Chapter 26 Plant Growth and Development Flashcards
What characteristics differentiate plants from animals?
meristems - permanent collections of stemc ells that allow growth through their lifetime
Postembryonic organ formation
Differential growth
What is differentail growth?
When resources are allocated for beneficial growth patterns - e.g. more leaves
What factors are involves in plant growth regulation?
environmental cues
Receptors to sense environmental cues
Hormones
Plant’s genome
How do seeds maintain dormancy?
- Exclusion of water or O2 by impermeable seed coat
- Mechanical restraint of embryo with tough seed coat
- Chemical inhibition of germination
What is photodormancy
When seeds require a period of light or dark to germinate
What is thermodormacy
When plants require a period of high or low temperature to germinate
What are the advantages of dormancy?
- Survival through poor conditions
- results in germination in good conditions
- Helps seed survive long distance dispersal - allowing plants to colonize new territory
What are some means for breaking seed dormancy?
- Passage through an animal’s digestive tract can damage seed coat
- Burial in soil
- Germination inhibitors may be washed away in rain
Define germination
Seed begins to grow or sprout
What is imbibition?
seeds take up water if seed coat is permeable
- FIRST step in germination
- Leads to enzyme activation, RNA and protein synthesis, increase in cellular respiration and metabolic pathways start
Where does the embryo get its food from?
From cotyledons or endosperm
When is germination complete?
when radicle (embryo root) emerges
At that point becomes a seedling
How are monocots and eudicots different regarding early shoot development?
Monocots - growing shoot protected by sheath of cells (Coleoptile)
Eudicots - growing shoot protected by cotyledons
What are photoreceptors?
proteins associated with pigments that absorb light
Why is Arabidopsis important?
model organism for understanding signal transduction
What is a genetic screen?
A large group of mutated plants that are created by mutagens or insertion of transposons
What were the first plant hormones identified?
Gibberellins
Auxin
What does the absence of gibberellins and auxin cause?
dwarfism
What are the actions of gibberellins?
Role in:
- stem elongation
- Fruit growth
- Seed germination (trigger hydrolysis of stored food molecules)
How are gibberellins used for agriculture?
sprayed on seedless grapes to get larger fruit
What was auxin discovered in the context of?
phototropism - response to light - where stems bend towards light source
What are the 4 processes that cause polar transport?
- Diffusion of auxin across cell membrane
- Membrane protein asymetry - carrier proteins for auxin are located only in basal end of cell
- Proton pump moves H out of cell = chemiosmotic gradient to drive transport of auxin
- Ionization of a weak acid (Auxin)
What determines the direction of growth from auxin?
pH and location of auxin efflux carriers
Stem elongates on side opposite to auxin
Which hormone has a role in gravitropism?
Auxin
