7 Transport Flashcards
Role of Phloem vessels
Glucose made by photosynthesis is converted into sucrose and transported to other parts of plants through phloem vessels.
Position of Xylem vessels in cross sections
In root: star shaped.
In stem: inner part.
In leaf: upper part but below strengthening cells.
(Check textbook)
Function of Xylem
Xylem tissue contain long, hollow xylem cells that for long tubes through the plant. Tubes are hollow remains of dead cells. Thick strong cell walls to help support plant. Tubes are important as they transport water and mineral ions from roots through stem to all parts of the plant that need them. Supply water for leaf cells for photosynthesis.
Function of Phloem
Phloem cells are living cells linked together to for continuous phloem tissue. Dissolved food materials: sucrose and amino acids, are transported all over the plant from leaves. This is called translocation.
Structure and function of Root hair cells
Root hair cells are adapted for absorption of substances. They have a fine extension that sticks out into the soil. This greatly increases surface area for absorption. Water enters through osmosis because water potential is higher outside the root; water molecules are moving down their water potential gradient. Water enters root hair cells, passes through root from cortex cell and then into xylem tissue. Dissolved mineral ions are absorbed through active transport because there is usually a higher concentration inside the root cells.
Explain what is meant by Transpiration
Water molecules in the leaf cross the cell membranes of the spongy mesophyll cells into the air spaces. This is called evaporation as the liquid water in cells becomes water vapour in the air spaces. When the stomata opens, water vapour diffuses out.
Factors that affect the rate of transpiration
Temperature
Wind
Humidity.
Effect of temperature on Transpiration
Increased temperature means increased kinetic energy which means faster movement of particles. The more they move, the easier it is for them to evaporate from cell surfaces into air space and diffuse out of leaf.
Effect of Humidity on Transpiration
If humidity is decreased, there is less water vapour in the air, so a lower concentration of water molecules outside the leaf than inside, so more transpiration occurs.
Define Cohesion
Water molecules show cohesion meaning that they stick together. So as water molecules move out of xylem cells in a leaf vascular bundle, they create a tension at the top of xylem tube, pulling water molecules up the plant.
Role of Sucrose
Glucose is converted into sucrose because it is less reactive so it can be transported without causing problems for other cells.
Used to be converted back for respiration, and production of other molecules in the cell for cell growth.
Role of Amino acids in plants
Used to produce proteins for formation of new plant tissue during growth and produce enzymes to control cell reactions.
Main sinks for glucose
Root, shoot tips and flowers.
Define the Circulatory system
A system of continuous blood vessels, with a pump (the heart) and valves to ensure one-way flow of blood.
Describe Double circulation
Blood passing through the heart twice for each time that it passes through body tissues. This is because when blood leaves left side of heart, it passes through tissues of the lungs before returning to the heart for pumping around the rest of the body.
