Responses of Tomato, Turnip, and Cotton to Variations in Boron Nutrition. II. Anatomical Responses

Abstract

1. Lack of boron in the nutrient medium results in a characteristic response in young, active organs of tomato and turnip. In upper internodes of tomato, root of turnip, and petioles and leaf blades of both plants, the cells of the cambial zone enlarge radially, become necrotic in some areas, and divide in association with the necrotic areas. The hypertrophy, necrosis, and hyperplasia extend outward into the phloem and, in extreme cases, inward into the xylem parenchyma. 2. Other less obvious responses, such as more secondary growth with smaller vessels, changes in quantities of tanniniferous substances, and changes in the amount and degree of maturation of fibers and collenchyma also occur in tomato and turnip and are found in cotton as well. 3. In cotton, however, there is no hypertrophy, necrosis, and hyperplasia in the cambial zone and phloem, but rather these responses are found in perimedullary pith parenchyma and protoxylem parenchyma. 4. In plus-boron plants of all three species sprayed with a solution containing sugar and boron or sugar alone, the various organs studied could not be readily distinguished anatomically from controls. 5. The same was true of minus-boron tomato and turnip plants sprayed with the sugar and boron mixture, but in cotton the organs of such plants were the smallest on any treatment and, while symptoms of extreme deficiency were eliminated, organs from such plants were anatomically intermediate between controls and unsprayed minus-boron plants. 6. In all three species, organs from minus-boron plants sprayed with sugar alone were quite similar in internal structure to those from unsprayed minusboron plants.