Chapter 5: Nutrition in Plants

Nutrition in Plants Introduction

Usually green plants make food using energy from sunlight. After reading this chapter, you will be able to understand that green plants make their own food from simple inorganic compounds like water and carbon dioxide.
This process is known as photosynthesis and it requires special conditions for it to yield its products that are both beneficial to plants and other organisms.
The leaves are the major plant parts that are uniquely adapted to facilitate the occurrence of the process of photosynthesis (Figure 5.1).

5.1: Photosynthesis
When you get hungry, you grab some food and eat it. But what can plants do when they need food? Most plants are able to make their own food whenever they need.
This is Known as photosynthesis.
This process is performed by all plants, algae, and even some microorganisms. In Activity 5.1, you will discuss the meaning of photosynthesis and the sites
where it occurs.
Activity 5.1: Discussing the meaning of photosynthesis
What you need: notebooks, braille paper, stylus, slate, Perkins brailler.
What to do:
In groups:
1.Using the knowledge from primary level science and the English dictionary,
find out the meaning of the following words;
(c) photosynthesis
(b) synthesis
(a) photo
2.Where does photosynthesis occur in a plant?
3.Identify the time or period of the day when photosynthesis occurs.
4.Present your findings in class
5./Individually write or braille the class conclusions.

Raw Materials, Conditions and Products of Photosynthesis
Many people believe they are “feeding” a plant when they put it in soil, water it, or place it outside in the sun, but none of these things are considered food.
Rather, plants need raw materials and specific raw materials to make their own food. In Activity 5.2, you will discover the raw materials, conditions and products of photosynthesis.
Activity 5.2: Ftndjng out the raw materials, conditions and products of photosynthesis
What you need: notebooks, braille paper, stylus, slate, Perkins brailler.

What to do:
In groups:

1. Study the Figure 5.2 and identify the raw materials, conditions and products
   involved in the process of photosynthesis.
2. Identify other conditions necessary for photosynthesis apart from those you
   identified in (1) above.
3. Explain why a plant put in darkness cannot make its own food.
4. Prepare your work and present to the class.
5. Individually write the class conclusions in your notebooks.
   From Activity 5.2, you have identified the raw materials required for photosynthesis to take place. These include carbon dioxide, water in the presence of light. The products identified include oxygen and carbohydrates.
   The carbohydrates are stored in the form of starch. Therefore, if you are to find out whether a plant has carried out photosynthesis, you just need to test for starch in the leaves. Carry out the project work to prove whether such raw materials, conditions and products are formed.

Project work
Activity 5.3: Investigating the raw materials used during the proccss of photosynthesis
Experiment 1
What you need: Potted plant, aluminium foil, water, ethanol, white tile, source of heat, wire gauze, dropper, boiling tube and razor blade, notebooks, braille paper, stylus, slate, Perkins brailler.
What to do:

1. Get a potted plant and place it in darkness for 24 hours to de-starch it.
2. Make a shape in an aluminum foil and make a stencil
3. Place the stencil around the leaf with the cut shape facing upwards where light strikes.
4. Place the plant in sunlight for 3 hours.
5. Remove the leaf with a stencil from the plant using a razor blade
6. Remove the stencil and carry out the test for starch.

Task:
a) Which condition required for photosynthesis has been investigated in the
experiment above?
b) Write the observations from your experiment.
c) Draft a report from this experiment including your observations, conclusions and explanations.
Experiment 2
What you need: Sodium hydroxide/Potassium Hydroxide, Conical flasks fitted with corks with a hole, well watered de-starched plants. Iodine, 99% alcohol, water beaker, white tile and test tubes, notebooks, raille paper, stylus. slate, Perkins brailler.
What to do:
1.The leaves of a potted plant are de-starched by keeping the plant in darkness for two days.
2.The petiole of the leaf (stalk) is passed through the hole in the cork so that the leaf is completely enclosed in a flask containing Sodium Hydroxide (The Sodium Hydroxide absorbs all Carbon dioxide enclosed in the flask.)
3.The flask is then made air tight by smearing Vaseline at the neck of the flask to prevent any air from entering.
4.A control experiment is also set up, however here the flask contains water which does not absorb Carbon dioxide.
5. The plant and the flasks are then placed in sunlight for 6 hours.
Task:
a) Which raw material has been investigated in the experiment above?
b) Write the observations from your experiment.
c) Draft a report from this experiment including your observations, conclusions and explanations.

Experiment 3
What you need: A fresh water weed(elodea plant), funnel and wooden blocks, test tube, beaker. water and sodium hydrogen carbonate, notebooks, braille paper, stylus, slate, Perkins brailler.
What to do:
I. The funnel is inverted in the beaker over the plant.

2. Sodium hydrogen carbonate is added to the water to provide C02
3. The funnel is raised slightly above the bottom of the beaker using small wooden blocks to allow water to circulate freely under it.
4. The apparatus is then placed in the bright sunlight.
5. Another similar set up is made and placed in darkness. This acts as the control experiment.
   Task:
   a) Which factor of photosynthesis has been investigated in the experiment above?
   b) Write the observations from your experiment.
   c) Draft a report from this experiment including your observations, conclusions and explanations.

Investigating the process of photosynthesis
Scientists are always curious: finding out details about life processes using experiments. As a scientist in the century, you can also conduct experiments the process of photosynthesis. In Activity 5.4. you will be able to demonstrate the photosynthesis that occurs in green plants in leaves.
Remember as earlier discussed when photosynthesis takes place, carbohydrates are formed. These carbohydrates are stored in the form of starch in the leaves.

Activity 5.4: Demonstration Showing that Photosynthesis occurs in plant Leaves
What you need: A green leaf, water bath. Iodine solution,Water. absolute
alcohol (99%), beaker. white surface or tile, notebooks, braille paper, stylus,
slate, Perkins brailler.
What to do
In groups:
1.Remove/ detach a leaf from a healthy plant which has been receiving sunlight.
2.Place the leaf in boiling water for about 5 minutes. This softens the leaf cell wall protoplasm and makes it permeable to Iodine.
3.Obtain the boiled leaf and place it in a beaker containing 99% alcohol.Boil the leaf in the alcohol using a water bath. Boil in alcohol until all the chlorophyll is dissolved out. This decolorises the leaf and makes
detection of any colour changes possible and easier.
4.After all the chlorophyll is dissolved out, boil the leaf again in hot water to soften it again.

5. Spread the leaf on a white surface tile and add drops of iodine onto it.
   Task
   a) Write the observations from your experiment.
   b) Draft a report from this experiment including your observations, conclusions and explanations.
   Adaptations of leaves to carry out the process of photosynthesis
   Have you ever asked your self how leaves trap sun light? Do you know that they have special features that enable them to carry out photosynthesis?
   Leaves are adapted for carrying out photosynthesis by virtue of their external features. In Activity 5.5, you will identify adaptations of leaves to carry out the process of photosynthesis structure.
   Activity 5:5 Identifying adaptations (external) of leaves to carry out the process of photosynthesis
   What you need: notebooks, braille paper. stylus, slate, Perkins brailler,
   leaves, handlens and flip charts.
   What to do:
6. n groups:
7. Observe the leaves in the Figure 5.3 below.
8. Move tothe compound and pick any leaves thatare notrepresentedinfigure 5.3
9. Use your collection and the Figure 5.3 and generate the external feature that make plants able to carry out photosynthesis.
10. Make a table for adaptations of leaves on a flip chart.
11. Present your work to the rest of the class
12. Individually, write the class summaries in your notebook.
    daptations (external) of leaves to carry out the process of photosynthesis

Leaves need water, sun light and carbon dioxide to carry out photosyntheis.Carbon
dioxide passes through the stomata into the leaf and sun light is trapped by chlorophyll.