Plant Physiology

Osmosis is a special type of diffusion that occurs when a semi-permeable membrane is required. In osmosis, solvent molecules move from an area of lower solute concentration to an area of higher solute concentration through a semi-permeable membrane. This process is important for maintaining the balance of water and solutes in cells and is commonly observed in biological systems.

Turgor pressure refers to the pressure exerted by the cell contents against the cell wall. In a flaccid cell, the cell is limp and lacks water, resulting in low turgor pressure. When a cell is flaccid, it is not fully hydrated and is in a state of reduced pressure. Therefore, the statement that turgor pressure is at the lowest in a flaccid cell is true.

Water potential is denoted by the symbol "Psi". Water potential is a measure of the potential energy of water in a system, and it determines the direction and rate of water movement. It is influenced by factors such as solute concentration, pressure, and gravity. The symbol "Psi" is commonly used to represent water potential in scientific literature and equations.

The statement is true because water potential is a measure of the tendency of water to move from one place to another. Protoplasm, which is the living substance within a cell, has a water potential that is equal but opposite to the diffusion pressure deficit. This means that if the diffusion pressure deficit is high, indicating a low concentration of water molecules, the water potential of the protoplasm will be low, causing water to move into the cell. Conversely, if the diffusion pressure deficit is low, indicating a high concentration of water molecules, the water potential of the protoplasm will be high, causing water to move out of the cell.

Plasmolysis is the process in which a plant cell loses water and shrinks due to being placed in a solution with a higher solute concentration than the cell's cytoplasm. In a hypertonic solution, the solute concentration outside the cell is higher than inside the cell, causing water to move out of the cell through osmosis. This loss of water leads to the cell membrane detaching from the cell wall and the cell undergoing plasmolysis. Therefore, a plant cell needs to be placed in a hypertonic solution for plasmolysis to occur.

The strip of young endodermal cells in the root that have suberised thickening on their lateral and radial walls is known as the Casparian strip. This strip acts as a barrier and prevents the passive flow of water and solutes between cells, forcing them to pass through the selective plasma membrane of the endodermal cells. This helps in regulating the movement of water and nutrients into the vascular tissue of the root.

Imbibition refers to the process of adsorption of water by hydrophilic colloids. This process occurs when the hydrophilic colloids attract and hold water molecules, causing them to be absorbed and retained. Diffusion pressure deficit and osmosis are not applicable in this context as they involve different mechanisms of water movement. Therefore, the correct answer is imbibition.

Turgor pressure is the correct answer because it refers to the pressure that develops in a cell as a result of osmotic diffusion of water. This pressure is responsible for maintaining the shape and rigidity of plant cells, and it plays a crucial role in various cellular processes such as cell growth and movement. Osmotic pressure, diffusion pressure deficit, and suction pressure are not specific terms used to describe the pressure developed in a cell due to osmotic diffusion of water.

When a solvent is separated from a solution, the solvent molecules will naturally move from an area of higher concentration (in the solution) to an area of lower concentration (outside the solution). This movement creates a pressure, known as diffusion pressure deficit, which drives the solvent molecules to diffuse towards the solution. Therefore, the correct answer is diffusion pressure deficit.

Incipient plasmolysis refers to the point at which plasmolysis just begins. Plasmolysis is the process in which plant cells lose water and shrink due to the movement of water out of the cell. At the stage of incipient plasmolysis, the cell membrane starts to pull away from the cell wall, indicating the beginning of water loss. This term is commonly used in biology to describe the initial stage of plasmolysis in plant cells.