When stomata are signaled to open, potassium ions (K+) enter the guard cells. This causes water to enter down its water potential gradient, creating a hydrostatic pressure in the guard cell that changes the shape of the stoma. Answer : (a)

When a plant cell is placed in a hypotonic solution, water enters into a cell by osmosis and as a result turgor pressure develops Answer : (a)

Water potential of pure water is zero because there is no solute present as well as the pressure in the system is zero. When a solute is dissolved it significantly decreases the water potential making the solute potential negative in value Answer : (d)

Answer : (a)

Answer : (b)

Dilute NaCl solution acts as hyotonic solution, So, when flower are cut and dipped in dilute NaCl solution Endosmosis occurs and cells of flowers swell. Answer : (b)

The increase in the solute potential and a decrease in water potential is affected by potassium ion in the plant. Answer : (b)

Cactus stomata are closed during daytime to prevent the loss of water in dry condition of the desert and during nighttime stomata are opened to cause transpiration. Answer : (a)

When guard cells gain water due to the process of endosmosis. They become turgid and swell. This leads to opening of stomatal pore Answer : (b)

Wooden doors swell up and get struck during the rainy season. this phenomenon is due to imbibition. Answer : (b)

Higher concentrations and higher temperatures increase osmotic pressure. If glucose is stored in plant cells, water will flows in. Cell expansion and an increase in turgor pressure is due to inward diffusion of water into the cell, and turgor pressure increases due to the increasing volume of vacuolar sap Answer : (b)

Water entering root due to diffusion is a part of passive transport because takes place without expenditure of energy. The water molecules move from higher concentration to the lower concentration which is towards the gradient. It takes place by two methods facilitated diffusion and simple diffusion. Answer : (c)

This theory was put forward by Sachs in 1878 to explain the ascent of sap by imbibitional activity of cell wall of the xylem elements. Water moves upwards due to imbibitional force between the cell wall of the xylem and the water column This theory was rejected as large quantity of water moves through the lumen of xylem which can be checked by artificially blocking the lumen by gelatin or oil Answer : (c)

Cohesion refers to the attraction of molecules for other molecules of the same kind, and water molecules have strong cohesive forces due to hydrogen bonds with one another. Answer : (d)

This turgidity is caused by the accumulation of K+ (potassium ions) in the guard cells. which opens the guard cell Proton pumps translocate H+ ions against their concentration gradient. Answer : (d)

Stomatal opening is under the control of Guard cells Stomatal pores in plants regulate the amount of water and solutes within them by opening and closing their guard cells using osmotic pressure. Answer : (d)

Osmosis provides the primary means by which water is transported into and out of cells Water moves into the roots from the soil by osmosis, due to the low solute potential in the roots The forces of cohesion and adhesion cause the water molecules to form a column in the xylem Answer : (c)

Osmosis is the movement of a solvent across a semipermeable membrane toward a higher concentration of solute Answer : (a)

Christian Wolf proposed this theory in 1873 and he suggests that water rises up in the narrow tubes of xylem vessels by surface tension. He proposed that when water is present in fine tubes then a force develops which causes ascent of sap which is known as capillary force. Answer : (b)

Chloroplasts found in guard cells have been found to synthesize malate by PEP carboxylase activity The glycollate and malate metabolism not only provides energy and hydrogen ions for ATPase pumps, but they also contribute in building up of osmotic concentration, which initiates the events like entry of water, increase in TP and finally the opening of the stomata. Similarly, increase in carbon dioxide and decrease in oxygen inhibits glycollate/malate metabolism; which further affects the osmoticum of guard cells. Finally it leads to closing of the stomata. Answer : (c)

Most of the water vapour lost from leaves occurs through the stomata, this is termed stomatal transpiration; smaller amounts of water vapour are also lost by direct evaporation from the epidermal cells, when the stomata are closed, through the cuticle; this is usually termed cuticular transpiration. Answer : (d)

Cuticular transpiration is the evaporation of water from a plant’s cuticle. The cuticle is a waxy film that covers the surface of a plant’s leaves. This form of transpiration does not account for much of a plant’s water loss; about 5-10 percent of the leaves’ water is lost through the cuticle. When plants close their stomata in dry conditions, more water is transpired this way. Answer : (d)

Imbibition is the uptake of water by substances that do not dissolve in water, so that the process results in swelling of the substance Answer : (d)

Ascent of sap takes place through xylem. Forces like transpiration pull, root pressure, capillary force, cohesive and adhesive force helps in this unidirectional movement of water Answer : (c)

DPD can be measured using the formula, DPD = OP - TP, where OP = Osmotic Pressure and TP = Turgor Pressure. Here, the water movement across the concentration gradient will be lower DPD to higher DPD. Cell A DPD 3 lower and Cell B DPD 5 atm higher Here, the water movement across the concentration gradient will be lower DPD to higher DPD. Movement of water from A to B Answer : (c)

Transpiration is regulated by movement of guard cell. Answer : (a)

Turgor pressure is the force within the cell that pushes the plasma membrane against the cell wall. Generally, turgor pressure is caused by the osmotic flow of water and occurs in plants, fungi, and bacteria Answer : (d)

Deplasmolysis is swelling of the cytoplasm of a plasmolyzed cell : reversal of plasmolysis plasmolysis contraction of the protoplast of a plant cell as a result of loss of water from the cell. endosmosis is the inward flow of a fluid through a permeable membrane toward a fluid of greater concentration exosmosis is the passage of a fluid through a semipermeable membrane toward a solution of lower concentration, especially the passage of water through a cell membrane into the surrounding medium. Answer : (b)

Guard cells can rapidly change shape so that the pores open or close to control leaf gas exchange and water transpiration. The guard cells contain chloroplasts, so they can manufacture food by photosynthesis (The epidermal cells do not contain chloroplasts) Guard cells are the only epidermal cells that can make sugar. Mesophyll cells (MC) are mainly parenchyma cells between the upper and lower epidermis specialized for photosynthesis. Answer : (c)

A common vital force theory about the ascent of sap was put forward by J.C. Bose (1923). It is called pulsation theory. The theory believes that the innermost cortical cells of the root absorb water from the outer side and pump the same into xylem channels. Answer : (a)