Concepts of Biology

Concepts of Biology (BIOL116) - 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/

Plant Life History & Structure: A Primer

I. Life Cycle of Rapid Cycling Brassica rapa
We will study the main features of the life cycle of RCBr, the experimental plant we are using in lab. In this section we will discuss features of the major "vegetative" phases of the life cycle. Flowering, fruiting and embryo development will be discussed later.

II. Seed Structure. (a baby in a suitcase carrying its lunch)

Coat (testa)
Embryo (cotyledon, hypocotyl, radicle, epicotyl)
Nutrients (endosperm, and/or cotyledons)
Types (monocot/grass; dicot with endosperm; dicot with minimal endosperm)
seeds vs. spores

III. Germination

Requirements (oxygen, temperature, water)
Imbibition
Radicle protrusion
Quiescent vs. dormant vs. dead
Breaking Dormancy (scarification, stratification, light, after ripening, leaching)
Early Metabolism - glycolysis, respiration, photosynthesis

IV. Plant Structures

A. Seedlings

corn

pea

bean

B. Life Span/General Terms

herb, shrub, tree, vine

herbaceous / woody

annual / biennial / perennial

deciduous / evergreen

C. Plant Cells (remember the hierarchy of biological organization? cells - tissues - organs)

Protoplast, wall, plasmodesmata

Types:

Parenchyma - living, thin-walled, storage and various metabolic functions

Collenchyma - living, irregular thickenings of the wall, especially in the corners, often beneath epidermis, support

Sclerenchyma - often dead, thick wall, primarily for support; fibers - long, thin, often associated with vascular tissue; sclerids - shorter, may be branched

D. Plant Tissues

vascular (i.e., xylem, phloem)

dermal (i.e., epidermis)

ground (i.e., pith, cortex)

E. Roots

root hairs and branch roots

root cap, region of cell division, region of elongation, region of maturation,

structure: epidermis, cortex, endodermis, stele, pericycle

F. Leaves

node, internode, bud, axillary or lateral bud, axil

blade, petiole, stipules

venation - parallel vs. net

structure: epidermis, cuticle, cutin, trichome, guard cells, stoma (stomata), mesophyll, palisade mesophyll, spongy mesophyll, vein (xylem, phloem), bundle sheath

adaptations - sunken stomata, spines, insectivorous plants

G. Stems

bud, axillary or lateral bud, terminal bud, node, internode, leaf scar, bud scale scar, vascular bundle scar

herbaceous stem structure (vascular bundles, pith)

woody stem structure (wood, bark, annual rings, cork, phloem, cork cambium, lenticels)

V. Monocots vs. Dicots: A Quick Comparison

Table 1: Comparison of Monocots and Dicots

Feature

Dicot

Monocot

Number of species 165,000 50,000

Growth form woody or herbaceous mostly herbaceous

Embryo cotyledons two cotyledon one (best character to distinguish)

Endosperm present or absent often present

Floral parts 4 or 5-merous 3-merous

Leaves net (reticulate) veined parallel veined

Petiole common, seldom sheaths stem not common, petiole often sheathing

Vascular system definite # bundles, ring (like broccoli) numerous, scattered (like asparagus)

Mature root system primary or adventitious, strong taproot often present wholly adventitious (primary root system of short duration, fibrous roots common, usually without strong taproot)

Last updated: January 03, 2004 Visitors to this site: Hit Counter
� Copyright by SG Saupe / URL:http://www.employees.csbsju.edu/ssaupe/index.html

Table 1: Comparison of Monocots and Dicots
Feature	Dicot	Monocot
Number of species	165,000	50,000
Growth form	woody or herbaceous	mostly herbaceous
Embryo	cotyledons two	cotyledon one (best character to distinguish)
Endosperm	present or absent	often present
Floral parts	4 or 5-merous	3-merous
Leaves	net (reticulate) veined	parallel veined
Petiole	common, seldom sheaths stem	not common, petiole often sheathing
Vascular system	definite # bundles, ring (like broccoli)	numerous, scattered (like asparagus)
Mature root system	primary or adventitious, strong taproot often present	wholly adventitious (primary root system of short duration, fibrous roots common, usually without strong taproot)