| Why is water important for plants | - to keep turgor pressure to support the plant
- to transport substances
- photosynthesis
- help plants to cool down in hot conditions |
| Where does water enter the plant | Water enters through the root hair cells and then passes through the root cortex, including the endodermis, to reach the xylem |
| How is water drawn into the roots | Through osmosis |
| Define symplast pathway | Water moves through the living parts of cells (he cytoplasm) via osmosis. The cytoplasm of neighbouring cells connect through plasmodesmata. |
| Define plasmodesmata | Small channels in the cell walls |
| Define apoplast pathway | Water moves through the non-living parts of the cell, the cell walls as well as intracellular spaces. It is the fastest movement of water as it provides the least resistance. |
| How does water move through the apoplast pathway | The water can carry solutes and move from areas of high hydrostatic pressure to areas of low hydrostatic pressure, example of mass flow. |
| Describe and explain the function of the casparian strip | When water in the apoplast pathway gets to the endodermis cells in the roots, it is blocked by a waxy strip in the cells walls called casparian strip. Now water has to enter through the symplast way. This prevents toxins from entering further as the cell membrane is partially permeable. |
| How is water transported through the leaves and out the stomata | - water leaves the xylem vessel and moves across the leaf cell either through apoplast or symplast pathway
- water evaporates from the cell walls into the spaces between the cells
- when the stomata opens, water diffuses out of the leaf into the surrounding air |
| How does water move up the plant | Water molecules form hydrogen bonds with the carbohydrates in the walls of the xylem (adhesion) as well as each other (cohesion). The combined effects of which cause water to move up the xylem via capillary action. |
