An Overview of Transport Mechanisms In Plants Relate the str

An Overview of Transport Mechanisms In Plants. Relate the structure of sieve-tube cells, vessel cells, and tracheids to their functions in bulk flow, Define the terms flaccid, plasmolyze, turgor pressure, and turgid. Explain how aquaporins affect the rate of water transport across membranes. Name the three major compartments in vacuolated plant cells. Distinguish between the symplast and the apoplast. Describe three routes available for lateral transport in plants. Define bulk flow and describe the forces that generate pressure in the vascular tissue of plants. Absorption of Water and Minerals by Roots Explain what routes are available to water and minerals moving into the vascular cylinder of the root. Explain how the endodermis functions as a selective barrier between the root cortex and vascular cylinder. Transport of Xylem Sap Describe the potential and limits of root pressure to move xylem sap. Define the terms transpiration and guttation. Explain how transpiration pull moves xylem sap up from the root tips to the leaves. The Control of Transpiration Describe the role of guard cells in photosynthesis-transpiration. Explain how and when stomata open and close. Describe the cues that trigger stomatal opening at dawn. Translocation of Phloem Sap Define and describe the process of translocation. Trace the path of phloem sap from a primary sugar source to a sugar sink. Describe the process of sugar loading and unloading.

Solution

4. Bulk flow transport in plants:

Sieve tube cells: These are elongated cells in the phloem structure which helps in sugar conduit.

Vessel cells: These are long dead xylem cells which help in transporting water around the cells.

Tracheids: These are also water-conducting cells of the xylem which also transports mineral salts.

5. These terms are related to the conditions of the cell when placed in solutions having different osmotic concentrations:

Flaccid: It is the condition when the cell contents have shrunken and reduced in size, upon placing the cell in hypertonic solution.

Plasmolyze: When the cells are subjected to or undergo the process of plasmolysis, they are said to be plasmolysed. This occurs when water flows out of the cells due to the presence of high solute concentration outside the cell.

Turgor pressure: It is the pressure created when water moves inside the cell from a region of low solute concentration, through the cell membrane.

Turgid: It is the condition when the cells are fully distended and increased in size due to the inward flow of water.

6. Aquaporins are transmembrane proteins which act as water channels for the movement of water across the cell membrane. These proteins are made of beta-barrel structures.

Due to the presence of aquaporins, the rate of water transport increases.

7. The three major compartments of the vacuolated plant cells are the cell wall, cytosol or cytoplasm and vacuole.