ch 13 Flashcards
what is phototropism
the response of the plant to light
what is +ve phototropism
when plant grows towards the light
what is -ve phototropism
when plant grows away from the light
what is geotropismn
the response of the plant to gravity
what is +ve geotropism
when plant grows towards gravity
what is -ve geotropism
when plant grows away from gravity
what tropism does shoot do and why [3]
–ve geotropism
-+ve phototropism
-grows up towards light to make photosynthesis
what tropism does root do and why [3]
- +ve geotropism
- -ve phototropism
-grows down towards gravity to absorb water and minerals
what are auxins
plant growth hormones
where are auxins produced
at tip of shoot
function of auxins
increase growth
for plant that is subjected to light from all directions (equal exposure to light)
-how are auxins distributed?
-how is the rate of growth?
-and how does plant grow?
-equal distribution of auxins on both sides
-equal rate of growth on both sides
-plant grows vericallly up
for plant that is subjected to light from one side (un-equal exposure to light)
-how are auxins distributed?
-how is the rate of growth?
-and how does plant grow?
-un-equal distribution of auxins, more on shaded side than bright side
-shaded side grows faster than bright side , unequal rate of growth
-plant bends towards the light , +ve phototropism
for plant that is placed in complete darkness
-how are auxins distributed?
-how is the rate of growth?
-and how does plant grow?
-auxins accumulate in the darkness , increase the rate if growth
-the whole plant grows rapidly verically up
-shoot becomes (thin, long, wavy) : etiolation
for plant that has removed shoot
-how are auxins distributed?
-how is the rate of growth?
-and how does plant grow?
-no shoot tip, so no auxins produced
-no growth
for plant that has tip removed then rejoined by jelly ajar (permeable)
-how are auxins distributed?
-how is the rate of growth?
-and how does plant grow?
- auxins can diffuse across the permeable jelly ajar then accumulate
-shaded side grows more than bright side
-plant bends toward light
for plant that has tip removed the rejoined by aluminum sheet (impermeable)
-how are auxins distributed?
-how is the rate of growth?
-and how does plant grow?
- auxins cant diffuse
-no growth of plant
what happens when auxins accumulate on one side
plant bends to the other side
advantages of +ve phototropism [3]
-grow towards light, so more photosynthesis, more growth
-flowers more likely to attract insects
-more likely to release seeds
advantage of +ve geotropism [2]
-better anchorage
-absorb water and mineral ions
what is clinostat
an appartus used to demonstrate the effect of gravity on the germinating seed (geotropism)
what does clinostat consist of
consists of electric motor that is connected to rotating disc , the disc has a cork base where the seedling is fixed
what happens when motor is turned on in clinostat [3]
-the different parts of root and shoot will be equally exposed to gravity,
-so auxins will be equally distributed on both sides of radical
- the shoot and root (radicle and plumule ) grow straight, horizontally (equal rate of growth)
what happens when motor is turned off in clinostat [4]
-unequal exposure of gravity , lower side of root more exposed
-unequal distribution of auxins , more auxins on lower side of radicle
-the root (radicle) will grow downward towards gravity , +ve geotropism and the shoot will grow upward, -ve geotropism
-unequal rate of growth
