© Boardworks Ltd 20071 of 39 Starter. © Boardworks Ltd 20072 of 39 Organization and maintenance...

© Boardworks Ltd 20071 of 39

Starter


Organization and maintenance

Plant nutrition


Learning objectives

Candidates should be able to:

Define photosynthesis as the fundamental process by which plants manufacture carbohydrates from raw materials using energy from light;

State the word equation for the production of simple sugars and oxygen in words.

State the balanced equation for photosynthesis in symbols:

6CO2 + 6H2O C6H12 O6 + 6O2

Light

Chlorophyll


What is photosynthesis?

light energy

The word photosynthesis comes

from the Greek language:

“photo” means “light”

“synthesis” means “putting together”

Photosynthesis just means “putting together with light”.

This process is a chemical reaction that uses light energy.


The raw materials for photosynthesis come from the air and the soil.

What are these raw materials called?

What else do plants need to turn

carbon dioxide

and water into food?

Photosynthesis: raw materials

carbon

dioxide

water


Photosynthesis is a chemical reaction between carbon dioxide and water.

Energy is needed for this reaction to take place.

Where do plants get this energy from?

Photosynthesis: energy for the reaction

carbon

dioxide

water

light energy


Plants use light energy from the Sun to power photosynthesis.

Where in the leaf does this reaction take place?

Photosynthesis takes place in what part of plant cells?

Photosynthesis: where it happens

carbon

dioxide

water

light energy


Photosynthesis takes place in plant cells

with chloroplasts.

Chloroplasts contain the green chemical called chlorophyll.

Chlorophyll absorbs the energy from sunlight that allows carbon dioxide and water to react.

What are the products of this reaction?

Photosynthesis: where it happens

carbon

dioxide

water

light

energy

chlorophyll


The products of the reaction between carbon dioxide and water are glucose

and oxygen.

Which of these products is used

by plants?

What happens to the ‘waste’ product?

Photosynthesis: products of the reaction

carbon

dioxide

water

glucose

oxygen

light

energy

chlorophyll


Glucose is the useful product for plants.

Some glucose is used straightaway by plant cells, some is converted to starch for storage and later used for food.

Oxygen is the ‘waste’ product. This gas is transported out of the leaf into the air.

Photosynthesis: products of the reaction

carbon

dioxide

water

oxygen

light

energy

chlorophyll

glucose

oxygen

glucose


Summary of photosynthesis

carbon

dioxide

water

light

energy

oxygen

glucose

chlorophyll

Summarize the process of photosynthesis.


Summarize the process of photosynthesis in one sentence.

Photosynthesis is the process in which light energy, trapped by chlorophyll, is used to convert

carbon dioxide and water into glucose and oxygen.

coslightchlorophyll

Carbondioxide water glu e oxygen

2 2 6 12 6 26 6 6lightchlorophyll

CO H O C H O O

Plenary



Identify conditions for photosynthesis


Learning objectives


Investigate the necessity for chlorophyll, light and carbon dioxide for photosynthesis, using appropriate controls.

Describe the test for starch (iodine solution);


Design of experiment

• Objective• Procedure (step by step)• Results• Conclusion

Pair work: finish the report for the experiment on page 61.


Testing leaves for starch


Homework

• Draw a labeled diagram to show ‘leaf structure’.


Testing leaves for starch – activity



Leaf structure


Learning objectivesCandidates should be able to: Identify and label the cuticle, cellular and tissue structure

of a dicotyledonous leaf, as seen in cross-section under the light microscope, and describe the significance of these features in terms of function, to include:

Distribution of chloroplasts—photosynthesis; Stomata and mesophyll cells—gas exchange; Vascular bundles (xylem and phloem)—transport and support.

Describe the intake of carbon dioxide and water by plants;

Explain that chlorophyll traps light energy and converts it into chemical energy for the formation of carbohydrates and their subsequent storage.


Wide—this create a large surface area to absorb as much light as possible

thin – this allows gases to reach cells easily

stomata – these are pores on the underside of leaves through which gases move in and out.

veins – these carry water to the cells and carry glucose away and also support leaves

How are leaves adapted for photosynthesis?

To increase photosynthesis, leaves have certain key features:


Take a look inside a leaf


How do gases enter and leave plants?

When guard cells gain water, they curve outwards. This opens the stoma, allowing gases in and out.

Losing water causes the guard cells to come closer together, closing the stoma. This stops the movement of gases, but also prevents water loss.


Discussion: Leaf structure is a compromise between maximising photosynthesis and minimising water loss.



Measuring the rate of photosynthesis


Learning objectives


Investigate and state the effect of varying light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis (e.g. in submerged aquatic plants);


Photosynthesis is a chemical reaction and so has a rate.

The rate of photosynthesis

light

glucose

light energy

chlorophyll

carbon

dioxidewater oxygen

The rate of photosynthesis varies depending on three main factors:

How do these factors affect the rate of photosynthesis?

carbon dioxide temperature



• Measure the uptake of CO2

• Measure the production of O2

• Measure the production of carbohydrates;

• Measure the increase in dry mass


Investigating photosynthesis – apparatus


Investigation photosynthesis - experiment


Investigation photosynthesis – results


Homework for holiday

• Vocabulary test



Limiting factors


Learning objectives


Define the term limiting factors as something present in the environment such short supply that it restricts life processes;

Explain the concept of limiting factors in photosynthesis;Explain the use of carbon dioxide enrichment, optimum

light and optimum temperatures in glasshouse systems.


Limiting factor

• Limiting factor: something present in the environment in such short supply that it restricts life processes.

? Limiting factor for human

population


What is the ideal combination of factors for the maximum rate of photosynthesis?

Limiting factor for photosynthesis?

enough light

enough carbon dioxide

ideal temperature (not too hot or cold)

How is the rate affected if one of these factors is restricted?

If one of the factors is restricted, the rate of photosynthesis will be below the maximum possible rate. And the factor is the limiting factor.


Photosynthesis and carbon dioxide – limiting factors

How does the amount of carbon dioxide affect the rate of photosynthesis on this labelled graph?

As the amount of carbon dioxide goes up, so does the rate. The limiting factor is carbon dioxide.

concentration of

carbon dioxide

rate

of

phot

osyn

thes

is

Here, increasing the amount of carbon dioxide has no affect on the rate. Light or temperature is now the limiting factor.

1

2

1

2


Photosynthesis and light – limiting factors

How does the amount of light affect the rate of photosynthesis on this labelled graph?

As the amount of light increases, so does the rate. The limiting factor is light.

light intensity

rate

of

phot

osyn

thes

is

Here, increasing the amount of light has no affect on the rate. The limiting factor is now carbon dioxide or temperature.1

2

1

2


Photosynthesis and temperature – limiting factors

How does temperature affect the rate of photosynthesis on this labelled graph?

1. As temperature increases, so does the rate because photosynthetic enzymes work best in the warmth. Here, the limiting factor is temperature.

temperature

rate

of

phot

osyn

thes

is

0oC 45oC

Most plant enzymes are destroyed at about 45°C. Here, photosynthesis stops and the rate falls to zero.

What is the limiting factor?

1

2

1

2


Greenhouse

What do you know about green house?

How would green house increase the yield?


Limiting factors – activity



Transport system in plant


Learning objectives

Candidates should be able to:State the functions of xylem and phloem; Identify the positions of xylem and phloem tissues as

seen in transverse sections of unthickened, herbaceous, dicotyledonous roots, stems and leaves.


How are plants adapted for transport?

Leaves are entry and exit points for the gases needed by plants.

Roots absorb water and minerals from the soil.

Stems connect the roots to the leaves, flowers and fruits.


What are vascular bundles?


Learning objectives

Candidates should be able to:Define translocation in terms of the movement of sucrose and amino acids in phloem:

From regions of production To regions of storage OR to regions of utilisation in respiration or growth;

Describe translocation throughout the plant of applied chemicals, including systemic pesticides;


Phloem sap from Source Sink

Source: produces or transports out sucrose, amino acids, plant hormones.

Sink : organ and tissue which consume or store assimilate.


Phloem


Ants ‘farm’ aphids (symbiotic)


Systemic insecticides

Systemic insecticides are sprayed onto the plant and absorbed into the phloem tissues, so they only kill aphids.


Transport in plant


Starter



Water uptake and transpiration


Learning objectivesCandidates should be able to: Define transpiration as evaporation of water at the surfaces of the mesophyll cells

followed by loss of water vapour from plant leaves, through the stomata. State the pathway taken by water through root, stem and leaf (root hair, root

cortex cells, xylem, mesophyll cells); Explain the mechanism of water uptake and movement in terms of transpiration

producing a tension (‘pull’) from above, creating a water potential gradient in the xylem, drawing cohesive water molecules up the plant.

Describe and explain the importance of a water potential gradient in the uptake of water by osmosis;

Identify root hair cells, as seen under the light microscope, and state their functions;

Relate the structure and functions of root hairs to their surface area and to water and ion uptake;

Describe how water vapour loss is related to cell surface, air spaces and stomata; Investigate, using a suitable stain, the pathway of water through the above-ground

parts of a plant.


Transpiration


Water transport pathway

Water in a plant moves along a gradient between the relatively high water potential in the soil to successively lower water potentials in the roots, stems, leaves, and atmosphere.


Learning objectives


Mineral uptake Discuss the importance of active transport as an energy-

consuming process by which substances are transported against a concentration gradient, e.g. ion uptake by root hairs.

Describe the importance of : Nitrate ions for protein synthesis; Magnesium ions for chlorophyll synthesis;

Describe the uses, and the dangers of overuse, of nitrogen fertilizers;

Explain the effects of nitrate ion and magnesium ion deficiency on plant growth.


The roots have formed a fine network, filling the available space.

high surface area to volume ratio

maximum contact with the soil

firm anchorage.


Magnesium (Mg2+ )

* Required for formation of chlorophyll

• Deficiency symptom: The leaves turn yellow.


Nitrogen (NH4+ /NO3

-)

*Required for

proteins, chlorophyll, DNA;

*Deficiency symptoms:

the whole plant is stunted, with a weak stem and yellowing, dying leaves.


Over-fertilization

• Fertilizer burn


Starter

• Name the process by which the root hair cell absorbs:i) Waterii) Mineral ions.


Learning objectives


Describe the effects of variation of temperature, humidity and light intensity on transpiration rate;


How is the rate of transpiration measured?

Transpiration can be measured using a potometer.

A cut plant stem is sealed into the potometer using a rubber bung.

An air bubble is introduced to the capillary tube.

Graduated scale shows how much water the stem has taken up.

The speed at which a plant loses water is called the rate of transpiration.


Drawing the table

• Heading, vertical line and horizontal lines are all required, better with frame around;

• Units with table headings only, not come with the figures;

• Stick to the same decimal places for all the figures;


humidity (amount of moisture in the air)

Is the rate of transpiration constant?

The rate of transpiration varies depending on the plant’s environment.

light intensity

temperature

air movement (wind).


Factors affecting transpiration rate

Factor Effect on transpiration Explanation

Temperature

Light intensity

Humidity

Air movement


Factors affecting transpiration rate

Factor Effect on transpiration Explanation

Temperature High fasterLow slower

Water evaporate faster when temperature is higher.

Light intensity High fasterLow slower

Stomata open when light is strong.

Humidity Humid slowerDry faster

When air is dry, then the concentration gradient will be bigger.

Air movement Windy fasterStill air slower

Wind can remove the water vapour after it gets out of stomata, to maintain a bigger concentration gradient.


Multiple-choice quiz


Homework

• Exercise sheet—‘a transpiration experiment’.

• Table--‘chemicals for life’


Learning objectives


Discuss the adaptations of the leaf, stem and root to three contrasting environments, to include pond, garden and desert, with emphasis on local examples (where appropriate) and the factors described in the core.


Plant adaptation

Leaf Stem Root

Desert

Pond


Leaf Stem Root

Desert *leaf reduced to spine—reduce surface area for water loss*Sunk stomata—avoid air movement*Thick waxy cuticle—reduce water loss

*Green stem—photosynthesis*Succulent stem—store water

*Shallow root—absorb water from rainfall*Deep root—penetrate to very low water table, have a great surface area for absorption

Pond *thin cuticle—no need to reserve water*stomata on the upper surface to absorb CO2 from the air

*little lignin—no need for lignin to support plant*air space in stem—increase buoyancy to support plant

*simple root system—no need to absorb water from soil*mainly for anchorage

© Boardworks Ltd 20071 of 39 Starter. © Boardworks Ltd 20072 of 39 Organization and maintenance...

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