Spring.wmf (18300 bytes) Plant Physiology (Biology 327)  - Dr. Stephen G. Saupe;  College of St. Benedict/ St. John's University;  Biology Department; Collegeville, MN  56321; (320) 363 - 2782; (320) 363 - 3202, fax;    ssaupe@csbsju.edu

Diffusion from a "Standard Leaf"

    The following table reflects data for water loss from a leaf model that is 100 cm2.  These data were supplied by Dr. Paul Birnberg.

Pores cm-2

Total Pores per Leaf Model

Pore Diameter (μm)

Area of Single Pore (μm2)

Total Pore area (mm2) per leaf

Diffusion Rate (μg hr-1 cm-2)

Diffusion Total (μg h-1)

1,250

125,000

4

12.6

1.6

150

3.0

1,250

125,000

7

38.5

4.8

50

3.1

1,250

125,000

14

153.9

19.2

25

6.1

1,250

125,000

28

615.8

77.0

19

18.6

1,250

125,000

42

1385.4

173.2

17

37.5

1,250

125,000

84

5541.8

692.7

16

141.1

2,500

250,000

4

12.6

3.1

150

6.0

2,500

250,000

7

38.5

9.6

50

6.1

2,500

250,000

14

153.9

38.5

25

12.3

2,500

250,000

28

615.8

153.9

19

37.2

2,500

250,000

42

1385.4

346.4

17

75.0

2,500

250,000

84

5541.8

1385.4

16

282.2

5,000

500,000

4

12.6

6.3

150

12.0

5,000

500,000

7

38.5

19.2

50

12.3

5,000

500,000

14

153.9

77.0

25

24.5

5,000

500,000

28

615.8

307.9

19

74.5

5,000

500,000

42

1385.4

692.7

17

149.9

5,000

500,000

84

5541.8

2770.9

16

564.5

10,000

1,000,000

4

12.6

12.6

150

24.0

10,000

1,000,000

7

38.5

38.5

50

24.5

10,000

1,000,000

14

153.9

153.9

25

49.0

10,000

1,000,000

28

615.8

615.8

19

149.0

10,000

1,000,000

42

1385.4

1385.4

17

299.9

10,000

1,000,000

84

5541.8

5541.8

16

1129.0

Data Analysis:

  1. Plot total diffusion (μg h-1) vs. total pores per leaf
  2. Plot total diffusion (μg h-1) vs. total pore area (μm2) per leaf.
  3. Plot on a single graph:  total diffusion (μg h-1) vs. pore diameter (μm); and diffusion rate (μg hr-1 cm-2) vs. pore diameter (μm). 
  4. Plot on a single graph:  total diffusion (μg h-1) vs. pore frequency (pores cm-2); and diffusion rate (μg hr-1 cm-2) vs. pore frequency (pores cm-2)
  5. Explain how each of the following variables affects diffusion of water from the leaf models:  total pore number, pore diameter, pore area.
  6. Support the statement:  Stomata are the "right" size.
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Last updated:  01/07/2009     � Copyright  by SG Saupe