| why transpiration occurs (mesophyll) | Water evaporates from the moist surfaces of mesophyll cells. |
| why transpiration occurs (stomata) | Stomata open so they can absorb carbon dioxide for photosynthesis. |
| why transpiration occurs (stomata 2) | This provides a pathway for water vapour loss through the open stomata. |
| why transpiration occurs (air spaces) | Water vapour moves down a water potential gradient from the air spaces in the leaf into the atmosphere. |
| factors affecting the transpiraiton rate | Light intensity - At high light intensities, stomata open for maximum CO2 absorption for photosynthesis, increasing the transpiration rate. |
| factors affecting the transpiraiton rate 2 | Temperature - At high temperatures, evaporation of water molecules is faster due to higher kinetic energy, increasing the transpiration rate. |
| factors affecting the transpiraiton rate 3 | Humidity - Low humidity increases the water vapour gradient between the leaf and atmosphere, increasing the transpiration rate. |
| factors affecting the transpiraiton rate 4 | Wind speed - High wind speeds increase the water vapour gradient between the leaf and atmosphere, increasing the transpiration rate. |
| pathway to leaf cells | After the xylem transports water up through a plant, water exits the xylem into leaf cells. |
| cohesion | Hydrogen bonding causes water molecules to stick together and move as one continuous column. |
| adhesion | Hydrogen bonding between polar water molecules and non-polar cellulose in xylem vessel walls pulls water upwards through the xylem. |
| transpiration pull | Evaporation of water at leaves creates the transpiration pull, and this tension is transmitted down the whole water column due to cohesion. |
