Synthesizing Factors Affecting Photosynthesis

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Synthesizing factors affecting

photosynthesis• Identify the factors affecting the rate of photosynthesis,

• Identify the factor that limits the rate of photosynthesis at

different light intensity,

• Explain the effects of temperature and concentration of

carbon dioxide on the rate of photosynthesis,

• Explain the difference in the rate of photosynthesis in

plants throughout the day based on the changes in light

intensity and temperature,

• Identify some ways to meet the need of increasing the

productivity of crops based on factors affecting the rate of

photosynthesis.

1



Factors affecting the rate of photosynthesis

• Light intensity

• Concentration of CO2

• Temperature

Limiting factor

• Factor that is in the shortest supply• Determines the rate at which photosynthesis

can take place at any one time

2



Light intensity

• Light tend to limit the rate of photosynthesis at low intensities

• As light intensity increases, the rate of photosynthesis

increases.

• A point is reach where the rate if oxygen produced is equal to

the rate at which oxygen is used for respiration. This is called

compensation point.

• At high light intensities, carbon dioxide concentration is the

limiting factor.

• The rate of photosynthesis will increase only when an increase

in the concentration of carbon dioxide. 3



• When the [CO2] & temperature is at constant,

rate of photosynthesis is directly proportional

to light intensity.

• Graph I shows the initial condition.

• As light intensity increases, the rate _________.

• At point P, the rate of photosynthesis becomes

constant.

• This is due to other factors which is limiting like

CO2.

• After this point, the rate of photosynthesis will

not increase even if light intensity increases.

• Graph II shows the condition when the level of

CO2 is increased.

• The rate of photosynthesis increases greatly as

the CO2 level increases until it becomes limiting

factor again.

Light intensity

Graph II

Graph IP Q

0.13% CO2

at 30oC

0.03% CO2

at 30oC

Light

intensity

R a t e

o f p h o t o s y n t h e

s i s

Effect of light intensity on the rate of

photosynthesis 4



• C02 is required in dark reaction for the synthesis of glucose

• Concentration of C02 in atm is between 0.03% - 0.04%.

•In places with high densities of plants, competition for C02

arises – will effect the rate of photosynthesis.

• Increase in C02 increases the rate of photosynthesis (if

there is no other limiting factor).

• If light intensity becomes a limiting factor, any increase in

C02 will not increase the rate of photosynthesis.

Concentration of C02

5



30oC at high

light intensity

30oC at low

light intensity

Carbon dioxide

concentration

R a t e

o f p h o t o s y n t h e s i s

Effect of carbon dioxide concentration on the

rate of photosynthesis

Concentration of C02

6



• Temperature has minimal effect on the rate of the light reactions in

photosynthesis. This is because this phase of photosynthesis

depends on the light energy and not heat.

• Raising the temperature will increase the rate of photosynthesis as

the dark reaction is enzyme catalyzed.

• Rise of 10 oC will double the rate of photosynthesis, until an

optimum rate is reached at a temperature of about 40 oC.

• If temperature increase further above 40 oC, photosynthesis slows

down and eventually stop altogether.

• Heat denatures enzyme and destroy their catalytic function in the

various stages in the Calvin cycle.

Temperature

7



Temperature

Temperature, 0 C

R a

t e

o f p h o t o s y n t h e s i s

Effect of temperature on the rate of photosynthesis

60405

8



Difference in the rate of photosynthesis

• In tropical countries, there are no seasons and photosynthesis occurs

throughout the year.

• However, the rate of photosynthesis is influenced by the changes in

temperature and light intensity, as can be seen during the day.

• In the morning and evening, the temperature and light intensity is rather

slow, and as such the rate of photosynthesis will be low.

• During mid day, the temperature and light intensity will be at its highest

and will cause photosynthesis to occur at its highest rate for the day.

• Photosynthesis stops at night when there is no light.

9



Need of increasing the productivity of

crops• Each of the seasons has it characteristics condition that have an effect on

the productivity of the plants there.

• Summer: Productivity is the highest since the rate of photosynthesis is the

highest in the year.

• Winter: Rate starts to slow down due to low temperature.

• Autumn: Rate of photosynthesis is low because the leaves fall.

• Plants can only grow throughout the year if they planted in green houses,

in which carbon dioxide concentration, temperature, light intensity, water

and mineral can be provided at optimal rates.

10



• Methane burners are used to help increase the

concentration of carbon dioxide and the temp.

• Artificial lighting is also used in green houses to

provide necessary light intensity to increases

the productivity of plants.

Need of increasing the productivity of crops

11



Technology Used In FoodProduction

• The efforts by various agencies to

diversify food production

• Methods used to improve the quality and

quantity of food production

12



The efforts by various agencies to diversify

food production

•

Ulam – Malay traditional food which is accepted by otherraces

– Rich in ions, vitamins, fibre & used in preparing herbal

medicine and drinks

– Ex: pegaga, shoots of papaya, kacang botol, petai

13



• Protein sources – Encouragement by government to consume meat products

– Main source of protein – chicken, fish & meat

– Ex: rabbit meat : soft texture, rich in protein, low cholesterol & suitable for

young kids

– Ex: freshwater fish like tilapia, jelawat & haruan are low in cholesterol

– Ex: ostrich meat : nutritious, rich in protein & low in fat


food production

14



• Consuming mushroom –

– Ex: button mushroom, abalone mushroom & shittake

mushroom

– Have high nutrient content

– Increases the body’s immune system


food production

15



Methods used to improve the quality

and quantity of food production

• Methods:

– Direct seeding

– Hydrophonics

– Aerophonics – Breeding of plants and animals

– Tissue culture

–

Genetic engineering – Proper soil management

– Biological control

16



Evaluating the technological

development in food processing

• Explain the necessity for food processing,

• Describe the development of food processing technology

• Relate food processing methods with factors causing food

spoilage,

• Assess the methods of food processing to justify the choice of

consuming certain processed food.

17



Necessity for food processing

• Food processing:

– Process of preparing food to make it more attractive, more

palatable and to last longer

– To preserve food from factors that cause food spoilage:

microorganism

• Necessity for food processing:

– To preserve food from spoilage

– To avoid food wastage

– To prevent food poisoning

– To increase commercial value

– To diversify the use of food substances 18



Causes of food spoilage

•

Microorganism: – Decomposing bacteria & fungi

– Acts on carbohydrate and protein – producing

CO2, water, NH3

– These spoils the food and makes it toxic

• Oxidation of food

– The condition in which oxygen acts on food.

– Usually fruits change color. Ex: apple turns brown

– Oily food becomes rancid and smells

– Rancid food is harmful to body19



Increasing commercial value of food

• Commercially processed food contains

additives

• Additives preserves the freshness of food,

improve the taste, appearance and texture of

processed food

20



Diversifying the uses of food

substances

• Food industry increases the variety of food

produced from one food source

• Ex: milk

– Used to make cheese, yoghurt, ice cream, butter

and chocolates

21



Relate food processing methods with

factors causing food spoilage

• Methods of food preservation:

– Cooking

– Pickling food

– Fermentation

– Drying

– Pasteurization

– Canning

– Refrigeration

22



Cooking• Heating at high temperature

•

Kills bacteria• Denature enzymes that causes food spoilage

Pickling food• Food immersed in acidic solution – vinegar

– pH reduced, microorganism is prevented from

growing

• Food immersed in salt and sugar

– Microorganism lose water through osmosis – dies.

23



Fermentation

• Addition of yeast to food

• Fermentation produces ethanol at highconcentration – prevents juices to become spoiled

• Tapai – a fermented traditional drink is produced by

the fermentation of tapioca

Drying

• Drying under hot sun removes water from food• Prevents microorganism from growing

• Ultraviolet ray from sun kills bacteria

24



Pasteurization

• Usually the preservation of milk

• To destroy bacteria that can cause disease like

tuberculosis and typhoid

• Retains natural flavour of milk

• Milk is heated to 630C for 30 minutes or 720C for 15

seconds and then cooled at temperature below 100

C

• Pasteurised milk can be refrigerated for few days.

25



Canning• Uses heat sterilization to kill microorganism

•Food is packed in cans, steamed in high temperature& drive pressure out

• Cans are then sealed and cooled

• Vacuum created within the cans prevents growth of

microorganisms.

Refrigeration

• Food stored at temperature 00C can remain fresh for

a long period of time

• Low temperature prevent the growth of

microorganisms or the germination of spores 26

Synthesizing Factors Affecting Photosynthesis

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