The primary factor limiting plant growth in ecosystems is nutrient availability, particularly nutrients like nitrogen, phosphorus, and potassium. These nutrients are essential for photosynthesis, energy transfer, and overall plant development. An ecosystem's ability to support plant life significantly depends on soil quality, including pH, moisture, and texture, which affect nutrient absorption. Moreover, competition with other plants and environmental conditions such as climate can also impact nutrient availability, potentially leading to limited growth and reduced biodiversity in the ecosystem.