield Characteristics of Wheat

Background: Light intensity is a fundamental environmental determinant of plant growth, influencing physiological processes such as photosynthesis, transpiration and assimilate partitioning. In northern India, elevated air pollution levels significantly reduce photosynthetically active radiation (PAR), adversely affecting wheat productivity. This study investigates the impact of varying light intensities, simulated through 50% and 75% shading, on physiological and yield attributes of two widely cultivated wheat genotypes, HD-2967 and HD-3086. Given the increasing threat of atmospheric dimming due to pollution, understanding crop responses to reduced light is vital for ensuring sustainable agricultural output in vulnerable regions. Methods: A field experiment was conducted over two consecutive rabi seasons (2022-23 and 2023-24) at the research farms of ICAR-IARI, New Delhi. Treatments included full sunlight (control), 50% and 75% shading applied for six weeks after six weeks of normal growth. Physiological parameters-plant biomass, root-shoot ratio, chlorophyll content, photosynthetic rate, stomatal conductance and transpiration rate-were monitored at 0, 7 and 14 days after shade removal. Yield attributes such as ear-bearing tillers, 1000-grain weight and final grain yield were recorded at harvest. Result: Results revealed that shading significantly reduced biomass accumulation, Pn, Gs, E and grain yield, while increasing chlorophyll content and root-shoot ratio. HD-2967 showed higher baseline productivity under optimal light but experienced greater yield reduction under stress. HD-3086 demonstrated comparatively greater resilience, particularly under 50% shade. These findings emphasize the need for breeding light-efficient wheat cultivars to enhance crop stability under pollution-induced light limitation.