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

Investigation of the factors affecting the rate of transpiration from a shoot of Privet.

Extracts from this document...


Biology planning exercise: investigation of the factors affecting the rate of transpiration from a shoot of Privet Introduction Transpiration is the evaporation of water from a plant, primarily from the leaves. This is because the undersides of the leaves have many small holes, called stomata, which are necessary for the absorption of carbon dioxide. Inside each stoma is an air space, and the surface of all the cells bordering that are coated with a thin film of water, in order to maximise the absorption of carbon dioxide. This inevitably means that some of the water evaporates - this is called transpiration. I intend to measure the rate of transpiration in a privet shoot (see preliminary work). However, it would not be very easy to directly measure the amount of water lost directly - the only way would be to measure relative humidity with the plant in an enclosed space, but humidity affects the rate of transpiration. Therefore, I will have to measure the rate indirectly. To do this, I could measure the weight loss of a plant over a period of time, but then I would also have to take into account the amount of gasses exchanged, so the best way would be to measure the amount of water taken up. This can be done with a potometer. Key Factors Transpiration is affected by the following factors, which will have to be taken into account during the experiment: Relative Humidity - if the air if humid, it has more water potential, so there is less evaporation. ...read more.


I found that almost all of the stomata were on the underside of the leaf - could not see any on the top, and also that privet leaves had a stomatal density more than three times greater than that of laurel. That is why I decided to do this experiment with a privet shoot, because more stomata will mean more transpiration, and so the results can be more accurate (it is easier to accurately measure a large amount of anything than a small amount). I also considered that a high density of stomata suggests that privet has adapted to live in conditions where water is plentiful, this might suggest that a privet shoot would be less likely to close its stomata than a laurel shoot, however I have no evidence for this. Prediction I predict that as I increase the wind speed, the rate of transpiration will increase, until the rate becomes so great that the stomata close, (and the leaves blow off). This is because an increase in the wind speed, means faster removal of any moisture from just below the stomata, and so means that the gradient of water from inside the stomata to the outside is steeper, and therefore the rate of transpiration increases. However, I think I can go further than this by saying that the steepness of the water gradient is directly proportional to the wind speed, and the rate of evaporation is directly proportional to the steepness of the water gradient. ...read more.


This plan is valid as I am confident that I have taken into account all the factors that could affect the rate at which a plant takes up water. Water is used for transpiration, making the cells turgid, and for photosynthesis, it is produced by respiration. I have made sure in my plan that the plant is water stressed at no point, so all the cells would already be turgid. The factors that affect photosynthesis, light intensity, temperature and the concentration of carbon dioxide in the atmosphere should all remain constant, and the of the factors that affect transpiration, only the wind speed will change. Therefore, I am confident that any changes in the rate of transpiration can be attributed to the change in the wind speed. It is reliable only as long as you use a very similar piece of privet that had been subjected to similar conditions before the experiment. But with the same piece of privet, under the same conditions, providing the privet hasn't died, and the stomata haven't closed, then similar results should be obtained every time. 1 I know light intensity does from a previous experiment, in which I measured the rate at which oxygen was produced from Elodea when a lamp was positioned at certain distances from the plant. I found out that the rate of photosynthesis was inversely proportional to the square of the distance the lamp was from the plant, hence was directly proportional to the light intensity. I found out that temperature has an effect on photosynthesis in the Jones and Jones Biology Textbook. Hector Guinness 03/05/2007 ...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

    Biology lab - transpiration

    5 star(s)

    CAM plants uptake CO2 at night and change it into crassulacean acid that can be broken down during the day for sugars. These plants can close their stomata during the day. Why did you need to calculate leaf surface area in tabulating your results?

  2. Marked by a teacher

    Investigate which surface of a leaf loses more water by transpiration.

    3 star(s)

    my second is not because of the anomalous result of leaf 4. EVALUATING EVIDENCE Accuracy of evidence Three sets of my results for three leaves were perfectly accurate. However, the other set was not because of the size of leaf four.

  1. The effect of wind speed on the rate of transpiration.

    Distance (cm) Water loss (g) Repeat 1 Repeat2 Average Percentage water loss (%) 20 (10mph) 40 (8mph) 60 (6mph) 80 (4mph) 100 (2mph) I will then repeat each experiment three times so that I can reach a good conclusion. Doing repeats enables me to identify any odd results because I am able to compare them with each other.

  2. Factors Affecting Infiltration Rates

    The purpose of the graphs is to show which factor affect infiltration the most. The graph displays all the results together, therefore it is easy to draw a conclusion. The infiltration rate depends upon the size and number of air spaces between the soil partials and other soil structures.

  1. How temperature affects the rate of photosynthesis.

    Same amount of time would be allowed for each piece of parent elodea from which the different lengths of elodea would be cut. These would be kept overnight for approximately 8 hours. Then, during the actual experiment, when the elodeas are introduced to a new light source, 2 minutes would

  2. Factors affecting the rate of transpiration

    The guard cell walls are unevenly thickened (seen on various scanning electron microscopes images). http://www.mcs.csuhayward.edu/sem/images/horsel4.gif The wall furthest from the pore (called the dorsal wall) is thinner than the wall next to the pore (the ventral wall). Also, the cellulose microfibrils that make up the walls are arranged so that the ventral wall is less elastic than the dorsal wall.

  1. Factors Affecting Cooling

    The only variable that I think is out of control will be the surrounding temperature. The tests that I do cannot be completed in a single lesson and so they will have to be spread out. If the surrounding temperature is different on each day I do the experiment then the rate of cooling will be different.

  2. An Experiment to investigate a factor affecting the rate of Transpiration From a Shoot ...

    When some water is lost and the cells become less turgid, more water is 'pulled' into the cell across a concentration gradient by osmosis. This chain of osmosis continues out of the leaf and into the stem and down the xylem into the root hairs, which then 'pull' more water, by osmosis, from the soil.

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