Factors affecting transpiration
Factors Affecting Transpiration
Transpiration is the process by which water vapour is lost from plant surfaces, primarily through the stomata in the leaves. Several factors influence the rate of transpiration, including environmental conditions and plant-specific characteristics:
Light Intensity
Higher light intensity increases the rate of photosynthesis, which in turn raises the demand for carbon dioxide. To meet this demand, stomata open wider, allowing more water vapour to escape. Thus, as light intensity increases, the rate of transpiration also rises.
Temperature
Elevated temperatures enhance the rate of evaporation of water from plant surfaces. This increases the water vapour gradient between the leaf interior and the surrounding environment, thereby accelerating transpiration. However, extremely high temperatures may cause stomata to close to prevent excessive water loss.
Humidity
Humidity refers to the amount of water vapour present in the air. Lower humidity increases the water vapour gradient between the leaf and the air, thus speeding up transpiration. Conversely, high humidity reduces this gradient, slowing the rate of transpiration as the air is already saturated with moisture.
Wind
Wind or air movement removes the boundary layer of still air around the leaf surface, which can become saturated with water vapour. Increased air movement enhances the diffusion of water vapour away from the leaf surface, thereby increasing the rate of transpiration. Still air reduces this effect.
Soil moisture
Adequate soil moisture is necessary for maintaining turgor pressure in guard cells, which regulate stomatal opening. When soil moisture is low, plants may close their stomata to conserve water, thus reducing the rate of transpiration. Conversely, well-watered plants can maintain open stomata and higher transpiration rates.
Plant type
Different plant species have varying transpiration rates based on their structural adaptations. For instance, xerophytes (plants adapted to dry conditions) have specialised adaptations such as reduced leaf surface area and sunken stomata to minimise water loss.
Interpreting Experimental Data with a Bubble Potometer
In experiments using a bubble potometer to investigate factors affecting transpiration, the rate of water loss is measured by observing the rate at which air bubbles move through the apparatus. A higher rate of water loss, indicated by a faster movement of bubbles, under conditions such as increased light intensity or higher wind speeds, suggests enhanced transpiration. This is because these conditions increase the evaporation of water from the leaf surface, thereby accelerating the movement of water through the plant and into the potometer.
