The decrease in photosynthetic rates due to drought stress has been well documented in research studies. Water relations within the plant and CO 2 and oxygen exchange are directly affected. In addition, if leaf-rolling occurs during drought, the effective leaf surface for collection of sunlight is reduced. Subsequent grain development depended entirely on stalk carbohydrate reserves. Reduced Sunlight Photosynthesis is most efficient in full sunlight.
Studies show that the rate of photosynthesis increases directly with intensity of sunlight.
Prolonged cloudy conditions during ear-fill often result in severely depleted stalk reserves. Any reduction in leaf area will limit total photosynthesis. Leaf area may be reduced due to hail, frost, disease lesions, insect feeding or mechanical injury. Whenever functional leaf area is reduced prior to completion of ear fill, stalks will be weakened. Even favorable growing conditions can have a negative effect on stalks.