Root and Stem Overview
Ch. 24 and 25
Terminology
•	Meristem-- location in which a plant part is growing (e.g. apices)
•	Pro- or proto--- tissue in the early stages of development (procambium, protoderm, protoxylem, etc.)
•	Meta-- tissue formed later in development (e.g., metaxylem, etc.)
Roots and Shoots are Environmental Interfaces
•	Roots harvest:
–	water
–	mineral nutrients
•	Shoots harvest:
–	light energy
–	carbon dioxide
–	small amounts of water and nutrients
Roots vs. Stems
•	Surface area of roots far exceeds that of stems
•	Stems produce buds that make more stems
•	Roots rarely produce buds and stems
–	Notable exceptions: pawpaw, aspen trees

•	Sharp differences between eudicots and monocots
–	Eudicot roots lack pith; stems have it
–	Monocot roots have pith; stems lack it
•	Can find roots above ground; stems below

•	Roots: two growth forms
–	tap roots
–	fibrous roots
–	roughly separates moncots & eudicots

•	Root cap
–	cells
–	mucigel

The endodermis allows selectivity in root uptake

Secondary root growth from the pericycle

Growth in root diameter from the vascular cambium

Secondary Growth

Specialized Roots
•	Adventitious roots
–	e.g., “prop” roots in maize, some mangroves
•	Pheumatophores 
–	e.g., mangrove, bald cypress
•	Aerial roots
–	e.g., epiphytic orchids
•	Storage roots
–	e.g., beet, carrot

Stems
Morphology
Fig. 25-1, p. 547
Stem Tip

Three kinds of stem arrangement

Structure of a maize vascular bundle