Glucose is osmotically active and will increase the osmotic pressure inside a cell and this will lead to physiological water imbalance. Hence, glucose is stored as osmotically inactive starch.

Diffusion pressure deficit or DPD is responsible for movement of water in a cell. DPD is calculated as the difference between osmotic pressure (OP) and turgor pressure (TP). Usually in a plant cell TP is equal to wall pressure or WP. When OP is equal to WP the calculated value of DPD will be zero and hence, there will not be any flow of water inside or outside the cell.

In living systems water is universal solvent. Water is the major constituent of protoplasm and is also a reagent in a number of biochemical reactions.

The water potential is calculated by the sum of osmotic or solute potential and pressure potential. The matrix potential is a minor factor in calculation of water potential and can be neglected.

The potential energy is due to number of molecules of water present in a system. More the number of molecules, more will be the potential energy. The term used to denote this energy is water potential i.e., potential to do work due to water molecules.

Water potential is expressed in units of pressure and hence, any unit which is used to express pressure can be used for water potential.

Water flows from a region of higher water potential to a region of lower water potential. In this case water will flow from cell B, which has a water potential of - 4 bars to cell A, which has a water potential of - 9 bars.

A solution will be having greater solute particles as compared to pure solvent. Osmotic pressure is dependent of concentration of solute particles. Hence, a solution will always have greater osmotic pressure than pure solvent.

Water potential of pure water is zero by convention and osmotic potential of pure water is zero, because there are no dissolved salts. In case some solute particles are there in solution then only some osmotic potential will develop.

Water potential is the algebraic sum of osmotic potential and pressure potential. Here, osmotic potential has a negative sign and pressure potential has a positive sign. Water potential of solution is always negative.

Water transport in living systems follows a water potential gradient and water flows from a higher water potential towards a lower water potential. It should be understood that water potential of pure water is zero. Hence, the water potential of all solutions is negative. Water flows from higher to lower water potential means from less negative to more negative value.

 

$$\textbf{Correct Option C}$$

$$\textbf{Solution}$$

$$\bullet$$ When the concentration of the solutes in the soil is low then it signifies that the water potential of the soil is high.

$$\bullet$$The water potential the plant is low and we know that water flows from a region of higher potential to a region of lower potential.
$$\bullet$$Due to which the water will flow from the soil to the plant and the water absorption of the plant will increase eventually.
$$\bullet$$So when the concentration of the solute in the soil is low the absorption of the water will increase.
$$\bullet$$So, the correct option is C.

  

• Water always flows from higher water potential to an area of lower water potential. 
• In a fully turgid cell, water potential inside cell will be same as outside the cell and no net movement of water will occur. 
• In such a cell osmotic pressure will be equal to turgor pressure and so water potential becomes zero.

The apoplastic route is non-living route comprising of cell wall only. Through this route movement of water is fast as water does not cross cell and its living components, while symplastic route comprises of cell and its living components. Movement of water from one cell to another occurs through plasmodesmata. Membrane permeability depends on nature of solute as well as membrane. Nature of solute is important and water soluble or hydrophilic molecules like ions cannot cross the membrane, because membrane is made of lipids and proteins. Lipophilic or lipid soluble molecules can easily diffuse through the membrane.

Water potential depends on the number of water molecules in the solution. If a cell is placed in hypertonic solution, water will flow out of the cell through the process of exosmosis. Hence, the number of water molecules will reduce. Consequently, there will be a decrease in water potential.

Guttation or exudation of xylem sap, is the loss of water in liquid state. It occurs through hydathodes. The force responsible for this process is root pressure. Guttation is easily observed in conditions of high humidity, when soil is well watered. In such conditions transpiration loss of water is less and extra water absorbed by roots oozes out through hydathodes in liquid state.

• Water flows from higher water potential to lower water potential. The water potential is calculated by the sum of osmotic potential and pressure potential. Using this formula water potential of cell A comes out to be -10 bars, 
• whereas the water potential of cell B comes out to be -12 bars. Hence, water will flow from cell A (higher water potential) to cell B (lower water potential).

The process of movement of water outside the plasma membrane and in the intercellular spaces is called as apoplastic pathway or apoplast. 

Water potential of pure water is zero. Addition of any solute will cause a reduction in the relative number of water molecules as compared to pure water. This reduction in number of water molecules is responsible for reduction in water potential. Hence, water potential of any solution will always be negative.

For $$C_{3}$$ plants the ratio is 500-800. it shows that $$C_{4}$$ plants transpire less and more efficient in conserving water than most of $$C_{3}$$ plants.

In girdling experiments phloem is removed so food cannot be transported to locations beyond the point of girdling. Hence root of such a plant dies because food supply from leaves is cut off.

Scholander et al. (1965) were the first to measure the pressure / tension directly by using pressure chamber method or pressure bomb technique. A pressure bomb or pressure chamber or Scholander bomb is an instrument with which it is possible to measure the approximate water potential of plant tissues. 

Solution

Correct answer is option B.
Explanation for correct option:

• Root pressure is the positive pressure that develops in the roots of the plants by the active absorption of nutrients from the soil.
• The active absorption depends on the active accumulation of solute in xylem sap.
• Root pressure is maximum when transpiration is very low and absorption is high because transpiration is the output of water from a plant, and absorption is the input of water into a plant.
• If the output is low and the input is high, the pressure will be at its greatest. 
  So, the correct answer is 'Transpiration is very low and absorption is high'.

Munch (1930) explained pressure flow theory. He postulated the mass flow of organic solute takes place from the site of higher concentration to the site of lower concentration. According to it model, phloem sap moves from sugar sources to sugar sinks through turgor pressure, due to the high concentration of organic substances inside source cell. This result in movement of food from source to sink. Thus, the correct option is A.

The cytoplasm of surrounding cells remains connected through each other by plasmodesmata. This continuity is called symplast. It is an intercellular connection through which small solutes can freely diffuse. Plasmodesmata allow the flow of small molecules and ions between cells.

Munch proposed bulk transport theory to explain transportation of sugars in plants. At the site of synthesis i.e., leaves sugars are synthesised, which leads to an increase in osmotic pressure inside leaf mesophyll due to which water from xylem moves inside mesophyll cells. At the site of sugar utilisation, sugars are used up and so water moves from inside the cells to the xylem vessels. The difference in sugar concentration at source and sink creates a pressure gradient and sugars move in bulk from source to sink.

Transportation of food requires living tissue. Sieve tubes in phloem tissue are living cells and are involved in transportation of sugars.

Imbibition is a physical process of adsorption of water by the solid and dry surface. It is the first process during seed germination which involves in the growth and development of plants. Thus, the correct answer is option B.

Water is an essential component of protoplasm and forms 80-90% of the fresh weight of actively growing tissues. Water acts as a solvent for the solutes, take part in photosynthesis and maintain turgidity of the cells and tissues.
Therefore, the correct answer is option D.

The innermost cortical layer of the dicot root is called the endodermis. Many cells get suberized on their radial and inner walls. The cells are barrel-shaped and are closely packed, such thickenings are called casparian strips which contain lignin and suberin. 
Thus, the correct answer is option C.

• Hydathodes are a type of secretory tissue in leaves of angiosperms that secrete water through pores in the epidermis or margin of leaves. 
• They are modified stomata and are involved in guttation. Hydathodes are connected to the plant vascular system by the vascular bundle.

All plants do not show guttation. It is restricted to about 345 genera of herbaceous and some woody plants.
e.g.: Garden nasturtium, Oat balsum, Tomato, etc.

• Due to the hydrophobic nature of the lipids that make up the cell membrane, polar molecules such as water and ions cannot cross it without the assistance of integral proteins known as channel proteins.
• A channel protein acts as a pore in the membrane that allows water molecules or small ions to pass through quickly by the process known as facilitated diffusion.

At 0 degree Celsius the respiration rate will be zero. At 20 degree Celsius only the respiration process will take place. Hence, the 5 gm initially absorbed is due to physical diffusion of mineral ions from a region of high to low concentration. Later on, respiration occurs, then extra 15 grams are actively absorbed.

Osmosis is defined as the movement of solvent molecules from a lower concentrated solution to a higher concentrated solution through a semi-permeable membrane.  Hence all the definitions are wrong. The correct answer is option D.

Transpiration is the loss of water by the stomatal openings of the aerial parts of the plant. This helps in the upward movement of water and minerals from the roots to the leaves by a cohesion-adhesion mechanism. 

It is the process by which the living organism oxidize their food and release energy. The energy released is utilized for various metabolic processes. The glucose obtained by the food is oxidized with the help of oxygen to form energy in form of ATP. Carbon dioxide and water molecules are produced along with energy.

Plasmolysis in a plant cell is defined as the process of shrinkage of the cytoplasm as a result of loss of water from the cell. It occurs when plant cells are placed in a solution that has a higher concentration of solutes than the cell does. In this, plant cell is kept in hypertonic solution. When cell is placed in hypotonic solution, cell is lysed. 

• One example of passive transport is diffusion, when molecules move from an area of high concentration (large amount) to an area of low concentration (low amount).
• In case of active transport movement of molecules can take place against the concentration gradient also i.e. from lower concentration to higher concentration.

Stomata are pores present on the leaves of annual plants. These are used for the exchange of gas in the leaves. These stomata open during daytime and close during the night. Oxygen produced during photosynthesis enters the leaves through the opened stomata.

Osmosis is movement of solvent molecules of a solution from their higher concentration to their lower concentration across a semi-permeable membrane.

Diffusion is a process in which the molecules intermingle due to their kinetic energy and movement of molecules is from higher concentration to lower concentration. During photosynthesis, the plant produces oxygen as a byproduct and hence the concentration of oxygen inside the cell is higher than the outer environment. Plant releases oxygen in external environment through diffusion process.

Professor K.C. Mehta is one of the eminent scientists of India. He is known for his contribution in the field of plant pathology. Plant pathology is a branch of science which deals with the study of diseases in plants which are caused by pathogens. Research of Professor K.C. Mehta related to recurrence of rust in the plains of India is most famous. He even worked on black rust of cereals in Cambridge University. From his researches, it has been concluded that Black rust in plains of India spreads from the Himalayas in the North and Nilgiri and Puleny hills in the South.

Osmosis is the process of the movement of solvent molecules through a semipermeable membrane. In this process, the water molecule moves from a region of higher solvent concentration to the region of lower solvent concentration. The energy which drives this process is called osmotic pressure. Osmosis is of great importance in biological processes in plants and animals both. Thus, the correct answer is option D.

Solution

Correct answer is option B.
Explanation for correct option:

• Imbibition is the physical adsorption of water molecules on the adsorbing surface. Seed absorb water due to imbibition.
• The imbibition of water is the first step in seed germination.
• Imbibant holds water through the processes of capillarity and adsorption.