CHAPTER 6 : NUTRITION

6.9 Macronutrients & Micronutrients in Plants

LEARNING OUTCOMES• List elements required by

plants,• Classify elements required by plants based on the amount needed,

• Relate the effects of macronutrient deficiency in plants.

• Explain the function of each macronutrient in plants,

• State the function of micronutrients & effects of micronutrient deficiency in plants.

•MACROnutrients : needed in LARGER quantities

•Carbon, Hydrogen, Oxygen, Phosphorous, Potassium (Kalium), Calcium, Magnesium & Sulphur.

•MICROnutrients : needed in SMALLER quantities.

•Boron, Molybdenum, Zinc, Manganese, Copper & Ferum

•Table 1

• Wilhelm Knop (scientist) successfully prepared a solution which can provide a plant with all the nutrients it needs

• The solution is known as Knop’s Solution.Calcium nitrate, Ca(NO3)2 0.8g

Potassium nitrate, KNO3 0.2g

Potassium dihydrogen phosphate, KH2PO4 0.2g

Magnesium sulphate, MgSO4 0.2g

Ferum (III) phosphate, FePO4 Trace

Distilled water 1 litre

LEARNING OUTCOMES• Describe the development that leads to the discovery of photosynthesis,

• State the substances required for photosynthesis,

• State the substances produced from photosynthesis,

• Draw & label the cross section of leaf• State the function of each part of the leaf with respect to photosynthesis,

• Explain leaf adaptation to optimise photosynthesis,

• Explain how plants from different habitats are adapted to carry out photosynthesis.

The Discovery of Photosynthesis

• 1692 – Dutch scientist, Van Helmont carried out an investigation to study the nutrition of plants.

• He filled a big pot with exactly 91kg of dry soil planted a plant (2.4kg) the surface covered with a metal sheet with small holes to allow water to enter Van watered the plants for 5 years consistently plant (increased to 75kg), soil (decreased by 0.057kg)

• Van Helmont concluded that the increase in weight of the plant came from the water & not the soil.

The Discovery of Photosynthesis

• 1772 – Joseph Priestly carried out an experiment using mouse, candle & plants.

• The plant had changed the air in the container.• 1770s – Jan Ingenhouse discovered that a plant

could only change the air container if there was light. He also discovered that only the green parts of the plant were able to do so. (light & chlorophyll both play a part in photosynthesis0

• 1780s – Jean Senebier showed that the plants gave out oxygen when they were provided with CO2

PHOTOSYNTHESISThe biochemical process through which light energy is absorbed by chlorophyll, and is used to fuel the synthesis of sugar molecules

“The process where organic compounds are synthesised from water & carbon dioxide in the

presence of sunlight & chlorophyll.”

STRUCTURE & FUNCTION OF THE PARTS OF A LEAF

Adaptations of Leaf for Optimal Photosynthesis

• The internal structure of a leaf, the shape of a leaf & the arrangement of leaves on a plants are all adapted for obtaining optimum light & CO2

• Table 2• The shape of a leaf is also adapted for

photosynthesis. Most leaves are broad & thin.• Large surface area enables the leaf to absorb

maximum light & CO2

• The thinness light & CO2 need not travel too far to reach every mesophyll cell

Adaptations of Leaf for Optimal Photosynthesis

•The arrangement of leaves is also adapted to optimize photosynthesis.

•Most plants spread out their leaves in such a way that there is minimal overlapping known as leaf mosaic every leaf can receive sunlight.

ADAPTATION OF PLANTS FROM DIFFERENT HABITATS FOR PHOTOSYNTHESIS

• Two main aspects :– The distribution of stomata– The distribution of chloroplasts

• Examples :– Hibiscus : land– Water lily : water surface–Hydrilla : in the water– Cactus : desert

6.11: THE MECHANISM

OF PHOTOSYNTHESIS

LEARNING OUTCOMES

• To identify the parts of chloroplast related to photosynthesis,

• To explain the light reaction & dark reaction of photosynthesis,

• To compare & contrast light reaction & dark reaction in photosynthesis,

• To relate light reaction with dark reaction in photosynthesis,

• To write an equation to represent the process of photosynthesis

• Photosynthesis occurs in in the chloroplasts of mesophyll cells & guard cells of the leaf.

• Consist of two part : stroma & grana

• Each granum contain chlorophyll that absorb energy of sunlight

• The process of photosynthesis is divided into two :

– Light reaction– Dark reaction

• Light reaction : occurs in the granum (contain chlorophyll) photolysis of water

• Dark reaction : occurs in the stroma (gel-like matrix – contain enzymes) CO2 is reduced to carbohydrate in a process called fixation of CO2 (reduction of CO2)

LIGHT REACTION• Occurs in granum• Chlorophyll captures light excites the

electrons of chlorophyll to higher level• Light energy is used to split the water molecules

hydroxyl ions + hydrogen ions (photolysis of water)

• 4H2O 4H+ + 4(OH)-

• The hydrogen ions combine with the electrons released by chlorophyll to from hydrogen atoms

• 4(H)+ + 4 electrons 4(H)

sunlight

chlorophyll

LIGHT REACTION• The hydrogen atom are used in ‘dark reaction’ to

reduce CO2.

• Each hydroxyl ion loses an electron to the chlorophyll hydroxyl groups combine together to form H2O & O2

• 4(OH)- - 4 electrons 4(OH)

• 4(OH) 2H2O + O2

• Oxygen is released into the atmosphere & later used for cellular respiration

• Energy released from the excited electrons is used to form ATP

DARK REACTION• Occurs in the stroma of the chloroplast

• Hydrogen atoms from ‘light reaction’ are used in dark reaction to reduce carbon dioxide to basic units of glucose (CH2O)

• Involves a series of complex chemical reactions which require enzymes– CO2 + 4(H) (CH2O) + H2O

• Six units of (CH2O) combine together to form a molecule of glucose

DARK REACTION• 6(CH2O) C6H12O6

• Glucose is converted into starch, cellulose, sucrose & lipids. When combined with nitrogen protein

• Overall process :12H2O + 6CO2 C6H12O6 + 6O2 + 6H2O

Water + carbon dioxide glucose + oxygen + water

sunlight

chlorophyll

sunlight

chlorophyll

COMPARISON OF LIGHT REACTION & DARK REACTION

LIGHT REACTION DARK REACTION

SIMILARITIES

•Both occur in the chloroplast

•Both involve chemical reactions

•Both are reactions related to photosynthesis

•Both occur during the day

DIFFERENCES

Occurs in granum Occurs in stroma

Requires sunlight Does not require sunlight

Involves photolysis of water Involves reduction of carbon dioxide

Produces water & oxygen Produces glucose

Substance required in reaction is water

Substance required in reaction is carbon dioxide

6. 12 :FACTORS

AFFECTING PHOTOSYNTHESI

S

LEARNING OUTCOMES• Identify the factors affecting the rate of

photosynthesis,• Identify the factor that limits the rate of photosynthesis at different light intensities,

• Explain the effects of temperature & concentration of CO2 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 & temperature,

• Identify some ways to meet the need of increasing the productivity of crops based on factors affecting the rate of photosynthesis.

CONCENTRATION OF CO2

• Conc. of CO2 in the atmosphere varies between 0.03% to 0.04%

• Light intensity & temperature are kept constant the rate of photosynthesis increases until a saturation point is reach

• After this point, any further increase in the conc. of CO2 has no effect on the rate of photosynthesis

• Limited by other factors (light intensity), not enough to increase the rate of photosynthesis

Effect of concentration of CO2 on the rate of photosynthesis

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1 2 3 4 5 6 7 8 9 10 11concentration of CO2

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LIGHT INTENSITY• Temperature &

concentration of CO2 are kept constant, the rate of photosynthesis can be increased by increasing the light intensity up to the light saturation point.

• After this point, any further increase in light intensity has no effect on the rate of photosynthesis (limiting factor : CO2 conc.)

• Can be increased by increasing the CO2 conc.

Effect of light intensity on the rate of photosynthesis at different levels of

CO2 concentration

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1 2 3 4 5 6 7 8 9 10 11light intensity

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karbon dioksida tinggikarbon dioksida rendah

TEMPERATURE• Dark reaction involves

enzymes• The rate of photosynthesis

increases as the temperature increase enzymes more active

• Optimum temp. is between 30oC to 35oC

• >40oC, the rate of reaction decrease enzymes denatured photosynthesis stops

• If the light intensity is too low, any increase in temperature will not increase the rate of photosynthesis

Effect of temperature on the rate of photosynthesis at different light intensity

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RELATIONSHIP BETWEEN THE RATE OF PHOTOSYNTHESIS THROUGHOUT THE

DAY WITH THE CHANGES IN LIGHT INTENSITY & TEMPERATURE

• Closely related & change throughout the day

• Light intensity high, the temperature is also high.

• Tropical country, LI & T are at their maximum at noon time. The rate of photosynthesis is also maximum.

• If temperature increases above 40oC, the rate of photosynthesis decreases.

• In temperate country (4 seasons), LI & T change throughout the year.

• Winter : LI & T are very low. Photosynthesis hardly occurs

• Autumn : the rate of photosynthesis is at its lowest plants shed their leaves & light intensity as well as the temperature are very low

• Summer : LI & T are at their optimum level for photosynthesis, the rate of photosynthesis is at its max.

• Summer is the best time for agricultural

• To overcome the problem, the plants need to be planted in greenhouse.

• In a greenhouse, the conc. of carbon dioxide, temperature & light intensity are at optimum levels for photosynthesis.

• The rate of photosynthesis is at its maximum throughout the year, ensure the crop production throughout the year.

6.13 Practising a Caring Attitude Towards Plants

• Must be thankful to plants & practise a caring attitude towards them

• Why?• Plants produce food as a source of energy for

us, maintaining the oxygen & carbon dioxide content in atmosphere

• Without plants, there will be more CO2 & less O2 in the atmosphere cause global warming

• Not destroy forests @ chop down plants indiscriminately. Should grow more plants around us.

6.14 – Technology in Food Production

• To improve the quality & quantity of food production in Malaysia through :– Direct seeding from rice– Hydroponics & aeroponics– Breeding– Tissue culture– Genetic engineering– Soil management– Biological control

6.15 : TECHNOLOGIC

AL DEVELOPMENT

IN FOOD PROCESSING

• Fresh food can last only for a short time, easily spoilt.

• Need to be processed in order to last longer

• Technology for food processing :– Changing raw food materials to other forms– Adding certain chemical

• The necessity for food processing are :– Destroying m/organisms– Extending the lifespan of food– Avoiding food wastage– Diversifying the uses of food, like milk & dairy

products– Ensuring sufficient food supply because

processed food can last longer & they can be easily sent to places with insufficient food supply

FOOD PROCESSING METHODS

• Cooking (to kill the bad bacteria)• Using salt, sugar & vinegar (osmosis)• Fermentation process (yeast is used glucose

ethanol + CO2)• Drying (dehydration)• Pasteurisation (heated to certain temp and

rapid cooling)• Canning (sterilised at high temp, above 120oC,

the container is vacuum to kill bacteria, prevent bacteria from growing)

• Refrigeration (slow down the action of microorganism, temp low to -15oC)