Which factor can stress plants during overwatering?

Overwatering plants can lead to significant stress primarily due to reduced oxygen availability at the roots. When the soil becomes overly saturated with water, the spaces between soil particles fill with water, displacing the air that would typically provide oxygen. Root systems require oxygen for respiration, which is essential for energy production and overall plant health. Without adequate oxygen, roots can suffer from suffocation, leading to poor nutrient uptake, root rot, and ultimately, plant decline or death.

While high soil temperatures can affect plant health, they do not directly relate to the stress caused by overwatering. Increased sunlight exposure may promote photosynthesis but does not directly connect to the issue of overwatering. Similarly, lower carbon dioxide levels can be a concern for plant respiration but are not a direct result of overwatering. Therefore, the most accurate answer is that reduced oxygen availability at the roots is a primary stress factor caused by overwatering.