European Journal of Sustainable Agroecosystems

Background and Objective: Increasing levels of COâ‚‚ in the atmosphere are forecasted to reach 550 parts per million (ppm) by the middle of the century, presenting both problems and possibilities for global agriculture. Despite being an important agricultural commodity, the reaction of Helianthus annuus L. (Sunflower) to higher concentrations of COâ‚‚ in the atmosphere is not fully understood. This research analyzed how the increased concentration of COâ‚‚ in the atmosphere has affected the growth, production of biomass, productivity, and adaptive methods in the plants in an environment with controlled conditions.
Methods: Sunflower plant entities characterized by cultivar HA-88 (an important Indian cultivar species) were grown under controlled environmental conditions, having ambient (400 ppm) and increased (600 ppm) concentrations of COâ‚‚. Measurements taken included the rates of photosynthesis (A), permeability of stomata (gs), water consumption efficiency (WUE), chlorophyll content in leaves, relative water capacity, biomass accumulation in roots and upper green part of the plant, as well as patterns of biomass allocation. Statistical analysis data was performed using a two-way ANOVA and correlation analysis.
Results: According to the research study, increase in COâ‚‚ concentration caused an increase in the photosynthesis rate by 28.4% (p < 0.01) and a decrease in the stomatal conductance by 19.3% (p < 0.05). The instantaneous water-use efficiency increased by 42.1%, which shows an increase in carbon uptake with a decrease in transpiration. The overall above-ground biomass increased by 35.6% when the COâ‚‚ level was raised (p < 0.001). Hence, more biomass was directed to the formation of shoots than to roots. Chlorophyll concentration increased significantly, while the relative water content of leaves remained stable, which indicates physiological acclimatization of the plants, despite the reduced stomatal conductance. Thus, the plants did not exhibit a down-regulation of photosynthesis during the 120 days period of the experiment.
Scientific Significance: The results indicate that Helianthus annuus has beneficial physiological responses to increased CO₂ levels in the atmosphere, especially in terms of increased carbon assimilation in photosynthesis and water-use efficiency, which is of great importance for crop yields under future climate conditions. The constant performance of the plant in terms of photosynthesis differs from some observations noted for certain C₃ species and indicates a possible potential for adaptation of specific cultivars.
Conclusion: Increased atmospheric carbon dioxide raises water-use efficiency and biomass production in sunflowers by coordinating physiological responses including raised photosynthesis rates, lowered stomatal conductance and maintained resistance to photosynthetic down-regulation. Results of the study support the principles of climate-smart sunflower production techniques and suggest ways to enhance crops resilience in climate-impacting agricultural systems.