Question

Describe EIGHT factors that affect the rate of transpiration

Answer 1

Environmental factors

1. Temperature-High temperature raises internal temperature of the leaf which in turn increases latent heat of vaporization enhancing evaporation from the leaf. Low temperature lowers the internal temperature of the leaf which in turn lowers evaporation
2. Humidity- in low humidity saturation deficit between the leaf and the atmosphere is high thus water vapour diffuses faster increasing the rate of transpiration. In high humidity saturation deficit is low thus water diffuses slowly reducing the rate of transpiration
3. Wind .wind carries away water vapour as fast as diffuses from the leaf hence water vapour does not accumulate around the leaf and this raises diffusion gradient between the inside and outside the leave hence increasing the rate of transpiration and vice vasa.
4. Light intencity.Light intensity increases the rate of photosynthesis forming sugar which is osmotic ally active causing stomata to open hence water diffuses out of the leaf at higher rate increasing the rate of photosynthesis and vice vasa
5. Atmospheric pressure. Low atmospheric pressure reduces the weight of gases acting on the leaf causing a lot of evaporation from the leaf hence high rate of transpiration. High atmospheric pressure increases the weight of gases acting on the leaf hence minimal evaporation from the leaf leading to reduced rate of evaporation

Structural factors

1. Cuticle. Plants whose leaves are covered with thick cuticle have reduced rate of transpiration while plant with thin layer of cuticle have high rate of transpiration
2. Leaf size and shape. Plant with broad leaves exposes a large surface area for water loss compared to plant with small or needle like leaves
3. Hairy leaves.Plants whose leaves are covered with hairs have reduced rate of transpiration since the hairs trap a layer of moist air on the surface of the lowering the diffusion gradient thus reducing the rate of transpiration
4. Stomata. Plants with leaves with stomata on the upper surface ,high number of stomata, large sized aperture have increased rate of transpiration and vice vas
5. Glossy leaf surfaces. Glossy leaf surfaces reflect light landing on the leaf surface thus reducing the internal heating of the leaf hence low transpiration rate