The Anatomical Basis for Hygroscopic Movement in Primary Rays of Daucus carota Ssp. carota (Apiaceae)

Elizabeth P. Lacey, Peter B. Kaufman, P. Dayanandan
1983 Botanical Gazette  
Polarization microscopy was used to examine the cause of hygroscopic movement in umbellet peduncles, or primary rays, of Daucus carota (Apiaceae). Net microfibril orientation of thick-walled parenchyma cells is perpendicular to the long axis of the cell. When the relative humidity rises, these parenchyma cells elongate. In contrast, net microfibril orientation of sclerified fibers is parallel to the long axis of the cell. These fibers do not elongate with increasing relative humidity. Because
more » ... ickwalled parenchyma cells predominate in the abaxial half of a ray and fibers in the adaxial half, and because the long axis of both cell types is parallel to that of the whole ray, the ray bends adaxially with increasing relative humidity and abaxially with decreasing relative humidity.
doi:10.1086/337385 fatcat:dxm3f2qki5clvfxogeo3d3jxvi