Passive absorption is the type where the water absorption is through the transpiration pull. This creates tension or force that helps in the movement of water upwards into the xylem sap. Higher is the transpiration rate, higher is the absorption of water. Answer : (b)

Water exudation through hydathodes is Guttation Answer : (a)

An increase in solutes induces an influx of water across the guard cell membrane. As the volume of the guard cells increase, they “inflate” into two kidney-bean-like shapes. As they expand, they reveal the stoma opening in the center of the two guard cells Answer : (a)

Cotton fibres dipped in water absorb water through Capillarity Capillarity the tendency of a liquid in a capillary tube or absorbent material to rise or fall as a result of surface tension. Answer : (c)

If carbon dioxide concentrations inside the leaf start to fall, the plant will open its stomata so that more CO2 can enter The opening of gas exchange pores requires the uptake of potassium ions into guard cells. wihch decreases H+ ion concentration Answer : (b)

In lotus or Water Lily type, the leaves float on the surface of water. Theis lower surface is in touch with water and only upper surface is exposed. So all the three above mentioned functions are performed by stomata which are restricted to upper surface only Answer : (d)

When plant cells are placed in concentrated sugar solutions they lose water by osmosis and they become “flaccid”; this is the exact opposite of “turgid”. Answer : (b)

A halophyte is a salt-tolerant plant that grows in soil or waters of high salinity, coming into contact with saline water through its roots or by salt spray, such as in saline semi-deserts, mangrove swamps, marshes and sloughs and seashores. To overcome this plants maintain a higher osmotic pressure in cell sap, so that they are able to absorb water inspite of high salt concentration in soil. Answer : (b)

Stomata open during day due to Accumulation of K+ ion and sugar Answer : (a)

When turgor is lost, the stoma closes. In angiosperms and gymnosperms (but not in ferns and lycopsids), ABA is the hormone that triggers closing of the stomata when soil water is insufficient to keep up with transpiration. The mechanism: ABA binds to receptors at the surface of the plasma membrane of the guard cells Answer : (c)

The water loss per g of biomass produced with C3 cycle is high (450 to 950) The water loss per g of biomass produced with C4 cycle is low (250 – 350) Answer : (a)

The cohesion-tension theory (C-T theory) by Boehm (1893) and Dixon and Joly (1894) postulates that the water ascent in trees is exclusively due to the transpirational pull from continuous water columns in the xylem conduit running from the roots to the leafs Answer : (a)

The mechanism by which sugars are transported through the phloem, from sources to sinks, is called pressure flow. At the sources (usually the leaves), sugar molecules are moved into the sieve elements (phloem cells) through active transport. Hence translocation of sugar from source to sink has no relation with transpiration Answer : (c)

Xylem forms vascular bundles with the phloem and helps in the conduction of water and minerals from the root to the other parts of the plant. Xylem tissue consists of a variety of specialized, water-conducting cells known as tracheary elements. Answer : (c)

Answer : (c)

According to starch-sugar interconversion theory, during night the glucose 1-phosphate (sugar) converts into starch in guard cells and thus increasing the osmotic potential. The guard cells release water, become flaccid and stomata closes. Answer : (a)

The formula for calculating water potential is ψ = π + p. Water always moves from the system with a higher water potential to the system with a lower water potential. cell a water potential = -0.5 cell b water potential = -0.3 cell c water potential = -0.6 cell d water potential = -0.4 Note the more solute there is, the more negative ψ becomes Now water will move from lower solute water to higher solute water Cell c have higest solute while cell b have lowest solute Water will move from cell b to other cells Answer : (d)

Answer : (a)

Depending upon the distribution and arrangement of stomata in the leaves five categories of stomatal distribution have been recognized in plants Apple or mulberry (hypostomatic) type : Stomata are found distributed only on the lower surface of leaves, e.g., apple, peach, mulberry, walnut, etc. Oat (amphistomatic) type: Stomata are found distributed equally upon the two surfaces, e.g. maize, oats, grasses, etc. Water lily (epistomatic) type: Stomata are found distributed only on the upper surface of leaf, e.g., water lily, Nymphaea and many aquatic plants. Potamogeton (astomatic) type: Stomata are altogether absent or if present they are vestigeal. e.g., Potamogeton and submerged aquatics. Answer : (c)

When a cell is placed in hypotonic solution (dilute solution), water enters into the cell, hence cell will show endosmosis. Answer : (c)

When the concentrations of solutes decrease in guard cells in the cases of ABA and elevated CO2, water potential increases in the cells and water flows out, causing a decrease of turgor pressure and closure of the pores. statement "a" not related to stomata opening When guard cells losses water, causes the cells to become flaccid and the stomatal opening to close Answer : (b)

Because permeability of cell membrane decreases as both membrane and water become viscous. At low temperature, the fatty acid tails of the phospholipids move less and become more rigid. This decreases the overall fluidity or become viscous of the membrane Answer : (d)

Osmometer will shrink when it is placed in a hypertonic solution. It loses water due to osmosis and shrinks. So the only solution which is hypertonic to the osmometer is 0.75 M. Answer : (b)

Transpiration pull,Cohesion is the phenomenon of attraction between similar molecules. The water molecules remain attracted by the cohesive force and cannot be easily separated from one another Due to cohesion between water molecules and transpiration pull, water rises upwards in the stem. Answer : (a)

The diffusion of water through a selectively permeable membrane is called osmosis. Statement (c) is NOT correct Osmosis is the movement of water through a semipermeable membrane according to the concentration gradient of water across the membrane, which is inversely proportional to the concentration of solutes.Statement (d) is NOT correct Answer : (a)

Abscisic acid (ABA) inhibits light-induced stomatal opening through calcium- and nitric oxide-mediated signaling pathways. Answer : (b)

The most widely accepted theory for ascent of sap in trees is, transpiration pull and cohesion theory of Dixon and Joly Answer : (d)

Stomatal responses to light and humidity (vapor pressure difference, VPD) are important determinants of stomatal conductance. Stomatal movements induced by light are the result of a transduction of the light stimulus into modulated ion fluxes in guard cells and concomitant osmotic adjustments and turgor changes. Answer : (d)

Under optimal conditions, the vacuoles are filled with water to the point that they exert a significant pressure against the cell wall Osmotic pressure is the pressure required to prevent fluid diffusing through a semipermeable membrane separating two solutions containing different concentrations of solute molecules. The difference between diffusion pressure of pure water and solution is called diffusion pressure deficit (DPD). The DPD of a cell is influenced by both osmotic pressure and wall pressure (turgor pressure) which opposes the endosmotic entry of water, i.e. DPD = OP - TP(wall pressure). Turgor Pressure(T.P) is defined as the amount of pressure inside a cell solely due to its water content. When a cell is fully turgid, its OP is equal to TP and DPD is zero Answer : (b)

EXPERIMENT TO DEMONSTRATET THE ROOT PRESSURE THEORY Root pressure is defined as hydrostatic pressure developed in the root due to accumulation of absorbed water. It the pressure exerted on the liquid contents of the cortical cells of the roots, under fully turgid condition this root pressure pushes the water up the xylem vessels to the aerial parts. It shows that water absorption is an active process. Experiment on root pressure: The root pressure can be demonstrated in a plant by the following experiment. Apparatus required: A well watered herbaceous plant, a knife, a rubber tube, a narrow glass tube and colored water. Procedure: Water a potted herbaceous plant. Keep it over night. Next morning, cut off the stem a few centimeters above the soil level or near to the root. Fix a long and narrow glass tube to the cut end of the stump with the help of rubber tubing. Pour a little colored water in the glass tube and mark its level. The glass tube is connected to a manometer and whole setup is then left for observation. Observation: After some time the level of the colored water rises in the tube. And rise in the level of the mercury of the manometer shows the measurement of root pressure. Result and conclusion: A rise in the level of water in the glass tube is due to the pressure exerted by water exuded from the cut part of the stem. The exuding of water from the cut end of the stem is called bleeding. The flow of water from the cut surface or bleeding when measured by mercury manometer is estimated to 3-5 atmospheres only. Answer : (c)