Chapter 16 Flashcards
What are three Plant responses to abiotic stress
Leaf loss- plants are growing very climates lose their leaves in the winter to conserve energy and re-grow in the summer to photosynthesise
Freeze prevention- plants produce sugars amino acids or proteins which act as antifreeze
Stomatal control- roots produced ABA when water levels in a song for which causes stomatal closure
Name five responses of plants to her ivory
Physical defences-thorns spikes inedible tissue and hairy leaves
Alkaloids -chemicals with bitter taste bad smells or poisonous characteristics
Tannins -toxic bitter taste in compounds which bind the digestive enzymes making it hard to digest
Pheromones chemicals which affect the behaviour of other organisms e.g. may cause nearby plants to produce tannins in danger
Mimosa pudica when touched they spread a signal causing the leaves to fold up knocking of small insects and scaring herbivores
What is a tropism
A tropism is a plant response to a directional stimulus
What is phototropism
Phototropism is the growth response of plants to unilateral light
How does phototropism work
in unilatural light auxins move laterally across the tip of the shoot towards the shaded side simulating cell elongation causing the shoot To bend towards the light
How can you investigate phototropism
Take three identical she’s covered the tip of one the base of the other and leave the final one exposed leave in front of light source and those with the uncovered tips should grow towards it
What is geotropism
Geotropism is the growth response of plants to gravity
How does geotropism work
Auxins move to the underside of shoots and roots due to gravity and shoot the underside elongates causing upward growth where is in roots the underside is inhibited closing downward growth
How can you investigate geotropism
Grow plants on a slowly rotating clinostat so gravitational stimulus is acquired equally to each side in the dark the shoot should grow straight
Names three other types of tropisms
Hydro tropism is plant growth in response to water
Thermotropism is plant growth in response to temperature
Thigmotropism is plant growth in response to contact with an object
What do auxins do
Auxin stimulate growth of the apical bad but suppress growth of lateral shoots maintaining apical dominance which saves energy and prevents competition from light along plants to grow towards the light source sideshoots at the bottom have a lower concentration of auxin so grown more
How can you investigate apical dominance
Take 30 similar plants And record the number of sideshoots of each then in 10 remove the tip and apply auxin paste in 10 remove the tip and apply non-auxin paste and leave 10 untouched leave for a number of days and then count the number of side shoots again
What do gibberellins do
Gibberellin stimulate seed germination stem elongation side shoot formation and flowering
How do gibberellin stimulate seed germination
By triggering the breakdown of food stores in the seed for respiration for energy
How can you investigate seed germination
Genetically altered states unable to produce Gibberellins are unable to germinate
