Anatomical responses of root tips to boron deficiency II. Effect of boron deficiency on the cellular growth and development in root tips

Abstract

Changes induced in the tissue structure and the cellular patterns of young tomato root tips by the absence of boron in the nutrient solution were investigated. Boron deficiency caused primarily the inhibition of cell division and cell elongation in root apices, and the cells of boron-deficient root tips were fully vacuolated. The cell wall in the apical region was thickened by boron deficiency and the intercellular spaces insufficiently developed. Boron deficiency also caused the radial enlargement of cortical cells, especially of endodermis, but this enlargement was not accompanied by an increase in water imbibition. In the advanced stage of boron deficiency, the disintegration of tissue structure had occurred. Primordia of lateral roots arose closely in root apices. Maturation of the vascular system, especially of the primary xylem, was exasperated abnormally, and frequently there occurred a differentiation of cambial layers close to the apical initials. Anatomical effects of boron deficiency appeared particularly in the root apex and not clearly in the region of successive maturation. The results are discussed with regards to the role of boron in cellular growth at apical growing points. The results are discussed with regards to the role of boron in cellular growth at apical growing points.