Transport In Plants Test 1 12/11/12

Guard cells help in regulating the opening and closing of stomata, which are small openings on the surface of leaves. By controlling the opening and closing of stomata, guard cells regulate the exchange of gases, such as carbon dioxide and oxygen, as well as the loss of water vapor through transpiration. Transpiration is the process by which plants release water vapor into the atmosphere. Therefore, guard cells play a crucial role in facilitating transpiration.

Stomata of a plant open due to the influx of Potassium ions. When the concentration of Potassium ions increases inside the guard cells surrounding the stomata, water moves into the cells by osmosis, causing them to swell and open. This influx of Potassium ions and subsequent water movement is triggered by various factors such as light, low carbon dioxide levels, and the hormone abscisic acid. Opening the stomata allows for gas exchange, facilitating photosynthesis and transpiration in plants.

Guard cells are specialized cells found in the epidermis of leaves that regulate the opening and closing of stomata. Stomata are small pores on the leaf surface that allow for gas exchange. Chloroplasts are responsible for photosynthesis, the process by which plants convert sunlight into energy. The presence of chloroplasts in guard cells allows them to produce energy through photosynthesis, enabling them to actively control the opening and closing of stomata in response to environmental cues such as light intensity and water availability.

Increasing transpiration can increase the rate of water absorption in plants. Transpiration is the process by which water is lost from the leaves through small openings called stomata. When transpiration is increased, more water is drawn up from the roots to replace the water lost through the leaves. This increased flow of water through the plant helps to enhance the rate of water absorption.

The continuous column of water in the vessel and tracheids during the ascent of sap does not usually get broken because of cohesion and adhesion. Cohesion refers to the attraction between water molecules, causing them to stick together. Adhesion refers to the attraction between water molecules and the walls of the vessels and tracheids. These two forces work together to create a continuous column of water, allowing it to be pulled up through the plant without breaking. The weak gravitational pull, transpirational pull, and lignified thick walls also play a role in the ascent of sap, but they do not directly prevent the column of water from breaking.

When a plant cell is immersed in water, water molecules move into the cell through osmosis. Osmosis is the movement of water from an area of higher concentration to an area of lower concentration across a semi-permeable membrane. As water continues to enter the cell, it will keep moving into the cell until the concentration of water inside the cell is the same as outside. This is because osmosis will continue until equilibrium is reached, where the concentration of water is equal on both sides of the cell membrane.

When beet root cylinders are washed and placed in cold water, if anthocyanin does not come out, it indicates that the plasma membrane is impermeable to anthocyanin. This means that the anthocyanin molecules are unable to pass through the plasma membrane and diffuse into the surrounding water. This suggests that the plasma membrane acts as a barrier and prevents the movement of anthocyanin molecules.

Guttation is the process by which water is excreted in liquid form from the tips of leaves, usually occurring during the night or early morning. This phenomenon is caused by root pressure, which is the force generated by the roots of plants to push water and dissolved nutrients up through the xylem vessels. As the roots absorb water from the soil, the excess water accumulates in the plant and is forced out through specialized structures called hydathodes, resulting in guttation. Diffusion, transpirational pull, and osmosis are not directly responsible for guttation.

The cohesion tension theory explains how water is transported in plants through passive absorption. This process relies on the cohesive properties of water molecules and the tension created by transpiration pull. As water evaporates from the leaves, it creates a negative pressure that pulls water up through the xylem vessels. This theory does not involve active absorption, which would require energy expenditure by the plant. Therefore, the correct answer is passive absorption.

P-proteins support the translocation of organic solutes in sieve tube members. P-proteins, also known as phloem proteins, are found in the sieve tube elements of the phloem tissue. They form a network of filaments that help regulate the movement of solutes through the sieve tubes. P-proteins can block the sieve plate pores, preventing the backflow of solutes, and also aid in sealing damaged sieve tubes. Therefore, P-proteins play a crucial role in facilitating the mass flow of organic solutes in the phloem.