Plant Response Flashcards
(26 cards)
What is tropism?
Directional growth due to a stimulus
What is Phototropism?
Growth towards light
What is Geotropism?
Growth towards gravitational pull
What is Chemotropism?
Growth towards chemicals.
eg. pollen tube growing towards ovary sac in plants for fertilisation
What is Thigmotropism?
Growth towards a surface in contact.
What are the plants response to herbivores?
Tannins
Alkaloids
Pheromones
How do plants use Tannins?
Leaves : taste bad
Roots: prevent pathogen entry
phenolic compounds
How do plants use Alkaloids?
Bitter
Derived from amino acids w/ nitrogen containing bases
What are Pheromones?
Chemicals released that affect another’s behaviour or physiology.
What is positive and negative tropic?
growth towards and away from the stimulus.
What is a non-directional response?
Nastic response
What are the plant hormones?
Abscisic acid Cytokines Ethene Gibberellins Auxins
What does Abscisic acid do?
Inhibit seed germination and growth
stomatal closure due to low water availability.
Auxins function
promote cell elongation inhibit side shoot growth prevent abscission ( leaf fall)
Gibberellins
promote seed germination and growth of stem
Function of ethene
fruit ripening
Cytokinins function
Overrides Apical Dominance
Promote cell division + expansion
Delay senescence ( leaf aging)
what is apical dominance?
Inhibition of lateral bud growth further down the shoot.
What is the evidence for auxin’s role in apical dominance?
Auxin transporter inhibitor applied on plant, below apex
Lateral bud grew.
What is the role of auxin in controlling plant growth?
Normal levels = inhibit growth in LB
Low levels = promote growth in LB
but the auxin levels and growth may have no affect on each other but a third variable is affecting them.
Role of Abscisic acid in controlling plant growth
A growth inhibitor
High conc auxins in the shoot == High abscisic acid in LB
so remove auxins = low Abscisic acid in LB
=more growth
Role of Cytokinins in controlling plant growth
Promote bud growth and overides apical dominance
Auxins act as sink
so cytokinins are concentrated in tip
remove auxin (tip) = even distribution = plant grows evenly
Experimental evidence for gibberellin’s role in stem elongation
Test gibberellic acid on dwarf plants which grew taller, suggesting GA is involved in stem elongation
Which two experiments are important in investigating phototropism?
Boysen-Gensen and Darwin’s
