Section 24-2 Quiz Transport In Vascular Plants

Guard cells regulate the rate of transpiration by causing the stoma to open and close. When the guard cells are turgid, they swell and create an opening, allowing gases, including water vapor, to escape through the stomata. This leads to an increase in transpiration. On the other hand, when the guard cells lose water and become flaccid, they close the stomata, reducing the rate of transpiration. This mechanism helps plants to control the loss of water through transpiration and maintain optimal water balance.

Water is a polar substance, meaning it has a slight positive charge on one end and a slight negative charge on the other. This polarity allows water molecules to form hydrogen bonds with other polar substances, such as the cell walls of plants. This adhesive property of water enables it to travel upwards through the xylem vessels of plants, against the force of gravity.

When potassium ions enter a pair of guard cells, the cells take in water by osmosis. Osmosis is the process by which water molecules move from an area of lower solute concentration (in this case, the guard cells) to an area of higher solute concentration (outside the guard cells) through a semi-permeable membrane. The entry of potassium ions into the guard cells increases the solute concentration inside the cells, causing water to move into the cells through osmosis. This water uptake leads to the swelling and opening of the guard cells, allowing for gas exchange and the regulation of plant stomatal openings.

The tension-cohesion theory explains how water is able to move up a plant against gravity. According to this theory, water moves up the plant due to two main factors: cohesion and tension. Cohesion refers to the attraction between water molecules, which allows them to stick together. Tension is created when water is lost from the leaves through transpiration, creating a pull or negative pressure that helps to draw water up from the roots. This cohesive and tensional force allows water to move upward in the plant's vascular system, supplying nutrients and maintaining its structure.

Transpiration refers to the process of water loss from a plant through its stomata. Stomata are tiny openings on the surface of leaves that allow for gas exchange, including the release of water vapor. This water loss occurs as a result of evaporation from the plant's leaves and stems. Transpiration is an important process for plants as it helps to regulate their temperature, transport nutrients, and maintain turgidity.

This statement is true because sugar molecules are too large to pass directly through the cell membrane. Therefore, they must be transported through the cytoplasm of living cells using various transport mechanisms such as facilitated diffusion or active transport. This allows the cells to uptake and utilize sugar for energy production and other metabolic processes.

A sink in a plant refers to the part of the plant to which sugar is delivered. This means that it is the location where sugars produced during photosynthesis are transported and stored for later use. It is important for the plant's growth and energy storage.

The statement "water flows freely through full xylem cells" is false. Xylem cells are responsible for transporting water and nutrients from the roots to the rest of the plant. However, these cells are not empty or freely flowing. They have specialized structures, such as vessel elements and tracheids, which form a continuous tube-like structure. These cells are interconnected, but they are not completely open. Instead, they have thick cell walls and narrow openings that allow water to move through them in a controlled manner.