lecture 10 Flashcards
what are elicitors?
distinctive molecules in pathogens that trigger plant defenses
what are Avr (arirulence) genes?
genes that code for elicitors
what are r (resistance) genes?
plant genes that confer resistance to specific pathogens
how to elicitors do what they do?
they bind with membrane receptor proteins encoded by R resistance genes (gene for gene)
what does the binding of elicitors do?
it sets in motion a signal transduction pathway leading to two main inducible responses
what are the two main inducible responses
local responses and systemic responses
what are the induced defenses
elicitors, avr genes, and r genes
what are examples of local responses (3 things)
- phytoalexins 2.pathogenesis 3.physical isolation
what are phytoalexins
antibiotics toxic to bacteria and fungi produced by dying cells surrounding infection
what are pathogenesis related proteins
some are enzymes that break down cell ways of pathogens
what is physical isolation in plants
infected regions die and plasmodesmata are plugged
what are examples of systemic responses (4 things)
- general increase in resistance of entire plant 2. salicylic acid 3. jasmonate 4.methyl salicylate
what does salicylic acid do
it initiates responses to pathogens that depend on living plant tissues and leads to systemic acquired resistance (SAR)
what does jasmonate do
it initiates responses to microorganisms that kill plant cells and feed on their remains as well as insects
what does methyl salicylate do
is volatile and can signal remote parts of plant or other species that attack
plant responses to environment cues that influence growth are regulated by
hormones and photoreceptors
what are plant hormones
chemical signals that act at very low concentrations at sites often far from where theyre produced
what are photoreceptors
pigments associated with proteins that absorb light
what is auxin
controls the direction and arrangement of apical growth, gravitropism, phototropism, and apical dominance, causes cells to elongate by cell wall acidification
what is negative gravitropism
the auxin travels to the bottom causing the shoot to grow UPWARDS
what is positive gravitropism
the auxin travels to the top side causing the shoot to grow DOWNWARDS
what is apical dominance
apical buds inhibit growth of axillary buds, the terminal bud produces auxin and prevents lateral buds from growing
what is ethylene gas
it promotes leaf abscission (falling) and senescence (part of plant die) and SPEES RIPENING OF FRUIT , presence of ethylene gas causes more ethylene gas to be made, and apical hook
what are phytochromes
photoreceptors that mediate effects of red and far red light
how can effects of red light be reverse
by exposure of far red light
how many isoforms does phytochromes exist in
2
the ratio of red and far red light determines what
seed germination, flowering, shoot development
what is the usual ratio of red light/far red light during day
1.2:1 having far red light predominate
what is the usual ratio of red light/far red light during the night
0.13:1 having red light predominate
how does phytochrome effect the plant
by stimulating gene transcription
what is a photoperiod
some plants only flower when days reach a specific length
what do long day plants like
they like short nights as they flower on long days (summer)
what do short day plants like
they like long nights and flower on short days (winter)
poinsettia are what time of photoperiod plant
short day plant
