nutrition in plants

Nutrition in Plants

How does trees on the fertile plain obtain their nutrients ? Or the algae in the sea ? Or the cacti in the desserts ?

Review Question
Which mode of nutrition do the green plants carry out?
A. Autotrophic nutrition B. Heterotrophic nutrition

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.

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

Nature of photosynthesis
Takes place in Chloroplast
Necessary factors :
Carbon dioxide
Water
Sunlight
Chlorophyll

Route of Carbon Dioxide for Photosynthesis

CO 2 Stoma Air Space Spongy Mesophyll Cell Chloroplast

CO 2 Chloroplast Palisade Mesophyll Cell Stoma Air Space

Light energy is trapped by chlorophyll in chloroplast
Light energy absorbed by chlorophyll splits water molecules into hydrogen and oxygen
Oxygen is released as a gas through stoma to outside
Hydrogen is fed into dark reaction
Light reaction

6 blue red % of light absorbed by chlorophyll green

Oxygen is produce as the by-product of photosynthesis.

Dark reaction
No light is required ; can take place either in light or darkness
Hydrogen produced in light reaction combines with CO 2 to form carbohydrates
Water is formed as a by-product

Dark Reaction H Summary of Photosynthesis Water Oxygen Glucose ( C 6 H 12 O 6 ) Light Reaction 6 CO 2 + 6 H 2 0 C 6 H 12 O 6 + 6 O 2 Light Carbon Dioxide

Fate of carbohydrate products in the plant

carbohydrates (e.g. glucose) carbon dioxide and water release energy by respiration photosynthesis

convert into starch for storage because glucose is not a very good storage molecule carbohydrates (e.g. glucose) carbon dioxide and water photosynthesis

change into sucrose and is transported to other parts through phloem carbohydrates (e.g. glucose) carbon dioxide and water photosynthesis

carbon dioxide and water photosynthesis carbohydrates (e.g. glucose) combine to form fats and oils to form cell membranes and as a food store fatty acids glycerol

carbon dioxide and water photosynthesis carbohydrates (e.g. glucose) mineral salts from soil (e.g. NO 3 - , SO 4 2- ) amino acids join together to become protein molecules

Experiments on photosynthesis

Destarching
Reason:
To avoid any existing starch in the leaves interfering with the result , and to show that any starch found after the experiment is produced during the period of investigation
Method:
By placing the plant in dark for at least 48 hours

To test a leaf for the presence of Starch Investigation 8.1

Why is the leaf first boiled in water ? Ans: Because the process can soften the leaf, break down the cuticle and kill the leaf. boiling water turn off Bunsen burner boiling alcohol hot water iodine white tile turn off Bunsen burner

Why is the leaf then boiled in alcohol ? Ans: To decolourize the leaf (to remove chlorophyll). boiling water turn off Bunsen burner boiling alcohol hot water iodine white tile turn off Bunsen burner

Why is it important to turn off the Bunsen burner when you are heating the alcohol ? Ans: Because alcohol catches fire easily. boiling water turn off Bunsen burner boiling alcohol hot water iodine white tile turn off Bunsen burner

Why is the leaf put in hot water after being boiled in alcohol ? Ans: Since the leaf becomes brittle after boiling in alcohol, so dipping it into hot water enables it to be softened. boiling water turn off Bunsen burner boiling alcohol hot water iodine white tile turn off Bunsen burner

What colour change can be observed if starch is present ? Ans: The leaf becomes blue-black when iodine solution is added to it. boiling water turn off Bunsen burner boiling alcohol hot water iodine white tile turn off Bunsen burner

To show that Chlorophyll is necessary for Photosynthesis Investigation 8.3

Which part of the leaf turns blue-black when treated with iodine solution ? Ans: Only the green part. green part purple part

Is chlorophyll necessary for photosynthesis ? Ans: Yes. green part purple part

What is the control in this experiment ? Ans: The green part of the leaf acts as the control. green part purple part

To show that Carbon Dioxide is necessary for Photosynthesis Investigation 8.4

Why is potassium hydroxide solution put in one of the flasks ? Ans: To absorb all the carbon dioxide in flask B. sunlight B A water potassium hydroxide solution

What happens to each leaf after testing the presence of starch at the end of the experiment ? Ans: The leaf in flask A changes to blue-black while the leaf in flask B stains brown. sunlight B A water potassium hydroxide solution

What do your results suggest about the relationship between carbon dioxide and photosynthesis ? Ans: Carbon dioxide is necessary for photosynthesis. sunlight B A water potassium hydroxide solution

Factors affecting the rate of photosynthesis

 Light intensity
 Rate of Photosynthesis
Light Intensity

 Carbon dioxide concentration
Carbon Dioxide Concentration

 Temperature
Temperature Temperature > 40 ℃ Rate  & Stop soon

If no water, stomata close
no gaseous exchange
photosynthesis ceases
Water Supply

Why is Photosynthesis important ? Green plants: the only organisms capable of trapping light to manufacture food from simple inorganic substances

Why is Photosynthesis important ?
Green plants(producers) starts the food chain & provide food for other organisms

Why is Photosynthesis important ?
Atmospheric carbon dioxide is absorbed & oxygen is released into the atmosphere which maintains the composition of the atmosphere constant

Parts of plant where photosynthesis takes place
Mainly in the leaf because
it contains a lot of chloroplasts
it is well adapted for performing photosynthesis

Internal Structure of Leaf

cuticle upper epidermis palisade mesophyll spongy mesophyll intercellular space (air space) guard cell lower epidermis cuticle stoma chloroplasts

Cross-section of a leaf of dicotyledon

upper epidermis protect internal tissues from mechanical damage and bacterial & fungal invasion

Cuticle
a waxy layer
prevent water loss from the leaf surface
protect the leaf

mesophyll

palisade mesophyll (layer) columnar cells closely packed together  absorb light more efficiently contains many chloroplasts

spongy mesophyll (layer) irregular cells loosely packed together to leave numerous large air spaces  allow rapid diffusion of gases throughout the leaf some (fewer than palisade mesophyll) chloroplasts for photosynthesis

lower epidermis same as upper epidermis except the cuticle is thinner

stoma (stomata) opening which allows gases to pass through it to go into or out of the leaf

guard cells control the size of stoma

Stoma stoma Guard cells thinner outer wall thicker inner wall

vascular bundle ( vein )

Internal Structure of Leaf xylem phloem

xylem
to transport water and mineral salts
towards the leaf
for mechanical support

phloem
to transport organic substances ( food/sugar/ glucose/ sucrose ) away from the leaf

Adaptation of leaf to photosynthesis

The leaf is thin decrease diffusion distance for gases & light The leaf is broad & flattened increase surface area to absorb more sunlight

Cuticle exists in upper epidermis and is transparent Allows most light to pass into photosynthetic mesophyll tissues

Palisade mesophyll cells are closely packed and contain many chloroplasts To carry out photosynthesis more efficiently

Spongy mesophyll cells are loosely packed with numerous large air spaces To allow rapid diffusion of gases throughout the leaf

Numerous stoma ta on lower epidermis To allow rapid gaseous exchange with the atmosphere

Extensive vein system
Allow sufficient water to reach the cells in the leaf
To carry food away to other parts of the plant

Mineral requirements in plants
In order to synthesize amino acids, nitrate ions which must be taken into the plant from the soil through the root
Other minerals are also necessary to maintain the life of the plant (N, Mg, P, K, S, etc)

The importance of nitrogen
For synthesis of proteins, chlorophyll, etc
Taken in form of nitrate ions
Deficiency symptoms:
Little growth ( - no protein made)
Yellowing of leaves ( - no chlorophyll made)

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
Continuous harvesting crops removes valuable mineral salts from soil
 Fertilizers are added to replace such loss
Two kinds of fertilizers:
Natural fertilizers
Chemical fertilizers

Natural fertilizers
From manure
Organic compounds in it are decomposed by the bacteria in soil to form mineral salts

Chemical fertilizers
Mainly nitrogenous and phosphorous compounds manufactured artificially

Comparison between natural and chemical fertilizers Natural fertilizers Chemical fertilizers 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 fertilizers Natural fertilizers Chemical fertilizers Less soluble in water so more difficult to be absorbed Very soluble in water so easier to be absorbed More readily to be used by the plants Time is needed for the decomposition to complete before nutrients are available to plants Very expensive Much cheaper

~ END ~

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nutrition in plants

by hiratufail on May 17, 2008

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nutrition in plants — Presentation Transcript