Transpiration and Translocation Flashcards
Translocation
The movement of dissolved glucose (produced in photosynthesis) from the leaves to the rest of the plant by the phloem tubes.
Purpose of Translocation
Transport sugar to cells in the plant so that it can be used for respiration, growth or glucose storage (starch).
What do phloem tubes transport?
CELL SAP: glucose dissolved in water - sugar made in the leaves can be transported long distances and across multiple cells.
Bidirectional
The phloem can transport substances in either direction, so, up or down the plant.
Phloem Vessels’ Specialisation
In between the adjacent cells in the tube, there is a semi-permeable membrane with pores, that allows (cell sap) to move through.
Transpiration
Evaporation of water from the leaves’ stomata: this pulls water up from the roots through the xylem and is called transpiration.
Transpiration Stream
The constant movement of water up the plant through the xylem due to transpiration.
Xylem tubes are…
long and hollow tubes found in the vascular bundles alongside the phloem which transport water and mineral ions in the plant.
Xylem Vessels Specialisation
Made up of dead xylem cells which are joined together with no end walls between them. In the xylem tubes, transport only goes one way.
Xylem vessels have thick walls strengthened by…
LIGNIN
The process of transpiration provides:
Water to cells which keeps them turgid.
Water to cells (in the leaf) for photosynthesis.
Mineral ions to leaves: e.g. nitrates for amino acids which form proteins/ magnesium for chlorophyll production.
Factors Affecting Rate of Transpiration: Temperature
Higher temperatures increase the rate of transpiration because water evaporates faster in higher temperatures.
Factors Affecting Rate of Transpiration: Humidity
Lower humidity increases the rate of transpiration because the drier the air, the steeper the concentration gradient of water molecules between the air and leaf,
Factors Affecting Rate of Transpiration: Wind Speed
More wind increases the rate of transpiration because the wind removes the water vapour quickly maintaining a steeper concentration gradient.
Factors Affecting Rate of Transpiration: Light Intensity
Higher light intensity increases the rate of transpiration because stomata open wider to let more carbon dioxide into the lead for photosynthesis.
