The primary environmental factor influencing plant growth is light, specifically sunlight. Sunlight provides the energy necessary for photosynthesis, the process through which plants convert light energy into chemical energy to produce food. Adequate light exposure affects the rate of photosynthesis, influencing overall plant health, growth rate, and productivity. Other environmental factors like water, nutrients, and temperature also play important roles, but light remains the most critical factor in determining how effectively plants can grow and thrive in their ecosystems.