Water potential in the leaf tissue is positive (+) during 
Pure water has maximum water potential (O). Water potential in the leaf tissue becomes greater than pure water under conditions of excessive humidity when the leaves cannot lose water by transpiration. Hence water is lost as droplets via hydathodes by the process of guttation.
Suppose an aquatic plant is placed in a test tube containing distilled water and the tube is stoppered. The tube is left outdoors for 24 hours and the pH value of the water is then measured at regular intervals. Which of the following is the most probable result? 
After sunrise, photosynthesis is carried out using CO2. Hence concentration of CO2 decreases hence increasing pH.
The water potential and osmotic potential of pure water are 
Osmotic potential is the potential of a solution to cause water movement into it across a semi- permeable membrane. Water potential is the tendency of water to leave a system.
If a cell A with DPD 4 bars is connected to cell B, C, D whose OP and TP are respectively 4 and 4, 10 and 5 and 7 and 3 bars, the flow of water will be 
D.P.D. or suction pressure (S.P.) = O.P. – T. P.
Hence D.P.D. for A = 4 bars, B = 0 bars, C = 5 bars, D = 4 bars We know that direction of movement of water is from lower D.P.D. (S.P.) to higher D.P.D. (S.P.). \ flow will be from B to A, C, and D.
Water potential of actively absorbing cells is 
Water potential is regarded as the tendency of water to leave a system. Pure water has the highest possible water potential which is zero. All solutions have a water potential lower than that of water.
Movement of ions or molecules in a direction opposite to that of prevailing electrochemical gradient is known as 
Movement of ions against concentration gradient involves the expenditure of energy. Diffusion involves the movement of solute particles from region of higher concentration to a region of lower concentration. Pinocytosis is cell drinking. Brownian movement is the random to and fro movement of atoms and molecules
Which of the following plant is found to have minimum transpiration 
Nerium is a xerophytic plant and have sunken stomata to reduce the rate of transpiration, confined to lower epidermis.
When water moves through a semi permeable membrane then which of the following pressure develops? 
The pressure required to stop the flow of pure water into a solution across a semi permeable membrane is a characteristic of the solution, and is called the osmotic pressure. Thus water will move from a region oflow osmotic pressure to a region of high osmotic pressure. Turgor pressure is the hydrostatic pressure set up within a cell by the water present acting against the elasticity of the wall. Suction pressure when referred to a cell, is the force which is available for taking in water.
Stomata of a plant open due to 
During day time, due to photosynthesis, malic acid forms which breaks to H+ and malate. H+ move out of guard cells and K+ enter forming potassium malate which makes guard cells turgid and stomata opens.
Dough kept overnight in warm weather becomes soft and spongy because of 
Cohesion is the force of attraction between similar molecules. Osmosis is the movement of solvent molecules from a region of low solute concentration to a region of high solute concentration through a semipermeable membrane.
The ability of the Venus fly trap to capture insects is due to: 
Bending of tentacles in Venus fly trap or Drosera after coming in contact with an insect is thigmonastic or chemonastic movement of variation or Turgor movements.
The mechanism by which the trap snaps shut involves a complex interaction between elasticity, turgor and growth. In the open, untripped state, the lobes are convex , but in the closed state, the lobes are concave It is the rapid flipping of this bistable state that closes the trap, but the mechanism by which this occurs is still poorly understood. When the trigger hairs are stimulated, an action potential involving calcium ions is generated, which propagates across the lobes and stimulates cells in the lobes and in the midrib between them
Potometer works on the principle of 
Potometer : It is an apparatus for measuring the rate of transpiration.
Sulphur is an important nutrient for optimum growth and productivity in 
Sulphur is an important nutrient of pulse crops. Pulses contain protein. Sulphur is an integral part of proteins.
The translocation of organic solutes in sieve tube members is supported by 
Munch's Mass Flow Hypothesis is the theory which explains the flow of food materials through the phloem from the higher concentration regions to lower concentration regions. The force is needed to move organic food materials downwards in the phloem. The energy for the translocation of the food is provided by the ATP which acts as a ligand to the sucrose and hydrogen ion symporter and allows the movement of the food through the sieve tubes.
Thus, the correct answer is option A.
Two cells A and B are contiguous. Cell A has osmotic pressure 10 atm, turgor pressure 7 atm and diffusion pressure deficit 3 atm. Cell B has osmotic pressure 8 atm, turgor pressure 3 atm and diffusion pressure deficit 5 atm. The result will 
Movement of water will be from low DPD to high DPD i.e from A to B
Which one of the following statements is correct? 
Extensive use of chemical fertilizers may lead to eutrophiction of nearby water bodies.
The rupture and fractionation do not usually occur in the water column in vessel/tracheids during the ascent of sap because of 
The rupture and fractionation do not usually occur in the water column in vessel/ tracheids during the ascent of sap because of cohesion and tension. The water molecules have a great mutual attraction with each other or in other words we can say that they have tremendous cohesive power which is sometimes as much as 350 atmospheres. Thus, the transpiration pull develops a negative pressure in the uppermost xylem cells. It is transmitted from there into the xylem of stems, and from there into the xylem of stems, and from there to the roots.
Carbohydrates are commonly found as starch in plant storage organs. Which of the following five properties of starch (a-e) make it useful as a storage material?  (A) Easily translocated (B) Chemically non-reactive (C) Easily digested by animals (D) Osmotically inactive (E) Synthesized during photosynthesis The useful properties are
Carbohydrates are commonly found as starch in plant storage organs. It is chemically non-reactive and osmotically inactive polysaccharides of much greater molecular weight. Carbohydrates performs a vital role in living organisms. Starch and other polysaccharides serve as energy storage in plants, particularly in seeds, tubers, etc. which provide a major energy source for animals, including humans.
Guard cells help in: 
Guard cells help in transpiration. Transpiration is the evaporation of water from the aerial parts of plants, especially leaves but also stems, flowers and roots. Stomatal opening allowing the diffusion of carbon dioxide and oxygen during photosynthesis.
Guttation is the result of : [2011M]
The main cause of guttation in plants is root pressure. During night when root pressure is high sometimes due to this
high pressure watery drops ooze out with the assistance of special structures which help in guttation called hydathodes.
Which of the following criteria does not pertain to facilitated transport? [NEET 2013]
Substance that have a hydrophilic moiety, find it difficult to pass through the membrane, their movement has to be facilitated by the membrane protein without expenditure of ATP energy. Facilitated diffusion cannot cause net transport of molecules from a low to a high concentration or uphill transport. Transport rate reaches a maximum when all of the protein transporters are being used (saturation). Facilitated diffusion is very specific.
Due to low atmospheric pressure, the rate of transpiration will
By the process of diffusion, water travels from high to low pressure. If atmospheric pressure is low, water will move out of the plant into the atmosphere as water vapour. Plants will lose water at higher rates by transpiration process. Hence, at low atmospheric pressure, the rate of transpiration increases.