SUMMARYSeedlings of Vicia faba L. were subjected to treatments with IAA, 2,4-D, tri-iodobenzoic acid, kinetin, 2-chloroethanephosphonic acid as well as those designed to prevent normal division in the primary meristem. Where division was inhibited with colchicine, trifluralin, dinitramine or surgical excision, a radial expansion of the root tip occurred. However, the anatomical aspects of the responses and their effects on phosphate absorption and incorporation were quite distinct from the effects produced in both boron deficiency and excess auxin treatments. Kinetin gave similar effects to mitotic inhibitors. The possibility that boron deficiency is associated with an excess level of endogenous auxin was examined. The effects of boron deficiency were compared with those associated with the presence of excess auxin.

SUMMARYBoron deficiency reduced absorption of phosphate in whole plants and root segments of Vicia faba. The overall phosphate metabolism of the whole root was unaffected but both the equilibrium pattern and initial rates of esterification were altered in the root tip region. The equilibrium ratio of inorganic phosphate to organic phosphate was not affected. Addition of boron at 10 / xM to the deficient plants for 1-2 h prior to absorption reversed the effects of boron deficiency in both absorption and metabolism of phosphate although it did not stimulate the initial rates of esterification of the absorbed phosphate.

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