Meristems & Plant Growth and Development
I. Some
Definitions
- growth - increase in size, cell
number
- development - progressive changes
that occur throughout the life cycle
- differentiation - specialization of
structures that occurs during development
II. Meristems
A.
General
- growth in plant occurs in meristems/meristematic regions
- meristems are areas of active cell division
- meristems are only the region of plant where cell division/growth occur
- growth is restricted in plants because of the cell wall &
architectural design
- typical pattern of growth: meristem
→
new cells
→
cells enlarge
→ cells differentiate (become
specialized)
B. Apical (or Primary) Meristems
- responsible for growth in length
- located at tip of roots & shoot
- derived from a meristem
originally present in the embryo (at tip of the embyro root end, called the radicle,
and the tip of the shoot end, called the epicotyl)
- remember plants grow in length from the tips (Check out Gink
& Go Visit the Playground for more information)
- root meristem - growth in length of the root; protected by root cap;
regions of roots (cell division = meristem, cell elongation,
differentiation)
- shoot meristem - produces growth in length of stem; source of new leaves
and buds;
produces buds at base of leaves
B. Buds
- produced at base of leaves (or a corollary, every leaf has a bud at its
base)
- a bud is an embryonic shoot - essentially miniature
stem with leaves that is
"waiting" to develop.
- buds give rise to branches
- some buds may also house flowers
C. Pericycle
- meristem in root
- beneath endodermis
- gives rise to lateral roots
- type of secondary meristem - ultimately derived from the primary (or apical) meristem
D. Vascular Cambium
- produces xylem (to inside) and phloem (to the outside)
- growth in width (girth)
- location in woody plants - stem
anatomy (bark, wood, heartwood, sapwood, phloem, xylem, rays, spring wood,
summer wood, annual rings)
- location in herbaceous plants - vascular bundles
- another secondary meristem
E. Cork cambium
- produces cork or periderm - protects phloem and wood
- secondary meristem
Last updated: January 24, 2008
� Copyright by SG Saupe
Introduction
to Organismal Biology (BIOL221) -
Dr.
S.G. Saupe; Biology Department, College of St. Benedict/St. John's
University, Collegeville, MN 56321; ssaupe@csbsju.edu;
http://www.employees.csbsju.edu/ssaupe/