EFFECT OF BORON DEFICIENCY UPON THE STRUCTURE OF ZEA MAYS

Abstract

Three series of cultures of Zea mays were grown in Shive''s nutrient solution both with and without B. External deficiency symptoms appeared in all series in 50% of the plants in 7 days and in all plants in 10 days, as a chlorosis of older leaves and the failure of young leaves to unroll. The tips of B-deficient roots appeared swollen and stunted with secondary roots starting just back of the tip. Growth of the deficient plants was almost completely checked in 3 weeks. All leaves formed after the beginning of the expt. were abnormal in having very little lamina. The first internal injury was seen in 4-5 days in young leaves as a collapse of small groups of parenchyma cells and of cells in the small veins. Advanced injury was seen in partly mature leaves as a constriction of leaves to a narrow band of disintegrated tissue. In young leaves it was seen as the failure of cells to differentiate followed by disintegration of groups of cells. Injury in the stem tip was first present at the end of 2 weeks. Age of the plant and previous history whether with or without B had no effect on the time required for the development of deficiency symptoms.