Water Absorption in Plants
Plant Transport
Plants are mostly made up of water. Lettuce is about 94% water and a potato is about 77% water. Plants need water for three main purposes: ------photosynthesis,
-support
-transport of chemicals Water is a raw material for photosynthesis. If water is in short supply, the rate of photosynthesis will be limited. Plants need water for support, otherwise they wilt. Water is needed to transport many chemicals within plants. Chemicals, such as mineral salts, dissolve in water and they can then be moved within the plant to the cells that need them.
Plants obtain water from the soil through their roots. The roots are adapted to absorb large volumes of water by having many tiny root hairs, which increase the surface area of the roots. Each root hair is an extension of an individual cell on the outside of a root, called a root hair cell. Water enters the root hair cell by osmosis. Osmosis is the movement of water from a dilute solution to a more concentrated solution, through a partially permeable membrane. The solution inside the root hair cell is more concentrated than that of the soil water, so water moves from the soil into the cell. The cell membrane is partially permeable. It has tiny holes which allow water molecules to pass through. These holes are too small for larger solute particles to pass through. Once inside the root hair cell, the water dilutes the solution in the cytoplasm, so the solution is less concentrated than that of cells closer to the centre of the root. Water therefore passes from cell to cell by osmosis across the root, until it reaches the xylem vessel at the centre of the root. The xylem vessel carries water up the plant.
Plants need minerals to stay healthy. Minerals are found dissolved in the soil water around the plant roots. When minerals dissolve, they form ions. These are very small and can pass through holes in the cell membrane. Some mineral ions diffuse from the soil into the root hair cells, because their
Plants are mostly made up of water. Lettuce is about 94% water and a potato is about 77% water. Plants need water for three main purposes: ------photosynthesis,
-support
-transport of chemicals Water is a raw material for photosynthesis. If water is in short supply, the rate of photosynthesis will be limited. Plants need water for support, otherwise they wilt. Water is needed to transport many chemicals within plants. Chemicals, such as mineral salts, dissolve in water and they can then be moved within the plant to the cells that need them.
Plants obtain water from the soil through their roots. The roots are adapted to absorb large volumes of water by having many tiny root hairs, which increase the surface area of the roots. Each root hair is an extension of an individual cell on the outside of a root, called a root hair cell. Water enters the root hair cell by osmosis. Osmosis is the movement of water from a dilute solution to a more concentrated solution, through a partially permeable membrane. The solution inside the root hair cell is more concentrated than that of the soil water, so water moves from the soil into the cell. The cell membrane is partially permeable. It has tiny holes which allow water molecules to pass through. These holes are too small for larger solute particles to pass through. Once inside the root hair cell, the water dilutes the solution in the cytoplasm, so the solution is less concentrated than that of cells closer to the centre of the root. Water therefore passes from cell to cell by osmosis across the root, until it reaches the xylem vessel at the centre of the root. The xylem vessel carries water up the plant.
Plants need minerals to stay healthy. Minerals are found dissolved in the soil water around the plant roots. When minerals dissolve, they form ions. These are very small and can pass through holes in the cell membrane. Some mineral ions diffuse from the soil into the root hair cells, because their