Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Plant Hormones
Plans growth is affected by internal factors (hormones) and external factors (light, nutrients, water,
disease agents, temperature)
 Plants responses are called tropisms
 Light (phototropism), gravity (geotropism), contact with objects (thigmotropism)
 Negative tropism (away), positive tropism (towards)
 Plants respond by releasing hormones which are transported in the phloem
Plant Hormones - Auxins (including Inodoleacetic acid IAA)
 Produced in shoot tips
 Stimulates elongation and enlargement of cells in stem but at high concentration, inhibits root
growth
 Inhibits lateral buds (apical dominance (particularly IAA))
 Promotes growth of flowers and fruits
Cytokinins
 Stimulate cell reproduction
 Produced in roots and young fruits
 Act on shoots, roots, fruits
 Interact with auxins to produce leaves or roots
 Regulates differentiation of unspecialised cells
Gibberellins
 Stimulate both cell elongation and cell reproduction in stems and leaves
 Produced in root and shoot tips (apical meristem which supplies cells for growing juvenile
tissue), embryos and juvenile leaves
...
g
...
g
...
They are more affected by levels of maturity
Water Movement
 Water moves up plant through Xylem
 Moves into roots via osmosis after ions have been drawn in via active transport



Moves via root pressure, adhesion, cohesion and transpiration

Vernalisation
 When a period of cold is required before flowering can occur
Pheromones
Chemical signalling molecules secreted by animals
 Influence the behaviour of other members of the same species
 Used mainly by insects but good evidence that they are used throughout the animal kingdom
 Secreted by one organism and are detected by other organisms through smell receptors
 Can be induced artificially to
o Deter parasitic insects
o In traps to attract parasites
o Enhance chances of pollination
o Some research suggests that they are utilised in the animal world
 Pheromones released by an organism to affect the behaviour of other organisms in that
species
 Hormones released internally to affect function of the organism that they are released in

---