PLANT HORMONES

I. Compounds which are produced in certain parts of a plant that  
   influence normal development in some way other than providing  
   nutrition and/or energy.

     A.  Unlike most animal hormones, plant hormones can influence
          development in the organs in which they are produced in 
          addition to organs removed from the source of production.

     B.  Exhibit multiple effects on plant development

     B.  Many plant hormones have synthetic analogs, which are used
          in scientific research, plant tissue culture,
          floriculture, and agriculture.

II. Auxins

     A.  Indole-3-acetic acid

     B.  Produced by leaves, transported basipetally

     C.  Enhancement of cell enlargement

     D.  Control of cell differentiation processes

     E.  Control of tropic responses

     F.  Dicot Herbicide's, inhibits fruit abscission 

III. Cytokinins

     A.  Zeatin (ca. 15 naturally occurring)

     B.  Produced in relatively large amounts in root tips,
          transported in xylem to stems, and in maturing fruits.

     C.  Enhancement of cell division

     D.  Prolong shelf life of flowers/vegetables

IV.  Some aspects of plant morphogenesis controlled by 
     Auxin/Cytokinin ratios

     A.  Apical dominance of terminal SAM over axillary SAM's

          1. Intact tSAM -> dormant aSAM's
          2. Remove tSAM -> active aSAM's
          3. Remove tSAM, replace with IAA -> dormant aSAM's
          4. Intact tSAM, add CK to aSAM -> active aSAM


     B.  Plant tissue culture of totipotent cells

          1. IAA/CK = 10/1 -> Stems
          2. IAA/CK = 1000/1 -> Roots
          3. IAA/CK = 100/1 -> Callus

V. Gibberellin

     A. Gibberellic Acid 3 (ca 52 naturally occurring)

     B. Produced by leaves and seeds

     C. Enhancement of cell division and cell expansion

     D. Release of some SAM's and seeds from dormancy

     E. Control of flowering in some species

VI. Abscisic Acid (1965)

     A. Abscision II (1962,USA) = Dormin (1949,England) 

     B. Produced by developing fruits and senescing leaves

     C. Inhibits plant growth

     D. Maintains dormancy in seeds and stems

     E. Promotes leaf abscission

VII. Ethylene

     A. Gas

     B. Produced in senescing leaves and in presence of high
          concentrations of auxin, and by ripening fruits

     C. Growth inhibitor

     D. Tropic responses of roots

     E. Ripening processes of fruits

     F. Induces flowering in some species

VIII. Hypothetical plant hormones of unknown nature

     A. Florigen induces plants to flower

     B. Morphogen influences pattern formation in plants