Plant Hormones. Stimulus A change in organism’s environment.

Plant HormonesPlant Hormones

StimulusA change in organism’s

environment

Stimulus

ResponseAn organisms reaction to change.

Response

Tropisms• Tropism = plant’s growth response toward

or away from a stimulus through the action of auxins.

PhototropismPlants grow toward a source of light

Explain how a plant grows towards light. (4 marks)

2.The auxins diffuse down the shoot and cause cells behind the tip to elongate.3.There is greater growth on the shady side of the young shoot.4. The shoot grows towards the light - this is known as PHOTOTROPISM.

1.Auxins are produced in the shady side of the tip.

Gravitropism A plant grows with or against gravity

A plant’s stems or trunk grow up, against the pull of gravity.

A plant’s roots grow down, with the pull of gravity

Can you explain the use of hormones in each diagram.Click to reveal the answer.

Applications of plant hormones

Can you explain the use of hormones in each diagram.Click to reveal the answer.

Fresh fruits are shipped around the world.

Plant hormones are used to slow the ripening of

the fruit, so they are just ripe as they reach the

supermarket.

Applications of plant hormones

Can you explain the use of hormones in each diagram.Click to reveal the answer.

Applications of plant hormones

When a gardener takes cuttings from a plant, the base of each

cutting is first dipped into a rooting compound to stimulate

the growth of roots.Many rooting compounds

contain auxin.

Can you explain the use of hormones in each diagram.Click to reveal the answer.

Applications of plant hormones

Can you explain the use of hormones in each diagram.Click to reveal the answer.

Applications of plant hormones

Auxins can be sprayed onto flowers so that the fruits

develop without pollination or fertilisation.

These fruits are seedless.

Can you explain the use of hormones in each diagram.Click to reveal the answer.

Applications of plant hormones

Can you explain the use of hormones in each diagram.Click to reveal the answer.

Applications of plant hormones

Applications of plant hormones

Weeds have broader leaves than the grass on a lawn. The weeds will take up more auxin than the grass when the lawn

is sprayed.

Can you explain the use of hormones in each diagram.Click to reveal the answer.

Auxins can be used as herbicides.

The weeds will grow too quickly and die.

Task

• Describe three uses of auxins. (3 marks)

True or false?

Young roots always grow downwards. This is because roots are...1. positively phototropic2. negatively hydrotropic3. positively geotropic

Which of the following statements is true?Click to reveal the answer.

True or false?

Young roots always grow downwards. This is because roots are...1. positively phototropic2. negatively hydrotropic3. positively geotropic

Which of the following statements is true?Click to reveal the answer.