As to why plants synthesize tocochromanols, the major reason appears to be for antioxidant activity. Different parts of plants, and different species, are dominated by different tocochromanols. The predominant form in leaves, and hence leafy green vegetables is α-tocopherol. Location is in chloroplast membranes, in close proximity to the photosynthetic process. The function is to protect against damage from the ultraviolet radiation of sunlight. Under normal growing conditions the presence of α-tocopherol does not appear to be essential, as there are other photo-protective compounds, and plants that through mutations have lost the ability to synthesize α-tocopherol demonstrate normal growth. However, under stressed growing conditions such as drought, elevated temperature or salt-induced oxidative stress, the plants' physiological status is superior if it has the normal synthesis capacity.