Botany Exam 4

What is morphinogenesis?

Generation of the shape of the plant and its various organs

What is differentiation?

Increase in complexity as cells become different from one another

What is a pattern establishment mechanism?

When the cells have to inform the cells around it of its location relative to the others

What help establish patterns of the cells and finally tissues?

Secretion, compression, and stretching

What environment do most organisms exist in?

Heterogenous

What do most plants exist in?

Several microenvironments that they cannot escape from

Why are intercommunication and coordination needed within a limited region of the plant body?

To withstand and have resistance to negative aspects of microenvironments and communicate to respond to them

What are the steps/levels of communication between plants and cells?

Perception, transduction, and asymmetric growth

What happens during the first step of plant-cell communication?

Organ receives greater stimulus on one side

What happens during the second step of plant-cell communication?

One or more hormones are unevenly distributed across organ

What happens during the last step of plant-cell communication?

Hormone gradient causes greater cell elongation on one side (asymmetric growth)

What is asymmetric growth a sign of?

Change in pattern for a plant/plant response

What is presentation time?

The length of time the stimulus must be present for the perceptive cells to react and complete transduction

What is threshold?

The level of stimulus that must be present during the presentation time to cause perception and transduction

What is the site of perception tentatively assumed (and typically is) the same as?

The site of transduction

When do all-or-none responses occur?

After the threshold and presentation time requirements are met

In dosage-dependent responses, what affects the level of response?

The amount or duration of the stimulus

What are hormones?

Organic chemicals produced in one part of a plant and transported to other parts, where they initiate a response

What do hormones help control?

Plant growth and development

How are hormones usually synthesized?

In one area and in very low concentrations

What is the exception to the fact that hormones are synthesized in one area and transported to another?

Ethylene gas

When do receptor molecules at the site of response, trigger a response?

When hormones bind to them

How do cells sense the hormone?

Receptors that are specific for that hormone, usually in the plasma membrane, that trigger a response for the hormones to bind to them

What do sensory systems and response mechanisms in plants tend to be like?

Simple

What is signal transport usually like?

Slow, involving movement through cortex parenchyma or phloem

What do tropic responses represent?

Growth oriented to a stimulus

What is positive tropism?

Growth toward the stimulus

What is negative tropism?

Growth away from the stimulus

What is plagiotropism?

Growth at an angle

What two types of information about the environment does light provide?

Direction/gradient of light and duration of light

What does direction or gradient of light do?

Allows the plant to orient leaves toward the source

What does duration of light (length of the day) provide?

Information about the time of the year

What respond to light with positive phototropism?

Shoot tips

What respond to light with negative phototropism?

Roots

How did Darwin observe phototropism>

Grew canary grass and fed it to his birds, noticed that it was very sensitive to light, and performed foil cover experiements

What did Went’s experience with coleoptile tips reveal?

Auxin is required for bending toward light, auxin is produced in the tip, and auxin promotes cell elongation

What is auxin important for?

Embryogenesis and asymmetric growth

Who discovered auxin?

Fritz Went

When exposed to light, what part of the stem tip receives extra auxin and grows more rapidly and bends toward the light?

Darker side of stem

What was Winslow Briggs’ experiment with maize coleoptile tips?

Put thin piece of glass down to tip of stem and measured the amount of auxin after light stimulation

What is the most effective wavelength for phototropism?

Blue

What are arabidopsis mutants lacking blue light response defective in?

Phototropin 1 or 2

What does blue light stimulate?

Chlorophyll production and stomatal opening at dawn

What kind of gravitropism do shoots show?

Negative

What kind of gravitropism do roots show?

Positive

What is shoot gravitropism correlated with?

Amyloplast sedimentation

What is the starch (bundle) sheath layer of coleoptile shoots like?

Contains cells with amyloplasts and surrounds vascular tissues

What do mutants with decreased amyloplasts show?

Agravitropic shoot growth

In positive gravitropism, what acts as the organ of perception?

The root cap

What happens after lower side of the root is detected by the root cap?

A growth inhibitor is transported to the lower side of the root then into the root, slowing growth on the lower side

What does high concentrations of auxin in the root do?

Inhibits primary growth

How does auxin affect shoots?

Increases growth

How does auxin affect roots?

In main — inhibits growth. In lateral and secondary — increases growth

What do roots sense gravity by?

Statocytes

What are statoliths?

Amyloplasts, which contain the starch granules

What are statocytes?

Cells that contain the amyloplasts in the root cap

What is the starch-statolith hypothesis of root gravitropism?

The statolith is the gravity sensor, amyloplasts act as statoliths, how movement results in differential growth is not known

What is the protoplast pressure hypothesis of root gravitropism?

The weight of the entire protoplast is the statolith, which influences the cell walls, growth, and elongation of certain cells

What is the tensegrity model of root gravitropism?

Tension between different structural components puts pressure on some of them to loosen and change; actin filaments are anchored on the plasma membrane, amyloplasts apply pressure on filaments, transient cytosolic Ca2+ increase, which results in differential growth

What is a PIN3?

A polar auxin transporter

Where does PIN3 transport auxin to?

The lower side of the root, through the cortex and to the elongation zone, which is the first region to respond

What can be used to “remove gravity” for a plant?

Clinostat

How does a clinostat work?

Motor rotates the plant in a horizontal position, removing the amyloplasts’ ability to settle and preventing auxin transport

What is thigmotropism?

Response to touch/contact with a solid object

What does thigmotropism allow?

Root navigation around rocks (negative), tendrils to wrap around structures (positive), and structures fusing together (positive)

Why do plants have such slow movements?

Varying growth rates in different parts

What experiment did Darwin do to discover nutations and spiraling stem movement?

Put carbon-covered paper on top of plant, then put a sliver of glass on the plant so that any time it moved it scraped the carbon

What plant family does nodding movements well?

Legumes

What does the legume family typically have in the hypocotyl?

A thickened crook/bend caused by ethylene production at germination

Where are most twining movements stimulated?

Internally

What are twining movements generally organized with?

Tendrils

How do some bulbs move deeper into the ground?

Contractile roots

How are contraction movements regulated?

Surface temperature fluctuations that cease and stop contracting as depth increases

What do nastic movements occur in response to?

Stimulus

What are nastic movements like?

Movement direction independent of stimulus origin, not based on growth, is affected by turgor pressure in the entire organ

What is turgor pressure?

How much liquid is in the cells; controls whether stomata open or close

What can nastic movements make plants look like and why?

Like they are moving because of one side of the organ growing a little faster than the other

What are examples of nastic movements?

Sleep and contact movements

What is a nastic response?

A non-growth response not oriented to the stimulus in any way

What is epinasty?

Downward bending of an organ

What usually does the turning in epinastic movements?

Leaf petiole

What hormones can be involved with epinasty movements?

Uneven auxin or ethylene flow

When do turgor movements occur?

When internal water pressure changes

What is turgor pressure often initiated by?

Contact with external objects

What cells are involved with turgor movements?

Parenchyma tissue in cortex or in special swellings (pulvini)

What allow turgor movement?

Pulvini structures

What are examples of turgor movement?

Bladderwort (electrical) and flower movements (stigmas close)

What are examples of turgor movement?

Barberry and moss rose flowers (snap inward suddenly)

What is nycanasty?

Leaves/petals fold in daily cycles, folding at dusk and unfolding in the morning in circadian rhythms

What are dinoflagellates?

Marine water algae

What are features of dinoflagellates?

Glow via bioluminsecence, chemical energy converted to light energy, 1 species grows brightly around midnight

When does giant bamboo produce huge flowering stalks?

Every 33 or 66 years; it uses all energy and kills the it, even after transplanting

What are heliotropisms?

Solar-tracking movements; sometimes no growth involved

What is an example of solar tracking?

Leaves twisting petioles to become perpendicularly oriented to light source

What do grass leaves have that helps with water conservation movements?

Bulliform cells

What are characteristics of bulliform cells?

Thin-walled, lose turgor when dehydrated, cause leaf to roll up or fold

What is taxis?

A response in which a cell swims toward (positive taxis) or away from (negative taxis) a stimulus

What is an example of chemotaxis?

Sperm cells swimming to egg cells by following a chemical gradient

What is an example of phototaxis?

In algae, sperm being allowed to swim toward light for photosynthesis or away from light that is too intense

What are examples of taxic movement?

Ferns (chemotaxic response in reproductive cells) and one-celled algae (phototaxic response)