theories and models about plant function Flashcards
What were Joseph Priestley’s experiments
noticed mouse would die and candle would go out if cut off from air.
However, if a mint plant was added, the mouse would continue living and the candle continued burning.
How were Van Helmont’s experiments wrong
proposed that mass gained by a plant overtime was from water.
no repetition, or consideration of other factors that affected mass of plants
What information can be gained by ringbarking
Ringbarking is the swelling of bark that occurs after the removal of tissues outside xylem such the phloem. This occurs from a build up of sugars. The part below the cut is cut off from glucose and hence shrivels.
Describe how aphids were used in learning about plant function
Analysing the contents of the sap sucked out from plant by the aphid, scientists can see which chemical species travel through the phloem, ie very sugary –> glucose
Outline transpiration-cohesion-tension theory
hydrogen bonding between water molecules and attraction between water molecules and the xylem ensures continuous movement of water analogous to pulling a rope. In this case, the act of transpiration serves as the pull of the rope and water molecules move up to the leaves from the roots.
Outline source-sink theory
is the movement (translocation) of a sucrose solution from the leaves to other areas of the plants facilitated by the tendency of water to flow from high pressure to low pressure.
High pressure is created through osmosis as water travels to areas of high sucrose concentration, the rest of the plant has comparatively low pressure and thus sucrose flows to these areas. analogous to water flowing through a hose.
