Plants & Human Affairs (BIOL106)  -  Stephen G. Saupe, Ph.D.; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321; ssaupe@csbsju.edu; http://www.employees.csbsju.edu/ssaupe

Plant Growth and Development

I.  Meristems

• Gink & Go at the Playground
• definition
• types:  apical, vascular cambium, pericycle, cork cambium
• primary vs secondary (not on exam)
• apical, lateral
• buds � what are they?
• growth and tree/plant height � i.e., carving initials in tree, swing height
• If meristems are terminal, how can grass keep growing?

II.  Determinate vs. indeterminate growth (not on exam)

• define
• bush beans = determinate (vegetative bud turns into reproductive)
• pole beans = indeterminate
• entire plant or just part can be determinate

III.  Patterns of growth (not on exam)

• plot growth curves:  height vs. time for indeterminate, determinate, terminal flowering cereal
• Timeline - life cycle of an annual

 
IV.  Apical Dominance

• Xmas tree shape
• apical bud dominates development of lateral buds
• auxin (IAA) and likely other plant hormones involved
• gardeners prune/pinching
• �chemical pruning� (not on exam)

 
V.  Senescence/Aging (not on exam)

• annuals to perennials
• perennials live from just a few years to many (bristlecone � 4000; aspen clones 10,000)
• Cultivars propagated for many years � Winter Permian apple in England cultivated at least since 1200 AD
• Black Corinth grape since Greeks
• Reine Claude plum since 1500 AD.
• deadheading � remove flowers to extend age
• senescence � programmed aging, designed to reclaim nutrients, etc.
• Fall color � click here for an essay about leaf color.

VI.  Pruning � maintaining shape  (not on exam)

• essentially a dwarfing technique
• why prune?
  • control size
  • shape
  • improve strength
  • increase light
  • decrease humidity, improve air flow
  • thin fruit � larger, prevent disease
• timing critical (prevent disease transmission, natural cycle of plant � i.e., lilac after flower)
• where to prune (leave stem collar, at bud, bud direction)

VII.  Hormones Regulate Plant Growth & Development (not on exam)

A.  What is a hormone?  - internal chemical, produced by the plant, low concentration, organic material 

B.  Auxins

• apical dominance
• root initiation
• abscission
• apples � June drop;  NAA used (later prevents)

 C.  Gibberellin

• seed germination
• break dormancy
• elongation
• elongate grape clusters
• overcome dwarfing

 D.  Cytokinin

• delay senescence
• cell division

 E.  Ethylene

• stimulate rubber flow
• triple response

 F.  ABA

• inhibit germination
• growth inhibitor

Last updated:  02/28/2005 / � Copyright  by SG Saupe