Investigating the effect of osmosis on plant tissues.

Aim

My aim for this investigation is to explore the effect of sucrose concentration on potato length.

Background Knowledge

My background knowledge was taken from a sheet I was given by my teacher on diffusion and osmosis also most of it has come of a teaching biology site on the Internet. All plants need water, to use in photosynthesis and to help cool the plant. They take water in through their roots, and it moves up through the plant to the leaves through special tubes called XYLEM TUBES. Water is then lost through holes in the leaves called STOMATA. However, plants do not want to lose much water, especially those in dry conditions, so they have thick waxy outer layers (called cuticles) on their leaves.

As the water moves up through the plant, it helps to keep the plant upright, because the vacuole in each of the plant's cells fills with water and becomes rigid. This is called "turgor pressure", as the vacuoles are said to be "turgid" when they're full of water.

Water is taken up water and moves it around inside them by a process called OSMOSIS. This is the movement of water molecules across a semi-permeable membrane e.g. the membrane around all cells. Water molecules will move from where there is a high concentration of them to where there is a low concentration of them. A high concentration of water molecules means pure water. A low concentration of water molecules means water with other substances, such as glucose, dissolved in it. Osmosis does not use any energy - it is a passive process. Other mechanisms by which substances are moved around in plants include DIFFUSION and ACTIVE TRANSPORT.

Diagram

Predicted Graph

Hypothesis

Osmosis is diffusion of water molecules from one side of high water potential to low water potential through a partially permeable membrane. Therefore I predict that if there is a low concentration of sugar molecules but high concentration of water molecules the chip size will increase and the chip will diffuse into will become turgid. This will happen because the water molecules will diffuse into the chip. As water molecules are smaller than sucrose molecules it will enter the chip unlike the sucrose molecules. This happens due to the partially permeable membrane stopping the bigger sugar molecules into the chip.

If there is a larger concentration of sugar/glucose than water molecules, the water inside the chip will be “sucked,” out of the chip decreasing it in SIZE and making the chip become flaccid. The water molecules have been “sucked,” out of the chip by the sucrose solution this makes the chip burn the flaccid.

So basically I think that when there is a low concentration of sugar molecules and high concentration of water the chip length will increase. This will happen because the water will want to diffuse by osmosis in the chip and as it is a smaller molecule ...