Transport In Plants

Reverse Osmosis is a process by which a solvent pass through a semi-permeable membrane in the direction opposite to that for normal osmosis when subjected to a hydrostatic pressure greater than the osmotic pressure.

In normal osmosis, the solvent flows from a region of low solute concentration to high solute concentration region across a semi-permeable membrane along the concentration gradient of solvent molecules. On application of an external pressure, the flow of the solvent molecules across its concentration gradient is reversed, which is known as reverse osmosis. Thus the process of reverse osmosis is against the concentration gradient and takes place with application of pressure which is greater than osmotic pressure so it is an active process and not a passive one.

(Active transport is the transport of molecules or ions across a cell membrane against its concentration gradient -from a region of lower concentration to higher concentration using energy).

Increased light intensity increases the rate of photosynthesis hence water is drawn into the leaves where photosynthesis takes place and this opening of stomata also leads to increased rate of transpiration.

When wind speed is more, then more molecules are carried away by the windi.e when air outside the stomata is less humid. Increased temperature increases the energy of the water molecules and hence leads to increased rates of transpiration in form of water vapour.

In dorsiventral leaf, upper epidermis is thickly cuticularised and contains high amount of chloroplast and no stomata whereas the lower epidermis contains numerous stomata and is without chloroplast -The leaf is hypostomatic.

The form of sugar transported through the vascular tissue, phloem from the source to the sink is sucrose.

Sucrose contains more energy than glucose so it is more energy efficient, both in its transport as well as in its storage. In addition to that sucrose is non-reducing so it does not undergo any kind of reactions with other molecules so can be transported in its original form other than glucose which is reactive.

Guttation is the loss of water in form of water droplets via structures called hydathodes. In the evening or early morning, the rate of absorption of water exceed the rate of transpiration due to which a lot of water accumulates which if not exudated out might be of damage to the plant. So plants opt for guttation.

Imbibition is a special type of diffusion where the water is absorbed by living or dead cells and increases the cell volume enormously causing it to swell up.

Plant senescence is the process of aging in plants. It can be either stress-induced or age-related. It is a highly regulated process during which the nutrients are translocated to the younger parts of the plant like the apical meristem by the process of diffusion or active transport. The growth of the vascular plant depends upon the activity of the meristems.

The water potential of pure water at standard temperature is always zero.

Water potential (Ψw) is the sum of solute potential (Ψs) and pressure potential (Ψp): Ψw= Ψs+ Ψp. So when solute is dissolved in water, the water potential of pure water decreases or starts assuming a negative value.

Mycorrhiza is a symbiotic association between a fungus and a plant. They have the ability to exchange nutrients between their surroundings and their host plant. With the increase in root surface area, the fungus is able to get mineral nutrient for its host plant.

Both the solution A and Solution B are separated by a semi-permeable membrane. The solute concentration is less in Solution A so the water potential is more in Solution A. So the movement of solvent molecules occurs from more dilute to less dilute solutioni.e the solvent molecules and not the solute molecules will flow from solution A to solution B. The solute particles wouldn't pass through the semi-permeable membrane.

Transpiration is the movement of water molecules in form of water vapour from aerial parts of the plant. Leaves have numerous pores called stomata. The guard cells surrounding the stomata open and close regulating the transpiration. Stomatal transpiration is one of the ways plants transpire. Hence, A)leaves has been matched with ii)transpiration.

Imbibition is a type of diffusionwhere movement of water takes place along a diffusion gradientand it is due to this process that almost dryobjects absorb water. Such substances that absorb are called adsorbants. The cell wall and the protoplasm of living cells absorb water by imbibition. It is required by dry seeds prior to its germination for it to swell up and germinate. Hence B) seed is matched with iv)Imbibition.

Roots are responsible for absorption of water, minerals and other nutrients from the soil. Water that is absorbed is required by the plant to perform photosynthesis and for other processes. Minerals and other nutrients are responsible for growth and development of the plant. Hence, C)Roots is matched with v)Absorption.

Anti-transpirants are substances that check the rate of transpiration. Aspirin is a kind of metabolic inhibitor that reduce the stomatal opening thus increasing resistance to diffusion of water vapour or to transpiration. Hence D)Aspirin is matched with i) Anti-transpirant.

A plasmolyzed cell loses water when placed in a hypertonic solutioni.e concentration of solute is more in the solution due to which water flows out of the cell to the region of higher concentration of solute or from region of more dilution to less dilution to perform exosmosis causing the cell to become plasmolyzed. The value of osmotic potential of a solution is always negative since the presence of solutes in it makes the solutionhave less water and more solute as compared to the same volume of pure water. Thus E)Plasmolyzed cell is matched with iii)Negative osmotic potential.

Amyloplasts contain dense starch grains. It is a kind of plastid which is colorless and non-pigmented. It produces starch for the plant by the polymerizationofglucose.

Smaller, lipid soluble molecules diffuse faster through cell membrane, but the movement of hydrophilic substances are facilitated by certain transporters which are chemically proteins.

These transporters can be carrier proteins or channel proteins. Transport by carriers can be either active or passive, whereas flow of substances through channel proteins is always passive.

When molecules move in opposite direction then it is antiport but when independent of each other then they follow uniport of facilitated diffusion.

Osmosis is a special kind of diffusion, in which water diffuses across the cell membrane. The rate and direction of osmosis depends upon both pressure and concentration gradient.

In osmosis, the flow of solvent molecules is along their concentration gradient i.e. from more dilute to less dilute solution. Reverse osmosis occurs when pressure applied does not allow this osmosis to take place and instead moves from the less dilute to the more dilute solute basis the pressure applied.

Exosmosis

A flowering plant is planted in an earthen pot and irrigated. Urea is added to make the plant grow faster, but after some time the plant dies. This may be due to exosmosis. Urea is added because it is a fertilizer aiding plant growth but excess of urea causes increase in concentration of solutes in the soil due to which water comes out from the plant's cytoplasm eventually leading to exosmosis and thus the plant gets plasmolyzed and dies.

Absorption of water from soil by dry seeds increases the pressure, thus helping seedlings to come out of soil. If not for the pressure by imbibition, dry seeds would not have been able to come out of soil.

Transpiration pull

Transpiration pull is the process responsible for the upward movement of water against gravity even for a tree of height up to 20m.

As the plant performs transpiration via stomata, it pulls water molecules upward to the leaf via xylem (adhesion and cohesion of water molecules). This creates a pressure gradient between the atmosphere and sub-stomatal cavity. This is transferred to the intercellular spaces of leaf then to xylem of the leaf vein. This pull is called the transpiration pull.

The specificity of transport of substances are mostly across the cell membrane because the cell membrane is selectively permeable and allows only transport of certain substances through the cell (usually small, non-polar, uncharged molecules)

The C4 plants are twice as efficient as C3 plants in terms of fixing CO2 but lose only half as much water as C3 plants for the same amount of CO2 fixed. In C3 plants, carbon dioxide is only fixed in the mesophyll leaves but in C4 plants, carbon dioxide is fixed in both mesophyll and bundle sheath cells. C4 plant regulate their constant supply of CO2 by keeping the stomata closed for a short span of time. CO2 fixation requires large amount of energy thus more water is lost in C3 than C4 plants.

When the plant is growing, the leaves act as the source of food carrying out photosynthesis. The vascular bundle, phloem is responsible for conducting the food from thesource to the sink. But the process is reversed during seasons like spring because during that term the food which is stored in sink is then supplied to the growing parts of the plant. The source and sink relation is hence variable so direction of movement of food via the phloem can be either upwards or downwards i.e. bidirectional.

But in the xylem, water transport only occurs when water is absorbed from the roots and is conducted via the xylem to the leaves. Thus this kind of absorption via the xylem occurs only in one direction which means that the movement of water and minerals is unidirectional via the xylem.

I) Uniport: When a single substance moves in a single direction across a cell membrane, it is called uniport.

II) Antiport: When two substances move in the opposite direction across a cell membrane, it is called antiport.

III) Symport: When two substances move in the same direction across a cell membrane, it is called symport.

Simple diffusion is the movement of molecules (usually small, uncharged and non-polar) along a concentration gradient from their region of higher concentration to a region of their lower concentration. It does not require ATP as it is moving along the concentration gradient.

Facilitated diffusion is the diffusion of those molecules which cannot generally pass through the cell membrane because of their size, charge, polarity etc. so they are passed through the membrane aided by channel proteins and carrier proteins which are specific for certain molecules. It also does not require energy because the movement of molecules is along the concentration gradient.

Active transport is the movement of molecules against their concentration gradienti.e from region of their lower concentration to region of their higher concentration with help of some energy. Hence ATP is required and it is an uphill transport that is highly selective allowing transport for a specific group of molecules.

Water potential (Ψw) is the sum of solute potential (Ψs) and pressure potential (Ψp): Ψw= Ψs+ Ψp. So when solute is dissolved in water, the water potential of pure water decreases or starts assuming a negative value.

Solute potential also known as osmotic potential is the potential of solution that allows the water to enter the solution by diffusion or osmosis due to presence of the solute in it.

Water potential (Ψw) is the sum of solute potential (Ψs) and pressure potential (Ψp): Ψw= Ψs+ Ψp. So when solute is dissolved in water, the water potential of pure water decreases or starts assuming a negative value.

Solute potential also known as osmotic potential is the potential of solution that allows the water to enter the solution by diffusion or osmosis due to presence of the solute in it. Pressure potential is the hydrostatic pressure that is exerted on water present in a cell. This usually has a positive value.

a) When the Tradescantia leaf epidermal peel was taken and placed in salt solution for five minutes, the cells would have shrinked when seen under the microscope because salt solution is hypertonic causing water to move out of the cell thus leading to exosmosis.

b) After that when it was placed in distilled water, the cell regains its turgidity as it absorbs water and deplasmolysis occurs.

Symplast pathway of water movement requires active transport.

Water moves from the soil to the roots via the process of osmosis. The water potential in the soil is more than in the cytoplasm of the root hair. So water passes across the semi-permeable membrane of the root hair cell into the root via osmosis. Then the water is passed on to the xylem vessels where water either would travel through cortex or would go through the cell walls. Now the water keeps on moving upwards via the xylem vessels by diffusion due to the water potential gradient present. The water upon moving to the leaves, it diffuses to the mesophyll cells then into the spaces between the cells after which it vaporizes out through the stomata via the process of transpiration (loss of water from the aerial parts of the plant in form of water vapour). This whole process is driven by capillarity and root pressure. The driving force is the water potential that is established.

Casparian strips are situated in the endodermal cell walls (radial and transverse) of plant roots. It prevents movement of water from pericycle to cortex thus promoting and establishing a positive hydrostatic pressure. Casparian strips blocks the apoplastic pathway due to which water has to enter the symplastic pathway.

Difference between guttation and transpiration are:

Transpiration is the process by which plants lose water in form of water vapour from aerial parts of the plant. When there is a huge amount of transpiration that takes place, it leads to huge amount of water loss thus causing wilting of the plant. But transpiration is needed for the pull of water and minerals from the root to the other parts of the plant and is needed for stomatal opening for the purpose of photosynthesis and respiration. So though it is a necessary evil and might also cause death of the plant if excessive water is lost, yet this process is necessary to carry out the other processes and for the need of water and minerals which is why transpiration is considered a necessary evil in plants.

The three physical properties of water which helps in ascent of water in xylem are:

i) Adhesion: It is the attraction between water molecules and other molecules other than water molecules (here surface of the xylem vessel).

ii) Cohesion: Cohesion is the force due to which molecules of water stay linked together due to hydrogen bonding in between them. It provides strength against the pressure by the transpiration pull.

iii) Surface tension: It is the property of the surface of a liquid to resist an external force applied owing to the cohesive nature of the molecules of the liquid.

Capillary action is a result of adhesion and cohesion.

(Hydrogen bonding and dipolarity explain adhesion and cohesion)

If the gardener forgets to water the plant for a day during summer, the rate of transpiration is more due to the higher temperature than the absorption of water so this will lead to wilting or losing of the plant's turgidity.

It is reversible only if the time for which it is not watered is short. If its long then the plant eventually dies but if its small then upon getting the required amount of water, the tissues again gain turgidity.

The type of molecular movement which is highly selective and requires special membrane proteins but does not require energy is passive diffusion.

Facilitated diffusion facilitates movement of molecules or ions which are larger in size, polar or charged to move across a cell membrane which is selectively permeable. It uses membrane proteins like carrier and channel proteins for facilitating the movement of the substances along the concentration gradient.

a) Cells shrink in hypertonic solution and swell in hypotonic solutions.

Explanation: A hypertonic solution has more concentration of solution thus the net movement of water is from the cell to the outside causing the cell to shrink as water moves out of the cell. A hypotonic solution has less solute concentration as compared to within the cell so there is a net movement of water inside the cell from outside causing the cell to swell.

b) Imbibition is a special type of diffusion when water is absorbed by dead or living cells.

Explanation: Imbibition is a special type of diffusion when water is absorbed by dead or living cells. Eg: absorption of water by seeds which is required for germination or absorption of water by dry wood that causes it to swell.

c) Most of the water flow in roots occur via the apoplast pathway.

Explanation:

In the symplast pathway, water moves between cytoplasm or vacuoles of the neighbouring cells. In the apoplast pathway can only take water near the xylem, where the Casparian strip forms an impermeable barrier to water in the cell walls, so water moves into the cytoplasm.

Water flows in the root via the apoplast pathway as the cortical cells are loosely packed and hence offers no resistance to movement of water. This mass flow of water occurs due to adhesion and cohesion properties of water.

Minerals are taken by the roots from the soil and are transported to various parts of the plants wherever needed via the xylem vessels. The mineral requirement is not same for all plants and neither for all plant parts so all the parts of the plants do not get the same amount of minerals. Growing parts of the plants usually require more of the minerals. Minerals exit the xylem and by diffusion gets into the cells where they are needed. Places where concentration of minerals is already higher, these minerals are taken there by active transport.

Exudates' analysis would help to find minerals and in the form that they are mobilised in the plant because exudates are often plant sap which contains xylem sap as well as phloem sap. It has a composition of amino acids, sucrose, organic and inorganic acids, water, ions, sugars etc. If we perform an analysis of the plant exudates, then we can find out which mineral nutrient is transported in the plant and in which form it is transported.

For eg: Nitrogen can be carried in organic forms like amino acids or as inorganic ions.

Some methods that can increase the life of cut plants in a vase are:

a) Using plant growth hormone called cytokinins that help delay senescence or aging of plant parts.

b)Placing the cut stem immersed in water in the vase to not allow water cavitation to occur by air.

c) Essential oils can increase vase life of cut plants.

No, different species of plants growing in the same area does not show the same rate of transpiration at a particular time because the rate of transpiration also depends on internal factors like the morphological characteristics of a plant. For eg: Leaf area, thickness of cuticle, number of stomata and whether it is sunken or not etc. So upon these difference, the rate of transpiration is also dependent.

Properties of water that makes it useful for all biological processes on the earth are:
(a) All polar substances are known to dissolve in polar solvents like water. All the essential substances in living organisms are solutes dissolved in water and transported from one place to another.

(b) Specific heat is the amount of heat required to increase the temperature of one gram of matter by one degree rise in temperature. Because of having high specific heat, it needs high amount of energy to increase its temperature. This is why living organisms have a constant temperature needed for metabolic processes in the body.

(c) Surface tension is the cohesion of the water molecules on the fluid surface of occupying the least volume. Viscosity is the resistance of a fluid to flowing water.

d) Water expands when its temperature becomes lesser than 4◦C. This decreases its density and making ice float. This helps living organisms to survive in frozen oceans and lakes and the upper frozen layer prevents the whole water to freeze acting as an insulator.

e) Water rises in capillary tubes which is a property that helps transport of water from roots of the plants to other parts of the plant.

Intracellular levels of ions are maintained higher then extracellular levels in animal cells because animal cells have ATP powered pumps like the Na⁺- K⁺ pump where 3Na⁺ is sent out in exchange of 2 K⁺ ions thus increasing the level of K+ ions in the intracellular region. This is how via the pumps, ion concentration is maintained higher intracellularly than in extracellular region.

Cut pieces of beetroot do not leave colour in cold water but do so in hot water because beetroot loses colour only when it is placed in hot water as the plasma membrane of the cells denatures at high temperature and breaks down leading to loss of content of cellwhich is the coloured protoplasm leaks out.

Girdling is the complete removal of a bark strip around the entire circumference of a trunk of a tree. In a girdled plant, when water is supplied to the leaves above the girdle, leaves may remain green for sometime because leaves have the capability of synthesizing their own food by photosynthesis using water and CO2 from air. But will eventually die because water will slowly be unavailable thus no photosynthesis can occur.

Simple diffusion is a kind of diffusion by which molecules are transported along the concentration gradient but too slowly. Also, not all kinds of molecules can pass through it. Only those which are non-polar and small can pass. But plants also require mineral nutrients and charged ions like potassium, sodium, etc. which cannot be transported via simple diffusion because the cell membrane which is selectively permeable does not allow large, polar and charged particles through. So processes like facilitated diffusion that used membrane proteins like carrier proteins and channel proteins aid in the exchange of required substances. These are specific and occurs along the concentration gradient. Even active transport is required to transport molecules against the concentration gradient. So to suffice the needs of the mineral requirements of the plant, only simple diffusion will not be enough.

Plants can be grown under limited water supply without compromising on metabolic activities by a number of ways:

Plants usually shrink when the rate of transpiration exceeds the rate of absorption of water by roots. So if we use anti-transpirants like Abscisic acid then it checks the rate of transpiration. This would reduce loss of water by plants but the metabolic activities shall go on along with diffusion of gases.

Ascent of sap will never be possible without the cohesion and adhesion of the water molecules because these are responsible for the same.

The continuous water column in the xylem vessels for the sap ascent is maintained by the adhesive and the cohesive forces of water. Absence of which would have led to cavitation of xylem vessels or breakage of the water column or the sap movement upwards.

This experiment can demonstrate which tissue is conducting water up the stem. Coloured strands are indicative that the food colour has been conducted upwards through a conducting vessel which is the xylem. We know how xylem conducts water upwards. This can be confirmed under the microscope to see the structure of the xylem. Plants contain xylem vessels from the roots to the tips of the leaves.

When a freshly prepared Spirogyra filament is kept in 10% potassium nitrate solution, then the protoplasm is observed to shrink in size because of the phenomenon of exosmosis.

a) This phenomenon is called exosmosis: process by which when a substance is placed in hypertonic solution, the water moves out of the cell of the substance to the outside leading to the shrinkage of the protoplasm.

b) If the filament is replaced in distilled water, then the protoplasm again becomes turgid as water flows in as the shrunken protoplasm swells up or gets deplasmolysed.

When sugar crystals are placed in ice cold water, the kinetic energy of the system is low so lattice structure is formed and remains. Very few water molecules are mobile in this stage. So dissolution or diffusion of the solid crystal of sugar does not occur since the number of striking water molecules is less when water is ice cold.

Salt solution being hypertonic, causes exo-osmosis in plants. 1 cup salt in 2 cup of water, fairly well dissolved when sprayed on weed plants, start killing them.

Chemical composition of xylem and phloem sap are as follows:

Xylem sap: Water and concentration of minerals in dilute form. It is mildly acidic.

Phloem sap: traces of minerals, water, sucrose and amino acids In some species, it also transports fructane or raffinose etc. It is mildly alkaline.

Tube B shows higher water rise than tube A because surface area is less in the narrow tube or tube B due to which the surface tension is more in that so the level of rise of water is more in that as well. Surface tension is inversely proportional to the surface area and surface tension arises from strong interactions between water molecules so lesser the space or area, more is the compactness and this results in more surface tension eventually leading to higher water rise in the tube.

Aquaporins are a kind of membrane proteins that form channels in the membrane and are usually facilitating transport of water between cells.

When aquaporins are present, more water molecules can travel from the more dilute solution to less dilution solution across the semi-permeable membrane so presence of aquaporins would increase the rate of osmosis thus facilitating it.

a) Stress hormone is a hormone which induces various changes/responses in a plant when subjected to stress. Abscisic acid is a stress hormone and during stress conditions it induces changes like closing of stomata to prevent further water loss during scarcity of water, aids in seed germination when conditions are favourable and dormancy when not and other changes as and when required.

b) This hormone, abscisic acid gets released in the leaves from the mesophyll cells of the plant.

Plants are harmed by excess water because when excess water is present, there is a deprivation of oxygen in the plant roots causing an anaerobic condition. Thus aeration is affected. But at the same time there are air which are trapped in the soil due to its structure and texture. But if the water logging is permanent then there is no way plants can survive because the oxygen would be used up and the lack of it will lead to the plant eventually dying in the anaerobic condition it will be subjected to.

Facilitated diffusion is different from diffusion in the following ways:

The mass flow hypothesis of transport in phloem is as follows:

Mass Flow Hypothesis proposed by Munch in 1930 explains the movement of sapvia thephloem. When there is a high concentration of sugar present in the source (which is where the food is prepared) then a diffusion gradient gets created between the sugar source and the sugar shrink where the sugar is stored. This is responsible for drawing water into the cells from the neighbouring xylem.When this happens, turgor pressure gets created (bidirectional movement).

A part of the glucose produced by photosynthesis is converted into sucrose. This is then transported actively to the companion cells and then to the sieve tubes via diffusion. The osmotic pressure moves the sucrose through the sieve tube towards the sink. When the sucrose reaches the sink, it is removed into apoplast. Water moves out of the sieve tube by osmosis establishing a pressure gradient. A low turgor pressure is created at the sink to maintain this gradient. Water passes back into the xylem later again.

Thus the mass flow hypothesis' mechanism is dependent on the turgor pressure as well as the osmotic pressure gradient between the source and the sink.

a) These types of guard cells are found in dicots because as we know the shape is bean shaped. Whereas for monocots, it is usually dumble-shaped.

b) Higher water content is shown in figure (i) because as we can see in that figure the guard cells are showing turgidity and the stoma is open carrying out transpiration as well as photosynthesis.

c) The element that plays an important role in the opening and closing of stomata is potassium ion. Potassium is responsible for the k+ or malate ion hypothesis. In short in this theory, the change in turgor pressure of the guard cells which is responsible for opening and closing of the stomata results in absorption andloss of K+ ions by guard cells.

Uniport, Symport and antiport are kind of facilitated diffusion where the diffusion is facilitated by carrier proteins and channel proteins along a concentration gradient so energy is not required directly. Symporters and antiporters though are also involved in active transport where they require energy.

Yes, plants need to adjust the type and quantity of solutes that reach the xylem. The transport proteins of end dermal cell help in maintaining and adjusting solute movement. As the minerals are" present in soil as charged particles with a very low concentration as compared of roots, they, all cannot be completely passively transported across cell membranes of root hairs. Thus, minerals are transported both by active and passive processes, to the xylem. Uponreaching xylem, they are further transported, i.e., upwards to sinks through transpiration stream. At the sink regions mineral ions are unloaded through diffusion and active uptake by receptor cells. Some of the mineral ions moving frequently through xylem are

(i) Nitrogen travels in plants as inorganic ions, but much of the nitrogen moves in the form of amino acids and related organic compounds.

(ii)Sulphur and Phosphorus small amount of these two nutrients are carried in organic forms.

(iii) Mineral ions are frequently remobilised particularly from older senescing parts. Older dying leaves export much of their mineral content to younger leaves. Similarly, before leaf fall in decidous plants, minerals are removed to other parts. Elements most readily mobilised are phosphorus, sulphur, nitrogen and potassium. Some elements that are structural components like calcium are not remobilised.

Difference between permanent and temporary wilting is as follows:

In temporary wilting, plants lose turgidity when rate of transpiration is more than rate of water absorption from the soil but in temporary wilting, wilting of the plant occurs and is a permanent phenomenon as the soil is unable to meet water requirement of the plant.

In temporary wilting, the plant regains turgidity when water requirement is met whereas in permanent wilting, the damage occurred is permanent causing eventual death of the plant.

Natural membranes like the cell membrane is selectively permeable, which means that it allows only certain molecules to get in or go out of the cell. This prevents random molecules from getting in like toxins which would otherwise be harmful for the cell.

Example of a cell membrane is where it allows only non-polar and small molecules through the lipid bilayer along the concentration gradient. To move other important molecules, it needs either energy (active transport) against the concentration gradient or needs aid from proteins like carrier and channel proteins that facilitate the movement of other specific molecules along the concentration gradient.

Halophytes are plants that grow in soils having high concentration of salt. Due to the higher concentration of salt, their cell cytoplasm is hypertonic causing water from the surrounding cells or region to enter the cell cytoplasm. So the turgor pressure of the cell is higher. To make sure this pressure doesn't exceed a certain level, they have salt-secreting glands that removes excess of salts and also has vacuoles that store salt.

If radio labelled carbon in carbon dioxide is supplied to potato plants in an experiment was seen in the tuber, it is due to the following:

When the potato plant carries out photosythesis using the CO2 which is radiolabelled, it forms Oxygen and glucose (C6H12O6) where the carbon in the glucose molecule has the radiolabelled carbon present. This glucose when is converted to sucrose takes the radioactive carbon which is transferred when the form changes. This molecules of sucrose moves via the phloem to the tuber where it is converted into starch which gets radiolabelled due to the same radiolabel carbon which is present and this starch is stored. The process of measuring is by autoradiography which detects the radioactive carbon and traces the components along with the movement in the plant body.

The process by which water molecules remain attached to one another via hydrogen bonding in between them is known as cohesion of the water molecules. The water column that moves upwards via the xylem vessels from the root to the leaves due to the transpiration pull does not break due to this property's contribution along with the contribution of the property of adhesion. The cohesion is responsible for providing tensile strength which aids in the pulling of the water from the roots to the tips of the leaves. The upward movement of water is via the xylem vessels where it is facilitated by three forces: adhesion ( where water molecules interact with other molecules like the inner walls of the xylem), cohesion (attachment of water molecules together forming an uninterrupted water column that does not break and does not allow cavitation to occur in xylem vessels) and surface tension.

a) the setup demonstrates the process of transpiration pull. Transpiration pull is the force with which water is pulled upwards from the roots to the leaves from where water is evaporated out via transpiration.

b) If a blower is placed close to the setup it will provide a wind speed due to which the rate of transpiration will increase this the level of water will rise even upwards as the transpiration pull will be more. Since when the wind intensity is more, its humid content is also less so it can carry away more number of water molecules from the aerial surfaces of the plant.

c) Phenyl mercuric acetate is an anti-transpirant. If it is sprayed on leaves, transpirational loss of water will cease or stop and mercy=ury levels will remain stable.