Physiological and Growth Responses of Helianthus annuus to Heat and Water Stress: Can Nature-based Solutions Help?
This study investigates how abiotic stresses—specifically heat and water stress—affect dwarf sunflower (Helianthus annuus) physiology, growth, and productivity. Key physiological parameters assessed include photosynthetic activity, stomatal conductance, and chlorophyll fluorescence. The study also evaluates whether two Nature-based Solutions (NbS), pollination services and enhanced soil fertility via clover intercropping, can mitigate the effects of these stresses. The experiment was conducted in a controlled greenhouse using 64 plants distributed across eight plots. Temperature stress was applied using heating sleeves (up to 40 °C) and plastic tents to simulate warming, while water stress was imposed by maintaining soil moisture at 40% of water-holding capacity. The factorial design combined two abiotic stress factors (temperature, water) with two NbS interventions, resulting in 16 treatment combinations (n=4 plants per treatment). Clover was intercropped 25 days post-planting to enhance soil fertility, and manual cross-pollination was performed during flowering. Preliminary results show that the warming treatment alone led to a greater than 30% increase in plant height compared to the controls, while water stress and combined stress resulted in a 30–40% reduction in growth. Elevated temperature led to increased stomatal conductance, indicating greater stomatal opening, but this response was observed only when water was sufficiently available. These results highlight distinct physiological responses to abiotic stress, with evidence of potential thermal acclimation. Ongoing analysis will determine the extent to which NbS buffer against stress impacts, offering insights for sustainable crop management under climate change.