Download Feb 8

Friday
Present a plant stressor, what is known about it, and why
it might affect plant 2˚ compounds in an ~ 10 minute
presentation.
Alternative: present another good plant/stressor response
to study and why we should choose it over the ones
already chosen.
John Austin:
Tom Nawrocki:
Maria Chinikaylo: effect of
Jared Nicholoff:
atrazine herbicide on glutathione
in corn
David Pupaza: Fungal attack
Cassia Cole:
Kyle Schimmel:
Christina Gambino: predation
on caffeine coffee plant
Nathan Seabridge: sulfur
Andrew Hasuga: ozone
deprivation on onions
Kenneth Werkheiser:
Kelvin Mejia: High soil salinity Agrobacterium tumefaciens
Alexis Morgan: Sulfur
deprivation on garlic
Matt Yatison: UV radiation
Michael Yucha: Cold Stress
Catherin Morocho:
Atrazine? Cold?
Ozone? Smog? Heavy metals? Shaking?Nutrient deprivation?
Predation? Heat?
Bacteria? Nematodes?
Natural Products
>100,000 types; 3 main groups
1. >30,000 terpenoids: made from isoprene units
2. >12,000 Alkaloids: derived from amino acids: contain
N
3. >8,000 phenolics: contain phenol ring
Other natural products
~ 100 cyanogenic glycosides
• Release cyanide when plant is damaged
• Found in seeds of apricots, cherries, other fruits
Laetrile
Other natural products
> 100 glucosinolates: contain S and N
• Mainly found in Brassicaceae (crucifers)
• Made from modified amino acids bonded to glucose
• Function in defense
Other natural products
The genus Allium produces sulfoxides derived from
cysteine
When plants are damaged they are converted to pungent
volatiles
Seeds
Seeds are unique feature of plants
• Plant dispersal units
• Must survive unfavorable conditions until they reach
suitable place (and time) to start next generation
• Are dormant; dehydration is key
• Germinate when conditions are right
Seed Development
Maturation: cell division ± ceases, but cells still expand
• Activate new genes for making storage compounds
• Storage compounds are key for seedlings and crops
• Proteins, lipids & carbohydrates but vary widely
• Many 2˚ metabolites
Seed Development
Next prepare for desiccation as ABA made by embryo
(+endosperm) increases
• Make proteins & other molecules (eg trehalose) that
help tolerate desiccation
Next dehydrate (to 5% moisture content) and go dormant
Seed Development
Coat-imposed dormancy (maternal effect)
1. Preventing water uptake.
2. Mechanical constraint
3. Interference with gas exchange
4. Retaining inhibitors (ABA)
5. Inhibitor production (ABA)
Embryo dormancy (Zygotic effect)
Seed germination
Seeds remain dormant until sense appropriate conditions:
• Water
• Temperature: some seeds require vernalization =
prolonged cold spell
• Many require light: says photosynthesis is possible
• often small seeds with few reserves
Seed germination
Seeds remain dormant until sense appropriate conditions:
• Many require light: says that they will soon be able to
photosynthesize: often small seeds with few reserves
• Hormones can also trigger (or stop) germination
• ABA blocks it
• GA stimulates it
Seed germination
Seeds remain dormant until sense appropriate conditions:
• Many require light: says that they will soon be able to
photosynthesize: often small seeds with few reserves
• Hormones can also trigger (or stop) germination
• ABA blocks it
• GA stimulates it
Germination is a two step process
• Imbibition
Seed germination
Germination is a two step process
• Imbibition is purely physical: seed swells as it absorbs
water until testa pops.
• Even dead seeds do it.
Seed germination
Germination is a two step process
• Imbibition is purely physical: seed swells as it absorbs
water until testa pops.
• Even dead seeds do it.
• Seeds with endosperm pop testa first, then endosperm
Seed germination
Germination is a two step process
• Imbibition is purely physical: seed swells as it absorbs
water until testa pops.
• Even dead seeds do it.
• Seeds with endosperm pop testa first, then endosperm
• Separate processes: can pop testa but not endosperm
Seed germination
Germination is a two step process
• Imbibition is purely physical: seed swells as it absorbs
water until testa pops.
• Even dead seeds do it.
• Seeds with endosperm pop testa first, then endosperm
• Separate processes: can pop testa but not endosperm
• Testa and endosperm have different genotypes!
Seed germination
Germination is a two step process
• Imbibition is purely physical: seed swells as it absorbs
water until testa pops. Even dead seeds do it.
• Seeds with endosperm pop testa first, then endosperm
• Next embryo must start metabolism and cell elongation
Seed germination
Germination is a two step process
• Imbibition is purely physical: seed swells as it absorbs
water until testa pops. Even dead seeds do it.
• Next embryo must start metabolism and cell elongation
• This part is sensitive to the environment, esp T & pO2
Seed germination
Germination is a two step process
• Next embryo must start metabolism and cell elongation
• This part is sensitive to the environment, esp T & pO2
• Hormones also play a complex role
Seed germination
Germination is a two step process
• Next embryo must start metabolism and cell elongation
• This part is sensitive to the environment, esp T & pO2
• Hormones also play a complex role
• GA, Ethylene and BR all stimulate
Seed germination
Germination is a two step process
• Next embryo must start metabolism and cell elongation
• This part is sensitive to the environment, esp T & pO2
• Hormones also play a complex role
• GA, Ethylene and BR all stimulate
• ABA blocks
Seed germination
Germination is a two step process
• Next embryo must start metabolism and cell elongation
• This part is sensitive to the environment, esp T & pO2
• Once radicle has emerged, vegetative growth begins
Vegetative growth
Once radicle has emerged, vegetative growth begins
• Juvenile plants in light undergo photomorphogenesis
Vegetative growth
Once radicle has emerged, vegetative growth begins
• Juvenile plants in light undergo photomorphogenesis
• Juvenile plants in dark undergo skotomorphogenesis
• Seek light: elongate hypocotyl, don’t unfold
cotyledons
Vegetative growth
Once radicle has emerged, vegetative growth begins
• Juvenile plants in light undergo photomorphogenesis
• Expand cotyledons, start making leaves &
photosynthetic apparatus
Vegetative growth
Once radicle has emerged, vegetative growth begins
• Juvenile plants in light undergo photomorphogenesis
• Expand cotyledons, start making leaves &
photosynthetic apparatus
• Initially live off reserves, but soon do net photosynthesis
Vegetative growth
Once radicle has emerged, vegetative growth begins
• Initially live off reserves, but soon do net photosynthesis
• Add new leaves @ SAM in response
to auxin gradients
• Add new branches from axillary
buds lower down stem if apical
dominance wanes
Vegetative growth
Once radicle has emerged, vegetative growth begins
• Add new leaves @ SAM in response to auxin gradients
• Add new branches from axillary
buds lower down stem if apical
dominance wanes
• Roots grow down seeking
water & nutrients
Vegetative growth
Once radicle has emerged, vegetative growth begins
• Add new leaves @ SAM in response to auxin gradients
• Roots grow down seeking water & nutrients
• 1˚ (taproot) anchors plant
• 2˚ roots absorb nutrients
Vegetative growth
Once radicle has emerged, vegetative growth begins
• Add new leaves @ SAM in response to auxin gradients
• Roots grow down seeking water & nutrients
• 1˚ (taproot) anchors plant
• 2˚ roots absorb nutrients
• Continue to add cells
by divisions @ RAM
Vegetative growth
Roots grow down seeking water & nutrients
• Continue to add cells by divisions @ RAM
• Form lateral roots in maturation zone in response to
nutrients & auxin/cytokinin
reproductive phase
Eventually switch to reproductive phase & start flowering
• Are now adults!
reproductive phase
Eventually switch to reproductive phase & start flowering
•Are now adults!
•Triggered by FT protein: moves from leaves to shoot apex
in phloem to induce flowering!
Transition to Flowering
Adults are competent to flower, but need correct signals
Very complex process!
Can be affected by:
• Daylength
• T (esp Cold)
• Water stress
• Nutrition
• Hormones
• Age
reproductive phase
• Are now adults!
• Very complex process!
• Time needed varies from days to years
reproductive phase
Eventually switch to reproductive phase & start flowering
• Are now adults!
• Time needed varies from days to years.
• Shoot apical meristem now starts making new organ:
flowers, with many new structures & cell types
Senescence
Shoot apical meristem now starts
making new organ: flowers,
with many new structures &
cell types
Eventually petals, etc senesce =
genetically programmed cell
death: controlled by specific
genes
Senescence
Eventually petals, etc senesce = genetically programmed
cell death: controlled by specific genes
Also seen in many other cases: deciduous leaves in fall,
annual plants, older trees
Senescence
Induce specific senescence-associated genes ; eg DNAses,
proteases, lipases
Also seen during xylem formation: when cell wall is
complete cell kills itself
Senescence
Also seen during xylem formation: when cell wall is
complete cell kills itself
Also seen as wound response: hypersensitive response
Cells surrounding the wound kill themselves
Senescence
Also seen during xylem formation: when cell wall is
complete cell kills itself
Also seen as wound response: hypersensitive response
Cells surrounding the wound kill themselves
Some mutants do this w/o wound -> is controlled by genes!
Light regulation of Plant Development
Plants use light as food and information
Use information to control development
Light regulation of Plant Development
Plants use light as food and information
Use information to control development
•germination
Light regulation of Plant Development
Plants use light as food and information
Use information to control development
•Germination
•Photomorphogenesis vs skotomorphogenesis
Light regulation of Plant Development
Plants use light as food and information
Use information to control development
•Germination
•Photomorphogenesis vs skotomorphogenesis
•Sun/shade & shade avoidance
Light regulation of Plant Development
•Germination
•Morphogenesis
•Sun/shade & shade avoidance
•Flowering
Light regulation of Plant Development
•Germination
•Morphogenesis
•Sun/shade & shade avoidance
•Flowering
•Senescence
Light regulation of growth
Plants sense
1. Light quantity
Light regulation of growth
Plants sense
1. Light quantity
2. Light quality (colors)
Light regulation of growth
Plants sense
1. Light quantity
2. Light quality (colors)
3. Light duration
Light regulation of growth
Plants sense
1. Light quantity
2. Light quality (colors)
3. Light duration
4. Direction it comes from
Light regulation of growth
Plants sense
1. Light quantity
2. Light quality (colors)
3. Light duration
4. Direction it comes from
Have photoreceptors
that sense specific
wavelengths
Light regulation of growth
Early work:
• Darwin showed that
phototropism is
controlled by blue light
Light regulation of Plant Development
Early work:
•Darwins : phototropism is controlled by blue light
•Duration = photoperiodism (Garner and Allard,1920)
Maryland Mammoth tobacco flowers in the S but not in N
Light regulation of Plant Development
Early work:
•Darwins : phototropism is controlled by blue light
•Duration = photoperiodism (Garner and Allard,1920)
Maryland Mammoth tobacco flowers in the S but not in N
= short-day plant (SDP)
Light regulation of Plant Development
Duration = photoperiodism (Garner and Allard,1920)
Maryland Mammoth tobacco flowers in the S but not in N
= short-day plant (SDP)
Measures night! 30" flashes during night stop flowers
Light regulation of growth
Duration = photoperiodism (Garner and Allard,1920)
Maryland Mammoth tobacco flowers in the S but not in N
= short-day plant (SDP)
Measures night! 30" flashes during night stop flowers
LDP plants such as Arabidopsis need long days to flower
Light regulation of growth
Duration = photoperiodism (Garner and Allard,1920)
Maryland Mammoth tobacco flowers in the S but not in N
= short-day plant (SDP)
Measures night! 30" flashes during night stop flowers
LDP plants such as Arabidopsis need long days to flower
SDP flower in fall, LDP flower in spring, neutral flower
when ready
Light regulation of growth
Measures night! 30" flashes during night stop flowers
LDP plants such as Arabidopsis need long days to flower
SDP flower in fall, LDP flower in spring, neutral flower
when ready
Next : color matters! Red light works best for flowering
Light regulation of growth
Next : color matters! Red light (666 nm)works best for
flowering & for germination of many seeds!
Phytochrome
Next : color matters! Red light (666 nm)works best for
flowering & for germination of many seeds!
But, Darwin showed blue works best for phototropism!
Phytochrome
Next : color matters! Red light (666 nm)works best for
flowering & for germination of many seeds!
But, Darwin showed blue works best for phototropism!
Different photoreceptor!
Phytochrome
But, Darwin showed blue works best for phototropism!
Different photoreceptor!
Red light (666 nm) promotes germination
Far red light (>700 nm) blocks germination
Phytochrome
But, Darwin showed blue works best for phototropism!
Different photoreceptor!
Red light (666 nm) promotes germination
Far red light (>700 nm) blocks germination