No abstract

The object of this investigation was to explain the variations in the boron content of boron deficient alfalfa and to outline a procedure for sampling plants which will give a more accurate measure of the plant boron status. Alfalfa, grown in nutrient solutions where the boron was excluded during a stage of active elongation of the plant, contained 8 ppm of boron in the apical part of the shoot and 23 ppm in the total shoot. Plants receiving a continuous supply of boron had equal distribution in apical and basal parts of the shoot. In field experiments, as the available soil moisture became limiting in the surface foot of soil, the boron content of the apical leaves of the alfalfa shoot was decreased from 30 to 20 ppm while the boron content of the bottom leaves remained at 30 ppm. Apical portions of boron deficient plants in several fields contained about 8 ppm. Because of the immobility of boron in the alfalfa shoot, a sharp reduction of boron supply can result in boron deficiency symptoms on alfalfa plants with relatively high amounts of boron in the total shoot. Therefore, the indicative analysis is of the apical part of the alfalfa shoot.