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PHOTOSYNTHESIS

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PHOTOSYNTHESIS - PowerPoint PPT Presentation


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PHOTOSYNTHESIS. Review Question. Which mode of nutrition do the green plants carry out?. A. Autotrophic nutrition. B. Heterotrophic nutrition. Sorry! You’re wrong!.

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review question
Review Question
  • Which mode of nutrition do the green plants carry out?

A. Autotrophic nutrition

B. Heterotrophic nutrition

sorry you re wrong
Sorry! You’re wrong!
  • Heterotrophic nutrition is the mode of nutrition in which organisms have to depend on other organisms or dead organic matters as their food sources. Green plants, however, can make organic food by themselves using simple inorganic substances.

Back

very good
Very Good!
  • Autotrophic nutrition is the mode of nutrition in which organisms can make organic food by themselves using simple inorganic substances.
  • The process by which the green plants obtain nutrients is called :-

Photosynthesis

overview of nutrition in green plants
Overview of nutrition in green plants

carbon dioxide and water

photosynthesis

mineral salts

(e.g. NO3-, SO42-)

carbohydrates (e.g. glucose)

fatty acids

glycerol

amino acids

water

nutrients for plants can be used to produce all plant materials (e.g. enzymes, cell wall, cytoplasm, cell membrane, chlorophyll)

nature of photosynthesis
Nature of photosynthesis
  • Anabolic process
  • Takes place in chloroplast
  • Necessary factors :
  • Carbon dioxide
  • Water
  • Sunlight
  • Chlorophyll
light reaction
Light reaction
  • Light energy is trapped by chlorophyll in chloroplast
light reaction13
Light reaction

Light energy absorbed by chlorophyll splits water molecules into hydrogen and oxygen

light reaction14
Light reaction

Oxygen is released as a gas through stoma to outside

light reaction15
Light reaction

Hydrogen is fed into dark reaction

dark reaction
Dark reaction

Hydrogen produced in light reaction combines with CO2 to form carbohydrates

Water is formed as a by-product

  • No light is required; can take place either in light or darkness
fate of product of photosynthesis

Fate of product of photosynthesis

PGAL

Pyruvate

+

coenzyme A

X 2

Glucose

&

Cellulose

Kreb

cycle

Fatty acid

Glycerol

Nitrate

Lipid

Protein

fate of carbohydrate products in the plant
Fate of carbohydrate products in the plant

carbon dioxide and water

photosynthesis

mineral salts

(e.g. NO3-, SO42-)

carbohydrates (e.g. glucose)

fatty acids

glycerol

amino acids

water

fate of carbohydrate products in the plant28
Fate of carbohydrate products in the plant

carbon dioxide and water

photosynthesis

mineral salts

(e.g. NO3-, SO42-)

carbohydrates (e.g. glucose)

fatty acids

glycerol

amino acids

water

release energy by respiration

fate of carbohydrate products in the plant29
Fate of carbohydrate products in the plant

carbon dioxide and water

photosynthesis

mineral salts

(e.g. NO3-, SO42-)

carbohydrates (e.g. glucose)

fatty acids

glycerol

amino acids

water

convert into starch for storage

fate of carbohydrate products in the plant30
Fate of carbohydrate products in the plant

carbon dioxide and water

photosynthesis

mineral salts

(e.g. NO3-, SO42-)

carbohydrates (e.g. glucose)

fatty acids

glycerol

amino acids

water

change into sucrose and is transported to other parts through phloem

fate of carbohydrate products in the plant31
Fate of carbohydrate products in the plant

carbon dioxide and water

photosynthesis

mineral salts

(e.g. NO3-, SO42-)

carbohydrates (e.g. glucose)

fatty acids

glycerol

amino acids

water

combine to form fats and oils to form cell membranes and as a food store

fate of carbohydrate products in the plant32
Fate of carbohydrate products in the plant

carbon dioxide and water

photosynthesis

mineral salts

(e.g. NO3-, SO42-)

carbohydrates (e.g. glucose)

fatty acids

glycerol

amino acids

water

join together to become protein molecules

mineral requirements in plants
Mineral requirements in plants
  • In order to synthesize amino acids, nitrate ions must be taken into the plant from the soil through the root
  • Other minerals are also necessary to maintain the life of the plant
the importance of nitrogen
The importance of nitrogen
  • For synthesis of proteins, chlorophyll, etc.
  • Taken in the form of nitrate ions
  • Deficiency symptoms:
    • Little growth (no protein made)
    • Yellowing of leaves (chlorophyll made)
the importance of magnesium
The importance of magnesium
  • Essential component of chlorophyll
  • Deficiency symptoms:
    • Yellowing of leaves (no chlorophyll made)
    • Poor growth (no food manufactured because of lack of chlorophyll)
use of fertilizers in agriculture
Use of fertilizers in agriculture
  • Continuous harvesting crops removes the valuable mineral salts from soil

Fertilizers are added to replace such loss

  • Two kinds of fertilizers:
    • Natural fertilizers
    • Chemical fertilizers
natural fertilizers
Natural fertilizers
  • From manure
  • Organic compounds in it are decomposed by bacteria in soil to form mineral salts
chemical fertilizers
Chemical fertilizers
  • Mainly nitrogenous and phosphorous compounds manufactured artificially
comparison between natural and chemical fertilizers
Comparison between natural and chemical fertilizers

Natural fertilizers

Chemical fertilizers

Very cheap

More expensive

Contain humus which can improve soil texture

No humus so cannot improve soil texture

Less soluble in water so less likely to be washed away

Very soluble in water so more likely to be washed away

comparison between natural and chemical fertilizers41
Comparison between natural and chemical fertilizers

Natural fertilizers

Chemical fertilizers

Less soluble in water so more difficult to be absorbed

Very soluble in water so easier to be absorbed

Time is needed for the decomposition to complete before nutrient is available to plants

More readily to be used by the plants

importance of photosynthesis
Importance of photosynthesis
  • It is the only method to convert energy in sunlight into chemical energy
    • Animals have to depend on plants for food supply
    • Plants: producers; animals : consumers
  • To maintain a constant oxygen level in the atmosphere
experiments to test for necessary factors of photosynthesis
Experiments to test for necessary factors of photosynthesis
  • Experimental set-up: To remove the factor under study and to see if photosynthesis still takes place
  • Control set-up: Identical to experimental set-up except that the missing factor is present
what is the purpose of setting up region a
What is the purpose of setting up region A?
  • As a control
  • Too simple and not explicit!

To show that photosynthesis cannot take place in the absence of light

destarching
Destarching
  • Reason:
    • To avoid any existing starch in the leaves interfering with the result, and to show that any starch found after the experiment was produced during the period of investigation
  • Method:
    • By placing the plant in dark for at least 24 hours
parts of plant where photosynthesis takes place
Parts of plant where photosynthesis takes place
  • Places where chloroplasts are found
  • Mainly in the leaf because
    • it contains a lot of chloroplasts
    • it is well adapted for performing photosynthesis
cross section of a dicot leaf
Cross-section of a dicot leaf

upper epidermis

protect internal tissues from mechanical damage and bacterial and fungal invasion

cross section of a dicot leaf50
Cross-section of a dicot leaf
  • Cuticle
  • a waxy layer
  • prevent water loss from the leaf surface
cross section of a dicot leaf52
Cross-section of a dicot leaf

palisade mesophyll

columnar cells closely packed together

absorb light more efficiently

contains many chloroplasts

cross section of a dicot leaf53
Cross-section of a dicot leaf

irregular cells loosely packed together to leave numerous large air spaces

allow rapid diffusion of gases throughout the leaf

less chloroplasts for photosynthesis

spongy mesophyll

cross section of a dicot leaf54
Cross-section of a dicot leaf

same as upper epidermis except the cuticle is thinner

lower epidermis

cross section of a dicot leaf55
Cross-section of a dicot leaf

stoma

opening which allows gases to pass through it to go into or out of the leaf

cross section of a dicot leaf56
Cross-section of a dicot leaf

guard cells

control the size of stoma

cross section of a dicot leaf57
Cross-section of a dicot leaf

vascular bundle (vein)

cross section of a dicot leaf58
Cross-section of a dicot leaf
  • xylem
  • to transport water and mineral salts
  • towards the leaf
cross section of a dicot leaf59
Cross-section of a dicot leaf
  • phloem
  • to transport organic substances
  • away from the leaf
adaptation of leaf to photosynthesis
Adaptation of leaf to photosynthesis

Upper epidermis and cuticle is transparent

Allows most light to pass to photosynthetic mesophyll tissues

adaptation of leaf to photosynthesis61
Adaptation of leaf to photosynthesis

Palisade mesophyll cells are closely packed and contain many chloroplasts

To carry out photosynthesis more efficiently

adaptation of leaf to photosynthesis62
Adaptation of leaf to photosynthesis

Spongy mesophyll cells are loosely packed with numerous large air spaces

To allow rapid diffusion of gases throughout the leaf

adaptation of leaf to photosynthesis63
Adaptation of leaf to photosynthesis

Numerous stomata on lower epidermis

To allow rapid gaseous exchange with the atmosphere

adaptation of leaf to photosynthesis64
Adaptation of leaf to photosynthesis
  • Extensive vein system
  • Allow sufficient water to reach the cells in the leaf
  • To carry food away from them to other parts of the plant
chemosynthsis
CHEMOSYNTHSIS
  • Iron bacteria
  • Colorless sulphur bacteria
  • Nitrifying bacteria
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