Which environmental factor is least likely to affect plant growth?

The influence of human emotions on plant growth is not supported by scientific evidence, making it the least likely factor to affect how plants grow. Unlike environmental factors such as water availability, soil pH, and air quality, which have direct physiological impacts on plants, human emotions do not play a tangible role in a plant’s biological processes.

Water availability is crucial because plants require water for photosynthesis and nutrient transport. Soil pH affects nutrient availability and can influence plant health, as certain plants thrive in specific pH ranges. Air quality is essential as it relates to the concentration of carbon dioxide and other gases that plants use for photosynthesis. These factors directly influence plant health and growth, while human emotions remain entirely irrelevant in the context of plant biology.