BIOL 191: Chapter 29
What does ethylene gas promote? How is ethylene related to fruit ripening?
-promotes leaf abscission, senescence (when a plant ends its lifespan); speeds ripening of fruit -Ethylene also causes an increase in its own production. Once fruit ripening begins, more and more ethylene forms (Ethylene gas is used to ripen stored fruit quickly.)
What are the effects of auxins on plant development?
Establishment of apical-base polarity of embryos Induction of vascular tissue differentiation
Which of the following are growth hormones of plants?
Ethylene Abscisic acid Brassinosteroids Cytokinins Auxins Gibberellins
When a plant pathogen induces systemic acquired resistance (SAR), the whole plant responds with a defense that is specifically tailored to that particular pathogen.
False
What are gibberellins what role do they play in plants? What are the 4 roles?
Gibberellins are hormones that have several roles in plant growth and development Stem elongation, Fruit growth, Flowering, Seed germination: they trigger hydrolysis of stored food molecule
Can Gibberellins make larger fruit?
Gibberellins are sprayed on seedless grapes in commercial crops to get larger fruit.
How are gravity and touch responses related?
Gravity and touch responses are related; if a root touches a rock or other barrier it will grow horizontally to get around the barrier then grow down again
How does gravity impact statoliths? How does this impact cause other impacts?
Gravity causes the relatively heavy statoliths to sink, which causes changes in calcium ion messengers->changes direction of auxin transport ->changes direction of shoot/root growth
How is gravity detected in plants?
Gravity is detected via starch-heavy plastids known as statoliths, located in specialized gravity-sensing cells called statocytes (cytes mean cell)
How does auxin affect plants throughout their lifetimes?
Mediates phototropism Stimulates fruit development Promotes formation of roots
Name the major components of the hypersensitive response in plants.
Nitric oxide Hydrogen peroxide
Auxin is transported out of cells by______ proteins.
PIN
Photoperiod is an external cue that iniitiates gene expression for flowering. Describe it.
Photoperiod (day length)—flowering only occurs when days reach a specific length
What is phototropism?
Phototropism ,growing towards a light source, is an example of a plant perceiving and responding to a stimulus
Identify all the ways that humans utilize the effects of auxin.
Plant cuttings are dipped in powdered auxin to stimulate root development. Auxin treatment is used to produce some types of seedless fruit.
How do buried seeds know if enough light is available to support seedling photosynthesis? How do plants know to flower at times of the year that are most beneficial for achieving pollination or seed dispersal?
Plants possess cellular systems for measuring light and determining the seasons of the year
Germination is stimulated by the conversion of:
Pr to Pfr.
Which of the following influence behavior in both plants and animals?
Temperature Hormones
Identify the true statements about the effects of gibberellins.
They enhance flowering. They enhance stem elongation. They foster seed germination.
In this diagram of plant cell signaling, the circle encloses:
a receptor.
Two hormones that protect against environmental stress are:
abscisic acid and brassinosteroids.
Photoreceptors are able to:
absorb light and switch on signal transduction pathways.
Both the hypersensitive response and systemic-acquired resistance:
are plant responses to pathogens.
The "master plant hormone" is often said to be_______ because it affects many aspects of plant structure, development, and behavior.
auxin
The plant hormone that has the greatest influence on plant structure, development, and behavior is:
auxin.
The response of plants to biological and environmental stimuli is called
behavior
Plants respond to _______that originate from inside or outside the plant body
biological and physical stimuli
Touch causes the release of________ ion messengers in plants.
calcium
When gravity causes statoliths to sink,________ ions act as messengers to affect the direction of auxin transport.
calcium
Auxin Blank______ proteins transport auxin into or out of cells. Multiple choice question.
carrier
The six major classes of plant hormones are auxins, abscisic acid, brassinosteroids, ________,_________, and________
cytokinins, gibberellins. ethylene
Plant hormones that are named for their major role in increasing cell division are:
cytokinins.
Flowering may be triggered by
environmental cues or aspart of predetermined development
A plant hormones that plays the major role in fruit ripening is:
ethylene.
Germination will not occur if a seed is treated with:
far-red light.
The plant hormone that enhances stem elongation, fosters seed germination, and retards fruit and leaf aging is called
gibberellins
The plant hormone that enhances stem elongation, fosters seed germination, and retards fruit and leaf aging is called_____
gibberellins
The upward growth of shoots and downward growth of roots in response to gravity are examples of
gravitropism
Gravitropism is defined as:
growth in response to gravity.
Plants are vulnerable to attack by _________(animals that consume plants) and ________(disease-causing microorganisms).
herbivores, pathogens
Attacking threats to plants include:
herbivores. pathogens.
The plant immune system is composed of receptor proteins, the_______ response, and the_________ _______ resistance.
hypersensitive, systemic acquired
The major role of cytokinins is to:
increase cell division
Plant behavior is influenced by:
internal and external signals.
Unlike the hypersensitive response, systemic-acquired resistance:
is a whole plant response.
A plant that flowers when nights are short is termed a(n) _________-day plant
long
A plant that flowers in spring when the night period is shorter than a certain length is a:
long-day plant.
Secondary metabolites deter herbivores by:
making plants taste bad.
Plants often protect themselves against herbivores using products of metabolism, including phenolics and alkaloids. These are examples of secondary
metabolites
The hypersensitive response to pathogen attack results from an interaction between:
nitric oxide and hydrogen peroxide.
When statoliths sink, auxin moves lower as well, which causes growth on the the lower side of a root to:
slow.
What are hormones? Why are hormones important for plants? What does auxin do?
-chemical signals that act at very low concentrations at sites often far from where they are produced -Each hormone plays multiple roles and interactions can be complex (Ex: Auxin primarily flows downward from leaf or shoot tip to root tip; Auxins inhibit lateral growth)
External cues include seed dormancy. What do dormant seeds mean?
-development of the embryo is stopped
Match each line of defense in plants with its major defensive feature(s.) Instructions 1st line of defense 2nd line of defense
-plasma membrane receptors -microRNAs and receptors in cytosol
Short-day plants flower when the......What seasons are do they flower in?
- the night is longer than a critical minimum (species specific) -Fall, Winter, or late summer flowers
How were Auxins (IAA) discovered? How does this relate to phototropism?
-Auxins (IAA) were discovered in the context of phototropism—response to light—stems bend toward a light source -Cells grow on the side far from light and stimulates them to elongate . In other words, a higher auxin concentration causes more rapid growth by cell expansion on the shaded side. The tip curves toward the light.
What are the major types of plant hormones?
-Auxins, -Cytokinins -Gibberellins -Ethylene -Absisic acid -Brassinosteroids pic for reference
What is cell communication? What does 3 stages does it typically involve?
-Cell communication is a process in which a cell perceives then responds to a signal (chemical or physical) -Cell communication typically involves 3 stages: receptor activation ,signal transduction which may use second messengers, and effectors that cause a cellular response
What 4 factors are involved in regulating plant growth and development?
-Environmental cues (e.g., day length) -Receptors to sense environmental cues(e.g., photoreceptors) -Hormones (chemical signals) - The plant's genome, which encodes regulatory proteins and enzymes
The effects of auxins includes....
-Establishing apical-basal polarity of seed embryos - Inducing vascular tissue differentiation -Promote: stem elongation, adventitious root initiation, fruit development - Inhibit: axillary bud outgrowth, leaf abscission, root elongation
What does ethylene influence? How does this happen?
-Ethylene influences cell expansion, often in combination with auxin -Ethylene stimulates cells to expand in all directions rather than elongating; ethylene increases the disorder of the microtubules
Why is ethylene important? When is ethylene gas produced?
-Ethylene is important in coordinating plant development and stress responses -Ethylene gas is produced during seedling growth, flower development, and fruit ripening
Where are statocytes located in shoots? An increase in auxins in shoots causes what? Where are statocytes located in roots? An increase in auxins in roots causes what?
-In Shoots, statocytes are located in the endodermis: -An increase in auxins stimulates cell elongation -In Roots, statocytes are located in the center of the root cap: -A increase in auxins inhibits cell elongation *Auxins can be binding to different receptors causing different processes to happen*
Plants lack specialized sense organs typical of animals. What is instead used to sense stimuli and cause responses? What happens when many cells receive and respond to a biological or physical stimuli?
-Plants lack specialized sense organs typical of animals, instead, receptor molecules located in plant cells sense stimuli and cause responses -When many cells receive and respond to a biological or physical stimuli, entire organs or plant bodies display behavior
What is the definition of behavior and how does this relate to plants?
-Plants, like all living things, respond to various types of stimuli, which is a definition of behavior
Auxins also have a role in growth. What is root initation? What is leaf abscission? Timing of leaf fall is determined by what?
-Root initiation: shoot cuttings of many species will develop roots if cut surface is dipped into an auxin solution -Leaf abscission (detachment of old leaves from the stem) is inhibited: Timing of leaf fall is determined by a decrease in the movement of auxin through the petiole
What are some examples of plant behavior?
-Shoot growth toward light -Root growth toward gravity -Seed germination -Seasonal flower production - Protective responses
What do cytokinins do? Where is cytokinins mainly produced? At shoot and root tips, how do cytokinins influence meristems? What do they promote that leads to increased branching? They are involved in the production of what?
-Stimulate cell division (increase rate of cytokinesis) -Mainly produced at root tips, transported to meristems -At shoot and root tips, influence meristem size, stem cell activity, and vascular tissue development -Promote development of axillary buds ,this can lead to increased branching -Involved in the production of flowers and seeds, and leaf aging
What are the auxins? What genes do they promote the expression of? What is an example of an auxin?
-a group of master hormones -Auxins promote the expression of diverse, auxin-responsive genes -IAA (indole-3-acetic acid)
1. When roots are vertical________settle onto the bottom ends of statocytes in the root cap. Auxin moves _______equally on all sides. Cells ______equally on all sides so the root grows______ 2. When roots are horizontal, statoliths settle to the _______of statocytes that now face ______. This causes auxin to be transported to the lower side of the root, _____cell elongation there. Cells on the upper side continue to elongate, causing the root to bend ______
-statoliths, upward, elongate, downward -sides, downward, inhibiting, downward
Describe the triple response that dicot seedlings have to ethylene.
1. Ethylene prevents the seedling stem and root from elongating 2. Ethylene induces the stem and root to swell radially, increasing in thickness 3. Ethylene changes auxin levels such that the stem bends, forming a hook that pushes up through the soil ⇒The embryonic leaves and meristem are protected
How do seeds maintain dormancy? (5 things)
1. Exclusion of water or O2 by an impermeable seed coat 2. Mechanical restraint of the embryo by a tough seed coat 3. Chemical inhibition of germination 4. Photodormancy - require light or dark periods 5. Thermodormancy - require exposure to specific temperatures
Place the steps in the cell signaling pathway in order, beginning with the first step at the top.
1. Receptor activation 2. Signal transduction 3. Cellular response
Name the two hormones that are most commonly involved in responses to environmental stress.
Abscisic acid Brassinosteroids
How does Abscisic acid (ABA) help plants cope with environmental stresses like flooding, drought, high salinity, cold, heat, attack by herbivores and microorganisms?
Abscisic acid (ABA) slows or stops plant metabolism when growing conditions are poor -It also induces bud and seed dormancy and prevents seed germination in unfavorable conditions -Water-stressed roots and leaves produce ABA, which helps limit water loss by inducing stomatal closure
Which of the following are examples of biological stimuli that cause plant behavioral responses?
Airborne pathogens Herbivores
What do auxin influx carriers do? What do auxin efflux carriers do?
Auxin influx carriers transport auxin into a cell; they are located at the apical ends of cells Auxin efflux carriers transport auxin out of a cell; they are located on the basal and lateral surfaces of cells
How do auxins play a role in gravitropism? What is negative gravitropism? Positive gravitropism?
Auxins also have a role in gravitropism. Negative gravitropism—upward growth of shoots (against gravity) Positive gravitropism—downward growth of roots (with gravity)
Identify the biological stimuli recognized by plants.
Beneficial microorganisms Viruses Fungal pathogens
How do Brassinosteroids help plants cope with environmental stresses like flooding, drought, high salinity, cold, heat, attack by herbivores and microorganisms?
Brassinosteroids induce vacuole water intake and influence enzymes that alter cell-wall carbohydrates, thereby fostering cell expansion -Occur in seeds, fruits, shoots, leaves, and flower buds of all types of plants; they are chemically related to animal steroid hormones -Impede leaf drop and stimulate xylem development
What are examples of physical stimuli recognized by plants?
Carbon dioxide Soil water Wind
Which of the following are functions of ethylene?
Control of number of cells in quiescent center of root tip Enhancement of fruit ripening Defense against plant pathogens
What response to dicot seedlings have to ethylene? How does this response help the meristems?
Dicot seedlings have a triple response to ethylene; this response avoids damage to delicate meristems as they grow through the soil
Directional transport of auxin is controlled by the distribution of______
Directional transport of auxin is controlled by the distribution of auxin carrier proteins located in the plasma membrane
Describe how gibberellins play a role in seed germination. Release of giberellins can also trigger what?
Step 1: Imbibation (taking up water) Step 2: Release gibberellins Step 3: Gibberellins induce aleurone to release digestive enzymes Uptake of water ⟹ release of gibberellins by seeds, this can also trigger growth of fruits
The process by which a plant measures day length is called
photoperiodism
Phytochromes play a critical roles in:
photoperiodism.
Molecules that are light sensors and play a role in photoperiodism are called:
photoreceptors.
Temperature, wind, gravity, and light are types of Blank______ stimuli that affect plant survival and reproduction.
physical
A critical role in photoperiodism is played by:
phytochrome.
Plant cells' first line of defense against pathogens consists of _________ _______receptors that specifically bind microbe-associated molecules. Their second line of defense includes receptors and microRNAs in the _______
plasma membrane, cytosol
Auxin is used by humans to:
retard premature fruit drop in orchards.
In plants, auxin is produced in:
shoot tips.
Auxin is produced in apical ________tips and young_______ .
shoot, leaves
A localized hypersensitive response can result in the production of long-distance signals, such as salicylic acid, that travel to noninfected regions of the plant and induce widespread resistance to diverse pathogens, a response known as _________acquired resistance.
systemic
Components of the plant immune system include:
systemic acquired resistance. receptor proteins. hypersensitive response.
The photoperiodic response in plants requires:
the presence of light receptors in membranes
Plant behavior is defined as:
the response of plants to internal or external stimuli
In plants, gravity responses are related to__________ responses. For example, when roots encounter rocks, they temporarily suspend their response to gravity. Such roots grow horizontally until they get around the barrier, whereupon downward growth in response to gravity resumes.
touch
Flowering represents a reallocation of energy from
vegetative growth to reproductive growth
