Think about… 9.1 Nutrition in plants 9.2 Gas exchange in plants Recall ‘Think about…’ Summary concept map.

Think about… 9.1 Nutrition in plants 9.2 Gas exchange in plants Recall ‘Think about…’ Summary concept map

9.1 Major Nutritional types
Based on Carbon source and Energy source that can be used to synthesize organic compounds:

9.1 Major Nutritional types

9.1 Nutrition in plants humans: eating Amoeba: phagocytosis

9.1 Nutrition in plants How about plants? How do they obtain their food?

Hydroponics – water culture

Supplied with a nutrient solution

Hydroponics – water culture

CO2 O2 light (by-product) chlorophyll carbohydrates water 9.1
Nutrition in plants CO2 O2 light (by-product) chlorophyll carbohydrates water

photosynthesis (光合作用)
9.1 Nutrition in plants CO2 O2 light (by-product) photosynthesis (光合作用) chlorophyll carbohydrates water

carbohydrates + oxygen
9.1 Nutrition in plants Process of photosynthesis: carbon dioxide + water light energy chlorophyll carbohydrates + oxygen

9.1 Nutrition in plants carbohydrates

carbohydrates lipids proteins plant materials minerals (礦物質) 9.1
Nutrition in plants carbohydrates lipids proteins plant materials minerals (礦物質)

carries out autotrophic nutrition
9.1 Nutrition in plants carbon dioxide + water inorganic autotroph carries out autotrophic nutrition plant carbohydrates organic

Significance of plants as autotrophs
9.1 Nutrition in plants Significance of plants as autotrophs

used by plants to make food
9.1 Nutrition in plants Significance of plants as autotrophs energy from the sun eaten by cows used by plants to make food eaten by humans

Significance of plants as autotrophs
9.1 Nutrition in plants Significance of plants as autotrophs plants act as producers (生產者) serve as basic food source

Mineral ions required by plants
9.1 Nutrition in plants Importance of minerals major elements (大量元素) Mineral ions required by plants minor elements (微量元素)

Importance of minerals
9.1 Nutrition in plants Importance of minerals required in relatively large amount e.g. N, P, K, Mg major elements (大量元素) required in very small amount e.g. Cu, Zn, Co minor elements (微量元素)

9.1 Nutrition in plants Importance of minerals insufficient minerals deficiency diseases (營養缺乏病)

9.1 Nutrition in plants Importance of minerals Nitrogen (N) Major form in soil Main function Deficiency symptom NO3- NH4+ Synthesis of proteins Poor growth Yellow leaves

9.1 Nutrition in plants Importance of minerals Phosphorus (P) Major form in soil Main function Deficiency symptom PO43- Synthesis of DNA, proteins For enzymatic reactions Poor root growth Purple patches on leaves

9.1 Nutrition in plants Importance of minerals Potassium (K) Major form in soil Main function Deficiency symptom K+ Promotes photosynthesis,transport For enzymatic reactions Poor growth Curled-up leaves with dark-coloured edges

9.1 Nutrition in plants Importance of minerals Magnesium (Mg) Major form in soil Main function Deficiency symptom Mg2+ Synthesis of chlorophyll Poor growth Yellow leaves

Investigation of the effects of different minerals on plant growth
9.1 Nutrition in plants 9.1 Simulation Investigation of the effects of different minerals on plant growth 1 Prepare 5 conical flasks with different nutrient solutions as shown. Wrap aluminium foil around each flask to prevent any algal growth.

9.1 Flask Solution A Complete nutrient solution B
Nutrition in plants 9.1 Flask Solution A Complete nutrient solution B N-deficient nutrient solution C P-deficient nutrient solution D K-deficient nutrient solution E Mg-deficient nutrient solution

9.1 Nutrition in plants 9.1 2 Observe the appearance of the seedlings. Put the flasks in bright light. Refill with fresh nutrient solutions every week. Observe the seedlings again after 2 weeks.

Results and discussion
9.1 Nutrition in plants 9.1 Results and discussion Except for those in flask A, all seedlings show poor growth. The result shows that the deficiency of any essential mineral will lead to poor growth in the seedlings.

How are water and minerals absorbed in plants?
9.1 Nutrition in plants How are water and minerals absorbed in plants?

9.1 Nutrition in plants mainly by roots

Structure of the root root cap (根冠) protects the tip of the root 9.1
Nutrition in plants Structure of the root 3D animation root cap (根冠) protects the tip of the root

Structure of the root epidermis (表皮) one layer of thin-walled cells
9.1 Nutrition in plants Structure of the root epidermis (表皮) one layer of thin-walled cells with root hairs protects the inner tissues

Structure of the root root hair (根毛) developed from epidermal cells
9.1 Nutrition in plants Structure of the root root hair (根毛) developed from epidermal cells provides large surface area for absorption

Structure of the root cortex (皮層) several layers of thin-walled cells
9.1 Nutrition in plants Structure of the root cortex (皮層) several layers of thin-walled cells stores food allows passage of water and minerals

Structure of the root phloem (韌皮部) transports food xylem (木質部)
9.1 Nutrition in plants Structure of the root phloem (韌皮部) transports food xylem (木質部) transports water and minerals vascular bundle (維管束)

Structure of the root root hair epidermis root cap 9.1
Nutrition in plants Structure of the root root hair epidermis root cap

9.1 Nutrition in plants Structure of the root

Structure of the root epidermis cortex phloem xylem 9.1
Nutrition in plants Structure of the root epidermis cortex phloem xylem

Structure of the root Adaptive features 1 Thin epidermis
9.1 Nutrition in plants Structure of the root Adaptive features 1 Thin epidermis one layer of thin-walled cells not covered by cuticle water and minerals can easily pass through

Structure of the root Adaptive features
9.1 Nutrition in plants Structure of the root Adaptive features 2 Numerous root branches and root hairs provide large surface area for absorption

Structure of the root Adaptive features 3 Long and fine root hairs
9.1 Nutrition in plants Structure of the root Adaptive features 3 Long and fine root hairs easily grow between soil particles to absorb water and minerals

 Absorption of water and minerals only occurs in roots. 9.1
Nutrition in plants Absorption of water and minerals only occurs in roots. 

9.1 Nutrition in plants Absorption of water and minerals can occur through any part of a plant which is not covered by cuticle.

Examination of the structure of roots
9.1 Nutrition in plants 9.2 Examination of the structure of roots 1 Examine the external structure of the root of a young seedling with a hand lens. Draw a labelled diagram of the root.

9.1 Nutrition in plants 9.2 2 Examine a prepared slide of the transverse secion of the root with a microscope.

9.1 Nutrition in plants 9.2 3 Identify the internal structure of the root. Draw a labelled low-power diagram.

Absorption of water in roots
9.1 Nutrition in plants Absorption of water in roots Animation

9.1 Nutrition in plants Absorption of water in roots root hair epidermis xylem vessel soil particle cortex water in soil

9.1 Nutrition in plants Absorption of water in roots 1a Water potential of the soil water is usually higher than that of the cytoplasm of the root hairs.

9.1 Nutrition in plants Absorption of water in roots 1b Water enters the root hair by osmosis.

9.1 Nutrition in plants Absorption of water in roots 2a Water potential of the cytoplasm of the root hairs increases.

9.1 Nutrition in plants Absorption of water in roots 2b Water passes across the cortex from cell to cell by osmosis or moves along the cell walls.

9.1 Nutrition in plants Absorption of water in roots 2c Water moves inwards until it reaches the xylem vessels.

9.1 Nutrition in plants Absorption of water in roots 3 Water is drawn up the xylem vessels by transpiration pull (蒸騰拉力).

Absorption of minerals in roots
9.1 Nutrition in plants Absorption of minerals in roots 1 Mostly by active transport concentration of minerals in soil lower than that in root cells against concentration gradient energy from respiration

9.1 Nutrition in plants Absorption of minerals in roots 2 From dissolved minerals water with dissolved minerals is absorbed

9.1 Nutrition in plants Absorption of minerals in roots 3 Rarely by diffusion when concentration of minerals in soil is higher than that in root cells down the concentration gradient

9.1 Nutrition in plants 1 Plants can make carbohydrates by photosynthesis and absorb and from soil to make other essential materials. photosynthesis water minerals

2 Plants serve as the basic food source for other organisms.
9.1 Nutrition in plants 2 Plants serve as the basic food source for other organisms. food source

9.1 Nutrition in plants 3 Plants will suffer from mineral deficiency disease if they do not have enough minerals. deficiency diseases

4 Adaptive features of roots for absorption:
9.1 Nutrition in plants 4 Adaptive features of roots for absorption: no covering epidermal cells for faster absorption cuticle

9.1 Nutrition in plants 4 Adaptive features of roots for absorption: numerous and root to increase surface area for absorption root branches root hairs

9.1 Nutrition in plants 4 Adaptive features of roots for absorption: , root hairs for penetrating into soil particles for absorption long fine

9.1 Nutrition in plants 5 Water enters the roots by It then passes across the cortex from cell to cell by or along the cell walls. It is then drawn up the by transpiration pull. osmosis osmosis xylem vessels

6 Most minerals are absorbed into the root cells by .
9.1 Nutrition in plants 6 Most minerals are absorbed into the root cells by active transport Some are absorbed in form of dissolved minerals . dissolved minerals

9.1 Nutrition in plants 7 If the concentration of minerals is higher in the soil than in the root cells, the minerals will be absorbed into the roots by diffusion. higher

9.2 Gas exchange in plants Gas exchange oxygen carbon dioxide
photosynthesis respiration oxygen carbon dioxide Gas exchange

Gas exchange in plants can occur in …
9.2 Gas exchange in plants Gas exchange in plants can occur in … stem leaf root by diffusion

1 Leaves main site of gas exchange in terrestrial plants
9.2 Gas exchange in plants 1 Leaves 3D animation main site of gas exchange in terrestrial plants structurally adapted

1 Leaves i) Structure of the leaf leaf blade upper epidermis
9.2 Gas exchange in plants 1 Leaves i) Structure of the leaf leaf blade upper epidermis palisade mesophyll spongy mesophyll stoma vein lower epidermis midrib

9.2 Gas exchange in plants 1 Leaves i) Structure of the leaf

1 Leaves i) Structure of the leaf upper epidermis
9.2 Gas exchange in plants 1 Leaves i) Structure of the leaf upper epidermis A layer of cells for protection lower epidermis

1 Leaves i) Structure of the leaf
9.2 Gas exchange in plants 1 Leaves i) Structure of the leaf Except guard cells, other epidermal cells have no chloroplasts guard cell (保衛細胞)

1 Leaves i) Structure of the leaf cuticle
9.2 Gas exchange in plants 1 Leaves i) Structure of the leaf cuticle It covers the epidermis to reduce water loss cuticle

1 Leaves i) Structure of the leaf palisade mesophyll (柵狀葉肉)
9.2 Gas exchange in plants 1 Leaves i) Structure of the leaf palisade mesophyll (柵狀葉肉) Cells are tightly packed and contain many chloroplasts

1 Leaves i) Structure of the leaf
9.2 Gas exchange in plants 1 Leaves i) Structure of the leaf Cells are irregular and contain fewer chloroplasts spongy mesophyll (海綿葉肉)

1 Leaves i) Structure of the leaf For gas exchange stoma (氣孔) 9.2
Gas exchange in plants 1 Leaves i) Structure of the leaf For gas exchange stoma (氣孔)

1 Leaves i) Structure of the leaf In midrib and veins in the mesophyll
9.2 Gas exchange in plants 1 Leaves i) Structure of the leaf In midrib and veins in the mesophyll phloem xylem vascular bundle

1 Leaves i) Structure of the leaf phloem xylem vascular bundle
9.2 Gas exchange in plants 1 Leaves i) Structure of the leaf Xylem transports water and minerals, phloem transports food phloem xylem vascular bundle

1 Leaves i) Structure of the leaf cuticle upper epidermis
9.2 Gas exchange in plants 1 Leaves i) Structure of the leaf cuticle upper epidermis lower epidermis

1 Leaves i) Structure of the leaf palisade mesophyll spongy mesophyll
9.2 Gas exchange in plants 1 Leaves i) Structure of the leaf palisade mesophyll spongy mesophyll xylem phloem

1 Leaves i) Structure of the leaf air space stoma guard cell 9.2
Gas exchange in plants 1 Leaves i) Structure of the leaf air space stoma guard cell

section through the leaf
9.2 Gas exchange in plants 1 Leaves ii) Gas exchange in leaves section through the leaf

1 Leaves ii) Gas exchange in leaves Gases in
9.2 Gas exchange in plants 1 Leaves ii) Gas exchange in leaves Gases in 1a Gases from the environment diffuse into the air space through the stoma

9.2 Gas exchange in plants 1 Leaves ii) Gas exchange in leaves Gases in 1b Gases dissolve in the moist surface of the mesophyll cells

9.2 Gas exchange in plants 1 Leaves ii) Gas exchange in leaves Gases in 1c Gases diffuse to the neighbouring cells

1 Leaves ii) Gas exchange in leaves Gases out
9.2 Gas exchange in plants 1 Leaves ii) Gas exchange in leaves Gases out 2a Gases diffuse from the cells towards the air space

9.2 Gas exchange in plants 1 Leaves ii) Gas exchange in leaves Gases out 2b Gases dissolve in the moist surface of the mesophyll cells

9.2 Gas exchange in plants 1 Leaves ii) Gas exchange in leaves Gases out 2c Gases diffuse into the air space and diffuse out through the stoma

1 Leaves iii) Structural adaptations of leaves for gas exchange
9.2 Gas exchange in plants 1 Leaves iii) Structural adaptations of leaves for gas exchange broad and flat large surface area

9.2 Gas exchange in plants 1 Leaves iii) Structural adaptations of leaves for gas exchange many air spaces allows gases to diffuse freely

9.2 Gas exchange in plants 1 Leaves iii) Structural adaptations of leaves for gas exchange surface of mesophyll cells kept moist allows gases to dissolve and diffuse easily

9.2 Gas exchange in plants 1 Leaves iii) Structural adaptations of leaves for gas exchange numerous stomata on the lower epidermis allows gases to pass easily

9.2 Gas exchange in plants 1 Leaves iii) Structural adaptations of leaves for gas exchange guard cells guard cells control the opening and closing of stomata rate of gas exchange can be regulated

Stomata opening

1 Leaves iv) Prevention of water loss in leaves How to prevent?
9.2 Gas exchange in plants 1 Leaves iv) Prevention of water loss in leaves gas exchange water vapour escapes dehydration (脫水) How to prevent?

1 Leaves iv) Prevention of water loss in leaves
9.2 Gas exchange in plants 1 Leaves iv) Prevention of water loss in leaves cuticle on the epidermis is impermeable to water

1 Leaves iv) Prevention of water loss in leaves
9.2 Gas exchange in plants 1 Leaves iv) Prevention of water loss in leaves if the upper epidermis faces the sun, few or no stomata on it

1 Leaves v) Distribution of stomata on leaves
9.2 Gas exchange in plants 1 Leaves v) Distribution of stomata on leaves Terrestrial dicotyledonous plants Upper epidermis Lower epidermis Apple Tomato 14100 1200 13100

1 Leaves v) Distribution of stomata on leaves
9.2 Gas exchange in plants 1 Leaves v) Distribution of stomata on leaves Terrestrial dicotyledonous plants more stomata on lower epidermis leaves are held horizontally, fewer or no stomata on upper epidermis can reduce water loss by evaporation Upper epidermis Lower epidermis Apple Tomato 14100 1200 13100

1 Leaves v) Distribution of stomata on leaves Submerged plants
9.2 Gas exchange in plants 1 Leaves v) Distribution of stomata on leaves Submerged plants Upper epidermis Lower epidermis Hydrilla

1 Leaves v) Distribution of stomata on leaves Submerged plants
9.2 Gas exchange in plants 1 Leaves v) Distribution of stomata on leaves Submerged plants few or no stomata on both epidermis without cuticle, dissolved gases, water and minerals can diffuse into leaves over the surface Upper epidermis Lower epidermis Hydrilla

1 Leaves v) Distribution of stomata on leaves Floating plants
9.2 Gas exchange in plants 1 Leaves v) Distribution of stomata on leaves Floating plants Upper epidermis Lower epidermis Water lily 9500

1 Leaves v) Distribution of stomata on leaves Floating plants
9.2 Gas exchange in plants 1 Leaves v) Distribution of stomata on leaves Floating plants stomata on upper epidermis only dissolved gases, water and minerals can diffuse into leaves through the lower epidermis Upper epidermis Lower epidermis Water lily 9500

9.2 Gas exchange in plants 9.3 Design an investigation of the distribution of stomata on both sides of a leaf In a lesson, David learnt that gas exchange in plants takes place mainly through stomata on leaves and its rate is affected by the number of stomata.

9.2 Gas exchange in plants 9.3 The teacher asked David whether the number of stomata on both sides of a dicotyledonous leaf was the same. Could you help David find out the answer?

9.2 Gas exchange in plants 9.3 Design and perform an experiment to compare the distribution of stomata on both sides of a leaf.

Young stems have stomata for gas exchange

Young stem vs woody stem

woody stems are covered with layers of cork cells which form the bark.

cork cells form bark to for :
Physical protection minimise water loss from the stem do not allow gases to pass through cork cells

cork cells lenticel gas in gas out
They are packed loosely in places to let gases pass through. These parts are called lenticels. cork cells

lenticel gas in gas out cork cells

2 Stems stems of herbaceous plants have stomata for gas exchange
9.2 Gas exchange in plants 2 Stems stems of herbaceous plants have stomata for gas exchange stems of woody plants are covered by cork (木栓), gas exchange occurs through lenticels (皮孔)

9.2 Gas exchange in plants 2 Stems lenticels

9.2 Gas exchange in plants 2 Stems cork lenticel gas exchange

3 Roots not covered by cuticle
9.2 Gas exchange in plants 3 Roots not covered by cuticle gas exchange takes place all over the surface

Root root hair xylem phloem soil particle lack a cuticle
gas exchange occurs all over their surfaces

Root CO2 O2 Root cells obtain O2 from the air spaces between soil particles by diffusion. CO2 produced diffuses out into the air spaces.

Plant adapted to waterlogged soil

Upward growing roots!

Gas exchange in the daytime and in the dark
9.2 Gas exchange in plants Gas exchange in the daytime and in the dark Animation gas exchange affected by respiration photosynthesis

9.2 Gas exchange in plants In the daytime light intensity is high

rate of photosynthesis
9.2 Gas exchange in plants In the daytime O2 rate of photosynthesis CO2 faster than rate of respiration O2 CO2

9.2 Gas exchange in plants In the daytime O2 net uptake of carbon dioxide and net release of oxygen CO2 O2 CO2 O2 CO2

9.2 Gas exchange in plants In the dark no light

In the dark photosynthesis stops and only respiration takes place O2
9.2 Gas exchange in plants In the dark photosynthesis stops and only respiration takes place O2 CO2

In the dark net uptake of oxygen and net release of carbon dioxide O2
9.2 Gas exchange in plants In the dark net uptake of oxygen and net release of carbon dioxide O2 CO2 O2 CO2

In the daytime Both photosynthesis and respiration occur
∵rate of photosynthesis > rate of respiration ∴net uptake of CO2 and net release of O2 PHOTOSYNTHESIS O2 CO2 O2 CO2 O2 CO2 O2 RESPIRATION

In the dark Photosynthesis stops and only respiration occurs
Net uptake of O2 and net release of CO2 O2 CO2 RESPIRATION

Effect of light intensity
9.2 Gas exchange in plants Effect of light intensity In the dark respiration only net uptake of CO2 CO2 O2 net release of CO2 light intensity A

2400 1200 1800 0600 Net uptake of CO2 Net release 1 In the dark, only respiration takes place. Plants absorb O2 and release CO2 . 1

2400 1200 1800 0600 Net uptake of CO2 Net release 2 As dawn comes, light intensity gradually increases and the rate of photosynthesis increases. Rate of photosynthesis < respiration. There is a net uptake of O2 and a net release of CO2. 2

2400 1200 1800 0600 Net uptake of CO2 Net release compensation point 3 When the rate of photosynthesis = respiration, there is no net gas exchange. 3

2400 1200 1800 0600 Net uptake of CO2 Net release 4 Light intensity further increases. Rate of photosynthesis > respiration. There is a net uptake of CO2 and a net release of O2. 4

2400 1200 1800 0600 Net uptake of CO2 Net release 5 Rate of photosynthesis reaches its maximum. Net uptake of CO2 and net release of O2 remain at the highest levels. 5

2400 1200 1800 0600 Net uptake of CO2 Net release 6 Light intensity decreases, but still photosynthesis occurs at a faster rate than respiration. There is a net uptake of CO2 and a net release of O2. 6

2400 1200 1800 0600 Net uptake of CO2 Net release compensation point 7 Light intensity decreases to a point at which the rates of photosynthesis = respiration, there is no net gas exchange. 7

2400 1200 1800 0600 Net uptake of CO2 Net release 8 Light intensity decreases further. Photosynthesis occurs at a slower rate than respiration. There is a net uptake of O2 and a net release of CO2. 8

2400 1200 1800 0600 Net uptake of CO2 Net release 9 In the dark, no photosynthesis occurs and only respiration takes place. The plants absorb oxygen and release CO2. 9

Living above compensation point
When plants are kept at intensities above the compensation point, they are doing photosynthesis faster than they are using up the products in respiration. So at these higher intensities, the plant can add to its reserves, can grow, or can reproduce.

Living below compensation point
However, whenever a plant is at intensities below the compensation point, it is burning up photosynthate faster than it is being produced. Kept here for any length of time it will be using up its reserves, and may even die.

Compensation point Compensation point Net uptake of CO2 Net release
Net release of CO2 2400 0600 1200 1800 2400

Compensation point

What does the Red area represent?
Compensation point What does the Red area represent? What does the Green area represent? Why it is important that the green > red area in the long run?

What does the Red area represent?
Compensation point What does the Red area represent? The amount of sugar consumed in a day What does the Green area represent? The amount of sugar produced in a day Why it is important that the green > red area in the long run? There is Net production of food reserve to allow growth

Two plant responses to light intensity are shown
Two plant responses to light intensity are shown. Assume that the rate of respiration in both plant A and plant B are the same. You will notice that plant B is far less efficient in photosynthesis; it takes much more light to reach its compensation point. Plant B is likely a crop plant such as corn or soybeans

High or low compensation point?

Sun plants Shade plants

How does photosynthesis differ between 'sun' and 'shade' plants or leaves?
Plants are usually adapted to growth in direct sunlight or shaded conditions. Similar differences are observed among the leaves of large trees; those leaves that develop under the shade of other leaves are anatomically and metabolically different from those that grow on exposed canopy surfaces. Which one? A or B is sun leaf or shade leaf

Shade-type leaves typically are thinner, have more surface area, and contain more chlorophyll than those of sun leaves. As a result, shade-leaves (curve B) often are more efficient in harvesting sunlight at low light levels; remember, the slope of the line observed under low light conditions is a measure of photosynthetic efficiency. However, sun-leaves (curve A) display a higher light saturation point and maximum rate of photosynthesis. Why do these differences make sense?

9.2 Gas exchange in plants 9.4 Video Investigation of the effect of light intensity on gas exchange in plants using hydrogencarbonate indicator The net change in carbon dioxide concentration can be used as a parameter for studying gas exchange. This can be detected by using hydrogencarbonate indicator.

1 Set up the boiling tubes as shown.
9.2 Gas exchange in plants 9.4 1 Set up the boiling tubes as shown. bench lamp freshly-picked leaf hydrogencarbonate indicator layers of muslin aluminium foil A B C D

9.2 Gas exchange in plants 9.4 2 Leave the set-up for 5 hours. Note any colour changes in the hydrogencarbonate indicator. bench lamp freshly-picked leaf hydrogencarbonate indicator layers of muslin aluminium foil A B C D

 There is no gas exchange at the compensation point. 9.2
Gas exchange in plants There is no gas exchange at the compensation point. 

9.2 Gas exchange in plants Gas exchange takes place all the time. There is no NET gas exchange at the compensation point.

9.2 Gas exchange in plants 1 Gas exchange takes place mainly through the of leaves, the of stems and the epidermis of roots. stomata lenticels epidermis

2 Adaptations of leaves:
9.2 Gas exchange in plants 2 Adaptations of leaves: Feature Adaptation Broad and flat leaves Provide a large surface area for gas exchange large surface area

9.2 Gas exchange in plants 2 Adaptations of leaves: Feature Adaptation Air spaces among the spongy mesophyll cells Allow gases to diffuse freely into and out of the leaves Air spaces

9.2 Gas exchange in plants 2 Adaptations of leaves: Feature Adaptation Moist surface of the mesophyll cells Allow gases to dissolve in it and then diffuse into and out of the cells dissolve diffuse

9.2 Gas exchange in plants 2 Adaptations of leaves: Feature Adaptation Numerous Allow gases to pass into and out of the leaf freely stomata

9.2 Gas exchange in plants 2 Adaptations of leaves: Feature Adaptation Control the opening and closing of the stomata Guard cells

9.2 Gas exchange in plants 3 Gases from the environment diffuse into the air spaces through the stomata . stomata They then dissolve in the moist surface of the mesophyll cells and diffuse to the neighbouring cells. moist surface

4 Gas exchange in plants depends on the relative rates of and .
9.2 Gas exchange in plants 4 Gas exchange in plants depends on the relative rates of and respiration photosynthesis

1 What is the importance of plants to
the environment and other organisms? Plants not only serve as the basic food source for other organisms, but also supply oxygen to them.

2 Why will the terrestrial plants die
soon after they are put under water? This is because gas exchange cannot take place through their stomata.

3 How can we distinguish between
aquatic plants and terrestrial plants? We can examine the stomata on their leaves and compare their distribution. Aquatic plants do not have stomata while terrestrial plants do.

Plants autotrophs food substances photosynthesis absorption
are make food substances by photosynthesis absorption

absorption nitrogen phosphorus water minerals magnesium roots
of phosphorus water minerals such as magnesium through roots potassium

leaves and herbaceous stems
Plants gases exchange through stomata lenticels roots on on leaves and herbaceous stems woody stems

Think about… 9.1 Nutrition in plants 9.2 Gas exchange in plants Recall ‘Think about…’ Summary concept map.

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Think about… 9.1 Nutrition in plants 9.2 Gas exchange in plants Recall ‘Think about…’ Summary concept map.

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