🔬 Biology · Class 11 · NEET
Transport in Plants - Practice Questions with Answers 75 free MCQs on Transport in Plants, each with its own worked answer and explanation. Water and mineral absorption, the ascent of sap, transpiration, and phloem transport via the pressure flow hypothesis.
Take the timed Transport in Plants chapterwise test → 75 practice questions on Transport in Plants , sorted Easy → Hard. Try each one first, then open its answer page for the worked explanation. Want the full theory first? Read the Transport in Plants notes .
Apoplast vs Symplast Pathway in the Root root cross-section (simplified) endodermis (Casparian strip) xylem apoplast (walls) - BLOCKED here symplast (cytoplasm) - must cross membrane Water can travel through cell walls (apoplast) or cell-to-cell through the cytoplasm (symplast) - but the Casparian strip at the endodermis blocks the apoplast route entirely, forcing everything through a selectively permeable membrane (symplast) before it can enter the xylem.
Easy - 25 questions Q1.
The waxy layer through which a little water still evaporates from a leaf is the:
A CuticleB CortexC PericycleD EndodermisShow answer & explanation →
Q2.
Transpiration occurring through the tiny pores in the bark of woody stems is called:
A Stomatal transpirationB Lenticular transpirationC Cuticular transpirationD Root transpirationShow answer & explanation →
Q3.
The attraction between water molecules and the walls of the xylem vessels is called:
A CohesionB TensionC AdhesionD DiffusionShow answer & explanation →
Q4.
Which of the following does NOT affect the rate of transpiration?
A Light intensityB Air humidityC Wind speedD Soil nitrogen levelShow answer & explanation →
Q5.
Movement of a substance across a membrane through a carrier protein, without using energy, is:
A Facilitated diffusionB Active transportC Simple imbibitionD Bulk mass flowShow answer & explanation →
Q7.
The process by which water evaporates from leaf surfaces is:
A TranspirationB PhotosynthesisC OsmosisD RespirationShow answer & explanation →
Q8.
Stomata open when guard cells:
A Lose water and become flaccid under osmotic stressB Are turgid (full of water)C Receive consistently reduced light intensityD Receive an ABA stress signal during droughtShow answer & explanation →
Q9.
Sugars produced in photosynthesis are transported in:
A Xylem as sucroseB Phloem as sucroseC Xylem as glucoseD Blood vesselsShow answer & explanation →
Q10.
The movement of water from a region of higher water potential to lower water potential across a semipermeable membrane is called:
A OsmosisB DiffusionC TranspirationD TranslocationShow answer & explanation →
Q11.
Root hairs increase the efficiency of water absorption mainly by:
A Producing root pressure that pushes water up the stemB Releasing enzymes that break down soil mineralsC Storing reserve water for use during dry spellsD Increasing the surface area in contact with soil moistureShow answer & explanation →
Q12.
The loss of excess water in the form of liquid droplets from leaf margins is called:
A RespirationB TranslocationC GuttationD TranspirationShow answer & explanation →
Q13.
Most of the water absorbed by plant roots is ultimately lost through the process of:
A GuttationB TranspirationC PlasmolysisD ImbibitionShow answer & explanation →
Q14.
Minerals absorbed by roots are transported to the rest of the plant mainly through the:
A EpidermisB CortexC XylemD PhloemShow answer & explanation →
Q15.
A plant cell placed in a hypertonic solution loses water and its cytoplasm shrinks away from the cell wall, a condition called:
A TurgidityB ImbibitionC TranslocationD PlasmolysisShow answer & explanation →
Q19.
The loss of water vapour from the aerial parts of a plant is called:
A transpirationB respirationC photosynthesisD digestionShow answer & explanation →
Q21.
The movement of water across a membrane from a dilute to a concentrated solution is:
A osmosisB only diffusionC active transportD respirationShow answer & explanation →
Q22.
In the xylem, water moves in which overall direction?
A roots to leavesB leaves to rootsC only sidewaysD downwardShow answer & explanation →
Q23.
The transport of food through the phloem is called:
A translocationB transpirationC respirationD filtrationShow answer & explanation →
Q24.
The dead, tube-like conducting cells of the xylem are the:
A vessels and tracheidsB the sieve tube cellsC the companion cellsD the guard cellsShow answer & explanation →
Q25.
The living conducting cells of the phloem are the:
A sieve tube elementsB the xylem vesselsC the tracheidsD the xylem fibresShow answer & explanation →
Medium - 25 questions Q26.
In desert plants (xerophytes), transpiration is cut down because their stomata are:
A On the upper surface onlyB Large and always openC Evenly spread outD Sunken in pitsShow answer & explanation →
Q27.
The water potential of a cell equals its solute potential plus its:
A Osmotic gradientB Pressure potentialC Matric tensionD Kinetic energyShow answer & explanation →
Q28.
Adding a solute to pure water makes the solute potential of the solution:
A More positiveB Remain at zeroC NegativeD Become infiniteShow answer & explanation →
Q30.
Whether water moves from one cell into a neighbouring cell depends on their difference in:
A Cell wall thicknessB Water potentialC Number of stomataD Chlorophyll contentShow answer & explanation →
Q31.
Pressure flow hypothesis explains:
A Upward water movement in xylem driven by transpirational pullB Sugar transport in phloem (source to sink via turgor pressure gradient)C Root pressure generated by active ion accumulation in root xylem at nightD Stomatal opening triggered by guard cell turgor changes at dawnShow answer & explanation →
Q32.
Cohesion-tension theory explains water movement in xylem by:
A Root pressure alone pushing water up through xylem vessels at all timesB Osmotic gradients generated by living stem parenchyma cells along the trunkC Cohesion between water molecules and tension from transpiration pulling water upD Active ATP-driven pumping of water molecules through xylem conduitsShow answer & explanation →
Q33.
Companion cells in phloem are connected to sieve tube elements by:
A Tight junctions sealing the membranes of adjacent cells togetherB Plasmodesmata (for loading and unloading sugars)C Lignified cell walls with no cytoplasmic continuity between cellsD Gap junctions formed from connexin protein channels as in animal cellsShow answer & explanation →
Q34.
Which ion channel opening triggers stomatal opening?
A Ca<sup>2+</sup> influx into guard cells that triggers turgor loss and pore closureB H+ ATPase pump exports H+ (protons), creating electrochemical gradient for K+ influxC Cl- efflux alone, which lowers guard cell osmotic potential without affecting K+D Na+ influx through mechanosensitive channels on the guard cell membraneShow answer & explanation →
Q35.
Abscisic acid triggers which response in stomata during drought?
A Stomatal opening to fix more CO<sub>2</sub>B Stomatal closure to reduce water lossC Increased transpirationD Stomatal neutral responseShow answer & explanation →
Q36.
The apoplast pathway of water movement in roots goes through:
A Cell membranes and cytoplasm via osmotic gradients between cellsB Cell walls and intercellular spaces (no membranes crossed)C Central vacuoles of cortical cells linked by tonoplast continuityD Plasmodesmata connecting the cytoplasm of adjacent cortical cellsShow answer & explanation →
Q37.
Water potential of a solution becomes more negative as the:
A Solute concentration in it decreasesB Applied pressure rises above atmosphericC Solute concentration in it increasesD Temperature drops, regardless of solutesShow answer & explanation →
Q38.
Transpiration pull, central to the ascent of sap, is generated by:
A Root pressure from active ion accumulation in roots according to standard textsB Active pumping of water by living xylem parenchyma cells under typical physiological conditionsC Evaporation from mesophyll cells creating tension that pulls water upD Osmotic flow of water moving from phloem into xylem in general clinical practiceShow answer & explanation →
Q39.
The symplast pathway of water movement across the root differs from the apoplast pathway in that the symplast route:
A Moves through cytoplasm of cells joined by plasmodesmataB Stays mainly within cell walls, rarely crossing a membraneC Is largely blocked by the Casparian strip in the endodermisD Occurs mainly within xylem vessels, rather than root cortex cellsShow answer & explanation →
Q40.
Translocation of organic solutes in the phloem can occur in both upward and downward directions because:
A Flow direction depends on relative source and sink position, not fixed anatomyB Phloem transports mainly water, for which direction is irrelevant in most reference accountsC Sucrose can move mainly from root to leaf, rarely the reverse under normal conditionsD Phloem sap flow is fixed in one direction by gravity as frequently documentedShow answer & explanation →
Q41.
The upward movement of water in the xylem is aided by the pull created during:
A transpirationB strong gravityC cell respirationD food digestionShow answer & explanation →
Q42.
The theory that explains water rise in tall trees by cohesion and transpiration pull is the:
A cohesion-tension theoryB simple cell theoryC microbial germ theoryD lock-and-key theoryShow answer & explanation →
Q44.
The uptake of mineral ions into root cells against a concentration gradient needs:
A active transport (energy)B only simple diffusionC plain osmosisD the force of gravityShow answer & explanation →
Q46.
When a plant cell loses water and its membrane pulls away from the wall, it is said to be:
A plasmolysedB turgidC only flaccidD enlargedShow answer & explanation →
Q47.
A plant cell that is fully swollen with water and firm is described as:
A turgidB plasmolysedC flaccidD completely deadShow answer & explanation →
Q48.
The firmness a plant cell gains when filled with water by osmosis is called:
A turgidityB transpirationC respirationD simple diffusionShow answer & explanation →
Q49.
Companion cells are closely associated with the ___ of the phloem:
A sieve tubesB xylem vesselsC tracheidsD xylem fibresShow answer & explanation →
Hard - 25 questions Q51.
An influx of K<sup>+</sup> ions opens the stomata because it:
A Raises guard-cell water potentialB Removes all guard-cell waterC Lowers water potential so water entersD Bursts the guard cells openShow answer & explanation →
Q52.
In the pressure-flow hypothesis, sugar loading at the source makes the sieve-tube water potential:
A Higher than the xylemB Equal to the airC Exactly zero alwaysD More negative (lower)Show answer & explanation →
Q53.
In guttation, water droplets are given out through special pores called:
A HydathodesB StomataC LenticelsD OstiolesShow answer & explanation →
Q54.
The rate of diffusion of a molecule depends on the concentration gradient, temperature and:
A The root pressureB The membrane's permeabilityC The number of stomataD The length of xylemShow answer & explanation →
Q55.
A mycorrhizal partnership chiefly improves a plant's uptake of:
A Only carbon dioxideB Only oxygen gasC Phosphorus and waterD Only sunlight energyShow answer & explanation →
Q56.
Guard cell closure in response to ABA involves:
A K+ entering guard cells through inward-rectifying channels to raise turgorB Ca<sup>2+</sup> as second messenger activating K+ efflux channels and anion channels, causing turgor lossC Selective inhibition of plasma membrane H+ ATPase with no change in ion channel activityD Water diffusing directly into the guard cell wall matrix independent of osmosisShow answer & explanation →
Q57.
The role of 14-3-3 proteins in stomatal regulation is:
A Forming the selective pore of the inward-rectifying K+ channel itself directly within the guard cell plasma membraneB Acting as signaling scaffolds that activate H+ ATPase when bound to its phosphorylated C-terminus, promoting stomatal openingC Hydrolyzing abscisic acid molecules directly into inactive breakdown products within the surrounding guard cell cytosolD Synthesizing entirely new K+ channel protein subunits specifically during the active stomatal opening response phaseShow answer & explanation →
Q58.
The Casparian strip in root endodermis forces water through:
A The apoplast pathway mainly, bypassing most endodermal cell membranes encountered along the wayB Symplast (through cell membrane), allowing selective mineral ion transport to xylemC Suberized cell walls alone, with little membrane crossing required at any point along the pathD Stomatal pores located within the endodermal cell layer of the root structure itselfShow answer & explanation →
Q59.
In the cohesion-tension theory, the continuous water column in the xylem does not normally break under tension mainly because of:
A Pressure generated by guard cells at the leaf surface under most conditions studiedB Continuous secretion of mucilage inside xylem vessels in most observed casesC Active pumping of water by living xylem vessel cells in standard reference materialD Strong cohesive forces between water molecules from hydrogen bondingShow answer & explanation →
Q60.
Root pressure can account for water movement up a stem only to a limited extent because it:
A Pushes water downward from shoot to root, not upward according to standard textsB Is generated by evaporation of water from leaf surfaces in daytime under typical physiological conditionsC Operates in plants whose xylem vessels are non-functional in general clinical practiceD Is a comparatively weak force, most active at night when transpiration is lowShow answer & explanation →
Q61.
Loading of sucrose into the phloem sieve tubes at the source mainly involves:
A Osmotic carrying of sucrose molecules along with water uptake under normal conditionsB Bulk flow of sucrose straight from xylem vessels into phloem in most reference accountsC Active co-transport of sucrose with protons, driven by an H+-ATPase gradientD Passive diffusion of sucrose with little carrier protein involvement as frequently documentedShow answer & explanation →
Q62.
Mineral ions move from the soil into the xylem of roots mainly by a combination of:
A Bulk flow driven by transpirational pull, bypassing active transport in typical laboratory settingsB Diffusion down a concentration gradient, with little active uptake as generally observedC Active uptake by root hair cells, then movement via symplast or apoplast to the xylemD Osmosis of dissolved minerals along the water potential gradient under usual circumstancesShow answer & explanation →
Q63.
The 'source to sink' direction of phloem transport can reverse seasonally in a plant because:
A Sucrose levels stay uniform across plant organs through the year in the majority of documented casesB Source and sink depend on current sugar export versus import, not on fixed anatomyC Phloem sap direction is set permanently by gravitational pull as widely reportedD Phloem moves sugars downward mainly, in a fixed one-way direction according to most studiesShow answer & explanation →
Q64.
Guttation, the exudation of water droplets from leaf margins, occurs mainly when:
A Root pressure exceeds a low transpiration rate, mostly at night or dawnB Xylem vessels get blocked internally by trapped air bubbles in most observed casesC Stomata remain wide open overnight under dry conditions under most conditions studiedD Transpiration runs highest during the hottest daylight hours in standard reference materialShow answer & explanation →
Q65.
Imbibition, as seen in a dry seed absorbing water, is distinct from osmosis mainly because it:
A Is adsorption of water by hydrophilic colloids like cell wall and storage proteinsB Takes place in animal tissue rather than plant tissue in general clinical practiceC Needs metabolic energy supplied by respiration in the seed according to standard textsD Needs a semi-permeable membrane separating two unequal solutions under typical physiological conditionsShow answer & explanation →
Q66.
The chief force responsible for the ascent of sap in very tall trees is:
A transpiration pullB root pressure aloneC capillary action aloneD downward gravityShow answer & explanation →
Q67.
Root pressure is best seen as ___ from the margins or tips of leaves:
A guttationB transpirationC sudden wiltingD photosynthesisShow answer & explanation →
Q68.
The cohesion between water molecules that keeps the water column intact is due to:
A hydrogen bondingB ionic bondingC only covalent bondingD metallic bondingShow answer & explanation →
Q69.
The movement of sugar in the phloem is driven by a difference in ___ between source and sink:
A pressureB temperatureC light levelD gravityShow answer & explanation →
Q70.
Stomata generally close when a plant experiences:
A a water shortageB excess soil waterC bright sunlightD cool weatherShow answer & explanation →
Q71.
The Casparian strip of the root endodermis controls the ___ taken by water and ions:
A pathwayB colourC temperatureD only the speedShow answer & explanation →
Q72.
Imbibition is the absorption of water by ___ substances such as dry seeds:
A solid hydrophilic onesB purely gaseous onesC purely liquid onesD purely metallic onesShow answer & explanation →
Q74.
Besides cooling the plant, transpiration also assists in the ___ of minerals:
A upward transportB food digestionC waste excretionD food storageShow answer & explanation →
Q75.
Water enters root hairs by osmosis because the soil solution is ___ compared with the cell sap:
A more diluteB more concentratedC exactly identicalD entirely gaseousShow answer & explanation →