Plant Flashcards
Phototropism
Response to LIGHT
-Auxin is produced in the TIP of the growing shoot/ root.
-Auxin is translocated /transported to dark side of the shoot.
-Auxin causes elongation of the cells on shaded side
-There is DIFFERENTIAL elongation between shaded and non-shaded side and plant moves.
towards light.
Geotropism
Response to gravity
-Auxin is produced in the TIP of the growing shoot/ root.
-Auxin is translocated /transported to lower side of the root/ shoot.
- (In SHOOTS ) Auxin causes elongation of the cells on lower side.
-In ROOTS high auxin inhibits elongation of the cells on lower side.
-There is DIFFERENTIAL elongation between cells on lower and higher side and shoot moves
upwards and the root moves downward as a result.
Thigmotropsim
Response to touch
- Auxin produced in the tip of the shoot.
-Transported to side that is not touching.
-Auxin causes elongation of the cells on non-touching side.
-There is DIFFERENTIAL elongation between touching and non-touching side and plant curls
around stick.
Diagrammmmmm
Roots – High IAA – does
NOT elongate!!
Low IAA - elongates
Positive PHOTOTROPISM
Bending toward the light ensures that the plant grows towards sunlight and can photosynthesize and thus more surface area exposed to the sun.= more glucose
production.
-Glucose/starch produced can be used to grow taller thus avoiding competition.
-OR for reproduction to produce flowers/seeds/fruits. If held higher – more chance
of wind/animals pollinating or dispersing
Positive GEOTROPISM roots and Negative geotropism roots
For roots – growing downward (positive geotropism) will ensure that the seedling
is better anchored and better access to water and nutrients for growth. Water key
ingredients of photosynthesis
For shoot – growing upward (negative geotropism) will ensure reach sunlight as
quickly as possible for photosynthesis and reproductive success before seed starch
supplies run out
Positive THIGMOTROPISM
-Can use other plants or structures for support- so it can climb up to get more light
for photosynthesis…..increase competitive success
-Use glucose for more rapid growth rather than support structures
Flowers/seed dispersal – higher up.
Nastic Response
The plant’s reaction bears NO RELATION to the direction of the stimulus.
- SO NO -ve/+ve response
-Due to the intensity of the stimulus.
Process of Nastic
Stimulus- PHOTO/GEO/GRAVI/HYDRO/THIGMO/CHEMO/THERMO
Photonasty- leaves collapse when exposed to high light intensity.
Nyctinasty- Open day and shut at night.
Thigmonasty- leaves close once touched.
REVERSIBLE
Nastic ( HOW)
-Osmotic potential changes in certain cells at base a stark.
-pulvini cells - pump-out K+ ions - then water follows.
-Drop in turgor pressure- causes collapse of cell - Leaf droops
Water can return and increase turgor pressure - the leaf goes back to normal.
The advantage in relation to niche ( Nastic)
Rapid response - thigmonasty - can expose thorns or branches making the plant less palatable - if plant leaves not eaten will be able to Photosynthesise better.
Flowers that shut at night the internal structures will be protected and thus save energy.
Orientation in Time
- Endogenous (internal) timing mechanisim
