SCI1186 Lecture Notes - Lecture 11: Infusion, Sap, Passive Transport
16 Jun 2018
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Week 11 – Water and Nutrients in Plants
TRANSPORT IN PLANTS
2 different sources of food and water in plants:
1. Shoot system: used to generate CO2 and light harvesting
2. Root system: used to harvest water and minerals
Minerals in the soil are dissolved in the water in the soil, before being taken up by the roots of the plant
This mineral infused water is then pushed to the leaves to be used. Meanwhile, sugars formed in the leaves travel
down to any parts of the plant where they are needed
PASSIVE TRANSPORT
Type of transportation that does not require energy
3 types:
1. Diffusion: When molecules go across the cell membrane from an area of high concentration to an area of
low concentration
2. Osmosis: when solutes (typically water) moves to an area where molecules are high in concentration in
order to dilute and even out concentrations
3. Facilitated Diffusion: when a protein channel is used to assist molecules getting through a membrane
In cell-to-cell passive transportation, it involves a selectively permeable membrane which only allows certain
molecules in (mainly depending on the chemical makeup and the size of the molecule)
All of the types of passive transport rely on a concentration gradient
Processes are slow as they don’t require energy
WATER POTENTIAL
The potential of a particular system to donate water to another place
As the concentration of molecules increases, the more negative the water gradient is
This negative value means that water does not want to be donated but instead, wants to attract more water in order to
dilute the molecule concentration
In land plants. The water potential is always negative as water will always enter unless the outside solution is even
more concentrated than the cell. Opposite for water plants
Pure water always has the potential of 0 and can be calculated by:
ΨP + ΨS = Ψ ΨP – Pressure Potential
ΨS – Solute Potential
Soil water and plant sap are both solutions while water is the solvent and minerals as well as other molecules are
solutes
As plant cell contain large amounts of solutes, water is attracted into the cell
Water potential is the potential of water to move from one area to another via osmosis
TRANSPORT PATHWAYS
Plant cells have different compartments that are used to transport molecules and solution in and out of the cell
These compartments are:
• The cell wall: outside of the cell
• Cytosol: fluid in the cell
• Vacuole: the center of the cell and is the air space
The simplistic route has the molecule travel through the dead part of the cell (cell wall) while the transmembrane
route has the molecule travel through the cell wall and the cytosol
Document Summary
Week 11 water and nutrients in plants. 2 different sources of food and water in plants: shoot system: used to generate co2 and light harvesting, root system: used to harvest water and minerals. Minerals in the soil are dissolved in the water in the soil, before being taken up by the roots of the plant. This mineral infused water is then pushed to the leaves to be used. Meanwhile, sugars formed in the leaves travel down to any parts of the plant where they are needed. Type of transportation that does not require energy. In cell-to-cell passive transportation, it involves a selectively permeable membrane which only allows certain molecules in (mainly depending on the chemical makeup and the size of the molecule) All of the types of passive transport rely on a concentration gradient. Processes are slow as they don"t require energy. The potential of a particular system to donate water to another place.
