Transpiration

• What is transpiration?

  Transpiration is the process where plants absorb water through the roots, which then moves up through the plant and is released into the atmosphere as water vapour through

  pores in the leaves. Carbon dioxide enters, while water and oxygen exit through a leaf’s stomata.
• What is the transpiration stream?

  The movement of water up the stem
• What does the transpiration stream enable?

  The transpiration stream enables processes such as photosynthesis, growth and elongation as it supplies the plant with water which is necessary for all these processes.
• What does the transpiration stream supply to the plant?

  The transpiration stream supplies the plant with the required minerals, whilst enabling it to control its temperature via evaporation of water.
• Which process is involved in transpiration?

  Transpiration involves osmosis, where water moves from the xylem to the mesophyll cells.
• Why is evaportation involved in transpiration?

  Transpiration also involves evaporation from the surface of mesophyll cells into intercellular spaces and diffusion of water vapour down a water vapour potential gradient out of the

  stomata.
• With which device can the rate of transpiration be investigated?

  The rate of transpiration can be investigated with the help of a potometer where water vapour lost by the leaf is replaced by water in the capillary tube. Therefore, measuring the

  movement of the meniscus can be used to determine the rate of transpiration
• What are the factors that impact transpiration?

  Number of leaves

  Number of stomata

  Size of stomata

  Position of stomata

  presence of a waxy cuticle

  Amount of light present

  Temperature

  Humidity

  air movement

  Water availability
• What is the name of a plant that has been adapted to live in dry conditions?

  Xerophytes
• Why are xerophytes able to live in dry conditions?

  Various adaptations which serve to minimise water loss are present. The adaptations include smaller leaves which reduce the surface area for water loss. Both densely packed mesophyll and thick waxy cuticles prevent water loss via evaporation.
• How do xerophytes respond to low water availability?

  xerophytes respond to low water availability by closing the stomata to prevent water loss. Apart from this, they contain hairs and pits which serve as a means of trapping moist air, thus reducing the water vapour potential. Xerophytes also roll the leaves to reduce the exposure of lower epidermis to the atmosphere, thus trapping air.
• What are hydrophytes?

  Hydrophytes are plants that live in water
• What are examples of adaptations in hydrophytes?

  They have a very thin or absent waxy cuticle as

  they don’t need to conserve water. Many constantly open stomata are found on the upper surfaces of leaves to maximise gas exchange. Wide, flat leaves give a large surface area for light absorbtion. Air sacs are found in some hydrophytes to enable leaves to stay afloat. Many large air spaces to make leaves and stems more buoyant.