Module 5, section 4: Plant hormones.

What is abiotic stress, and provide examples.

A potential danger to the plant that is non-living. Storms, extreme cold etc.

What are plant defences for herbivory?

1.Alkaloids. plants that produce poisonous chemicals to deter predators.

2. Pheremones. Attract hostile organisms to kill/deter the herbivore, signal to the plant.

What other ways can plants defend against being eaten?

Plants can curl/fold up in response to being touched. This could deter herbivores, or knock off insects.

What is geotropism and phototropism, and how are roots and shoots related to these terms?

Geotropism is the growth of a plant in response to gravity. Phototropism is the growth of a plant in response to light

roots are positively geotrophic and negatively phototropic, and shoots are negatively geotropic and positively phototrophic.

What are growth hormones, and where are they produced?

Substances that promote or inhibit growth. they are produced in the growing parts of the plant.

What do gibberellins stimulate?

Seed germination, stem elongation, flowering, and side shoot formation

How do auxins work differently in roots and shoots?

Auxins inhibit growth in roots and promote growth in shoots

How do auxins stimulate the growth of shoots?

Cell elongation.

How does high concentration of IAA alter growth in roots/shoots?

Inhibits root growth, but promotes shoot growth.

What are apical buds?

Inhibitors of side shoots.

What are gibberellins inhibited by

how does ABA trigger stomatal closure?

1. ABA binds to guard cell receptors, causing ion channels to open, so calcium ions enter the cytosol.

2. Increased ion conc. causes other ion channels to open, increasing water potential.

3. Water then leaves the stomata, causing them to become flaccid, so the stomata shut.