BIO203H5 Lecture Notes - Lecture 7: Secondary Growth, Xylem, Meristem
Document Summary
Plants increase in girth & undergo structural reinforcement: plants can become woody with age, strengthening the plant, primary growth is from the shoot apex & the root apex. Increase in girth is due to different meristem= the cambium: secondary growth meristem, giving rise to secondary growth & secondarily-thickened stem. To add xylem/phloem, cambial cells divide in longitudinal periclinal fashion. To add vascular cambium (compensate for increasing girth) initials divide anticlinically. Rays: living parenchyma cells: storage of nutrients in winter, allow passage of water/nutrients out of xylem to other regions= lateral transport. Inner bark: secondary phloem: much less of it than secondary xylem, typically contains many fibers, youngest cells are closest to cambium, oldest become crushed, only most recently formed cells are active. Xylem: later in development new cork cambium is often initiated below existing cork layers to compensate for increasing width. Woody" monocots utilize extensive primary thickening (eg. leaf bases)
