Explain the mechanism of Pressure Flow Hypothesis involved in the movement of sucrosemolecules from the leaf to the root.
Question
Explain the mechanism of Pressure Flow Hypothesis involved in the movement of sucrosemolecules from the leaf to the root.
Solution
The Pressure Flow Hypothesis, also known as the Mass Flow Hypothesis, explains the movement of sucrose molecules from the leaf (source) to the root (sink) in plants. Here's a step-by-step explanation:
-
Photosynthesis: The process begins in the leaves where photosynthesis occurs. The plant uses sunlight, carbon dioxide, and water to produce glucose, which is then converted into sucrose.
-
Loading of Phloem: The sucrose is actively transported into the phloem tissue, specifically into the sieve tube elements, by companion cells. This process requires energy in the form of ATP.
-
Creation of Pressure Potential: The high concentration of sucrose in the phloem lowers the water potential, causing water to move into the phloem from the xylem through osmosis. This creates a pressure potential in the phloem tissue at the source end (leaf).
-
Mass Flow: The pressure potential causes the sucrose solution to flow down the phloem towards the sink (root). This is a passive process and does not require energy.
-
Unloading of Phloem: At the sink, the sucrose is actively unloaded from the phloem tissue into the root cells. This again requires energy in the form of ATP.
-
Return of Water: The decrease in sucrose concentration at the sink end increases the water potential, causing water to move out of the phloem and back into the xylem. This reduces the pressure potential at the sink end, maintaining the pressure gradient that drives mass flow.
This cycle continues, allowing the plant to transport sucrose from the leaves where it is produced to the roots where it is needed.
Similar Questions
Describe how water moves from roots to the leaves.
Which statement is TRUE about transpiration pull?*1 pointIs an active transport.The root generates hydrostatic pressure.Xylem sap was pushed downwards.The mesophyll cells in leaves have low water potential.
Water is transported in plants by a variety of means. However, transport over long distances isprimarily the result of:A. root pressure.B. transpiration.C. active transport of water from xylem vessels into leaf cells.D. higher water potential in leaf cells as compared to root cells.E. active transport of water into xylem vessels.
Atmospheric pressure can support a column of water up to 10 meters high. But plants can move water much higher, the sequoia tree can pump water to its very top, more than 100 meters above the ground. Until the end of the nineteenth century, the movement of water's in trees and other tall plants was a mystery. Some botanists hypothesized that the living cells of plants acted as pumps, but many experiments demonstrated that the stems of plants in which all the cells are killed can still move water to appreciable heights. Other explanations for the movement of water in plants have been based on root pressure, a push on the water from the roots at the bottom of the plant. But root pressure is not nearly great enough to push water to the tops of tall trees, Furthermore, the conifers, which are among the tallest trees have unusually low root pressures.If water is not pumped to the top of a tall tree, and if it is not pushed, to the top of a tall tree, then we may ask. How does it get there? According to the currently accepted cohesion-tension theory, water is pulled there. The pull on a rising column of water in plant results from the evaporation of water at the top of the plant. As water is lost room the surface of the leaves, a negative pressure or tension is created. The evaporated water is replaced by water moving from inside the plant in unbroken columns that extend from the top of a plant to its roots. The same forces that create surface tension in any sample of water are responsible for the maintenance of these unbroken columns of water. When water is confined in tubes of very small bore, the forces of cohesion (the attraction between water molecules) are so great that the strength of a column of water compares with the strength of a steel wire of the same diameter. This cohesive strength permits columns of water to be pulled to great heights without being broken.
State the forces involved which helps in transport of water through plants.
Upgrade your grade with Knowee
Get personalized homework help. Review tough concepts in more detail, or go deeper into your topic by exploring other relevant questions.