Plant Responses

Question 1

What are alkaloids?

Answer 1

• Large group of bitter tasting nitrogenous compounds found in many plants
• Examples include caffeine, nicotine, morphine and cocaine

Question 2

What is a pheromone?

Answer 2

Chemical made by an organism that affects the social behaviour of other members of the same species

Question 3

What are some potential abiotic stresses in plants, and how can they impact the plants?

Answer 3

• Changes in day length, cold and heat, lack of/excess water, high winds, changes in salinity
• Can affect the growth, productivity and survival of plants

Question 4

How do plants protect their cells in freezing conditions, and how do they react to high temps?

Answer 4

• By producing polysaccarides, sugars, amino acids and even proteins that act as antifreeze chemicals in plants
• These chemicals prevent the cytoplasm in plant cells from freezing
• Open stomata (in moderation) in high temps for more evaporation in transpiration

Question 5

How should shoots be prepared when investigating phototropism?

Answer 5

• Cover tips with foil
• Cover base with foil
• Leave without foil

Question 6

Outline the procedure to investigating geotropism

Answer 6

1. Line up 3 petri dishes with moist cotton wool
2. Space out 10 cress seeds on the surface of the wool and put a lid on each dish
3. Wrap the dishes in foil to prevent light reaching the seeds
4. Leave the dishes where the temperature is warm and constant
5. Set up the dishes at different angles - 90, 45 and zero degrees
6. Leave the seeds for 4 days and then note the direction of the shoot and root growth of cress seedlings, record in a table

Question 7

How do auxins affect apical dominance?

Answer 7

• Auxins stimulate the growth of the main apical shoot, and suppress the growth of lateral shoots
• This results in apical dominance

Question 8

What is the dependent variable when investigating the effect of auxin and gibberellin?

Answer 8

• Auxin - The number of side shoots that have grown from the main stem
• Gibberellin - stem length

Question 9

What is hormone rooting powder, and what is its effect on plant cuttings?

Answer 9

• A substance that contains auxins
• The application of it to cut shoots stimulates the production of roots, making it easier to propagate new plants from plant cuttings

Question 10

How do synthetic auxins act as weedkillers?

Answer 10

• Synthetic auxins are absorbed by weeds, which are typically broad-leaf plants, and affect their metabolism
• The growth rate increases and becomes unsustainable, so the plants die