Which of the following is CORRECTLY matched:a)Positive pressure theory...
While movement of water and minerals through the xylem is driven bynegative pressures (tension) most of the time, movement through the phloem is driven by positive hydrostatic pressure. This process is termed translocation, and is accomplished by a process called phloem loading and unloading.
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Which of the following is CORRECTLY matched:a)Positive pressure theory...
Understanding the Positive Pressure Theory
The Positive Pressure Theory primarily explains the mechanism of translocation in phloem, which is essential for the distribution of nutrients and energy throughout the plant.
Key Points about Positive Pressure Theory:
- Translocation in Phloem:
- This theory posits that the movement of sap (which contains sugars and other nutrients) in the phloem occurs due to a positive pressure created by the process of photosynthesis.
- When photosynthesis occurs, sugars are produced in the source tissues (leaves) and actively loaded into the phloem, increasing osmotic pressure.
- This pressure drives the flow of sap towards areas of lower concentration, such as growing tissues or storage organs (sinks).
- Mechanism of Pressure Generation:
- The accumulation of solutes in the phloem draws water from adjacent xylem vessels, creating a positive pressure that pushes the sap through the phloem.
- Importance in Plant Physiology:
- This mechanism is crucial for the distribution of essential nutrients, allowing plants to grow and develop properly, especially during periods of growth and fruiting.
Rationale for Incorrect Options
- Negative Pressure Theory:
- Related to water movement in xylem, not mineral absorption or translocation in phloem. It explains how water is pulled up from roots through transpiration.
- Water Absorption by Root Hairs:
- This process is primarily driven by osmosis and the concentration gradient, not by any pressure theory.
In conclusion, option 'A' is correctly matched because it accurately aligns the Positive Pressure Theory with its role in translocation within the phloem. Understanding this concept is fundamental in the study of plant physiology and the transport mechanisms essential for plant health.
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