Taxes and Kinesis and Plant hormones Flashcards
How can organisms increase chance of survival?
By responding to changes in environment (stimuli) to provide a suitable response
2 types of simple movement responses organisms can make due to stimuli
Taxes
Kinesis
Taxes
A directional response there a whole organism moves either towards (pos) or away (neg) from a stimuli
This is directly to it
Kinesis
Random movements by the whole organism to find favourable conditions, without moving directly in 1 direction
If organism is in unfavourable conditions (Kinesis)
Moves fast and turns little so more likely to find favourable conditions by random
If organism is in favourable conditions in Kinesis…
Moves slowly and turns a lot so will remain in favourable conditions
Net effect of Kinesis
Moves randomly towards favourable conditions and will remain there
Answering questions on Kinesis/taxis
Requires stating an evolutionary benefit
Statistical test on practical for kinesis/ taxes
Chi squared
When is a chi squared test used?
Comparing experimental results with theoretical ones
If the data is in categories
If the data is in its raw counted form (no rates, means or percentages)
Tropism
A directional response that involves an organism either growing towards (positive tropism) or away from (negative tropism) a stimulus
How can tropism in plants occur?
Growth factors move from growing regions to other tissue, to regulate the growth of the plant in response to a directional stimuli eg tropism
Why do plants show tropism?
So they can grow to:
get enough light for photosynthesis (towards light upwards )
and roots get access to enough water and inorganic nutrients for growth (away from light underground)
Growth factor to learn THAT EXPLAINS HOW TROPISM OCCURS
IAA
Where is IAA made/
Tips of roots (underground, grows down)
And tips of shoots (grows up)
Both are growing regions
What 2 kinds of tropism are there?
Gravitropism
Phototropism
Gravitropism
A directional response of a plant where it moves either in the direction of or against gravity (force of gravity acts as directional stimulus)
How does gravitropism occur in shoot tip?
IAA accumulates in lower side of tip (high conc)
STIMULATES cell elongation in lower side of tip so growth continues UPWARDS AGAINST GRAVITY on the upper side
What kind of gravitropism occurs in the Shoot tip?
Negative gravitropism - against the force of gravity UPWARDS
How does gravitropism occur in root tip?
IAA accumulates in lower side of root tip (high conc)
INHIBITS cell elongation in lower side of tip so growth occurs on the upper side of root tip DOWNWARDS IN DIRECTION of gravity
What kind of gravitropism occurs in the ROOT tip?
Positive gravitropism - in the direction of gravity DOWNWARDS
Where does IAA always accumulate in gravitropism resposnes?
THE LOWER SIDE in both roots and tips
The roots and tips just have different responses to cell elongation due to high conc of IAA
Phototropism
A directional response of a plant where it moves either in the direction of or against light (direction of light acts as directional stimulus)
How does phototropism occur in shoot tip?
IAA accumulates on shaded side
STIMULATES cell elongation in the shaded side so shoot grows towards light
What kind of phototropism occurs in a shoot tip?
POSITIVE because the plant shoot grows toward direction of light
How does phototropism occur in a root tip?
IAA accumulates on the shaded side
INHIBITS cell elongation of the shaded side causing plant growth away from the direction of light
What kind of phototropism occurs in a root tip?
NEGATIVE because the plant root grows against direction of light
How does IAA distribute itself around the plant?
By diffusion within growing tips to where it is needed
Where does IAA always accumulate in root tips?
THE SHADED SIDE
Roots/ shoots just have different responses in terms of stimulating or inhibiting elongation
How does cell growth occur?
New cells are produced by mitosis at the tip
Growth continues due to cell elongation behind the tip
