Confirm which factors increases or decreases the rate of photosynthesis.

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Introduction

Aim

My aim in this coursework is to investigate the factors, which affect photosynthesis. My aim is to confirm which factors increases or decreases the rate of photosynthesis.

The factors are

* Carbon dioxide,

* Chlorophyll

* Light intensity

* Water

The building-up of complex food molecules from simpler substances is called a synthesis and it needs enzymes and energy to make it occur. Enzymes those are present in the plant's cells and the energy for the first stages in the synthesis comes from sunlight. The process is, therefore, called photosynthesis ('photo' means light).

Photosynthesis is the main type of auto tropic nutrition. There are two fundamentally different methods of nutrition. Animals and certain other organisms take in ready-made organic substances; this is known as heterotrophic nutrition. Other organisms, notably plants, take in simple inorganic substances which they then build up into complex organics substances, this is known as auto tropic nutrition.

The importance of photosynthesis

Heterotrophs, including humans, all depend on photosynthesis for making their food. The manufacturing of sugar (starch) during the process of photosynthesis is astounding. For example: a hectare of maize can convert as much as 10 000 kg of carbon form carbon dioxide into the carbon of sugar in a year, giving a total yield of 25 000 kg of sugar per year. This example is a fact that was ascertained by my previous Biology teacher.

For photosynthesis to take place a plant requires carbon dioxide, water, light, chlorophyll and a suitable temperature. The necessity for these factors can be demonstrated by simple experiments either on whole plants or single leaves.

The main product that is produced during the process of photosynthesis is sugar, although this is often built up into starch for storage. As an indication of whether or not photosynthesis has been taking place, leaves are tested for starch. At first the plant has to be de-starch a plant. This has been explained further during this coursework. Hence photosynthesis is a very important to take place.

Experiment to test photosynthesis

In this case the hypothesis is that plants make their food by photosynthesis. The following equation is one of the ways to test photosynthesis:

Sunlight & chlorophyll

6CO2 + 6H2O C6H12O6 + 6O2

Uptake of CO2 uptake of H2O release of oxygen

Production of sugar

In order to keep the equation simple, glucose is shown as the food compound produced. This does not imply that it is the only substance synthesized by photosynthesis.

If photosynthesis is going on in a plant, then the leaves should be producing glucose (sugar). In many leaves, as fast as sugar is produced it turns into starch. Since it is easier to test for starch that for sugar, we regard the production of starch in a leaf as evidence that photosynthesis has taken place.

In all the experiments described are designed to see if the leaf can make starch without chlorophyll, sunlight or carbon dioxide, in turns. If the photosynthesis story is sound, then the lack of any one of these three conditions should stop photosynthesis, and so stop the production of starch.

In designing the experiments, it is very important to make sure that only one independent variable is altered. If, for example, the method of keeping light from a leaf also cuts off its carbon dioxide, it would be impossible to decide whether it was the lack of carbon dioxide, which stopped the production of starch. To make sure that the experimental design has not altered more than one variable, a control is set in each case. This is an identical solution, except that the conduction missing from the experiment.

De-starching a plant

Apparatus required during the experiment

* A plant

* A dark cupboard

It is not possible to remove the starch chemically, without damaging the leaves; so simply leaving in the darkest for 2 or 3 days de-starches a plant. Leaving them in a dark cupboard for a few days de-starches potted plants. In the darkness, any starch in the leaves will be changed to sugar and carried away from the leaves to other parts of the plant. For plants in the open, the experiment is set up on the day before the test. During the night, most of the starch will be removed from the leaves. If better results are needed, then the leaves are wrapped in aluminium foil for 2 days while they are still on the plant. Then one of the leaves is tested to see that no starch is present.

Starch test

Apparatus required during the experiment

* Boiling H2O in a beaker

* Beaker

* Ethanol (alcohol)

* Test tube

* Heatproof mat

* Tripod

* Iodine

* Bunsen burner

This starch test shows us that if the plant contained starch or not. The process of the starch test is shown below:

Background information

There are many different types of leaves; they are called evergreen, monocot, succulents and pin variegated. Simple demographic carnivorous and compound stages of evolution are going through these leaves. This means when the leaves change and adapt to their surrounding such as climate, etc.

Evergreen plant has chlorophyll present in it. Chlorophyll is a green substance, which contains chloroplasts and makes the leaves green. Chlorophyll is important for photosynthesis. Magnesium is a green element, which is found in chlorophyll. Therefore plants are green.

Chlorophyll covers a large amount of area of a plant. The chlorophyll contains many rows of membranes and chlorophyll.

Limiting factors are important to plants in their natural surroundings. For instance, on a warm summer day, light and temperature are generally well above their minimum value for plants living in the open, and carbon dioxide is the factor that is limiting of photosynthesis. But in a cool day, morning or evening, light or temperature may become limiting factor as they do not get much light when it is winter.

Habitat is also important for living plants that live in shady places such as the floor of a forest or wood, light will be the limiting factor most, it not all, the time. This has been explained in the above paragraph.

When a chemical process depends on more than one essential condition being favourable, its rate is limiting by that factor which is nearest its minimum value.
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Where photosynthesis takes place.

Stomata

The above diagram shows a thin slice cut out from any plant leaf. It is a magnified picture. The process of photosynthesis that takes places are described in the following points:

* Water moves into the leaf cells by osmosis. This water is then evaporated into the air spaces and diffuses out of the leaf as vapour.

* Water and dissolved minerals move through the xylem vessels to the stem and then to the leaves.

* The process of osmosis does this.

* Light enters the leaf ...

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