Biology 2: Rest of test prep for test #2

what is Signal Transduction?

a process in which a cell converts and amplifies an extracellular signal into an intracellular signal that affects some function in the cell

what are the responses of signal transduction?

transcriptional or post-translational modification

what is transcriptional modification?

when DNA is transcribed into RNA

what is post-translational modification?

RNA into proteins

what is Etiolation?

when a plant tries to grow without light, it is pale, the stem elongates, leaf expansion is reduced

what is De-etiolation?

when the plant grows with access to light, and the plant becomes more green

what is a phytochrome?

a protein and light sensing molecule

what happens during reception

the phytochrome that has a protein senses light and is activated

what happens during transduction

the phytochrome activates the cGMP or the Ca2+ channel opening

what is the definition of a Hormone

a chemical produced by one part of the body and then is transported to another where it binds to a specific receptor on or in a target cell which then triggers a response

what is the conclusion of the Darwin and Darwin bending vs opaque and clear tip cap?

that the coleoptile is a sheath that on a young plant. At the tip of the plant is the sheath that causes the plant ot bend toward the light

what is the conclusion of the Boyson Jensen experiment with the permeable gelitin and the impermeable?

that its the chemicals at the tip of the plant that causes the bending throughout

what is the conclusion of the Went experiment

that the chemical Auxin which loosens cellulose and causes elongation on that side of the plant

what does Auxin do?

stimulates stem elongation at low concentrations

promotes growth of lateral and adventitious roots

regulates fruit development

enhances apical dominance

functions in phototropism and gravitropism

promotes vascular differentiation

retards leaf abscission

what does Cytokinins do

regulates cell division in roots and shoots

modify apical dominance

promotes lateral bud growth

promotes movement of nutrients

stimulates seed germination

delays leaf senescence

what do Gibberellins do?

stimulate stem elongation, pollen development, pollen tube growth, fruit growth, seed development/ germination

regulates sex determination and transition from juvenile to adult phases

What does Abscisic Acid do?

inhibits growth

promotes stomatal closure during drought

promotes seed dormancy

inhibits early germination

promotes leaf senescence

promotes desiccation tolerance

What does Ethylene do?

promotes ripening, leaf abscission, triple response in seedlings

enhances rate of senescence

promotes root and hair formation

promotes flowering in pineapples

What is the triple response in seedlings

stem thickens, stops growing upward, bends to the light, forms a curve

What do Brassinosteroids do?

promotes cell expansion and division in shoots

promotes root growth at low concentrations

inhibits root growth at high concentrations

promotes xylem differentiation

inhibits phloem differentiation

promotes seed germination and pollen tube elongation

What does Strigolactones do?

promotes seed germination, the control of apical dominance, and the attraction of mycorrhizal fungi to the root

what does signal transduction allow for?

the chemicals to work inside the cell

what is Photomorphogenesis? What is it regulated by?

the effect of light on plant growth and development

this is regulated chiefly by blue and red light

What what is phototropism? What is it affected by?

bending towards or away from light, light induced opening of the stomata, light induced slowing of hypocotyl elongation when seedling beaks ground

affected by blue light

what are red light photoreceptors called?

phytochromes

Phytochromes exist in what two interconvertable forms?

Pr and Pfr

these depend on the type of light

What does the Pr phytochromes do?

absorb red light and is converted to Pfr

What does the Pfr phytochromes do?

absorbs far red light and is converted to Pr

Which form (Pr or Pfr) triggers the developmental responses of plants to light?

Pfr

The biological clock controls what in plants?

circadian rhythmns

Definition of biological clock

the internal timer that approximates a 24 hr cycle

Definition of circadian rhythm

the internal physiological cycle of about 24 hrs that persists even in the absence of external cues

What are two examples of circadian rhythms in plants?

the opening and closing of stomata independent of light and darkness

sleep movement in shamrocks and beans

What entrains the biological clock to exactly 24 hrs?

light

How does light entrain the biological clock to exactly 24 hrs?

through photoreceptors (blue-light and red-light)

In red-light photoreceptors, the phytochrome conversion marks what?

sunrise and sunset, providing the biological clock with environmental cues

Definition of photoperioism?

physiological response to relative lengths of night and day

What does photoperiodism determine?

time of seed germination, onset and breaking down of bud dormancy, and time of flowering

a short day plant requires what to blossom?

a short day and a long night with no interruptions to blossom

which is more important for blossoming: short day or long night?

long night

For a long day plant, which is more important: a short night or long day?

a short night

In short day plants, the light period is… and when do they flower?

shorter than a critical length

flower in late summer/fall

In long-day plants the light period is… and when does it usually flower?

longer than a critical length

flowers in spring/ early summer

day-neutral plants are…

unaffected by the photoperiod

short day plant =

long day plant =

short day plant = long night plant

long day plant = short night plant

what is the effect of a brief dark period during the day?

nothing

what is the effect of a brief light period during the dark?

no blossoming, depending on the type of light (Pr or Pfr)

what does the P represent?

the phytochrome molecule

Pfr is ___ blooming

active

Pr is ___ blooming

inactive

With a single burst of Pr light during the night, what happens to the blooming?

the Pr is converted to Pfr and the plant recognizes it as a short night

With a burst of Pr then Pfr red light during the night, what happens to the blooming?

the Pfr is converted back to Pr, and the plant recognizes it as a long night

During a short day, will a long day plant grafted to a short day plant blossom? What flowering hormone is present?

yes, florigen

What is gravitropism? What are the types?

the response of a plant to gravity (positive and negative)

positive gravitropism

negative gravitropism

positive is roots down

negative is shoot up

What is thigmotropism?

mechanical stimuli, the response of a small plant to contact witht he touch of an object, animal, plant, or wind

ex. tendrils

What are environmental stresses on plants?

Drought → plants increase demand for water, release hormone, close stomata, grow deeper roots

Flooding → produce ethylene to create air tubes

Salt → lowers water potential and causes inability to absorb water

Heat → kills plant enzymes, heat proteins are produced to help protect the pant

Cold → alters the lipid concentration and produces unsaturated fatty acids to keep the plant from freezing