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

Transpiration stream

Extracts from this document...


Transpiration stream Transpiration is the loss of water from a plant by evaporation. Water is essential for plants as it is required for photosynthesis to produce glucose; all organisms derive their energy from the oxidation of glucose, minerals and ions are dissolved in water and bring them from the roots to other plant tissue that require the minerals. Also, water keeps the plant cool. The plant undergoes several processes in order for it to lose the amount of water through the lower epidermis of a leaf. Firstly, soil, is a very dilute solution of ions, which means a lot of water has been dissolved in to solution, and therefore the soil solution has a very high water potential. On the other hand the root hair cells have an insufficient amount of water molecules, resulting in root cells having low water potential. Root cells have a partially permeable membrane, which allows water to travel through them due to osmosis, where water travels from high water potential to low water potential. ...read more.


before entering the xylem vessels. Each cell in the endodermis has a waterproof 'band' around it called the casparian strip. This means that water must pass through the cell in some way, rather than around the outside. The purpose of the casparian strip is to remove water travelling through the cell walls across the apoplastic route and redirect the route so water can travel through the symplast or vacuolar pathways. After passing the root hair cells, water enters the xylem. The xylem vessels are internally lined with lignin, this substance is waterproof and it also provides structural support to the xylem vessels. Xylem tissue is composed of dead cells joined together to form long tube-like structures, the side cell walls have pits/holes to allow water to travel to other plant tissue which require water. As water enters the xylem, root pressure gives an initial upward force to water. Water travels up the xylem by capillarity, which is the upward movement of a fluid in a narrow tube (xylem). ...read more.


The role of stomata is to allow gaseous exchange (Carbon dioxide entering and oxygen leaving) and also to control the amount of water lost from a leaf. Stomata are openings in the leaf controlled by two very specialised cells called guard cells. When guard cells are turgid (high water content), they change shape depending on their turgidity, which is controlled by osmosis. However, when guard cells are flaccid (low water content) the stomata are closed to reduce the amount of more water being lost. There are several factors that affect the rate of transpiration light, temperature, and humidity. Light stimulates the stomata to open/close for gaseous exchange and as a result increases the rate of transpiration. If the temperature is high, the rate of evaporation of water in the leaf will increase, this will result in the plant needing more water at a quicker rate, therefore transpiration increases. If the humidity is high, this means there is a smaller difference of water potential between the leaf and the air consequently there will be less evaporation, decreasing the rate of transpiration. http://www.pitlochry.pkc.sch.uk/biology/World-of-Plants/making-food/ Picture of xylem vessel http://www.botany.hawaii.edu/faculty/webb/BOT311/BOT311-00/PlantWatMove/RootPrimXSDrawApoSymLab.jpg Image of different routes taken by water in root hair cells The Hutchinson Encyclopedia Information on transpiration ...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

Here's what a star student thought of this essay

4 star(s)

Response to the question

This essay ably explains the transpiration stream in plants. In parts it is slightly unclear. For example, in the introduction they mention the importance of transpiration in plants for photosynthesis, then mentions the oxidation of glucose. At GCSE level, I ...

Read full review

Response to the question

This essay ably explains the transpiration stream in plants. In parts it is slightly unclear. For example, in the introduction they mention the importance of transpiration in plants for photosynthesis, then mentions the oxidation of glucose. At GCSE level, I think it's sufficient enough to say that plants are the producers, so if they cannot photosynthesise then consumers cannot get energy. It's best not to complicate things, and this is not helped by the sentence structure in the introduction.

Level of analysis

This essay explains all the relevant points for transpiration, and at times is above GCSE level. I liked how the essay follows the path of water, showing a logical progression. It was nice to see reference to the various pathways - these are easy marks to gain and are reasonably simple concepts to understand when talking about transpiration. Scientific terms are used throughout, and it includes a great explanation of cohesion. If you are struggling to understand this concept, I would recommend reading through this answer, as it puts it quite simply, yet still manages to access the marking points! It was nice to see some awareness of the factors which affect the rate of transpiration. One query would be the use of diagrams: there is no point including a diagram if it is unclear, or of poor quality. A good diagram can make it easier to revise the topic, and shows a full understanding in a piece of coursework.

Quality of writing

This essay is structured well, and spelling and grammar are used effectively. If I were answering this question, I would've explained the transpiration stream, explained the factors affecting the rate of transpiration and then commented on its importance. Placing the importance in the introduction doesn't allow any incorporation of evidence to strengthen the argument. For example, I would've mentioned at the end how key it is for xerophytes to reduce transpiration by closing their stomata, which had been mentioned earlier in the essay as reducing the rate of transpiration. Other than this, the essay is strong.

Did you find this review helpful? Join our team of reviewers and help other students learn

Reviewed by groat 08/02/2012

Read less
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)

    The structure and cell types of a stem cross-section can be observed under a microscope. Materials Exercise 9A: Transpiration The materials needed for this exercise were a pan of water, timer, a beaker containing water (heat sink), scissors, 1-mL pipette, a plant cutting, ring stand, clamps, clear plastic tubing, petroleum

  2. Marked by a teacher

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

    3 star(s)

    I then covered the topside of one of them in Vaseline, the underside of the second and both of the surfaces on the third. I left the fourth one with no Vaseline on it. I then weighed the leaves again to obtain a weight for the Vaseline on that particular leaf, and hung them up on a line using paperclips.

  1. Determine the water potential of potato tuber cell with the varying affect of solute ...

    However to keep it under control a cloth could be placed over it or you could just leave it out of the light. Another variable that must be kept in mind is the mass of the potato which makes it a dependant variable.

  2. Effect of Surface Area on Transpiration

    At night therefore, and only small amounts of water are lost through the waxy cuticle. As stomata open in the morning, transpiration rates increase. TEMPERATURE- the higher the temperature, the greater the rate of evaporation of water from mesophyll cells.

  1. How temperature affects the rate of photosynthesis.

    Bisphosphate from the triose phosphate and inevitably less carbon fixation would have taken place and the whole Calvin cycle could have stopped and no more glucose (a product of photosynthesis) would have been formed. If this was the case, then no ADP, Pi and NADP would have been made available

  2. Factors affecting the rate of transpiration

    The key variables in this experiment are temperature, humidity, light, type of plant, wind intensity as well as source of wind and distance of source of wind. I started setting up the potometer finding out which plant will be the easiest one to use.

  1. An Investigation into Water Loss from Plants.

    Percentage mass lost through bottom surface % mass lost (x - x )� 4.46 0.0361 5.49 1.488 4.48 0.044 3.73 0.291 3.19 1.117 Mean = 4.27 Standard Deviation = 3.0255 / 4 S = 0.8697 Percentage mass lost through top surface % mass lost ( x - x )� 3.07

  2. Compare stomatal densities of the upper and lower epidermis of a leaf.

    X (0.01575) � = 0.0007793 1 0.0007793 = 1283.2 1283.2 x = After I calculated how many stomata per cm� where in my field of view, I gathered the calculated results from the other groups & constructed a table. Group No. Of stomata per cm� on the upper epidermis No.

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