Lecture 7 - development of plant architecture Flashcards
What are the 6 general principles ?
- plants develop their body plan post- embryonically
- plants have great developmental plasticity
- plants grow from meristems
- meristems produce plant parts sequenctially
- growth is often indeterminate
- cell fate assigned by position
What is meant by the developmental problem?
cells develop —-> coherent multicellular organisms
this occurs by genetics and environment together
what underlies the developmental problem?
differential gene regulation
What is differential gene regulation?
- gene expression that responds to signals or triggers
- a means of gene regulation, effects of certain hormones on protein biosynthesis.
are the principles for early development in animals and plants similar?
- yes
cell division - patterning and organogenesis - differentiation and growth
What is a crucial part of animal development , but not as important in plants?
- embryogenesis
in plants most development happens post embryogenesis. - animals are small but fully formed at the end of embryogenesis !
- plants continually make new organs as they grow - leaves , roots and flowers
n. b. plants dont move - so cant be sure where they will land and grow
what is the first general priniciple ?
plants develop their body plan post - embryonically
plants develop almost all of their bodies after embryogenesis
whereas animals emerge with a determined body plan/
What are the advantages to developing in situ ?
Animal development is largely buffered against environmental changes, and the embryo generates the same genetically determined body structure unaffected by external conditions
Disadvantages? – takes lots of energy to do this. Energy which could be used to fight off pathogens etc. Actively growing tissues are especially suseptible to attack because they have not yet laid down strong secondary cell walls.
will plants with the same genetics grow the same ?
Plants with same genetics might not grow the same if they are grown in different environment – in comparison to animals which will generally stay similar
What does Plastic mean?
Many aspects of plant development are altered in response to external conditions These traits are considered PLASTIC
Plant growth is said to be plastic !
What is the second general principle ?
plants have a great developmental plasticity
a genotype could be influenced by infection , stress, signals which could result in different phenotypes.
Plasticity itself is genetically determined and specific to species , trait and environmental cue.
plasticity is itself strongly controlled by genotype. Plastic responses are not random – they are specific for the character and for the environmental stress/cue and they have specific adaptive or maladaptive value
What does it mean to be canalised?
plant form is not 100 % dependent on the environment - many traits are canalised
Canalisation (or canalization) is a measure of the ability of a population to produce the same phenotype regardless of variability of its environment or genotype. In other words, it means robustness.
genotype - infection, stress , signals – phenotype ( canalised.)
canalisation reflects developmental robustness
How do seedlings emerge?
- embryonic stem ( hypocatyl) embryonic root ( apical/ basal and radial axes)
- embryonic leaves ( cotyledons )
- shoot and root tips
n.b all aerial growth in arabidopsis derives from about 35 cells at the shoot tip
What is the third general principle?
plants grow from meristems
- shoot and root tips each have a meristem
What are meristems ?
A central packet of dividing stem cells which fuel the growing plant body
Stem cells are undifferentiated , and can differentiate into any different cell – they are totipotent,
Meristems are constantly dividing , to send some ccells out as well as some cells for continuing the development
