Biology 408 Test 3 Flashcards

Front 1

What is a turgid plant cell?

Back 1

the cell has positive turgor pressure so the protoplasm presses against the cell wall ( like blowing up a balloon)

Front 2

What is a flaccid plant cell?

Back 2

water will leave the cells when placed in a salty solution; drooping without elasticity; wanting in stiffness

Front 3

What is a plasmolyzed plant cell?

Back 3

if placed in a highly salty solution, water will continue to leave the cell, and the protoplasm will shrink and will separate from the cell wall (on the verge of death); plant cells where the plasma membrane pulls away from the cell wall due to the loss of water through osmosis

Front 4

Define free energy in physiological terms.

Back 4

capacity to do work

Front 5

How are changes in water potential brought about?

Back 5

by changes in pressure potential and/or changes in solute potential

Front 6

What is the pressure potential in plant cells caused by?

Back 6

the effect of pressure exerted by the cell wall

Front 7

What is the pressure potential of most plants?

Back 7

equal to or greater than 0 (living cells do not have negative pressures); equals 0 if at atmospheric pressure (1 atm)

Front 8

What is the osmotic potential in plant cells caused by?

Back 8

the effect of solutes (does not matter which kind, just how many)

Front 9

What is the osmotic potential in plant cells equal to?

Back 9

equal to or less than 0; equals 0 if there are no solutes

Front 10

How is water lost by transpiration replaced?

Back 10

by absorption of soil water by roots

Front 11

Does removing bark of a tree affect transpiration?

Back 11

no

Front 12

When plant roots are exposed to soluble dyes, where does the dye travel?

Back 12

the dye travels through the plant only in the xylem

Front 13

What is water-saturated soil?

Back 13

all pores filled with water

Front 14

What is field capacity soil like?

Back 14

gravitational water removed; macropores are air-filled; micropores are water filled

Front 15

What is the permanent wilting point?

Back 15

Pores in the soil are air-filled; films of hygroscopic water exist (not available to roots); capillary water exists (available to roots)

Front 16

When does the permanent wilting point occur?

Back 16

when the water potential of the soil is less than or equal to the water potential of the root

Front 17

How are water/nutrients uptaken by the root?

Back 17

Tension, due to transpiration and a more negative water potential in the roots than the surrounding environment, draws water/nutrients into the root hairs, through a semipermeable membrane, allowing apoplastic/symplastic (through plasmodesmata) transport through the epidermis and cortex to the endodermis.

Front 18

What is the casparian strip?

Back 18

The Casparian strip retains water in the endodermis (because it contains suberin), forcing apoplastic transport through the cell membrane, controlling the chemicals entering the plant.

Front 19

What is the cohesion-tension theory?

Back 19

water transport in xylem

-Water at the top of a tree (or plant)
develops a large tension (a negative
hydrostatic pressure) that pulls water through the xylem.
• Requires cohesive properties of water to sustain large tensions in the xylem water column.

Front 20

The water within xylem vessels moves towards the top of a tree because of...

Back 20

transpiration

Front 21

In chloroplasts, chemiosmosis translocates protons from...

Back 21

the stroma to the thylakoid space

Front 22

Where do the enzymatic reactions of the Calvin cycle take place?

Back 22

thylakoid space

Front 23

Describe the mechanism of photoactive opening of stomata. What are the stimuli leading to photoactive
opening?

Back 23

Stimuli: Light and reduced CO2 inside the leaf.

Mechanism: light/reduced CO2 stimulate H+ transport out of guard cell => uptake of K+ by guard cells.

This results in an increase in osmotic potential of the guard cells => water potential lowers => water moves into guard cell => increase turgor pressure => opening stomate.

Front 24

In theory, a plant kept in total darkness could still manufacture glucose IF it were supplied with what
molecules?

Back 24

If the plant was supplied with the molecules needed for the Calvin Cycle, glucose could still be made. The plant would need: CO2 , ATP, and NADPH. Protons would also need to be placed in such a way for activation of Rubisco, that is normally done by the effects of the light reactions.

Front 25

Describe the differences in anatomy between a C3 and C4 leaf. What is the significance of these differences?

Back 25

Leaves of C3 plants have two distinct tissues— tightly packed palisade mesophyll cells and loosely arranged spongy mesophyll cells. The bundle sheath cells of C3 plants do not contain chloroplasts; hence no
photosynthesis. In a C4 plant, there is only one type of mesophyll cells: spongy mesophyll. These mesophyll cells are close to bundle sheath cells. The bundle sheath cells have chloroplasts and are photosynthetic. Plasmodesmata connect bundle sheath cells and mesophyll cells, allowing transfer of chemicals. Carboxylation reactions occur in the mesophyll cells, producing a 4-carbon acid. Since the mesophyll cells are physically close to the bundle sheath cells and because of the presence of plasmodesmata, this arrangement allows transport of the product of the carboxylation reaction to into the bundle sheath cells. Once in the bundle sheath cells, this 4-
carbon acid is decarboxylated, producing CO2. This pathway allows for high concentrations of CO2 within the bundle sheath cells, the site of the Calvin Cycle, and thus C4 plants do not photorespire. The remaining 3-C acid can easily be sent back to the mesophyll cell for the regeneration step via the plasmodesmata.

Front 26

Name 3 different environmental conditions where a C3 plant would be more productive than a C4 plant.
Explain why using physiological reasoning.

Back 26

(1) Lower temperatures. Since photorespiration in C3 plants is reduced under these conditions and C4 plants would be using more ATP than C3 plants, the C3 plant may be more productive.
(2) C4 plants require higher light conditions than C3 plants and may not be as competitive as C3 plants in areas of low irradiance.
(3) In conditions of high atmospheric CO2 concentrations (or low O2 concentrations), the rate of photorespiration in C3 plants is reduced and so C3 plants may show higher productivity.

Front 27

Xerophytes have stomata that are somewhat different from those of Mesophytes. Discuss these 2
modifications and why each of these modification benefits these Xerophytes using physiological reasoning.

Back 27

1. They have sunken stomata, less air movement and thus less water loss.
2. They have stomata on lower leaf surface only. The lower surface is cooler and more humid and thus
less water loss.

Front 28

Plants open stomates for...

Back 28

photosynthesis

Front 29

Plants close stomata for...

Back 29

water conservation

Front 30

How does k+ move into the guard cells?

Back 30

active transport

Front 31

How does a stomate open?

Back 31

Guard cell walls are unevenly thickened; increase turgor pressure causes cells to bow

Photoactive opening: Low CO2, light (stimulates K+ uptake by guard cells), or the internal clock (diurnal rythm) affect the stomata

Front 32

How does a stomata close?

Back 32

When K+ pumped out of guard cells, water follows osmotically

Hydroactive closing: water availability in roots and leaves affect the stomata

Front 33

How are stomata photoactively opened?

Back 33

activation of H+ -ATP-ase,
stimulates H+ transport out of guard cell => membrane polarization (-120 mV) => activation of K+ channels=> uptake of K+ by guard cells, accompanied by Cl-. (Sensitivity to blue is much higher than to red which is important for opening of stomata in the early morning)

3. Radiation can have indirect effect:
stimulate photosynthesis in mesophyll cells and thus decrease internal CO2 concentration.
4. Reduced CO2 => K+ uptake by guard cells. Result: More K+ in guard cells: osmotic potential lowers => water potential lowers => water moves into guard cell =>increase turgor pressure =>opening stomata (final result: more CO2 enters leaf)

Front 34

How are stomata hydroactively closed?

Back 34

• 1. Water loss => Abscisic Acid (ABA) production.
• 2. ABA moves into guard cells with water transport.
• 3. ABA stimulates K+ transport out of guard cells.
• 4. Loss of K+ => rise of osmotic potential => rise in water potential => water moves out => drop in turgor pressure =>stomata close (result: water conservation)

Front 35

What is the result of an increase in abscisic acid (aba) in plants?

Back 35

stomatal closure

Front 36

In water-stressed plants, an increase in abscisic acid (aba) is an early response to...

Back 36

a decrease in leaf water potential