EFFECTS OF BORON DEFICIENCY AND EXCESS ON PLANTS

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Abstract
Sunflowers and soy beans were grown in quartz sand with Shive''s 3-salt nutrient soln. to which B at various concs. was added. In the case of the sunflower the concs. were varied from 0 to 15 p.p.m., to study both deficiency and excess; with the soy bean, only B deficiency was studied. The main symptoms of B deficiency observed in these plants were a dying of the stem tip, chlorosis of the young leaves, and certain malformations of these leaves; the main symptoms of B toxicity in the sunflower were a mottling of the older leaves, followed by the death of this tissue. The sunflower required more B for optimal growth than did the soy bean. The soy bean developed B-deficiency symptoms more quickly when grown in the spring than when grown in the autumn. The range between B deficiency and toxicity in the sunflower was narrow. The greatest growth of the sunflower was at a conc. of B which was toxic as indicated by the effects on the older leaves.