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New Senior Secondary Mastering Biology Oxford University Press 2014 (Second Edition)
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9 Nutrition and gas exchange in plants
9.1 Nutrition in plants (Book 1B, p. 9-3)
A Plants as autotrophs (Book 1B, p. 9-3)
� Plants can make their own food (in the form of (1) _______________) from
(2) _______________ _______________ and water using light energy through the process of
(3) _______________.
carbon dioxide + water carbohydrates + oxygen
light energy
chlorophyll
� The light energy is trapped by the (4) _______________ in plants. (5) _______________ is
released as a by-product (副產物).
� Plants absorb (6) _______________ (礦物質) from the soil. They are vital for the synthesis of
other materials needed by the plants.
oxygen
(into the air)
light
chlorophyll
photosynthesis
carbon dioxide (from air)
minerals (from soil)
water (from soil)
inte
rmed
iate
s
carbohydrates
lipids
proteins
plant materials,
e.g. enzymes,
chlorophyll,
cell membrane and cell wall
▲ Plants make their own food by photosynthesis
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� Since plants are able to use simple inorganic substances to make the (7) _______________
substances (e.g. carbohydrates) they need, they are known as (8) _______________ (自養生物).
Their mode of nutrition is called (9) _______________ _______________ (自養營養).
� Plants are (10) _______________ (生產者). They serve as the basic food source for other
organisms.
B Mineral requirements of plants (Book 1B, p. 9-4)
� For healthy growth, plants need to absorb a variety of (11) _______________ in the form of
(12) _______________ (離子) from the soil.
� The elements that form these mineral ions can be divided into two types:
(13) _______________ elements (大量元素) and (14) _______________ elements (微量元素).
� Examples of major elements and their importance on plant growth:
Element Main function Deficiency symptom
Nitrogen
(N)
� For the synthesis of
(15) _______________
� Poor growth
� (16) _______________
leaves
Phosphorus
(P)
� For the synthesis of
(17) ______________ _____________
� Required in some enzymatic reactions
� Poor growth, particularly
of (18) _______________
� (19) _______________
patches on leaves
Potassium
(K)
� Promotes photosynthesis and the
transport in plants
� Required in some enzymatic reactions
� Poor growth
� Curled-up leaves with
dark-coloured edges
Magnesium
(Mg)
� For the synthesis of
(20) _______________
� Poor growth
� Yellow leaves
� Go to
Practical 9.1 Design an investigation of the effects of different minerals on plant growth
(Book 1B, p. 9-6; Practical Workbook for SBA 1B, p. 9-1)
New Senior Secondary Mastering Biology Oxford University Press 2014 (Second Edition)
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9.2 Gas exchange in plants (Book 1B, p. 9-8)
� Plants exchange gases with the surrounding air by (1) _______________.
� In terrestrial plants, (2) _______________ are the main sites of gas exchange. Gas exchange
also takes place through (3) _______________ and (4) _______________.
1 Gas exchange in leaves
� Structure of a dicotyledonous leaf:
midrib (中脈)
network of veins
leaf blade
air space
cuticle
(8) _______________
(角質層)
vascular
bundle (維管束)
upper epidermis
(上表皮)
(5) _______________
_______________
(柵狀葉肉)
(6) _______________
_______________
(海綿葉肉)
lower epidermis
(下表皮)
(7) _______________
(氣孔)
xylem (木質部)
phloem
(韌皮部)
(9) _______________
_______________
(保衛細胞)
Structure Feature and function
Cuticle � A thin waxy layer covering the epidermis
� Reduces (10) _______________ loss from the leaf surface
Upper and
lower epidermis
� Protect the inner layers of cells
� No chloroplasts except the (11) _______________ _______________
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Palisade
mesophyll
� Made up of tightly-packed cylindrical cells that contain many
(12) _______________
Spongy
mesophyll
� Made up of irregularly-shaped cells that contain fewer chloroplasts
� Many (13) _______________ _______________ among the cells
Stoma
� Pore on the epidermis where (14) _______________ _______________
takes place
� Each surrounded by two (15) _______________ _______________
Guard cell � Contains chloroplasts
� Controls the opening and closing of the stoma
Vascular bundle � (16) _______________ transports water and minerals
� (17) _______________ transports food
� How gas exchange takes place in leaves:
Gases in
3
Gases out
2
1 iii
ii
i
Gases in Gases out
1 Gases from the environment diffuse into
the air space through the
(18) _______________.
2 Gases (19) _______________ in the moist
surface of the mesophyll cells and diffuse
directly into the cells.
3 Gases diffuse to the neighbouring cells.
i Gases produced by the cells diffuse to the
neighbouring cells.
ii Gases diffuse to the moist surface of the
mesophyll cells.
iii Gases diffuse into the
(20) _______________ _______________
and diffuse out.
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� Structural adaptation of leaves for gas exchange:
Feature Adaptation
Broad and flat leaves Provide a large (21) _______________
_______________ for gas exchange
Thin leaves Reduce the diffusion distance of gases
Many (22) _______________
_______________ among the spongy
mesophyll cells
Allow gases to diffuse freely
(23) _______________ surface of
the mesophyll cells
Allows gases to (24) _______________ in it and then
diffuse into the cells easily
Presence of (25) _______________
on the epidermis
Allow gases to pass into and out of the leaves freely
Presence of (26) _______________
_______________
Regulate the rate of gas exchange by controlling the
opening and closing of stomata
2 Gas exchange in stems and roots
� In herbaceous plants (草本植物), the stems also have (27) _______________ for gas exchange.
� In woody plants (木本植物), gas exchange also takes place through small broken parts in the
cork layer called (28) _______________ (皮孔) on the stem.
� Roots are not covered by (29) _______________. Gas exchange takes place all over their
surfaces.
3 What is the effect of light intensity on gas exchange in plants?
� Plants produce (30) _______________ and consume (31) _______________ ______________
during photosynthesis. They produce (32) _______________ _______________ and consume
(33) _______________ during respiration. The net uptake and release of gases by a plant
depend on which process occurs at a faster rate.
� (34) _______________ takes place all the time at a rather constant rate. However, the rate of
(35) _______________ is greatly affected by light intensity (光強度). Therefore, the net uptake
or release of gases by a plant would be affected by light intensity.
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At high light intensity
(e.g. in the daytime)
At low light intensity
(e.g. at night)
photosynthesis
CO2
O2
net exchange
of gas
net release of O2
net uptake of CO2
respiration
O2
CO2
photosynthesis
stops
net exchange
of gas
net uptake of O2
net release of CO2
respiration
O2 CO2
� The rate of photosynthesis is
(36) _______________ (higher / lower)
than that of respiration.
� As a result, there is a net
(37) _______________ (uptake / release)
of carbon dioxide and a net
(38) _______________ (uptake / release)
of oxygen.
� (39) _______________ stops and only
(40) _______________ occurs.
� As a result, there is a net
(41) _______________ (uptake / release)
of oxygen and a net
(42) _______________ (uptake / release)
of carbon dioxide.
� The relationship between light intensity and carbon dioxide exchange in a plant:
A B C D E
light intensity darkness
compensation point
net release of CO2
net uptake of CO2
New Senior Secondary Mastering Biology Oxford University Press 2014 (Second Edition)
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Description
A
CO2
O2
In the dark:
� Only (43) _______________ takes place
� The plant releases carbon dioxide and takes in oxygen
B
CO2
O2
Light intensity slowly increases as the morning comes:
� Photosynthesis takes place at an increasing rate, using up more and
more carbon dioxide
� Carbon dioxide released in respiration remains (44) ______________
� Net release of carbon dioxide and net uptake of oxygen decrease
C
At (45) _______________ _______________ (補償點):
� The rate of photosynthesis is (46) _______________ to the rate of
respiration
� No net exchange of gases
D
CO2
O2
Light intensity increases further:
� Photosynthesis occurs at a (47) _______________ rate than
respiration
� Net uptake of carbon dioxide and net release of oxygen
E CO2
O2
Light intensity increases even further:
� Net uptake of carbon dioxide does not increase
� Another factor (e.g. carbon dioxide concentration) limits the rate of
(48) _______________
� Go to
Practical 9.2 Examination of the structure of leaves
(Book 1B, p. 9-9; Practical Workbook for SBA 1B, p. 9-6)
Practical 9.3 Investigation of the effect of light intensity on gas exchange in plants using
hydrogencarbonate indicator
(Book 1B, p. 9-13; Practical Workbook for SBA 1B, p. 9-9)
Practical 9.4 Investigation of the effect of light intensity on gas exchange in plants using a
data logger
(Book 1B, p. 9-14; Practical Workbook for SBA 1B, p. 9-12)
New Senior Secondary Mastering Biology Oxford University Press 2014 (Second Edition)
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Answers
Ch 9 Nutrition and gas exchange in plants
9.1 1 carbohydrates 2 carbon dioxide 3 photosynthesis 4 chlorophyll 5 Oxygen
6 minerals 7 organic 8 autotrophs 9 autotrophic nutrition
10 producers 11 minerals 12 ions 13 major 14 trace
15 proteins 16 Yellow 17 nucleic acids 18 roots 19 Purple
20 chlorophyll
9.2 1 diffusion 2 leaves 3 stems 4 roots 5 palisade mesophyll
6 spongy mesophyll 7 stoma 8 cuticle 9 guard cell 10 water
11 guard cells 12 chloroplasts 13 air spaces 14 gas exchange 15 guard cells
16 Xylem 17 Phloem 18 stoma 19 dissolve 20 air space
21 surface area 22 air spaces 23 Moist 24 dissolve 25 stomata
26 guard cells 27 stomata 28 lenticels 29 cuticle 30 oxygen
31 carbon dioxide 32 carbon dioxide 33 oxygen 34 Respiration 35 photosynthesis
36 higher 37 uptake 38 release 39 Photosynthesis 40 respiration
41 uptake 42 release 43 respiration 44 constant 45 compensation point
46 equal 47 higher 48 photosynthesis