Biology Edexcel Igcse Chapter 12: Chemical Coordination In Plants

Front 1

Tropism

Back 1

growth response of a plant to a directional stimulus

Front 2

Response of shoots and roots to a hyrdotropism

Back 2

Shoots: none
Roots: towards water

Front 3

Response of shoots and roots to a geotropism

Back 3

Shoots: negative, away from gavity
Roots: positive, towards the direction of gravity

Front 4

Response of shoots and roots to a phototropism

Back 4

Shoots: positive, towards light
Roots: most have no response but some roots have a negative phototropism, away from the light

Front 5

What is the chemical which causes plant shoots to grow towards light?

Back 5

auxin

Front 6

Where is auxin produced?

Back 6

The tip of the shoot, from where it diffuses down

Front 7

How does auxin cause a shoot to grow towards the light if the shoot is half in the dark?

Back 7

Diffuses from tip, down to dark side where it stimulates the 'dark side' to grow more and therefore bend towards the light.

Front 8

Experiment to show the tip needs to be uncovered for a phototropism (so it can detect light)

Back 8

put an opaque cap on the tip and it won't bend

Front 9

Experiment to show the tip needs to be connected to the shoot for auxin to diffuse.

Back 9

Replace the tip on a mica sheet and there will be no bending however if you put it on a gelatin block (permeable) auxin diffuses through and it does bend.

Front 10

Experiment to show that the whole tip doesn't need to be connected.

Back 10

Replace half the tip on the shoot and normal bending will occur.

Front 11

Experiment to show the tip itself doesn't need to be on the shoot for it to grow.

Back 11

Put the tip on an agar block, allowing the auxin to diffuse into it. Then put the agar block where the tip would usually be and normal bending will occur.

Front 12

Experiment to show geotropisms.

Back 12

Put a climostat on its side and have a control experiment on the side. The control experiment roots will grow straight down towards gravity but the root in the climostat will grow straight out as the direction towards gravity is constantly changing.