Increased light intensity will increase the rate of photosynthesis, so more water is drawn into the leaves where photosynthesis primarily takes place and therefore the rate of transpiration is greater. We sweat to cool our internal body temperature, plants transpire. Unfortunately, much more water leaves the leaf than CO 2 enters for three reasons: H 2 O molecules are smaller than CO 2 molecules and so they move to their destination faster. In strong light, the rate of transpiration is more because stomata are wide open. The rate of transpiration is more during the day to keep the plant cooler. Warm conditions, wind and bright sunlight speed up transpiration rate. This transpiration rate is the combined rate of all the leaves working together. This is because a plant with more root surface area will absorb more water provided that soil water is available. A potometer measures how factors such as light, temperature, humidity, light intensity and wind will affect the rate of transpiration. (b) Humidity of the atmosphere: If the air outside is humid the rate of transpiration is reduced, since the outward diffusion of internal water vapour is affected. 1. Plants transpire more in sunny and hot days due raise in temperature because of this plants transpire as water evaporates rapidly. If we had run this experiment with fewer leaves, the rate would be lower; if we had run it with more leaves, it would be higher. If leaf area is more, transpiration is faster. Plant Factors Affecting the Rate of Transpiration. The change in water level over a day gives the evaporation rate from that area for that day. That's why, and that's how it helps the plant. 2. However, the rate of transpiration per unit area is more in smaller leaves than in larger leaves due to higher number of stomata in the small leaf. To measure the rate of transpiration we use a piece of equipment called a potometer. May transpiration in plants occur during night? The main type of potometer is the ‘bubble’ potometer shown in the figure below. Since measurements were taken every 10 minutes for an hour, the total cumulative transpiration at the end of the 60 minute period will be the transpiration rate per hour. Light also speeds up transpiration by warming the leaf. Question Date: 2008-11-26: Answer 1: Plants that live in extremely hot and arid climates often keep their stomata closed during the day, to reduce the amount of water that is lost in transpiration, and open it during the cooler and more humid nighttime. This is largely because light stimulates the opening of the stomata . In dim light or on a cloudy day the stomata are partially closed reducing the rate of transpiration. I = S/E+S × … Number of stomata per unit area of leaf is called stomatal frequency. CO 2 is only about 0.036% of the atmosphere (and rising!) For a more detailed answer read on: Transpiration is when water goes into the roots, goes up via the xylem, and eventually goes out the stomata. Conclusions: Different environmental conditions have an effect on transpiration rate in plants. The rate of transpiration can be affected by light intensity, air movement, temperature, and humidity. Environmental factors that affect the rate of transpiration. When the relative humidity in a plant's environment rises, its rate of transpiration lowers, and a decrease in humidity causes the transpiration rate to rise. More water within the plant will mean a steeper plant-to-atmosphere vapor pressure gradient and more water to transpire within a time duration. Air that is humid does not accept water vapor easily, and drier air makes it easier for a plant to release water by evaporation through the stomata on its external surfaces. 1. 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