Question

A coastal area was flooded with sea water and resulted in heavy salt deposits in the nearby area. After a few days, it was observed that many plants died. Based on these statements, which of the following is the most probable cause of the plant deaths? A. Plants died due to infection from sea water borne germs. B. Plants died due to absence of sunlight. C. Plants died due to plasmolysis in the plant cells. D. Plants died because they were eaten by sea organisms.

• A. A
• B. C
• C. D
• D. B

Answer 1

Answer:

B. C

Plasmolysis and Salinity Stress in Plants

The Scenario:

• A coastal area experienced flooding by seawater.

• This resulted in significant salt deposits in the adjacent land.

• Subsequently, many plants in this area died.

The Most Probable Cause: Plasmolysis

• Plasmolysis is the process in plant cells where the plasma membrane pulls away from the cell wall due to the loss of water through osmosis.

• This occurs when the external environment has a higher solute concentration (like salt) than the cytoplasm inside the plant cell.

Mechanism of Salt Damage to Plants:

• Osmosis: Plant cells contain water and dissolved substances (solutes). Water moves from an area of lower solute concentration to an area of higher solute concentration across a semipermeable membrane (like the cell membrane).

• High External Salt Concentration: Seawater is highly saline, meaning it has a very high concentration of dissolved salts. When the soil or surrounding environment becomes saturated with salt from seawater, the external solute concentration becomes much higher than that within the plant's cells.

• Water Loss: Due to the high external salt concentration, water is drawn out of the plant cells and into the soil/environment via osmosis.

• Cell Shrinkage and Death: This excessive loss of water causes the cell contents to shrink, pulling away from the cell wall. This condition is plasmolysis. Severe plasmolysis leads to the death of the plant cells and, consequently, the entire plant.

Why Other Options Are Less Probable:

• A. Infection from sea water borne germs: While seawater can carry microorganisms, the primary and immediate effect of high salt concentration on plants is osmotic stress, not typically widespread pathogenic infection leading to mass death in this manner.

• B. Absence of sunlight: The problem states a flooding event and salt deposits, not a condition that would inherently block sunlight from reaching the plants. Plant death due to lack of sunlight takes a longer period than typically observed after such an event.

• D. Eaten by sea organisms: While some marine organisms might be washed ashore, it's unlikely they would consume large numbers of plants to cause widespread death in this specific scenario. The scale of plant death points to an environmental factor rather than predation.