3.3.4.2 Mass Transport in Plants Flashcards
Q: What is the main function of xylem tissue in plants?
A: The xylem tissue transports water and dissolved minerals from the roots to the stems and leaves.
Q: What theory explains water movement in the xylem?
A: The cohesion-tension theory.
Q: What is the cohesion-tension theory?
A: The cohesion-tension theory suggests that water molecules stick together (cohesion) and are pulled up through the plant as water evaporates from the leaves (tension).
Q: What is the main function of phloem tissue in plants?
A: The phloem tissue transports organic substances, like sugars, from sources (e.g., leaves) to sinks (e.g., roots, fruits).
Q: What hypothesis explains the movement of substances in the phloem?
A: The mass flow hypothesis.
Q: What is the mass flow hypothesis?
A: The mass flow hypothesis suggests that organic substances move through the phloem due to pressure differences between the source (high pressure) and the sink (low pressure).
Q: What is a ringing experiment and what does it demonstrate?
A: A ringing experiment involves removing a ring of bark (including the phloem) from a stem. It demonstrates that sugars are transported through the phloem because the region above the ring swells with accumulated sugars.
Q: What evidence supports the mass flow hypothesis?
A: Evidence includes the accumulation of sugars above the ring in ringing experiments and the movement of radioactive tracers through the phloem.
Q: What is a potometer used for?
A: A potometer is used to measure the rate of transpiration in plants.
Q: How can a potometer be used to investigate the effect of an environmental variable on transpiration?
A: By changing one environmental variable (e.g., light, temperature) and measuring the rate of water uptake by the plant using the potometer.
Q: What is transpiration?
A: Transpiration is the process by which water evaporates from the leaves of a plant, creating a negative pressure that pulls water up through the xylem.
Q: What is the role of cohesion in water transport through the xylem?
A: Cohesion refers to the attraction between water molecules, which helps to form a continuous column of water in the xylem.
Q: What is the role of tension in water transport through the xylem?
A: Tension is created by the evaporation of water from the leaves, pulling the column of water upward through the xylem.
Q: What factors can affect the rate of transpiration?
A: Environmental factors such as light, temperature, humidity, and wind.
cohesion tension theory step 1
- Water is lost from the leaf by transpiration as water evaporates from the mesophyll cels and
diffuses out of the Stomata down a water potential gradient.
