Atmospheric carbon dioxide levels have been rising steadily, and this elevated carbon dioxide can cause some plants to grow more rapidly. However, increased carbon dioxide can also have undesirable effects.
For example, the Agricultural Research Service says high carbon dioxide can worsen the adverse effects of high light intensity.
Grass crops such as barley and wheat grown in high light will exhibit early aging and oxidative stress. Oxidative stress occurs when too much “active” oxygen accumulates in the plant, breaks down membranes and interferes with normal life processes such as photosynthesis. Exposure of wheat and barley seedlings to elevated carbon dioxide in high light levels for prolonged periods causes a breakdown of the chlorophyll that gives leaves their green color and is essential for photosynthesis. Thus, the leaves develop a bleached appearance.