how plants get their food
DESCRIPTION
How Plants Get Their Food . 2. 199.8 lb soil. 200 lb soil. In 1649, A Belgian physician, van Helmont , set up an experiment in which he planted a willow sapling, weighing 5 lb , in 200 lb of soil. How do plants get their food ?. - PowerPoint PPT PresentationTRANSCRIPT
How Plants Get Their Food
How do plants get their food ?
199.8 lb soil
The soil was watered but nothing else was added. After 5 years, the tree had gained 169.2 lb in weight but the soil had lost only 2 pounds. van Helmont concluded that the tree had made 169lb of new growth from water alone.
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200 lb soil
In 1649, A Belgian physician, van Helmont, set up an experiment in which he planted a willow sapling, weighing 5 lb, in 200 lb of soil.
van Helmont’s experiment was effective in showing that the plant’s food did not come from the soil.
But he had overlooked the fact that air was available to the plant as well as water.
Could it be that the plant made 169 lb of material from just air and water?
This might seem unlikely, but we now know that plants do indeed make their food using carbon dioxide from the air and water from the soil.
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FeedingAnimals get their food by eating plants, or other animals Carnivores eat animals Herbivores eat plants
Plants make their own food They combine carbon dioxide from the air with water
and dissolved salts from the soil Plants do NOT get their food from the soil
The first stage by which plants make food is called PHOTOSYNTHESIS
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by eating plants or ...
Animals get their food …
... plant products,
or (c) other animals
Plants make their food by photosynthesis
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Photosynthesis6
Green plants take in carbon dioxide (CO2) from the airThey take up water (H2O) from the soil
The plants combine the CO2 with the H2O tomake the sugar, glucose (C6H12O6)
6CO2 + 6H2O = C6H12O6 + 6O2
Oxygen (O2) is a by-product of this reaction
C6H12O6
CO2
CO2
CO2
CO2
CO2
CO2
H2O
H2O
H2O
H2O
H2O
H2O
6O2
+
6 molecules of carbon dioxide combine with 6 molecules of waterto make one molecule of glucose and 6 molecules of oxygen
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Energy
It takes energy to make CO2 combine with H2O
This energy comes from sunlight
The energy is absorbed and used by a substance called chlorophyll
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sunlight(energy)
waterwater
carbon dioxide
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Chlorophyll
Chlorophyll is a green colored chemical
It is present in the leaves of green plants
The chlorophyll in the cells is packaged into tiny structures called chloroplasts
The next slide shows a diagram of leaf cells with their chloroplasts
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Leaf cells with chloroplasts
cell wall
nucleus
chloroplast
cytoplasm vacuole
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All the reactions to combine CO2 and H2O take place in the chloroplast
sunlight
water
carbon dioxide
in the chloroplast,carbon dioxide andwater combine tomake sugar
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palisade cell of leaf
Cell structure of a leafThe palisade cells are in theuppermost layers of the leaf
epidermis
palisade cell ( photosynthesis)
vessel (carries water)
stoma (admits air)
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Carbohydrates• Glucose is one example of a carbohydrate
• Other examples are starch, sucrose and cellulose (in cell walls)
• Carbohydrate molecules contain the elements carbon, hydrogen and oxygen
• Living organisms can easily change one carbohydrate into another
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What happens to the glucose? The glucose made by the chloroplast is either (a) used to provide energy for the chemical
processes in the cell ( by respiration)
(b)turned into sucrose and transported to other parts of the plant
(c) turned into starch and stored in the cell as starch
grains
In darkness the starch is changed back into glucose and transported out of the cell
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GLUCOSE
storage e.g. starch in potato
starch
fruitsother sugars
e.g. seed germination
energy
cytoplasm
protein
cell walls
cellulose
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