Effect of Boron on Growth and Development of the Radish

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Abstract
Radish plants (Raphanus sativus, var. Scarlet Globe) deficient in B produced small leaves with light bluish green color, which were (especially the petioles) brittle and curled down. The thickened underground portions were light in color, narrow and elongated, and severely cracked. Plants receiving B for first 18 days only produced underground portions of larger size and more normal shape but they were also cracked. B-deficiency symptoms were much less pronounced under short photoperiod. The thickened underground portion (root and hypocotyl) was used for a histological study. The vascular tissue near the center of the axis was not affected by B deficiency. Normally developed and lignified vessels in the area between the central, unaffected vascular tissue and the outer cambium region were absent, and the phloem cells in this region had disintegrated. The cambium region, if located at or near a crack, had slightly developed vascular bundles; if not located at or near a crack the bundles were well developed and arranged in pronounced domes and circular areas, although the vessels were unlignified. In both cases the xylem parenchyma and ray cells were highly active. The splitting is caused by the failure of normal vascular tissue development, coupled with differential growth pressure.