Photosynthesis in K‐ and Mg‐Deficient Maize (Zea mays L.) Leaves

Abstract
Rates of photosynthesis in maize leaves were closely related to K or Mg concentrations in the leaf tissue. The critical concentrations were about 2 mg/g for K and 200 µg/g for Mg on a fresh weight basis. Normal‐appearing leaves of K‐stressed plants had sharply diminished photosynthesis rates, whereas Mg deficiency affected photosynthesis rates only after the appearance of chlorosis. Apparently Mg deficiency exerted an influence through chlorophyll deterioration while K deficiency decreased stomatal apertures. Application of the deficient nutrient caused marked recovery within 24 hours of K‐deficient leaves but not of Mg‐deficient leaves.