Plant hormones Flashcards
Name the 3 ways in which cells can communicate
- direct contact; interaction of proteins on cell surface
- local signalling; secreting cell targets nearby cells
- long distance signalling; release of hormone into blood stream
Which form of cell communication only occurs in animals?
- long distance signalling
Name the 3 things that plant hormones are important for
- growth
- development and differentiation
- responses to environment
What are hormones?
- signal integrator which enable responses of teh plant to teh environment it is in
what is the range in which hormones can work?
10^4 - 10^9 M
What are the 2 things that plant growth requires?
cell division and cell elongation
Where does cell division take place?
in localised meristems
What are meristems?
the tip of the shoots and roots
Where does cell elongation occur?
away from meristems
Name the 3 main tissues in a plant
dermis
ground tissue
vascular tissues
What is the function of vascular tissue?
transports material root to shoot and vice versa
Name the 5 classic plant hormones
auxin cytokinin ethylene abscisic acid gibberellin
What is the function of coleoptile?
protects the developing leaves as they pushing out teh soil during germination
How was auxin discovered?
- by observing the growth of movement of coleoptiles
- impermeable barrier between tip and rest of shoot
- lack of response
- meaning movement of light activated chemical from tip to rest of plant (auxin)
How was phototropism discovered?
- grass seedling placed where light was incoming from one direction
- seedling grew towards light
- cells on illuminated side of coleoptile were shorter, elongated less than shaded side
Name the 4 plant Reponses involving auxin
- tropisms
- root branching
- apical dominance
- vascular differentiation
What is the difference between root hairs and lateral roots?
root hair = single celled extensions
lateral roots = multicellular structure
What is the role of auxin in root branching?
auxin induces root branching
What is apical dominance?
a condition in plants where the stem apex prevents the development of lateral branches near the apex
What is the name of the amino acid in which auxin is derived from?
tryptophan
What are cytokinins derived from?
adenine which is a component of both RNA and DNA
What is the role of cytokinins? (3)
- cell differentiation
- cell division
- in combination with auxins
Where are cytokinins made?
in actively growing tissues
How are cytokinins transported around the plant?
in teh xylem in aqueous solution
What does the combination of cytokinin and auxin allow?
shoot and root differentiation
Name 3 process cytokinins are involved in?
synthesis of RNA and proteins
inhibit protein breakdown
nutrient mobilisation related to growth
What is gibberllin?
An endogenous hormone
What are the 2 main roles of gibberellin?
=stem elongation
= germination
What is bolting?
elongation of a flowering stem
How does gibberellin cause cell elongation and growth?
they activate cell wall loosening enzymes
What is the endosperm?
a storage tissue which noursishes the embryo while its developing
What is teh role of absicic acid (ABA)?
inhibits germination and maintains seed dormancy
Why does ABA maintain seed dormancy?
so the seed will remain dormant until conditions for survival are more favourable
How does ABA prevent drought in the plant?
signal passes from the roots to teh shoot promoting stomatal closure
What is the role of gibberellin in germination?
- the embryo makes a lot of gibberellin
- causes the aleurone layer to secrete lots of digestive enzymes
- breaking down starch within endosperm
- embryo consumes these sugars to start to grow as endosperm gets smaller
What is the 2 processes that ethylene has a role in, in order to avoid leaf desiccation in winter?
leaf abscission and senescence
What is senescence?
it involves cell death and recycling of resources
Name the 2 hormones involved in germination
ABA and Gibberellin
Name the 2 hormones in stem elongation
Auxin and Gibberellin
Name the 2 hormones involved in plant cell division and differentiation
Cytokinin and auxin
