5.4 Plant Responses Flashcards
Plants respond to what changes in their environment?
Lack of water
Light
Gravity
What are some limitations of plants?
Don’t have a nervous system
Rely on hormones which are much slower
(Hormones) what role do auxins play in plants?
Control cell elongation Prevent abscission Maintain apical dominance Tropisms Stimulate ethene release
(Hormones) what is the role of gibberellins in plants?
Cause stem elongation
Pollen tube growth
Mobilisation of food stores in germination
(Hormones) what is the role of ethene in plants?
Causes ripening
Promoted abscission
(Hormones) what is the role of ABA in the plant?
Maintains dormancy of deeds and buds
Stimulates protective responses such as antifreeze and stomatal closing
(Gibberellins in germination) for a plant to start growing it must do what?
Germinate
(Gibberellins in germination) 1. How is the embryo activated?
Seed absorbs water
(Gibberellins in germination) 2. The seed begins producing what?
Gibberellins
(Gibberellins in germination) 3. Gibberellins stimulate production of enzymes that do what?
Breakdown food stores
(Gibberellins in germination) 4. The embryo uses the food stores to make what?
Building materials to break through the seed coat
(Gibberellins in germination) 5. Gibberellins switch in genes coding for what?
Amylase and protease
(Gibberellins in germination) 6. ABA acts with gibberellins to determine what?
When the seed will terminate
What are auxins and where are they made?
Growth stimulants in plants
Made at tips of roots and shoots
(Auxins) what do auxins do in plants?
Stimulate growth of social shoot
Suppress lateral shoot growth
Promote root growth
(Auxins - apical shoot growth) 1. Auxin is synthesised where?
Meristems
(Auxins - apical shoot growth) 2. Auxins diffuse away from where?
Tip
(Auxins - apical shoot growth) 3. Auxins bind to what?
Receptor sites on cells
(Auxins - apical shoot growth) 4. vacuoles form web what develops?
Low ph
(Auxins - apical shoot growth) 5. Low pH does what to cell walls?
Keeps them flexible allowing cells to expand as they absorb water
Vacuoles get bigger
(Auxins - apical shoot growth) 6. A large central vacuole forms, cell walls become rigid and no more what is possible?
Cell elongation as auxins are destroyed
(Auxins - apical dominance) growth in the main apical shoot is stimulated by what?
Auxin produced at tip
(Auxins - apical shoot growth) as the auxin moves down the stem what happens?
Lateral shoots are inhibited
(Auxins - apical shoot growth) further down the stem auxin concentration is lower making what?
Lateral shoots grow more strongly
(Auxins - apical shoot growth) what happens to the lateral shoots if the main apical shoot is removed?
They grow as they are no longer inhibited
(Auxins - root growth) up to a certain concentration the more auxin that reached the roots the more they what?
Grow
(Auxins - root growth) high concentrations of auxins do what to the roots?
Inhibit their growth
(Auxins - root growth) if the apical shoot is removed the auxin reaching roots is what?
Reduced
Slowing and stopping root growth
(Gibberellins) what are gibberellins important in?
Stem elongation
Germination of seeds
(Gibberellins) gibberellins affect the length of what?
Internodes
(Gibberellins) how were they discovered?
Fungus infecting rice plants producing gibberellins making them grow long and thin
(Gibberellins) modified plants have been produced to produce little gibberellins and remain short, this is beneficial as..
They are less damaged by weather
What is synergism?
Different hormones working together complimenting each other
What is antagonism?
Hormones having opposite effects e.g. One promoting growth one preventing it
