taxes and kinesis

stimuli?

change in environment detected by receptors

response to stimuli allows for increased chance of survival

(±) taxis?

directional response towards or away from a directionl stimulus

(±) kinesis?

non - directional response

speed of movement/ rate of direction change in response to a non-directional stimulus

dependant on intensity of stimulus

kinesis response to negative stimuli? 

rate of direction change decreases to keep in a straight line to increase chances of finding another location with favourable conditions 

kinesis response to area with harmful stimuli?

increase rate of direction change to return to area with favourable stimuli

tropism?

growth of plant/elongation of cells in response to a directional stimulus

role of growth factors in flowering plants?

specific growth factors (eg. IAA), diffuse from growing regions eg. shoot/root tips where they are produced

to other tissues where they regulate growth in response to a directional stimuli

IAA in roots?

high concs. inhibit cell elongation

IAA in shoots?

high concs. stimulate cell elongation

phototropism in flowering plants in shoot + root?

• tip produces IAA

• IAA initially diffuses down evenly

• then moves to shaded side, increasing conc.

• stimulates/inhibits cell elongation

• causing it to bend towards/away from light

gravitropism in flowing plants?

• tip produces IAA 

• IAA initially diffuses down evenly 

• then moves to lower side, increasing conc.

• stimulates/inhibits cell elongation 

• so shoots bend away from gravity, and roots towards 

protective effect of a simple (eg. 3 neurone) reflex?

rapid as only 3 neurones and few synapses (as synaptic transmission is slow)

autonomic so doesnt have to be learnt

protects from harmful stimuli, eg. escape predators / prevents damage to body tissues

how does IAA affect cell wall plasticity?

increased conc. increases plasticity
increased plasticity results in cell elongation

investigate effect of dif conc/amount of a plant growth factor on growth of stems

use distilled water (control) + dif concs/amts of factor w/ 10 stems in each
measure stem length at start + end
place stems in same vol solution/ expose to same amt of factor
leave for same period of time
ensure stem thickness, and solution vol is the same for all