Ch. 39 A Flashcards
What is etiolation?
Morphological adaptations for growing in darkness
Etio
Cause
What is de-etiolation?
After exposure to light, a plant (ex. potato) will go changes and grow normally
phyto
plant
chrome
color
What causes receptor protein to change shape?
Response to stimulus
Ex. Phytochrome capable of detecting light which causes de-etiolation
What are second messangers?
Transfers and amplify signals from receptors to other proteins that cause responses
what are examples of secondary messangers?
Ex. calcium ions and cyclic GMP
What does the phytochrome receptor respond to and what does it do?
Respond to light and:
1) opens Ca channels, Increases Ca levels in cytosol
2) Activates an enzyme to produce cGMP
Phytochrome
Plant color
What reaction causes GMP to turn into Cyclic GMP
Dehydration Synthesis
kin
movement
Ase
Enzyme
What are kinases?
Enzymes that catalyze the transfer of a phosphate group from ATP to a specified molecule
Responses to stimulation that involve changes in activity of enzymes can occur by?
1) Transcriptional Regulation
2) Post-translational modification
What does Post-translational modification involve?
Modifications of existing proteins in the signal response
Common Modifications of Post-translational modification are
1) Phosphorylation of specific amino acids
2) Secondary messengers activate protein kinases directly
How do protein kinases often work?
Cascade linking initial stimuli to gene expression through phosphorylation of transcription factors
Phosphorylation
Activation, addition of phospate group
Dephosphorylation
inactivation, remove phosphate group
How does Transcriptional Regulation work
Specific transcription factors bind directly to specific regions of DNA and control transcription of specific genes
Are transcription factors activators or repressors?
They are both, they can increase or decrease transcription of a specific gene
De-etiolation activates enzymes that? (3)
1) Function in photosynthesis
2) Supply chemical precursors for chlorophyll production
3) Affect the levels of plant hormones that regulate growth
What are plant hormones?
Chemical signals that modify or control one or more specific physiological processes within a plant
Also known as plant growth regulators
Growth promoters (3)
1) Auxins
2) Cytokinins
3) Gibberellins
Growth inhibitors (2)
Ethylene
Abscissic Acid
Are plant hormones produced in high or low concentrations?
LOW
but has huge effect on growth and development
Each hormone:
multiple hormones:
Each hormones have multiple effects
Multiple hormones can influence a SINGLE process
plant responses depend on what _______ and _______ of hormones?
1) concentration of specific hormones
2) combination of present hormones
Extra hormones to know
Brassinosteroids
Jasmonates
Strigolactones
What is a tropism?
Any response resulting in curvature of organs toward or away from stimulus
Examples of tropism (3)
1) Phototropism
2) Thigmotropism
3) Gravitropism
What is auxin?
Any chemical that promotes elongation of coleoptlies
What is Indoleacetic acid?
Common auxin in plants also known as IAA
think in-dole-acetic acid
Is transport of auxin polar or nonpolar?
Polar
Produced in shoot tips and transported down stem
What are auxin transporter proteins?
Move hormone from basal end of one cell into the apical end of the neighboring cell
explain the effect of gravity on the direction of auxin
NO EFFECT
What is the role of auxin in cell elongation?
1) Auxin stimulates proton pumps in the plasma membrane (ACID GROWTH HYPOTHESIS)
2) Causes pH level to drop and increase membrane potential
What does reduced pH cause?
Activates expansins, enzyme that loosens fabric of the cell wall
What does osmotic of water into cell cause
Increased turgor pressure
What does cell wall plasticity and increased turgor pressure enable
Causes cell to elongate
Acid growth
Loosens cell wall which allows cell to passively elongate
What happens when reduced auxin flow is caused from the shoot?
Stimulates growth in lower branches
What is phyllotaxy
The arrangement of leaves on the stem
Auxin plays a role in this
What determines leaf venation pattern?
Polar transport of auxin from margins
What is controlled by auxin?
1) Activity of the vascular cambium (transport)
2) Organization of female angiosperm gametophytes (maybe)
Activity of the vascular cambium is controlled by what hormone?
auxin
Use of indolebutyric acid (IBA)?
1) Stimulates adventitious roots
2) Used in vegetative propagation of plants by cuttings
Use of synthetic auxins?
Used as herbicides such as 2,4-d (weed killer) kills eudicots by hormonal overdose
(monocots can inactivate the hormones)
What promotes fruit development
Auxin
Seeds produce auxin to make fruits
What are cytokinins?
hormone that stimulates cytokinesis
Where are cytokinins produced?
Growing tissues such as roots, embryos, and fruits
What do cytokinins control
Cell division and differentiation with the help of auxin
What is apical dominance?
The terminals bud’s ability to suppress development of axillary buds
What controls apical dominance? (4)
1) Sugar
2) cytokinins
3) auxin
4) strigolactone
What does removal of apical bud do? (3)
1) increases sugar availability
2) decreases auxin and strigolactone levels
3) initiates axillary bud growth
How does cytokinins slow aging of plant organs? (3)
1) inhibiting protein breakdown
2) stimulating RNA and protein synthesis
3) mobilizing nutrients from surrounding tissues
