Suppressive effects of CPPU on lignification of xylem parenchymatous cells and on hollowing in the root of Japanese radish ( Raphanus sativus L.)

Abstract

To see the effects of CPPU on the development of hollowing and lignin formation in the roots of Japanese radish ( Raphanus sativus L.) ‘Wakayama’, ‘Yamada’ and ‘Osakashijunichi’, solutions of 5 mg l −1 of 1-(2-chloro-4-pyridyl)-3-phenylurea (CPPU) were sprayed on the leaves of plants every 3 days from the 11th to the 40th days after sowing (DAS). The size of the hollow cavity in the roots of ‘Wakayama’, ‘Yamada’ and ‘Osakashijunichi’ became significantly smaller with CPPU treatment, in contrast to that of the control. Vessels in the roots of all cultivars became more sparsely arranged with CPPU treatment, compared with vessels in the root of the control. In addition, the central region of the root of all cultivars treated with CPPU was filled with parenchymatous cells and these cells showed little staining reaction to phloroglucinol-HCl reagent. In contrast, in the controls, there was clear evidence of the presence of lignin in parenchymatous cells facing the intercellular space.