Biology 12. Plant transport systems Forces acting on transport.

Biology 12

Plant transport systems

Forces acting on transport

Forces in the leaves

• Transpiration – water lost from leaves

• Evapo-transpiration – water lost from leaves as water evaporates

• Transpiration stream – water is pulled up the stem as water is lost from the leaves in transpiration

Forces in the stems

• Adhesion – water molecules stick to the sides of the walls in the xylem

• Cohesion – water molecules stick to each other

• Capillarity/capillary action – water is drawn upwards through thin tubes

Forces in the roots

• Active transport – salts are actively absorbed, increasing the osmotic pressure within the roots

• Osmosis – water is pulled in due to the concentration gradients

Translocation

Movement of sugar

• Translocation – movement of sugar – sugar is actively transported from leaf to phloem (source) and from phloem to roots (sink), thus setting up a concentration gradient from leaf to roots

• Diffusion – sugar will diffuse downwards because of this concentration gradient

• Osmosis – water will be pulled out of the xylem near the leaves, and move downwards, then return to the xylem near the roots, due to the concentration gradient.

Plant transport systems

Roles of • Leaves – carry out photosynthesis and

transpiration• Stomata – allow water and gases to enter and

leave the leaf. Opening is controlled by guard cells

• Xylem – transports water and salts upwards• Phloem – transports sugars, mostly downward• Roots – draw in water and salts• Root hairs – increase surface area

Leaves and stomata 1

Leaves and stomata 2

• Leaves are responsible for photosynthesis and exchange of gases and water

• Gases and water enter and leave through the stomata

• Epidermis provides protection• Palisade cells carry out photosynthesis• The spongy mesophyll layer allows storage of air

and water vapour• Vascular bundles contain xylem and phloem for

the transport of water, salts and sugars

Control of stomal opening

Control of stomal opening 2

• Stomatal opening is controlled by turgor pressure in the guard cells

• This is controlled by pumping salts into the cells, thus bringing in more water (opening stoma) or pumping salts out of the cells, thus forcing water to leave (closing stoma)

• Turgor pressure increases when water availability is high

• Turgor pressure decreases when water availability is low

Structures in the stem

Xylem and phloemXylem Phloem

Cells living/dead Dead Living

Cell walls:

Thickness

Material

Permeability

Thick

Lignin

Impermeable

Thin

Cellulose

Permeable

Cross walls None Sieve plates

Cytoplasm None Yes

Function Carries water & salts Carries sugars

Direction of flow Upwards Down and up

Special features Fibres Companion cells

Roots and water transport

Image from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates and WH Freeman

Root hairs and water transport

Water moves in by osmosis• Osmotic pressure in root

hair cell is higher than in soil

• This can be maintained by active transport of salts into the root hairs

• Root hairs increase the surface area available

Measuring water loss• This can be done with a

device called a potometer• The rate of transpiration is

shown by movement of a bubble of air through the tubing

• Key features include – air tight seal between plant and tubing, narrow tubing, intact stem (cut under water so it will draw up water), air bubble, scale

Water loss in plants

Factors affecting water loss

• Temperature

• Humidity

• Air movement

• Water availability

• Light intensity

Decreasing water loss also decreases p

Water balance – freshwater fish

Problems:

Solutions:• Produces urine• Does not drink• Eats• Gills • Kidneys

Water balance – marine fish

Problems:

Solutions:• Produces urine• Constantly • Gills • Kidneys

Water loss in animals - rats

Which rat would need to drink more?What differences would you expect in their kidneys?

Kangaroo rat Lab rat

Input - barley 54 mL 54 mL

Output – urine

faeces

evaporation

13.5 mL

2.5 mL

44 mL

22 mL

13.6 mL

77 mL

Deficit

Arid

Name body (kg) RMT kidney (g) habitat RMT/body kidney/body

M niata 0.181 8.1 1.86 D 44.75 10.28

A cinererea 0.85 6.9 1.4 D 8.12 1.65

C lanigera 0.312 6.7 2.02 D 21.47 6.47

O glyroides 0.187 8.5 1.72 D 45.45 9.20

O degus 0.16 6.7 1.4 D 41.88 8.75

X inauris 0.4 14.1 2.2 D 35.25 5.50

D merriami 0.0367 8.5 0.4534 D 231.61 12.35

D microps 0.062 8.61 0.75 D 138.87 12.10

C penicillatus 0.0159 17.6 0.1886 D 1106.92 11.86

J jaculus 0.042 9.3 0.41 D 221.43 9.76

A olivaceus 0.017 8 0.22 D 470.59 12.94

Abrothrix andinus 0.022 7.6 0.18 D 345.45 8.18

A andinus 0.017 8.1 0.22 D 476.47 12.94

B lacteris 0.036 7.1 0.28 SD 197.22 7.78

A varius 0.033 7.5 0.18 SD 227.27 5.45

A berlepschii 0.018 7.8 0.32 D 433.33 17.78

A albiventer 0.023 7.3 0.32 SD 317.39 13.91

C callosus 0.016 6.8 0.24 SD 425.00 15.00

C musculinus 0.015 7.2 0.26 SD 480.00 17.33

E puerulus 0.018 8 0.18 D 444.44 10.00

E typus 0.016 7.8 0.18 SD 487.50 11.25

E hirtipes 0.017 9 0.18 D 529.41 10.59

E marica 0.017 7.5 0.24 SD 441.18 14.12

G griseoflavus 0.056 7.1 0.996 SD 126.79 17.79

G domorum 0.082 6.7 0.88 D 81.71 10.73

A edax 0.065 6.4 0.38 D 98.46 5.85

A sublimis 0.036 7.1 0.28 D 197.22 7.78

Averages 0.10 8.22 0.66 284.27 10.64

Rodents from arid regions

Wet

Name body (kg) RMT kidney (g) habitat RMT/body kidney/body

D leporina 2.6 3.9 15.39 M 1.50 5.92

A bennetti 0.197 7.1 1.12 M 36.04 5.69

O bridgesi 0.163 5.4 0.92 M 33.13 5.64

O lunatus 0.171 5.3 1.34 M 30.99 7.84

A fuscus 0.128 6.2 1.12 M 48.44 8.75

A sagei 0.128 5.9 0.68 M 46.09 5.31

S cyanus 0.099 6.2 0.5 M 62.63 5.05

F pennanti 0.0929 6.8 0.484 M 73.20 5.21

S beecheyi 0.468 7.07 2.36 M 15.11 5.04

C ludovicianus 0.972 5.96 2.76 M 6.13 2.84

C leucurus 1.11 6.17 3.72 M 5.56 3.35

N ebriosus 0.062 6.3 0.2 M 101.61 3.23

O longicauditas 0.029 6.8 0.2 M 234.48 6.90

A xanthorhinus 0.022 7.9 0.3 M 359.09 13.64

A longipilis 0.025 7.1 0.46 M 284.00 18.40

C macronyx 0.049 5.8 0.58 M 118.37 11.84

C lepidus 0.014 6.2 0.26 M 442.86 18.57

L pikumche 0.043 5.2 0.52 M 120.93 12.09

P leucopus 0.0268 7.28 0.117 M 271.64 4.37

M agretis 0.03 5.8 0.48 M 193.33 16

C cricetus 0.108 5.69 0.996 M 52.69 9.22

R norvegicus 0.17 6.5 1.78 M 38.24 10.47

M musculus 0.012 6.6 0.08 M 550 6.67

O angioniensis 0.1158 4.06 1.21 M 35.06 10.45

O irroratus 0.1723 3.39 1.76 M 19.67 10.21

O s robertsi 0.1023 4.3 0.96 M 42.03 9.38

0.27 5.96 1.55 123.95 8.54

Rodents from wet regions

Kidney adaptations- averages

Arid Wet

Relative Medullary Thickness (RMT)

8.22 5.96

Kidney mass (g) 0.66 1.55

Body mass (g) 0.01 0.27

RMT:body mass 284.27 123.95

Kidney:body mass 10.64 8.54

General trends – animals from arid regions have comparatively larger kidneys, with thicker medullas than those from wetter areas – this allows these animals to reabsorb more water

Kidney adaptations 2RMT: body mass (arid)

0

5

10

15

20

0 0.2 0.4 0.6 0.8 1

body mass kg

RM

T

RMT

kidney mass : body mass (arid)

0

0.5

1

1.5

2

2.5

0 0.2 0.4 0.6 0.8 1

body mass kg

kid

ney

mas

s g

kidney (g)

RMT: body (wet)

0

2

4

6

8

10

0 0.5 1 1.5 2 2.5 3

body mass kg

RM

T

RMT

kidney mass : body mass (wet)

02468

1012141618

0 0.5 1 1.5 2 2.5 3

body mass kg

kid

ney

mas

s g

kidney (g)

General trends – animals from arid regions have comparatively larger kidneys, with thicker medullas than those from wetter areas – this allows these animals to reabsorb more water

Multiple choice questions

1. Which of the following is an inference?(a) Commercial timber produced from older trees is denser than timber

from young trees of the same species.(b) The outer layer of sapwood of a tree is often a different colour from

the inside of the trunk.(c) Areas of forest that currently produce the best timber will remain

the best areas for future timber production.(d) The timber of some species of tree is unsuitable for commercial

use.

2. A bird in a cold environment can reduce heat loss by which of the following processes?

(a) Panting(b) Flying vigorously(c) Increasing its metabolic rate(d) Erecting its feathers

Multiple choice questions 2

3. Which statement about photosynthesis is correct?(a) The rates of photosynthesis and respiration are equal at all times in

plants.(b) The overall chemical change in photosynthesis is the opposite of

aerobic respiration.(c) The part of the photosynthesis reaction that does not involve oxygen

occurs in the cytoplasm.(d) Photosynthesis occurs in the mitochondria.

4. Which of the following statements about enzymes is most correct?(a) Enzymes are usually specific for a particular substrate.(b) Enzymes are used up in the chemical reactions they catalyse.(c) Enzymes usually catalyse many different chemical reactions.(d) Enzymes decrease and increase the rates of chemical reactions.

Multiple choice questions 35. You have a freshwater aquarium at home and have just

purchased a new fish. To your dismay, the fish dies within a day of placing it in your tank. You later discover that it was a marine fish. Select the best explanation of the fish's death.

(a) The fish gained too many salts by active transport across its gills.(b) The fish produced too much urine.(c) The fish gained too much water through its body surface.(d) The fish drank too much fresh water.

6. Which of the following statements about the way endothermic animals regulate their body temperature is NOT correct?

(a) The metabolic rate decreases during periods of inactivity.(b) The metabolic rate decreases in warm conditions.(c) The metabolic rate increases in cool conditions.(d) The metabolic rate increases during periods of activity

Biology 12. Plant transport systems Forces acting on transport.

Documents

Transcript of Biology 12. Plant transport systems Forces acting on transport.