• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

This experiment is to show that light intensity if effecting the rate of photosynthesis, but before we do this we need to know that photosynthesis is actually occurring.

Extracts from this document...


Light Intensity on the rate of photosynthesis Photosynthesis: Plants are autotrophic nutritious, which means that they produce their own food. They do this by a process called photosynthesis by which chlorophyll containing organisms (green plants) - capture energy in the form of light and convert it to chemical energy to form complex substances from carbon dioxide and water. Virtually all the energy available for life, in the Earth's biosphere, which is the zone in which life can exist; is made available through photosynthesis. Photo means light and synthesis means to manufacture. Using energy from the sun, cells in the leaves turn simple materials into energy rich food. Water, carbon dioxide and other minerals are the inorganic substances, which the plants use to tun into carbohydrates, fats, proteins and vitamins. The process takes place in chloroplasts. These are special structures in the leaves. A leafs skin is the upper epidermis, beneath this lies the palisade cells which are chief food producers. Spongy cells are partly surrounded by pockets of air, which enable the cells to exchange gases with the atmosphere. There are small openings called stomata, under the leaf in the lower epidermis. Veins in the leaf carry water and nutrients from the roots around the leaf. Carbon dioxide enters through the stomata. Cells in the palisades and spongy layer contain chlorophyll, which helps to absorb and trap energy from the sunlight, which helps to convert light energy into chemical energy. ...read more.


To show that light is necessary for photosynthesis: This experiment probably helped us the most. First we placed a growing plant in a cupboard for 2 -3 days, to de-starch the plant. It cannot photosynthesis because all the starch in the plant is already used up. A leaf is taken from the de-starched plant and is tested for starch, it should remain the same colour as there will be no starch present. A stencil (black paper or foil with a cut our shape) in foil is then placed over another leaf and the plant is left out in the sun. Later the stencil is removed and the leaf it tested for starch. The regions that had been exposed to the light will turn black when tested with iodine for starch. Those regions that had foil or the black paper, which should be cream or of a lighter colour should remain the same, showing that there is no starch present, therefore no photosynthesis was taking place, showing that light is needed for photosynthesis. So these experiments showed that carbon dioxide, light and chlorophyll is needed for photosynthesis. Meaning that if any one of them was subtracted from the formula or reduced in volume given to the plant then the rate of photosynthesis would decrease. Chlorophyll uses light energy to perform photosynthesis. It can only do this as fast as the light source is arriving. ...read more.


> The same lamp should be used through out the experiment, so that the same amount of light energy / wavelength is released throughout the experiment. > The equilibrium time for each distance should be kept the same, 5 minutes so that it is a fair test. It would not be fair to have different equilibrium time for each distance. > The time measured for each distance should be the same, 5 minutes > The same volume of water should be kept for all the distances and experiments, 250mm > The temperature should try to be kept constant, although the temperatures will increases with the number of people in the lab and so windows will need to be opened when needed, as there is no way of keeping it constant so it can be monitored to see if there is change, which will explain any anomalous results > The temperature of the water should try to be kept the same, yet again there is no way of keeping it constant as the light may change the temperature, so this to can be monitored and can help to explain any anomalous results. > The weight of the weed should be constant so the same weed will be used > The pH number should be constant to so that it is a fair test, yet there is no way of keeping it constant so it will just be noted, to explain any anomalous results. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Green Plants as Organisms section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Green Plants as Organisms essays

  1. Marked by a teacher

    Light Intensity and Photosynthesis.

    4 star(s)

    It also shows that while my outer limits are justified, it would be better to take more readings between the distances of 10 and 20 centimetres, as the distance between the points is large at this point, and so I have decided to take readings at the following distances: 5,

  2. Confirm which factors increases or decreases the rate of photosynthesis.

    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

  1. Experiment to Compare Stomata Density in Different Dicotyledonous

    I predicted for the evergreen clematis an average number of stomata, however the investigation showed that the results were way below that of the average at just 77.00 stomata per 4.91mm compared to the average of 154.31 stomata per 4.91mm.

  2. Investigating the effect of temperature on the rate of photosynthesis

    Therefore instead of counting bubbles we will pull through all oxygen bubbles after the time is finished. Therefore all bubbles will be together and give a more accurate reading as bubbles will not be missed. The rate of photosynthesis is measured by oxygen released.

  1. Investigation To Find The Effect Of Temperature On The Rate Of Photosynthesis Of Elodea.

    The Blu-Tac / Plasticene / paperclip is used to weigh down the Elodea specimen in the boiling tube.. This makes sure that the entire plant is submerged in the Na+HCO3- solution and therefore the entire plant is exposed to the CO2 released by the Na+HCO3-.

  2. Investigating the effect of Light Intensity on Elodea.

    Light energy is in the form of a photon. The energy from a photon is absorbed by the green pigment of chlorophyll and used to transfer electrons from one chlorophyll pigment to the next. This energy is stored as chemical potential energy in the covalent bonds of sugar molecules.

  1. Investigate the effect of light intensity on the rate of photosynthesis in an aquatic ...

    would not effect the investigation by very much, if at all. Though I still bared this point in mind.. I decided randomly, that the distances at which I would place the lamp to complete my preliminary procedure were going to be 0cm, 50cm & 100cm.

  2. Investigate the effect of light intensity and the colour of light on the rate ...

    Find the length of the bubble collected. Repeat for all other readings, Sciencetific knowledge: Only green plants can make their own food by the process called photosynthesis. Hence, green plants are known as food producers. All other organisms are called food consumers as they depend directly or indirectly on green plants for food.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work