Phytochrome & Photoperiodism, and Genetic Engineering Flashcards
signal transduction how plants perceive enviormental factor (process)
E.g. Light, gravity, temperature
___
Phytochrome
_____
Affects hormone levels
____
Get a response
Phytochrome
preception of light
Phytochrome is not a
plant harmone
what color pigment that detects light quality
blue
Two stable forms of phytochrome:
Pr
Pfr
Pr
absorbs red light
Pfr
absorbs far light red
when either Pr or Pfr absorbs light it
it is converted to
the other form
Far-red light is light with wavelengths
700-800 nm
not visible becuase any number > 760 nm is not visible
inactive form
Pr
active form
Pfr
Pr are where
In dark grown plants In plants not under canopy
or shaded plants under In plants in Spring & Fall
canopy of leaves
*Leaves in canopy absorb red
light; far-red makes it to forest floor
Pfr are where
In plants not under canopy
or shaded plants under In plants in Spring & Fal
Pr and Far-red light: does what to plants that have them
1) Plants are etiolated (long and spindly)
2) Seed germination inhibited (in some species)
3) No flowering
Pfr and Red light does what to plants that have them
1.) promote normal growth (de-etiolation)
2) Germination of seeds promoted
3) flowering
Photoperiodism
Plant responses to day length
Photoperiodism in flowering short day plants
spring plants
Flower if day is shorter than 12-14 hours
spring
violet
strawberries
long night plants
fall plants
“Long night” plants need 10-12 hours of uninterrupted
darkness to flower
Aster
ragweed
mums
poinsettias
Short day plants
Aster
poisettias
straberries
ragween
mums
violets
Long day plants =
short night plants
Flower if days are longer than 12-14 hours
* “Short nights”: plants need <10-12 hours of darkness to
flower (or continuous light)
* E.g. spinach, potatoes, lettuce, wheat
Day-neutral plants=
= unaffected by photoperiod
* Often tropical
* E.g. carnations, garden beans, tomatoes, roses, cotton,
dandelions
Phytochrome
Germination and
Form of Seedlings
why do Some plants require red light to germinate
Red part of the spectrum converts Pr to Pfr,
unblocking the germination mechanism
At first emergence from soil, light changes
Pr to
Pfr in a seedling
– This reduces ethylene production,
straightening the seedling.
– Pfr inhibits elongation of stems
–Leads to de-etiolation.
de-etiolation.
is a series of physiological and biochemical changes a plant shoot undergoes in response to sunlight.
Transgenic plants
Produced by inserting
genes from virtually any organism into plants
Study of crown galls caused by Agrobacterium
tumfaciens has opened up the field of
plant
genetic engineering
Agrobacterium
tumfaciens
Soil dwelling bacterium
Causes Crown Gall Tumor:
1) wound
2) bacteria enter wound
3) tumor forms
Can grow crown gall cells in tissue culture after
removing the bacterium on a medium without auxins
and cytokinins.
-Normal cells require auxins and cytokinins for cells to
divide in tissue culture
* Crown gall tumors overproduce auxins and cytokinins
Agrobacterium tumefaciens inserts its
DNA (in form of
plasmids) into plant cell DNA
Plasmids are
Circles of DNA
Ti plasmid=
tumor inducing plasmid causes crown
gall, has genes for auxin and cytokinin synthesis
-Ti plasmid inserts into plant cell DNA which now
contains bacterial plasmid DNA
* Genetic transformation of plant cell DNA to now
overproduce auxins and cytokinins resulting in tumor
formation
Crown gall forms on
dicots not monocots
Agrobacterium tumefaciens are used as to do what
Agrobacterium tumefaciens used as a vector
for introducing foreign DNA into plant cells.
the agrobacteriums used as a vecto only works in
dicots not monocts
particle guns
Particle guns - Shoot DNA into plant tissue
– Tungsten or gold pellets coated with cloned gene
shot into plant cells.
– Process of how this works is a mystery.
Transgenic Plants
- Transgenic corn, soybean,
cotton, and canola varieties have
herbicide and insect resistance. - Golden rice has genes for beta
carotene synthesis (Vitamin A
precursor). - Ornamental varieties not seen in
nature have been engineered. - Moonshadow carnations have
a petunia gene for blue color.
Pros of transgenic plants
Farmers may use fewer and less noxious chemicals for crop
production if insect resistance genes have been inserted.
