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Effect of Surface Area On The Rates Of Transpiration

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Effect of Surface Area On The Rates Of Transpiration Aim... Compare the effects of a named factor (surface area) on the rates of Transpiration of two different plant species. Transpiration is the evaporation of water vapour from plants; it takes place at three sites. * Stomata: Occurs in leaves and herbaceous stems, and amount for 90% of all water loss. * Cuticle: A wavy external layer on plant surfaces which serves to limit water loss through cell walls, although up to 10% of water nevertheless escapes by this route * Lenticels: Areas of loosely packed cells on the surface of woody stems through which gas exchange, and therefore water loss, takes place. Most of the water entering a plant does so via the root hairs. It travels across the root cortex to the xylem, ascends in the xylem to the leaves and is lost by evaporation from the surface of the mesophyll cells before diffusing out through the stomata. ...read more.


* All joints must be watertight to prevent air breaking the continuous columns of water. Tight-fitting rubber tubing and/or petroleum jelly is used at all joints. * When making comparisons, e.g. the rate of transpiration at different temperatures, all other factors, e.g. humidity, wind speed etc. Must be kept constant. Effects of Environmental Factors... Light: Effects transpiration because stomata usually opens in light and closes in darkness. At night therefore, and only small amounts of water are lost through the waxy cuticle. As stomata opens in the morning, transpiration rates increase. Temperature: The higher the temperature, the greater the rate of evaporation of water from mesophyll cells. It increases the capacity of air to absorb water from leaves and it warms the water inside leaves making it evaporate more quickly. Direct sunlight has the same effect since it warms leaves to a higher temperature than the atmosphere. Transpiration is generally faster on warm, sunny days than on cold, wet days. ...read more.


All the other factors which alter the transpiration rate will be kept constant. I believe this will guarantee a fair test. Obtaining of Results The experimentation was performed with meticulousness and proficiency as 5 results were taken for each number of leaves, and an average was made. The amount of water uptake is recorded in cm as read of the capillary tube on the potometer. After the experiment the leaves were put onto graph paper, and the surface areas were recorded in mm�. Water uptake Leaves 1 2 3 4 5 Average(cm) Water uptake(average) Surface area(mm ) Prediction... I envisage that the higher the surface area of the leaves, the more water uptake will occur. This is because; greater surface is accompanied with greater quantity of stomata. More stomata means greater value of water vapour can be lost by evaporation from the surface of the mesophyll cells before diffusing out through the stomata. The graph of water uptake against surface area should therefore be a realistically straight line. ?? ?? ?? ?? David Johnson Oragui Coursework Biology Master Piece David Johnson Coursework Biology ...read more.

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