Final answer:
Diffusion is the passive movement of substances from high to low concentration areas in plant cells, critical for the exchange of gases and small solutes. Osmosis, a form of diffusion for water, is vital for cell turgidity. Plant cells in hypertonic solutions lose water and shrivel due to osmosis.
Step-by-step explanation:
Diffusion is a passive process by which substances move from an area of higher concentration to one of lower concentration, eventually reaching equilibrium. In plant cells, diffusion plays a crucial role in the movement of gases, such as oxygen and carbon dioxide, and small solutes across cell membranes and cell walls. Osmosis, a specific type of diffusion involving water, is essential for maintaining cell turgor and is critical for plant stability and nutrient transport.
When a plant cell is placed in a solution with a higher concentration of solutes compared to its cytoplasm, it is in a hypertonic solution. This causes the cell to lose water through osmosis, leading to the cell shriveling up, a condition known as plasmolysis. Conversely, in a hypotonic solution, where the surrounding solution has lower solute concentration than the cell's cytoplasm, water enters the cell, potentially causing it to swell and even burst if the cell wall cannot contain it.
For long-distance transport within plant tissues, structures such as the xylem and phloem use a process called bulk flow, which allows for the efficient movement of water and solutes over greater distances. This is a pressure-driven process and differs from diffusion, which is effective only over small distances within the plant structure.