PRACTICAL 1: BASIC NEEDS OF PLANTS

Objective: To determine the basic needs of plants: sunlight, air and water

Problem: Do plants need sunshine?

Introduction: Plants need sunshine in order to make chlorophyll. Chlorophyll is the chemical that makes plants green. Chlorophyll is used for the plant to carry out photosynthesis process.

Hypothesis: If plants do not get sunlight, they cannot produce chlorophyll and they will lose their green colour and eventually die.

Inferences: Plants need sunshine to make chlorophyll for photosynthesis process

Variables: a) manipulated: The condition of the leaves

b) responding: The colour and the freshness of the leaves

c) fixed: The condition where the plant is placed

Literature review:

A Dutchman, Jan Ingenhousz , who was court physician to the Austrian empress, to make the next major contribution to the mechanism of photosynthesis. He had heard of Priestley's experiments, and a few years later spent a summer near London doing over 500 experiments, in which he discovered that light plays a major role in photosynthesis.

"I observed that plants not only have the faculty to correct bad air in six to ten days, by growing in it...but that they perform this important office in a complete manner in a few hours; that this wonderful operation is by no means owing to the vegetation of the plant, but to the influence of light of the sun upon the plant".

Materials:

Growing plant with large leaves, Vaseline, black construction paper and paper clips

Procedure A:

1) Green plant is placed in well-lighted place where it can be seen without being handled by class members.

2) Both sides of several leaves are covered carefully with Vaseline3) These leaves are observed each day and they are compared with uncoated

leaves. The colour and the freshness of the leaves are noticed.

Procedure B:

1) The pattern on one side of a folded piece of black construction paper is cut out.

2) The pattern on the leaf is clipped and left it attached for several days.3) After several days, the construction paper is removed and the results are

observed.

Results:

Observation InferencesProcedure A The leaves that had

Vaseline coat on the both side died.  The other leaves remained unchanged.

Openings on the underside of plant leaves called stomata that allow gases to move into and out of the leaves.  The Vaseline plugged the openings and the leaf was not able to receive necessary carbon dioxide gas and eliminate excess oxygen.

Procedure B The leaf that had been under the cover of the construction paper has began to lose its green colour , pale yellow spot formation and eventually wilt and die.

This is because the leaf is unable to continue to make food without the help of sunlight.

Observation :

Before experiment After experiment

Leaf coated with vaselineLeaf becomes wilting and eventually

dessication occurs.

Leaf covered with black construction paper

Yellow spot formation on the leaf

Discussion:

Question:

1) What would happen if only the topside were coated? The bottom side?

If the topside of leaves were coated with Vaseline, the plant will live and transpiration process can occurs whereas if the bottom side of leaves were coated, the plant will die because the Vaseline has locked in some of the

water and made the leaf transpire less thus the plant eventually become wilt and die.

2) Would leaf continue to die if the coating were removed after one day?

No. This is because when the coating has been removed from the leave, the stomata can carry out transpiration processes.

3) What would happen if only half the leaf were covered? (half the top side and half of the bottom side)

Half of the leaf will began to lose its colour, pale yellow spot formation and the other half will remains green.

4) What happen to the plant leaf after the mask is removed? Observe for several days.

The plant leaf will returns to its green colour because now it is able to receive direct sunlight and can produce its own food.

Conclusion:

Plants require light in order to grow, but there is a stage of growth that can occur without light is the first few days of growth.

Problem: Can plants live without water?

Introduction: A plant, like all living organisms, needs water to live and grow. Water carries nutrients from the soil to all parts of the plant and carries food from the leaves back to the roots. Water is also needed to create the pressure that holds up a plant. Without water, the plant will wilt and eventually die.

Hypothesis: If plants do not get accurate amount of water, the leaves will lose its green colour and become wilt.

Inferences: Plant needs water to transport nutrients to the whole part of the plant

Variables: a) manipulated: The amount of water

b) responding: The colour and the freshness of the leaves

c) fixed: The condition where the plant is placed

Literature review:

People have always known that plants need water to grow and stay healthy but the way they transport water was actually discovered by an English vicar called Stephen Hales. He was born in 1677 and lived until 1761. He was the first person to measure transpiration in a plant. He also grew a plant in a closed container and measured the volume of air above the surface of the water. He saw that it went down by about 14% and concluded that the plant was using up part of the air.

His other experiments showed that the sap in plant stems flows upwards, against gravity and he published his work in 1727. Hales' observations were interesting in themselves but, now that we can look back with a historical perspective, we can see that they were important stepping stones in the scientific process that lead to our current understanding of plant physiology and biochemistry.

Materials: Bean seeds, two small flowerpots, water, soil and humus

Procedure:

1) Some bean seeds are plant in each of the flowerpots.2) Both plants are placed in the sunshine3) Plant ‘A’ is watered lightly each day.4) Do not water plant ‘B’

Results:

Observation InferencesPlant “A” Plant grow healthy and

green This is because the plant get enough water for grow healthy and green.

Plant “B” Plant do not grow This is because the plant does not get enough water to grow.

Observation:

Before experimentPlant A Plant B

After experimentPlant A Plant B

Discussion:

1. Water helps a plant by transporting important nutrients through the plant. Nutrients are drawn from the soil and used by the plant. Without enough water in the cells, the plants droop, so water helps a plant stand.

2. Water carries the dissolved sugar and other nutrients through the plant. So without the proper balance of water, the plant not only is malnourished, but it is also physically weak and cannot support its own weight.

3. Different types of plants require different amounts of water. With outdoor plants, you can’t control the plants getting too much water if your area gets a lot of rain, so you need to make sure that the soil has the proper drainage, because too much water will affect plant growth just as much as too little.

4. If the plants get to little water they wilt. Plants wilt when they lose water faster than they gain it from the soil. Before the plant wilts the stomata pores close up. This helps keep water inside but means less carbon dioxide is able to enter the plant. The plant needs carbon dioxide to grow, so growth of the plant slows down because of lack of water.

5. If the plants get to much water they cannot get any air from the soil to be used for respiration and because it is so damp this will encourage disease causing organisms which may affect the plant as well as root rot in the roots. Also the leaves may turn yellow and fall off because of lack of nitrogen in the soil.

6. It is common knowledge that plants need water to survive. But too much or too little water will cause a plant to die. Before purchasing the plant, research how much water it will need. The amount of water required varies from plant to plant. Most plants should be watered when the soil is slightly dry. When watering, give the plant water until it begins to come out of the hole in the bottom of the holder. Make sure that the soil is moist but not saturated

Questions:

1) Would the same results be possible with different kind of seeds?

Yes. It is because water is one of the factors that affect the growth of the plant although using different kind of seeds.

2) Is it possible to give a plant to much water?

No. If the plants get too much water, the roots can easily rot, and the plant cannot get enough oxygen from the soil. A plant cannot grow if it doesn’t have healthy roots, so the proper balance of water is a key when growing plants.

3) How can farmer tell if a plant is receiving enough water? Not enough water? too much water?

There are a few simple things that a farmer can do to check the amount of water in the soil and ensure that there is the correct entry of water in a plant. One of the quickest ways is to just put his finger in the soil, up to his knuckle. If the soil is moist, it has enough water. If the soil is dry, he needs to water the plant. If the pot feels lighter than usual, or if the soil is pulling away from the sides of the pot, it needs more water. If the water in the pot is expanded on the soil, that’s mean the plant has too much water in it.

Conclusion:

Plants require water for survival; however, too much water is just as bad as not enough.

Problem: Can plants live without air?

Introduction: Air is taken in through the plants' leaves.  Plants and animals constantly exchange air with one another.  Animals breathe in oxygen and breathe out carbon dioxide.  Meanwhile, plants breathe in carbon dioxide and breathe out oxygen.

Hypothesis: if the air is presence, the plant will grow healthy

Inferences: Plant needs air for growth and carry out photosynthesis process.

Variables: a) manipulated: The presence of air

b) responding: The growth and condition of the plant

c) fixed: The types of seed used

Literature review:

Oxygen was discovered for the first time by a Swedish Chemist, Carl Wilhelm Scheele, in 1772. Joseph Priestly, an English chemist, independently, discovered oxygen in 1774 and published his findings the same year, three years before Scheele published. Antoine Lavoisier, a French chemist, also discovered oxygen in 1775, was the first to recognize it as an element, and coined its name "oxygen" - which comes from a Greek word that means “acid-former”.

In August of 1771, Joseph Priestley, put a sprig of mint into a transparent closed space with a candle that burned out the air until it soon went out. After 27 days, he relit the extinguished candle again and it burned perfectly well in the air that

previously would not support it. And how did Priestley light the candle if it was placed in a closed space? He focused sun light beams with a mirror onto the candle wick (Priestley had no bright source of light, and had to rely on the sun). Today, of course, we can use more sophisticated methods to light the candle like focusing light from a flood light through converging lens, or by an electrical spark.

So priestly proved that plants somehow change the composition of the air.

In another celebrated Experiment from 1772, Priestley kept a mouse in a jar of air until it collapsed. He found that a mouse kept with a plant would survive. However, we do not recommend to repeat this experiment and hurt innocent animals.

These kinds of observations led Priestley to offer an interesting hypothesis that plants restore to the air whatever breathing animals and burning candles remove - what was later coined by Lavoisier "oxygen".

In these experiments, Priestly was the first to observe that plants release oxygen into the air - the process known to us as photosynthesis.

Materials: Bean seeds, two jars and two plastic cups, soil, humus, cotton and water

Procedure A:

1) Bean seeds are planted in the jars.2) Both soils are watered fairly well. When the air bubbles cease to rise the air

has been expelled from the soil.3) The first jar is cap. This cuts off the air supply to the plant.4) The second plant is kept moist by watering as needed.

Procedure B:

1) The two cups is filled with water.2) A cotton pad is placed on top and some beans on the cotton. This will keep

the seeds moist.3) The seeds are dropped into the water of the second cup thus eliminating the

air.4) The temperatures and light are kept the same for both cups.

Result:

Observation InferencesProcedure A Plant A: Spore formation

on the plantPlant B: The plant grow healthy

Plant A: This is because no air in the plantPlant B: This is because there is air in the plant

Procedure B Plant A: The plant grow healthyPlant B: The plant does not grow

Plant A: This is because there is air in the cupsPlant B: This is because there is no air in the cups

Observation:

Procedure A

Procedure B

Discussions:

1. Seeds also need air (carbon dioxide and oxygen) to grow. When a seed is completely submerged in water, gaseous oxygen needed to metabolize sugars and starches is not available. Therefore, the seed dies.

2. Plants need air for growth and reproduction.

3. Air consists of many things, including nitrogen, carbon dioxide, and oxygen. Plants must have carbon dioxide, light, and water in order to make their own food of sugars and starches. This process is called photosynthesis.

4. Plants must also have oxygen in order to convert the sugars and starches to energy required to grow. The photosynthetic process provides more than enough oxygen for plants.

5. Extra oxygen is released into the atmosphere and used by humans and other living organisms.

6. In simple terms, plants provide animals with the oxygen they need, and animals provide plants with carbon dioxide. (It is theoretically possible for plants to exist without the presence of animals. However, animals release

carbon dioxide when they respire and increase the amount of carbon dioxide available to the plants. This allows the plants to grow vigorously.)

7. The unique relationship between plants and animals must stay in balance so all living things can co-exist.

Questions:

1) What other ways might air be eliminated from the cup?

By using vacuum pump

2) Is too much air ever a problem to the farmer?

No. The amount of air does not given a problem to the farmer because more air means more oxygen and carbon dioxide provides the plant to grow.

3) Would the same results occur with different types of seeds?

Yes.

4) Plants make their food but they do need a supply of minerals. Choose three mineral and describe what happens to plant growing without them.

Minerals Functions Effects of deficiency Nitrogen Synthesis of proteins, nucleic

acids, chlorophyll and enzymes for photosynthesis and respiration.

Important for rapid stem and leaf growth

Increases seed and fruit yields

Stunted growth Chlorosis

Phosphorus Synthesis of nucleic acids, ATP, and phospholipids of plasma membranes

Acts as a coenzyme in photosynthesis and respiration

Poor root growth Formation of dull,

dark green leaves Red or purple

spots on old leaves

Potassium Protein synthesis Carbohydrate metabolism A cofactor for enzyme

Reduces protein synthesis

Yellow-edge leaves

Premature death of plant

5) Animals and plants need food. Give two reasons why animals and plants need food.

1) Animals and plants need food for growth 2) Animals and plants need food for energy to carry out various types of life

processes.

Conclusion: Plant needs air for grow healthy

References:

http://www.boston.com/bostonglobe/ideas/brainiac/2008/12/the_man_who_discover

http://www.saskschools.ca/~pvsd/vsfprojects/foodforlife/foodforlife/www.simplydivinecatering.com/history_of_plants.htm

http://www.nytimes.com/2009/01/03/books/03gewen.html

http://www.juliantrubin.com/bigten/photosynthesisexperiments.html