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Applied Grapevine Ecophysiology > Photosynthesis & Respiration / Xylem & Phloem > Flashcards

Photosynthesis & Respiration / Xylem & Phloem Flashcards

1
Q

For photosynthesis, CO2 must move from the atmosphere to the leaf interior. This happens by way of diffusion through the

A

Stomata

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2
Q

The diffusion path for CO2 is almost entirely through the stomata, whereas the path for water vapour involves

A

Both Stomata and cuticle

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3
Q

Between C02 and H20 which meets more points of resistance and why?

A

C02 because it must cross additional cell walls and membranes before it can be assimilated in the chloroplast.

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4
Q

The concentration gradient of CO2 from the outside air to the leaf’s interior is

A

Very small

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5
Q

the gradient for H2O diffusion out of the leaf is…

A

More than 40 times steeper than that for CO2 diffusion into the leaf.

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6
Q

Leaves develop fewer stomates when they…

A

Unfold under elevated atmospheric CO2 concentrations.

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7
Q

The stomata opening is akin to what?

Describe the process of the entry of CO2 and the exit water vapor from the stomates

A

A sliding door.

CO2 wants to enter and water vapor wants to exit through the same door. Only one molecule can go through, so there is a type of competition between the two and CO2 has a disadvantage because the Chloroplast is the final stopping point for CO2, CO2 meets more points of resistance than water vapor.

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8
Q

What is the difference in diffusion from CO2 and H2O?

A

Because water molecules are smaller they diffuse 1.6 times faster than CO2

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9
Q

In terms of Carbon uptake and assimilation what is the equation that we can use to calculate net photosynthesis, explain the vairables

A

A = (ΔC) x gl

A: Net photosynthesis
∆C: (Ca - Ci) carbon in and carbon out
gl: combined gas conductances of the boundary layer (gb) and the stomata (gs)

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10
Q

The combined gas conductances of the boundary layer (gb) and the stomata (gs), increases with…

A

stomatal aperture

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11
Q

On cloudy days or days with almost 100% humidity the boundary layer is…

With low humidity it…

A

Increases

Decreases

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12
Q

Combining glucose and fuctose gives the disaccharide…

A

Sucrose

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13
Q

What is Hexose?

A

Hexose is a sugar molecule (glucose and fructose n=6) i.e. it has 6 carbon atoms. It is produced directly in the chloroplast or cytosol

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14
Q

Difference between Hexose and Sucrose

A

Hexose has 6 carbon atoms, while sucrose has 12. Sucrose is formed when glucose and sucrose are combined.

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15
Q

Sucrose is the predominant organic compound transported in the…

A

Phloem

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16
Q

What is starch?

A

A long chain of sucrose. They are dependent on the nature of bonding between glucose molecules.

17
Q

What is a linear chain of starch called?

A

Amylose

18
Q

What is a branched chain of starch called?

A

Amylopectine

19
Q

When does the Calvin cycle feeds carbon into starch production

A

When the export of sucrose from the cell cannot keep pace with photosynthesis.

20
Q

Discuss the feedback inhibition, what it is and what it does and what it prevents (3)

A
  1. The feedback inhibition (Pi) is when the sucrose that accumulates in the leaf cells slows its own formation
  2. It functions as a regulator. High Pi indicates a high rate of sucrose export and vice versa
  3. It prevents the leaf from exploding
21
Q

Starch also accumulates in leaves when a phloem of a shoot is either obstructed or injured. How can we identify this?

A

They turn red due to anthocyanins production, from surplus sugar.

22
Q

the starch pool is depleted by ______ and replenished by _____

A
  1. Sunrise
  2. Sunset
23
Q

Glucose molecules can also be linked together as linear glucans forming chain (polymers) of 2000-25,000 glucose units called…

A

Cellulose

24
Q

What forms the basic framework of the plant cell walls?

A

Cellulose (which has fibers with a tensil strength greater than that of steel.

25
Q

Net Photosynthesis is equal to…

A

Gross photosynthesis - photorespiration - Mitochondrial respiration

NP= GP - (pr + mr)

26
Q

What is Rubisco and discuss how it works…

A

Rubisco is the main photosynthetic enzyme. It can use either CO2 or O2, but we would rather it use CO2 because if it uses O2 it will produce CO2 (photorespiration)

27
Q

Discuss the role of temperature with photorespiration…

A

Because at higher temperature the soluability of CO2 decreases. Because the ratio of O2:CO2 is around 24:1 at 25 C. Higher temperatures will favor photorespiration.

28
Q

Approximately how many CO2 molecules entering the leaf is released back to the atmosphere.

A

One in five

29
Q

Photorespiration is initiated when RUBISCO acts as an ______ instead of a _______

A
  1. oxygenase
  2. carboxylase
30
Q

What does photorespiration compete with?

A

Photosynthesis

31
Q

The net rate of photosynthesis is higher in air with ….

A

Low oxygen levels

32
Q

What is the goal of respiration?

A

To produce ATP. It is also very important for producing carbon skeletons.

33
Q

What is the starting point for respiration?

A

Sucrose

34
Q

What are the three types of plant ground tissues and their abilities?

A
  1. PARENCHYMA (storage and photosynthesis, thin cell wall)
  2. COLLENCHYMA (flexible support, uneven cell wall)
  3. SCLERENCHYMA (Strength and support, thick cell wall)
35
Q

Xylem properties (5)

A
  1. Carries Water and dissolved nutrients
  2. UPWARD movement
  3. DEAD at maturity
  4. Has Vessel Elements: Pitted Cell Wall (Water Pipeline)
  5. Other tissue is tracheids (pitted)
36
Q

Phloem Properties (6)

A
  1. Carries products of photosynthesis
  2. UP AND DOWNWARD movement
  3. ALIVE at maturity
  4. Vessel is a SIEVE TUBE with perforated end walls
  5. Transports sugars
  6. Has Companion cells
37
Q

Role of Companion cells:

A

To swirl cytoplasm in order to push sugar up or down.

38
Q

Why is the flow of the xylem upwards?

A

The passive flow is upwards by the suction pressure created by water being evaporated from leaves.

39
Q

3 types of tissue in the phloem

A
  1. Sieve tube element
  2. Companion cells
  3. Sieve plates

Applied Grapevine Ecophysiology (19 decks)

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