Question

Define diffusion and osmosis. Explain how osmosis helps plant leaves remain firm. What is the term for water pressure inside plant cells?

Short answer

Diffusion is the movement of molecules from an area of high concentration to one of lower concentration, while osmosis is the movement of water molecules across a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration. Osmosis helps plant leaves remain firm by allowing water to move into plant cells, filling the central vacuole, and creating "turgor pressure" against the cell wall, thus maintaining the structure and firmness of the leaf. The term for water pressure inside plant cells is "turgor pressure."

Step-by-step solution

Definition of Diffusion

Diffusion is the process by which molecules move from an area of high concentration to one of lower concentration, eventually resulting in the even distribution of the molecules. This movement occurs due to the random motion of the molecules and does not require any external energy. The process continues until the concentration of molecules becomes equal in all areas.

Definition of Osmosis

Osmosis is a special type of diffusion that involves the movement of water molecules across a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration until the concentrations on both sides of the membrane become equal. This process helps to maintain the balance of water and solute concentration inside and outside the cells.

Role of Osmosis in Maintaining Plant Leaves Firmness

Plant cells have a rigid cell wall that surrounds the cell membrane. Inside the cell, there is a large central vacuole that stores water and other substances. When there is a higher concentration of solutes inside the cell compared to its surrounding, water moves into the cell through osmosis. As the central vacuole fills with water, it pushes against the cell wall, creating an internal pressure called turgor pressure. Turgor pressure is essential for maintaining the structure and firmness of plant leaves. When a plant has enough water, the turgor pressure inside the cells is high, and the leaves remain firm. If there isn't enough water, the turgor pressure drops, causing the leaves to wilt and lose their firmness.

Term for Water Pressure Inside Plant Cells

The term for water pressure inside plant cells is "turgor pressure."

Key concepts

Diffusion

Diffusion is a natural phenomenon where molecules travel from regions of high concentration to regions of low concentration. It occurs because molecules are always in random motion. This process does not need any energy since the molecules rely on their inherent kinetic energy to spread out evenly. For example, if you add a drop of dye to water, it will eventually spread throughout the water, creating a uniform color. This illustrates how diffusion works to achieve balance or equilibrium.

• No energy required: Diffusion happens passively.
• Occurs until equilibrium: Continues until molecules are evenly distributed.
• Random motion: Molecules move randomly during diffusion.

Turgor pressure

Turgor pressure refers to the pressure of the cell contents against the cell wall in plants. It occurs when water enters a plant cell, filling the central vacuole, creating an outward pressure on the cell wall. This pressure is critical for supporting the plant structure and maintaining the firmness of plant tissues, especially the leaves.
When a plant has ample water, it absorbs it into the cells, and the vacuoles get filled, leading to high turgor pressure. Conversely, during droughts or when a plant is not watered sufficiently, the vacuoles lose water, causing turgor pressure to drop, leading to wilting.
A few key points about turgor pressure include:

• Vital for plant rigidity: It helps maintain plant shape and firmness.
• Dependent on water availability: The more water, the higher the turgor pressure.
• Loss of turgor leads to wilting: Insufficient water causes plants to droop.

Plant cell structure

The structure of plant cells is unique and essential for their survival. Plant cells have a rigid cell wall made of cellulose that offers protection and structural support. Inside each plant cell, you'll find a cell membrane that regulates what enters and exits.
A key feature of plant cells is the central vacuole. It is a large, water-filled organelle that plays a crucial role in maintaining the cell's turgor pressure, thus contributing to the plant's overall strength and rigidity.
Other vital components include:

• Chloroplasts: Contain chlorophyll for photosynthesis.
• Endoplasmic reticulum and Golgi apparatus: Involved in producing and transporting proteins.
• Ribosomes: Sites for protein synthesis.

Together, these structures enable plants to make their food, grow, and stay firm.

Water balance in plants

Maintaining the correct water balance is crucial for a plant's health. Water is absorbed by plant roots and travels through the plant, playing several roles. It aids in transporting nutrients and is a reactant in photosynthesis, the process by which plants produce food.
One of the primary ways plants control water retention is through opening and closing stomata, tiny openings on the leaf's surface. The process of osmosis also allows water to move into cells, balancing water and solute concentrations. Maintaining this balance ensures that cells maintain proper turgor pressure and stay firm.
Here are some essential aspects of water balance in plants:

• Root absorption: Water is drawn into the plant primarily through roots.
• Transpiration: Loss of water through leaves helps in nutrient transport but requires coherence in replenishment.
• Stomatal regulation: Balances water loss and retention, following environmental changes.