EFFECT OF 2,6-DICHLOROBENZONITRILE (DCB) ON SECONDARY WALL DEPOSITION AND LIGNIFICATION IN THE STEM OF HIBISCUS CANNABINUS L.

摘要

Light and electron microscopic studies were carried out on the secondary xylem of actively growing shoots of Hibiscus cannabinus treated with cellulose synthesis inhibitor 2,6-dichlorobenzonitrile (DCB). Treatment with 20μM DCB induced differentiation of xylem fibres with thin secondary walls and parenchyma cells with abnormal wall thickening and lignification. At concentration above 50 μM resulted in the disappearance of cambial zone, inhibition of secondary wall deposition, lignification of primary walls, deformed vessel walls and dispersed lignin distribution in secondary walls. Transmission electron microscopic study revealed the initiation and formation of large intercellular spaces between the walls of differentiating xylem elements. Abnormal pattern of wall deposition and inhomogeneous lignin distribution was evident in fibres and vessel. The length and width of both fibres and vessel elements were reduced significantly even with lower concentrations of DCB.