Transpiration
Transpiration is the process by which water moves out of the plant through the leaves, and is also essential in allowing water to enter the plant as well. When the stomata open, this allow for water to escape from the plant, and be lost to the atmosphere through evaporation. When this water is lost through the leaves, more water is brought up to replace it. The water loss will provide a negative pressure in the xylem tube, resulting in water naturally travelling up the tube into the leaves. Due to the cohesion of water, when one water molecule is evaporated, another will be replaced as it moves, pulling up the following molecules in a process called transpiration pull. Adhesion also allows for water to travel up the xylem tube, and move against the pull of gravity. The water molecules will stick to the sides of the xylem, since the water molecules are attracted to the inner sides of the xylem tube. This allows for the molecules to move up through the tube and up the stem of the plant, and so transpiration can occur [1]. The movement of water into the plant through the roots also causes root pressure, which helps the movement of water by providing pressure which pushes the water molecules up the xylem tube, against the pull of gravity [18]. Transpiration is an essential process for many plants and the movement of water due to transpiration pull is what allows plants to receive resources such as water and minerals [13].
There are many factors which affect the rate at which transpiration will happen in plant. These factors help determine how slowly or quickly transpiration occurs.
A major factor is temperature. Since transpiration involves water evaporating, the temperature of the surrounding environment will affect how fast the water is lost. When the temperature is high, water molecules will be moving faster, so the water will move faster from the high concentration to the low concentration so osmosis will occur faster. This means the process of transpiration will also occur faster [1].
Humidity will also have a big impact on transpiration. If the surrounding air is very humid, it will have a higher water potential. This will mean that the concentration gradient is not as great between the inside of the leaf and the outside environment, so osmosis will occur more slowly. In contrast, if the outside air is very dry, the low amount of water will increase the concentration gradient between the inside and outside of the leaf, so osmosis and therefore transpiration, will occur faster [1].
Another factor that will impact the rate of transpiration is wind speed. If the wind speed is high, water will be rapidly blown away from the stomata. This will increase the concentration gradient between the inside of the leaf and the outside, so osmosis will occur faster. This will result in a faster rate of transpiration, and therefore more water being lost [1].
There are multiple adaptations plants have, which manage how quickly the process of transpiration is recurring, and help reduce water loss.
There are many factors which affect the rate at which transpiration will happen in plant. These factors help determine how slowly or quickly transpiration occurs.
A major factor is temperature. Since transpiration involves water evaporating, the temperature of the surrounding environment will affect how fast the water is lost. When the temperature is high, water molecules will be moving faster, so the water will move faster from the high concentration to the low concentration so osmosis will occur faster. This means the process of transpiration will also occur faster [1].
Humidity will also have a big impact on transpiration. If the surrounding air is very humid, it will have a higher water potential. This will mean that the concentration gradient is not as great between the inside of the leaf and the outside environment, so osmosis will occur more slowly. In contrast, if the outside air is very dry, the low amount of water will increase the concentration gradient between the inside and outside of the leaf, so osmosis and therefore transpiration, will occur faster [1].
Another factor that will impact the rate of transpiration is wind speed. If the wind speed is high, water will be rapidly blown away from the stomata. This will increase the concentration gradient between the inside of the leaf and the outside, so osmosis will occur faster. This will result in a faster rate of transpiration, and therefore more water being lost [1].
There are multiple adaptations plants have, which manage how quickly the process of transpiration is recurring, and help reduce water loss.