Transport in Plants

Transport in Plants
Matthew H. 9A 131002

Today I will be discussing our experiment and the basics of transport of minerals and water in plants. Transport in plants are called transpiration. Water evaporates from the leaves which cause a type of suction that draws water from the roots. The water travels up via the vascular bundles. This flow of water is called transpiration stream. Some pressure is created forcing some water out of the cells in into the spaces between the cells. The water evaporates and through the process of diffusion into the air spaces in the mesophyll and out of the stomata. It is because of this process of water leaving the leaves it is called transpiration. (Mackean, D. G.;, 2002)

Our experiment was to find the rates of water uptake in different conditions. The conditions we use are sunlight, shadow, wind, and no air getting to the plant at all. The apparatus we were using is called a potometer. The potometer includes a beaker, a capillary tube with scale, a three way tap, and a syringe. First you fill the syringe with water. Then you put it on the side of the three way tap. Turn the tap down and push water though the syringe until water comes out the top. Put in the leafy shoot, and turn the tap up. Push water until it comes out the bottom of the tube and turn the tap to the middle. Then you wait to see the change in the water level. I worked with Niamh and Kristen who were doing the same experiment. We put mine in indirect sunlight and theirs in direct sunlight. We’ll call mine “A” and Kristen and Niamh’s “B.”

The starting point in the capillary tube for “A” was 6.5mL and for “B” it was 9mL. We check back at 2nd break and “A” was at 7.5mL and “B” was at 9.2mL. After school we checked back again. “A” was at 8mL and “B” was at 8.8mL. Now I have a bad feeling that the leafy shoots we chose were not big enough. The stem, I mean. Now according to the biology text book I got the experiment from, the water in the tube should be rising (which in the case of “A” it was) because of the suction described above. But, “B” had fallen to 8.8mL at the end of the day. What was supposed to happen was this. “B” should have been pulling up water faster because it was in the direct sun. This is because the water from the leaves evaporates and creates a suction pulling the water up. “A” was not in the sun, so therefore it should not have pulled up as much water. My guess [for the mistake] was the stem was not thick enough to stop the air from getting in the hole [where the stem was pushed in]. If I were to do this again, I would choose a plant with a thicker stem and if that was not possible tape the area between the stem and the tubing to stop the air [from entering].

Bibliography
Mackean, D. G.;. (2002). IGCSE Biology. London: Hodder Murray.

Bibliography: Mackean, D. G.;. (2002). IGCSE Biology. London: Hodder Murray.