Autumn.wmf (12088 bytes) Concepts of Biology (BIOL116) - Dr. S.G. Saupe; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321;;

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)

III.  Germination

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:
  1. Parenchyma - living, thin-walled, storage and various metabolic functions
  2. Collenchyma - living, irregular thickenings of the wall, especially in the corners, often beneath epidermis, support
  3. 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




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)
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