Stomata

• Tiny pores called stomata in the leaves of green plants respond to light exposure. The stomata open widest in strong light and close in darkness. Stomata use light effectively to accomplish photosynthesis. Carbon dioxide passes through stomata, combining with water in the presence of sunlight to produce glucose. Stomata begin to open during the low, predominantly blue light of dawn, readying the plant to begin the process of photosynthesis at earliest sunlight. The opening and closing of stomata is not visibly apparent.
  
  

Perennial Flowers

• Crocus flowers open during the daylight hours.Goodshoot/Goodshoot/Getty Images
  
  Osteospernum are commonly called African daisies. These woody perennial plants open their flowers in sunlight and close them on cloudy days and at night. Flower colors are white, pink or lavender shades, with often contrasting rays. A vase of cut tulips in the home demonstrates the flowers opening during the day and folding in low light. Crocuses open wide in bright sunlight, closing to display often interesting patterns on petal backs under cloudy skies.
  
  

Annual Flowers

• Annual morning glories open their pink or blue flowers with the sun. Portulaca, commonly known as moss rose, produces masses of double, rose-like flowers in a wide range of colors on low-growing plants. The flowers open in the sun and close at night and on cloudy days. Gazania are perennial flowers grown as annuals in cold climates. Daisy-like flowers in colors ranging from yellow and bronze to orange and pink shades open on sunny days and fold at night or in cloudy weather.
  
  

Foliage

• Certain legumes with divided leaves begin the day with their leaflets horizontal in the cool morning hours. As the heat increases, leaflets turn to an orientation perpendicular to the sunlight, allowing the plant to conserve moisture and avoid overheating. The leaves reorient to a horizontal position as dusk approaches. The ornamental maranta, or prayer plant, folds its leaves at night in what is called a sleep movement. Prayer plants appear to open or close their leaves in response to light conditions, but the movement is a circadian response.