Growth in plants occurs as the stems and roots lengthen. Some plants, especially those that are woody, also increase in thickness during their life span. The increase in length of the shoot and the root is referred to as primary growth, and is the result of cell division in the shoot apical meristem. The major stages of the flower life cycle are the seed, germination, growth, reproduction, pollination, and seed spreading stages. Plant growth is the process by which the plant grows in size. A matured plant has a strong stem and healthy leaves. The growth process is enhanced by the nutrients and the light energy that is used during photosynthesis. Plants are vital to all life on Earth. They are important because plant stake in carbon dioxide from the atmosphere and produce oxygen. In addition, plant smake up the base of the food web by producing their own food using light, water, carbon dioxide, and other chemicals.