Which of the following is an effective mitigation for heat stress in greenhouse crops?

• A. Cold stress via insulation
• B. Drought stress via reduced irrigation
• C. Increased fertilization to boost growth
• D. Cooling, increased ventilation, and shading

Answer: (D)

Mitigating heat stress in a greenhouse relies on reducing heat gain and increasing heat removal. The best approach combines cooling, increased ventilation, and shading because it tackles both sides of the problem.

Cooling lowers the air and leaf temperatures, often through evaporative or misting systems, so plants stay within their optimal range. Increased ventilation exchanges hot interior air with cooler outside air, carrying away heat and reducing humidity buildup that can worsen heat stress. Shading cuts the amount of solar radiation reaching the crops, directly reducing heat input and helping keep the canopy cooler.

Together, these methods prevent overheating, preserve stomatal function, and support photosynthesis and growth. The other options don’t address heat load effectively: insulation to reduce heat loss is counterproductive in hot conditions, reducing irrigation creates water stress and can worsen heat damage, and simply adding more fertilizer elevates metabolic demand without reducing heat input and can cause other issues like nutrient imbalances.