December 5, 2016

Transpiration (Science)

Transpiration is the method of that is used to get water moving through a plant in tubes and the evaporation of water on the leaves, stems and flowers. Water travels through plants by moving in tubes, which are made of dead xylem cells, from the roots all the way through the plant. Dissolved minerals also travel within the tubes along side the water. The water evaporates only if it is on palisade cells (on the edge of the leaf). Transpiration is very beneficial as it helps plants and the environment. Therefore it is very good that the rate of transpiration can be quickened. But first the process of transpiration needs to be explained.

Water enters the root hair cells by osmosis and then travels through cells until it gets to the xylem tube at the centre of the roots by osmosis. Osmosis is the movement of water from a less concentrated side to a higher concentrated side by going across permeable membranes. Using diffusion, water goes through cell walls. Diffusion is where water would move from a higher concentrated space to a lower concentrated space and so helps water go through cell walls. Gas can also diffuse since particles need to be spread out for diffusion to be carried out. Water then enters leaves through the stomata, which is a small opening that allows gas exchange and water to pass through. One entered the water moves to the palisade cells and then evaporates into the atmosphere.  Water can only travel like this as it is cohesive, meaning it can move across a different surfaces. If something was adhesive it would only be able to travel across itself.

Transpiration is vital for plants for many reasons. One being that it keeps plants cool in hot weather so it does not end up killing them. It also helps photosynthesis, therefore the balance between oxygen and carbon dioxide is good. The water that evaporates from plants go back into the water cycle so it returns the water back to the environment. The water vapour evaporated can turn into fog and clouds. Transpiration also helps plants grow and their metabolism.

The rate of transpiration can change due to natural and environmental factors. Light, temperature and wind can make transpiration faster. If the plant is in bright light, transpiration quicken since the stomata opens wider meaning more carbon dioxide can be inhaled by the plant for photosynthesis. Higher temperatures mean evaporation and are faster. Windy days means that the water vapour can be taken away quickly and then the water can evaporate quicker off the palisade cells. However humidity can slow down the rate of transpiration since the water cannot evaporate if the air is already moist.

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