Plant Phys Exam 3 review question | Quizlet

Which statement is true regarding cell wall polysaccharides?

-Cellulose is a (1🡪4)β-D-glucan chain (i.e., a glucose polymer) with many side branches

Which component of the primary cell wall contributes to most of the cell's structural rigidity?

-lignin

In the image representing a cell wall- what component of the walls would the prominent blue/black lines most likely represent?

-lignin

The fundamental chain of events in a signal transduction cascade is?

- signal --> receptor --> signal transduction --> response

Which statement is most FALSE regarding signal transduction cascades in plants?

-plant cascades are usually a series of positive activation steps

The expression "one bad apple ruins the batch" can be applied figuratively to a disruptive student in a lecture hall, but in literal, botanical terms, this expression refers to the action of:

-ethylene

The hormone most associated with cell expansion is:

-auxin

The hormone most associated with cell division is:

-cytokinins

During a response to a signal, the response is usually shutdown

-once the response threshold is reached

A secondary messenger in a signal transduction cascade

-transmit the signal from the receptor to the site of the response

5 processes that contribute to the pool of active hormones (activation side):

-increase

-biosynthesis

-activation

-release from internal stores

-uptake

5 processes that detract from the pool of active hormones (inactivation side):

-decrease

-degradation

-inactivation

-sequestration

-efflux/export

In several signaling pathways we looked at, ubiquitin played an important role. Describe a signaling pathway in plants that includes ubiquitin with sufficient detail to convince me you understand the mechanism

-The pathway is an AUX/IAA protein repressor that binds to the ARF. The ubiquitin is bound to AUX/IAA and degraded. Ubiquitin is a TAG protein that is a marker for degradation.

Photomorphogenic responses to far red light are mediated predominantly by

-phytochrome

Under which of the following conditions would the red:far-red ratio of ambient light be the lowest?

-on the forest floor, under the canopy of larger plants

Why do small seeds commonly need light exposure to germinate while larger seeds do not

-Small seeds do not have the same energy storage reserves as larger seeds. small-seeded plants need to perform photosynthesis early in seedling development or they will starve. They need to germinate in direct sunlight. The large-seeded plants can support seedling growth for a relatively long time without photosynthesis.

In the classical experiment of exposing lettuce seeds to short bursts of red and far red light in rapid succession, explain mechanistically why the germination response is photoreversible

-The seeds are being used to test whether or not the light environment is suitable for growth. A burst of red would cause germination. And a burst red light followed by a burst of far red light would not trigger germination. If red then far red then red again the seeds would germinate

What is cryptochrome and describe at least two biological responses in plants mediated to cryptochrome

-It is a flavoprotein that is heavily involved in blue light responses. Stem curvature and hypocotyl growth arrest.

One mechanism to activate / inactivate gene expression in response to light or other signal is to shuttle a transcription factor into or out of the nucleus. (T/F)

-True

During the embryogenesis in higher plants, the zygote undergoes an asymmetric division and the lower, larger cell then goes on to contribute most to the plant body. (T/F)

-False

During embryogenesis, cell fate is determined by:

-Cell lineage within the embryo

-Cell position within the embryo

-Hormone gradients in the embryo

-All of the above are correct

-B and C only are correct

-All of the above are correct

Cell to cell movement of macromolecules in developing tissue tends to become more restrictive as the tissues ages. This is because intercellular movement through ___________________________ becomes more restrictive.

-Plasmodesmata

The shoot apical meristem of a developing embryo

-Matures late (~late heart stage) in embryogenesis, at the site of an auxin maxima

An example of plant hormones have antagonistic interactions would be ______________ promoting embryo dormancy and ________________ promoting seed germination.

-Abscisic acid and gibberellic acid

When an embryo fails to enter dormancy and enters vegetative growth while still attached to the maternal plant, it is called

-vivipary

A common herbicide used to kill broad leaf weeds (dicots) but not lawns (grasses/monocots) is ________________________ and is an analog (mimic) of __________________________

2,4-dichlorophenoxyacetic acid ; indole acetic acid

Auxin transport from cell to cell is in part based on auxin existing as

• charge neutral in the apolast

• an anion in the cytoplasm

• polar distribution of efflux carriers

Beefsteak tomatoes derive from a proliferation of tissues leading to extra locules (the gooey compartments containing the seeds). This is called fasciation. Based on what you know about plant development, the strongest hypothesis for this fasciation would be

-WUSCHEL activity became uncoupled from control by CLAVATA3

Which statement is most true about seed dormancy and germination

-ABA promotes dormancy; GA promotes germination

If I wanted to make a thousand gallons of corn whiskey in a forested region several miles from the nearest paved road, what plant hormone should I include in my nefarious operation?

-gibberellic acid

Water impermeability, mechanical constraints, interference with gas exchange and retention of inhibitors are examples of

-seed-coat imposed dormancy

When the radicle emerges from the seed, how does it know which direction it should grow?

-The radicle responds to gravity and demonstrates gravitropism

Describe how auxin contributes to the direction of shoot growth in response to directional light - be sure to explain where the auxin levels are higher and lower in relation to that growth

-Auxin is the rooting hormone. The Auxin is stimulating root growth.

-Auxin is actively transported to the shaded side of the shoot.
-Higher auxin levels cause faster cell elongation on the shaded side.
-This differential growth leads the shoot to bend toward the light (positive phototropism).

Photorespiration refers to

-Recovery of reduced carbon after Rubisco oxygenation

The cost of performing 2 cycles of photorespiration is

-1 C (as CO2), 2 ATP, 2 NADPH equivalents

The cost of NOT performing 2 cycles of photorespiration is

-4 C in the form of 2 molecules of phosphoglycolate

As temperature increases, the quantum yield of photosynthesis in C3 plants is directly affected by

-The decreasing ratio of CO2 to O2 in the aqueous phase

In CAM plants and 'regular' C4 plants, the enzyme that first fixes CO2 into an organic molecule is

-Phosphoenolpyruvate carboxylase (PEPC) for both

In CAM (crassulacean acid metabolism) plants, when and where are sugars produced?

-During the day, in mesophyll cells

In 'regular' C4 plants, when and where are sugars produced?

-During the day, in bundle sheath cells

A plant that has Krantz anatomy likely conducts

-C4 metabolism

In photosynthesis research, what is the light compensation point?

-this is when the light is strong enough for photosynthesis to equal respiration

Leaves exposed to full sunlight absorb a lot of energy and need to dissipate heat effectively to prevent damage. Which of the following are used by leaves to dissipate excess heat energy?

-Radiative heat loss

-Sensible heat loss

-A and C only.

-Latent heat loss

-All of the above

-All of the above

If two plants of the same species are growing on the sunny side and the shady side of a building, the plant growing on the sunny side may have "sun leaves" that are broader and thinner than "shade leaves". (T/F)

-False

If there is no shortage of water available to a plant, what is the approximate conversion of light energy (i.e., sun light) into biomass assuming that light levels are near but not dramatically exceeding the light saturation intensity?

- ~5%

Which of the following enzymes is very important in determining the partitioning of glyceraldehyde-3-phosphate/dihydroxyacetone phosphate between starch synthesis and sucrose synthesis

-Triose-phosphate translocator

The accumulation of phosphorylated sugars in the cytoplasm will

-promote starch synthesis in the chloroplast

A tomato fruit growing on a vine will receive most of its nutrients and water from

-the mature leaves closest to it

What is true of phloem sieve tubes

-they are membrane lined

In order move a neutral solute, like sucrose (C12H22O11), from an area if low concentration, such as the cell wall space, to an area of high concentration, such as the cytoplasm of phloem cells, it needs to be transported by

-co-transport with a proton

Movement of water and the products of photosynthesis (sugars, etc) from source to sink is through

-the phloem by positive pressure

What structure allows phloem sap to flow from one sieve element to another sieve element along the sieve tubes?

-sieve-plate pores

Phloem transport is expected to remain fairly constant during diurnal cycles (day/night cycles) because

-Sucrose and starch are produced during the day, and starch is converted to sucrose at night

What is true of phloem companion cells (select all that apply, ½ pt for each correct, ½ pt deducted for each wrong)

-They have large central vacuoles like mesophyll cells

-They are closely associated with sieve elements

-They have a hollow central lumen to allow phloem sap to flow

-They are cytoplasmically dense

-They are dead at maturity

-they are closely associated with sieve elements

-they are cytoplasmically dense

At a roadside stop in Arkansas, adjacent to the men's room, I found a peculiar plant producing a fruit I had not seen before. Knowing that phloem transport would carry sugars from leaves into the fruits, and knowing that type of sugar present would provide information on the type of phloem loading employed, I collected a few fruits and analyzed them back in my research laboratory at UNT. From my analysis, I concluded that this plant used the polymer trap mechanism of symplastic phloem loading. What sugar did I find in high concentrations that led me to my conclusion?

-raffinose and stachyose

Classify the following as either a "source" tissue or a "sink" tissue (Note: this answer will be graded by the computer, so use the words "source" or "sink" only, without quotation marks, contact me if you think your answers were graded incorrectly and I will grade you answers manually).

-Cotyledon in a developing seed

-Cotyledon in a germinating seed

-Mature leaf

-Immature leaf

-Mature flower

-Immature flower

Cotyledon in a developing seed

-sink

Cotyledon in a germinating seed

-source

Mature leaf

-source

Immature leaf

-sink

Mature flower

-sink

Immature flower

-sink

Which of the following statements is true of receptors in a signal transduction cascade

-the receptor can be anywhere in the cell that the signal can reach

In a plant phosphor-relay system, which are thought to be derived from bacterial two-component signaling cascades,

-A phosphate is passed from a sensor histidine kinase to a histdine phosphotransfer protein (Hpt) and then to a response regulator (ARR)

Which statement is most FALSE regarding signal transduction cascades in plants

-Plant cascades are usually a series of positive activation steps

When auxin promotes cell wall expansion, it does so by:

-Enhancing ATPase activity to pump protons into the extracellular space

The expression "one bad apple ruins the bunch" can be applied figuratively to a student in a crowded lecture hall, but in literal, botanical terms, this expression refers to

-Ethylene

Which of the following plant hormones is best known for promoting cell division?

-cytokinin

If I want to extend the photosynthetic longevity of a leaf, and delay the onset of senescence, which of the following hormones should I spray on the foliage?

-cytokinin

Who among the following scientists is most closely associated with some of the earliest work on the hormone concept in plants?

-charles darwin

The "Green Revolution" was a series of agricultural advances through the 1950s and 1960s that included intensive use of fertilizer, irrigation, mechanization, and crop breeding to produce very productive cultivars. Many of these cultivars were bred for a stocky stature (shorter and sturdier) and were less susceptible to lodging (falling over and getting stuck in mud) and crop loss in inclement weather. Knowing that these crops were shorter than ancestral lines, what hormone-signaling pathway do you think was most repressed during selective breeding?

-gibberellic acid

Sugar (sucrose) is collected from the stem of sugarcane and increasing the height of the sugarcane plant increases yield. Based on this information, which plant hormone is commonly sprayed in plantations to increase yield?

-gibberellic acid

In plants, which of the following targets a component of a signal transduction cascade for degradation?

-an E3 ubiquitin ligase

Which colors in the visible spectrum have a strong influence of plant development and response to the environment? (Select all that apply)

-blue

-red

The shade avoidance response is controlled by phytochrome, and when a sun plant is shaded it will

-Elongate its stems to grow as a spindly plant with few branches until it finds quality sunlight

Which of the following is true of the phytochrome system

-Pr (the inactive form) is converted to Pfr (the active form) by red light

With respect to phytochrome activated responses in plants, very low fluence responses (VLFR) are not reversible by far red light because

-Pfr is never fully converted to Pr

Guard cells open stomata in response to light. The strongest stimulation to open is mediated by

-cryptochrome

Fill in the blank for the action or characteristic of phytochrome with either true or false (hint, three are true and three are false)

i. Phytochrome can shuttle between the cytoplasm and nucleus

ii. Phytochrome has kinase activity and can directly phosphorylate other proteins

iii. Phytochrome is needed for photosynthesis

iv. Phytochrome causes the response that Darwin observed in his experiments

v. Phytochrome helps plants detect the quality of light

vi. Phytochrome functions in the thylakoid membrane

i. Phytochrome can shuttle between the cytoplasm and nucleus

-true

ii. Phytochrome has kinase activity and can directly phosphorylate other proteins

-true

iii. Phytochrome is needed for photosynthesis

-false

iv. Phytochrome causes the response that Darwin observed in his experiments

-false

v. Phytochrome helps plants detect the quality of light

-true

vi. Phytochrome functions in the thylakoid membrane

-false