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Transpiration Flashcards

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1
Q

Why is transpiration a very useful process for plants?

A
  1. Creating suction force in the stem to enable the
    roots to absorb water and mineral nutrients
  2. For cooling the plant in hot weather
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2
Q

How much water is used up by the plant in photosynthesis and other activities?

A

2 %

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3
Q

What happens to 98% of the water absorbed by the roots?

A

It is almost lost to the atmosphere as water vapour as a result of transpiration

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4
Q

Define transpiration

A

Transpiration is the process of loss of water in the form of water vapour from the leaves and other aerial parts of the plant

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5
Q

State the requirements for the experiment demonstrating transpiration

A
  1. Two medium-sized well-watered potted plants

2. Two transparent polythene bags

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6
Q

State the setup for the experiment demonstrating transpiration

A

Cover the plant with a transparent polythene bag and tie its mouth around the base of the stem. Leave the plant in sunlight for an hour or two.

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7
Q

State the observations in the experimental setup of the experiment demonstration transpiration

A

Drops of water will soon appear on the inner side of the bag due to the saturation of water vapour given out by the leaves

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8
Q

Give the control setup for the experiment demonstrating transpiration

A

An empty polythene bag with its out mouth tied and kept in the sunlight

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9
Q

State the observations in the control setup of the experiment demonstration transpiration

A

No drops of water

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10
Q

What is the condition for water vapour condensing?

A

Only if the outside temperature is cool enough

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11
Q

How will the drops be confirmed as water in the experiment demonstration transpiration?

A

If tested with dry cobalt chloride paper, drops will be confirmed as water only if the blue paper turns pink

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12
Q

What is in the first bell jar in the 3BJE?

A

Take a small well-watered potted plant, preferably one with broad leaves. Enclose the pot completely within a polythene bag and tie the mouth of the bag firmly around the base of the stem. Now cover the entire plant under the bell jar

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13
Q

What is in the second bell jar in the 3BJE?

A

Arrange a small well-watered potted plant, preferably one with broad leaves. Enclose the pot completely within a polythene bag and tie the mouth of the bag firmly around the base of the stem. Now cover the entire plant under the bell jar and cover it with a bell jar exactly in the same manner as the first one, except that here you also keep a piece of dry cobalt chloride paper by the side of the plant inside the bell jar (B). The paper may be pinned to a wooden stick or to a strip of cork street

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14
Q

What is in the third bell jar in the 3BJE?

A

Take a third bell jar without the plant, but still containing a similar piece of cobalt chloride paper (C)

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15
Q

Why is a polythene bag tied around the base of the stem in experiments demonstrating transpiration?

A

To prevent the escape of water vapour from the soil in the pot

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16
Q

What is the use of cobalt chloride paper?

A

It is an indicator of moisture

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17
Q

How does cobalt chloride paper indicate the presence of moisture?

A

It is blue when dry, but pink when exposed to moisture

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18
Q

State the observation in the first bell jar in the 3BJE

A

The first bell jar would show water vapour condensing on its inner walls

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19
Q

State the observation in the second bell jar in the 3BJE

A

The second bell jar would show water vapor condensing on its inner walls and at the same time, the initially blue cobalt chloride paper in it would turn pink

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20
Q

State the observation in the third bell jar in the 3BJE

A

The blue colour of the cobalt chloride paper in the third bell jar does not change at all and there are no water drops on the jar’s inner walls either

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21
Q

What does the third bell jar in the 3BJE prove?

A

It is a control that proves that there was no moisture in the air due to transpiration as there was no plant in it

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22
Q

What is the benefit of the 3BJE?

A

There is a double visual proof of transpiration:

  1. condensation of water vapour into droplets
  2. change of colour in cobalt chloride paper
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23
Q

Name the methods to measure transpiration

A
  1. Weighing method

2. Potometer method

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24
Q

What is the basic programme of the weighing method?

A

A small lightweight potted plant can be weighed before and after the end of a certain period of time. The soil surface and the pot should be fully covered to prevent evaporation from surfaces other than the plant. The loss in weight by the plant during that time is due to the loss of water by transpiration

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25
Q

What is the improvement in the weighing method?

A

Using a glass bottle linked by a rubber tube to a graduated side tube, filled with water. The water level in the side tube falls to demonstrate the loss of water through transpiration from the leaves.

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26
Q

How can the volume of water loss be compared with the loss in weight in the improved weighing method?

A
  1. With the help of a weighing machine

2. By converting cc into grams (1 cc water weighs 1 g)

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27
Q

How is a test tube filled with water and a leafy shoot a weighing method?

A

Use a test tube filled with water and insert a leafy shoot (no roots) in it, pouring some oil on the surface. Place the test tube in a small beaker and weigh them together. Remove the intact test tube and keep it straight in the test tube stand for a few hours. Weigh it again by keeping it in the beaker. Any difference in weight will indicate loss of water by the shoot due to transpiration

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28
Q

Why is oil poured on the surface of the test tube in the weighing experiment?

A

To prevent loss of water from the test tube by evaporation

29
Q

Why is a leafy shoot without any roots taken in the weighing method with the tt?

A

So that there are no roots to actively absorb the water. Therefore, water loss through transpiration will be much less

30
Q

What is a potometer?

A

Potometer is a device that measures the rate of water intake by a plant and this water intake is almost equal to the water lost through transpiration

31
Q

Give the meaning of potometer

A

Poton: drink, meter: measure

32
Q

Name the potometers that help to measure the rate of water intake by a plant

A
  1. Farmer’s potometer

2. Ganong’s potometer

33
Q

What does Darwin’s potometer help to do?

A

To demonstrate the suction force created due to transpiration

34
Q

What does Garreau’s potometer demonstrate?

A

Unequal transpiration from the two surfaces of a dorsiventral leaf

35
Q

In Ganong’s potometer, what is the entire apparatus filled with? Why?

A

Filled with water so that no air spaces are left

36
Q

Where is the air bubble introduced in Ganong’s potometer?

A

It is introduced into the horizontal graduated capillary tube which is dipping into the beaker containing water

37
Q

How is the air bubble introduced in Ganong’s potometer?

A

By lifting the bent capillary tube above the coloured water so that air may be sucked in due to suction pull and is again dipped into the water

38
Q

How does the bubble in the capillary tube on Ganong’s potometer move along?

A

As transpiration proceeds, i.e., as the water is lost from the twig, a suction force is set up which pulls the water from the beaker and the bubble in the capillary tube moves along

39
Q

How fo we find out the volume of water lost in a given time in Ganong’s potometer?

A

Through the readings on the capillary tube

40
Q

How is the bubble brought back to its original position in Ganong’s potometer?

A

By releasing some more of water from the reservoir into the capillary tube by opening the stop cock

41
Q

What do potometers not measure?

A

The water lost during transpiration

42
Q

What do potometers actually measure?

A

The water uptake by the cut shoot

43
Q

Give the precautions in the use of potometer

A
  1. It should be made completely watertight.

2. The twig should be cut obliquely and under water

44
Q

Why should the twig in Ganong’s potometer be cut obliquely?

A

To allow larger surface of water intake

45
Q

Why should the twig in Ganong’s potometer be cut underwater?

A

To avoid suction of an air bubble into the twig which will stop the absorption of water into the xylem

46
Q

Name the limitations in the use of potometer

A
  1. Introducing the air bubble isn’t very easy
  2. The twig may not remain fully alive for a long time
  3. Any changes in the outside air temperature may affect the position of the air bubble in the capillary tube
47
Q

Name the three kinds of transpiration

A
  1. Stomatal transpiration
  2. Cuticular transpiration
  3. Lenticular transpiration
48
Q

What is stomatal transpiration?

A

From the leaves through the stomata

49
Q

What is cuticular transpiration?

A

Directly from the surface of the leaves and stems

50
Q

What is lenticular transpiration?

A

From the lenticels which are the minute openings on the surface of old woody stems

51
Q

Through what does the major part of transpiration occur?

A

Through stomata

52
Q

What are stomata?

A

Minute openings occurring in large numbers on the lower epidermis of leaves

53
Q

What is a stoma surrounded by?

A

Two bean shaped guard cells

54
Q

What is the state of the stomata during the day time?

A

The stomata are wide open during day time, primarily for the intake of CO2 for photosynthesis

55
Q

What is the no. of stomata?

A

1,000-10,000 per cm2

56
Q

What is the process of stomatal transpiration?

A

Water, after absorption by roots from the soil, rises up through the stem and reaches the tissues of the leaves through veins. A large number of spongy mesophyll cells in the leaves have their surfaces exposed to the intercellular spaces. These surfaces of the cell give out sone of the water as a thin film. The water from this film evaporates and the water vapour formed saturates the air in the intercellular spaces. The vapour then diffuses into the other connecting intercellular spaces and finally reaches the in stomatal space, from where it escapes through stomata

57
Q

What is mesophyll?

A

Parenchyma cells

58
Q

Which process results in the entire movement of water vapour from surface of cell to outside atmosphere?

A

Diffusion

59
Q

In what combination is stomata and guard cell used?

A

open stomata + turgid guard cell

closed stomata + flaccid guard cell

60
Q

Why do surfaces of spongy mesophyll cells give out some of the water as a thin film?

A

The cell sap in each cell exerts a turbot pressure on the cell wall. This pressure forces some water out of the cell wall into the air spaces between the cells

61
Q

The movement of water through a leaf

A

movement by osmosis in the palisade mesophyll

movement by evaporation from the mesophyll cells to sun stomatal space

62
Q

Probable pathway of water through leaf cells

A

Xylem vessel -> cells after losing water through diffusion through stomata -> draw water from xylem vessel -> most of this water travels along cell walls (imbibition) -> only a small quantity enters the cell by osmosis

63
Q

How much water can transpirational pull draw?

A

about 50 metres or so in tall trees

64
Q

More transpiration occurs from which side of what leaf?

A

More transpiration occurs from the lowest surface of a dicot leaf as its lower surface has more stomatal openings

65
Q

What is the upper and lower surface of a dicot leaf called?

A

upper surface -dorsal
lower surface - ventral
hence dorsiventral

66
Q

What are the precautions in the experiment to demonstrate the different magnitudes of transpiration from the two surfaces of a dicot leaf?

A
  1. seal with vaseline

2. dry cobalt chloride paper

67
Q

Give differences between isobilateral and dorsiventral leaf

A

Isobilateral -> parallel venetian, equal stomata on both sides, mesophyll is all spongy

Dorsiventral -> Reticulate venation, more stomata on lower side of the leaf, differentiated into palisade and spongy

68
Q

What is the opening and closing of guard cells regulated by?

A

The amount of water and solutes present in the guard cells

69
Q

What does diffusion through stomata fulfil the need of?

A

Fulfilling the need for photosynthesis as well as allowing transpiration

Biology (4 decks)

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