biology 12. plant transport systems forces acting on transport
TRANSCRIPT
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
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 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 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
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 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
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 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
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