Capillary action helps bring water up into the roots, hence nota part of transpiration pull At night, when stomata shut and transpiration stops, the water is held in the stem and leaf by the adhesion of water to the cell walls of the xylem vessels and tracheids, and the cohesion of water molecules to each other. When plants release water through transpiration, cohesion is responsible for moving more water throughout the xylem. The water deficit or suction force developed in leaf cells due to transpiration is responsible for pulling the water column in the upward direction (ascent of sap) Answer : (a)

Antitranspirants are the substances used to reduce rate of transpiration Phenyl mercuric acetate reduces the transpiration by partial closure of stomata Abscissic acid (ABA) also acts as antitranspirants Answer : (d)

Passive absorption of water takes place when rate of transpiration is usually high. Rapid evaporation of water from the leaves during transpiration creates a tension in water in the xylem of the leaves. This tension is transmitted to water in xylem of roots through the xylem of stem and the water rises upward to reach the transpiring surfaces. Answer : (b)

Excess fertilizer in water makes hypertonic solution, kills plant roots by the process of osmosis Answer : (d)

Root pressure is caused by this accumulation of water in the xylem pushing on the rigid cells Root pressure occurs in the xylem of some vascular plants when the soil moisture level is high either at night or when transpiration is low during the day Answer : (d)

The stomata open only for a few hours in a day, eg., Barley and other cereals Answer : (a)

A sunken stomata is a stomata in a small pit, which protects the escaping water vapor from air currents, decreasing water loss from the leaf. Sunken stomata are commonly found in plants in arid environments as one of their adaptations to preserve water Oleander (Nerium oleander) leaves are drought resistant. To survive in an arid environment, an oleander has to limit transpiration through its leaves. The upper leaf surface, which is more exposed to the heat of the sun, has a thick, waxy coating. Called the cuticle, it limits transpiration by the epidermal cells. Answer : (b)

DPD = OP - TP If TP is negatve DPD >OP Turgor pressure, potential of xylem in a transpiring plant, which is under considerable tension, will be negative Answer : (c)

Upward movement of water is called as Ascent of Sap. Answer : (d)

Imbibition is a special type of diffusion that takes place when water is absorbed by solids-colloids causing an increase in volume. Examples include the absorption of water by seeds and dry wood. Answer : (b)

Levitt (1974) proposed the proton – transport concept to explain the mechanism of opening and closing of stomata. According to this theory, sentry (influx) of K+ ions into guard cells from surrounding subsidiary and epidermal cells causes opening of stomata. Answer : (a)

We know that direction of movement of water is from lower D.P.D. (S.P.) to higher D.P.D. (S.P.). DPD can be described as the actual thrust of a cell for water and can be expressed as DPD=OP-TP Cell A DPD = 10 - 4 = 6 Cell B, DPD = 4 - 4 = 0 Cell C, DPD = 10 - 5 = 5 Cell D, DPD = 7 - 3 = 4 All cells other than cell B (DPD = 0) have more DPD Water will flow from Cell B to all other cells Answer : (b)

Stomatal movement is caused by turgor changes in guard cells. The potassium ion is considered to be the main osmoticum in guard cells, and the level of K+ in guard cells increases during stomatal opening and decreases during stomatal closing (Outlaw 1983). Answer : (d)

Rate of water absorption can be increased through Increased transpiration Answer : (d)

Rate of diffusion is directly proportional to the concentration gradient (dC/dx) across the membrane A concentration gradient occurs where the concentration of something changes over a certain distance : option a is not correct Diffusion time increases with the square of diffusion distance..Option (b) not correct When there are unequal concentrations of an ion across a permeable membrane, the ion will move across the membrane from the area of higher concentration to the area of lower concentration through simple diffusion. Ions also carry an electric charge that forms an electric potential across a membrane. If there is an unequal distribution of charges across the membrane, then the difference in electric potential generates a force that drives ion diffusion until the charges are balanced on both sides of the membrane. option "c" correct. opening of scent or ammonia bottle is not diffussuion but spreding of scent to other parts of room is diffussuion. option "d" not correct Answer : (c)

Number of stomata/sq cm. is 1000 — 60,000 in different plant species. The number of stomta per unit area of leaf is called Stomatal Frequency. Stomata frequency of trees and shrubs is higher than herbs. Stomata nearly occupy one to two percent of total leaf area when fully open. Answer : (d)

Plants absorb water and minerals salt from the soil with the help of root hairs. They absorb water by the process of osmosis. Osmosis is the movement of water molecules (solvent) from a lower concentration solution to a higher concentration solution through a semi permeable membrane. Answer : (a)

Water potential is the potential energy of water in a system Answer : (b)

The pressure flow hypothesis, also known as the mass flow hypothesis, is the best-supported theory to explain the movement of sap through the phloem. It was proposed by Ernst Munch, a German plant physiologist in 1930. a - r Godlewski (1884) proposed his clambering or relay-pump theory to explain the vertical movement of water through the plant. b - s Transpiration pull or cohesion theory proposed by an Irish botanist Henry H. Dixon and a physicist Jhon Joley (Jolly) in 1894, is variously known as Dixon and Jolly's Theorey of cohesion, cohesion tension theory or transpiration pull theory.c - t A common vital force theory about the ascent of sap was put forward by J.C. Bose (1923). It is called pulsation theory. d - p Answer : (d)

A cell increases in volume if the external medium is hypotonic environment, where water moves into the cell by osmosis and causes its volume to increase to the point where the volume exceeds the membrane's capacity and the cell bursts. Answer : (a)

Epithem cells play a significant role in Guttation process Hydathodes are specialized secretory tissue structures and they are mainly responsible for secreting water in liquid form. hydathode-trichomes actively secreting water (guttation), a space found just behind the pore is surrounded by a special parenchymatous tissue. It is called Epithem Answer : (b)

Transpiration flux is defined as the quantity of water transpired by a unit area of leaf surface in a unit time. When half the leaves are removed randomly , number of stomata will also reduce, so water loss is less through stomata, but transpiration rate ( flux) is high. Answer : (b)

Xylem sap consists primarily of a watery solution of hormones, mineral elements and other nutrients. Answer : (d)

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 : (c)

Hypoosmotic: solution with a lesser concentration of solute Answer : (b)

If a plant cell is placed in a hypertonic solution, the plant cell loses water, causes contraction of the protoplast of a plant cell as a result of loss of water from the cell (Plasmolysis) Answer : (d)

Answer : (d)

Photoactive stomata open in response to light. The action spectrum of photoactive stomata consists of red and blue light. Blue light is more effective in stomatal opening. Since, most of the transpiration is stomatal, the action spectrum of transpiration is red and blue light. Answer : (d)

Isobilateral leaf are those leaf which possess equal number of stomata on both side of leaf such like dorsal and ventral side, example:- of isobilateral leaf are monocot leafs. Bulliform cells are present in monocot leaves on the adaxial ( upper/ dorsal) surface. a - ii Stomata are pores in the plant epidermis that are surrounded by two guard cells, which control the opening and closing of the aperture. These guard cells are in turn surrounded by subsidiary cells which provide a supporting role for the guard cells. b - iii, Hydathodes are made of a group of living cells with numerous intercellular spaces filled with water, but few or no chloroplasts, and represent modified bundle-ends. These cells (called epithem cells) c - iv, The complementary cells is a mass of cells in plants, formed from the cork cambium at the position of the lenticels. d - i Answer : (c)

Answer : (d)