AS Level Biology chapter 7: Transport in plants MCQs with answers
By Team Megalecture · Updated 4 Nov 2026
24 exam-style questions on Transport in plants, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.
Try each one, then open the answer. These ten stay the same; the test draws new ones every time.
1. Radioactive sucrose is injected into the phloem of a mature leaf of a healthy plant. Some days later radioactivity is found in the root tips and in developing seeds, but not in the other mature leaves. What does this show?
A
the root tips and seeds are sinks that use or store sucrose, while mature leaves are sources
B
sucrose moves only downwards in the phloem, so it cannot reach the seeds
C
the root tips and seeds are sources that make sucrose by photosynthesis
D
sucrose was carried to the roots and seeds in the xylem by transpiration pull
Show answer
Answer: A. Assimilates move in the phloem from sources (such as mature photosynthesising leaves) to sinks (such as growing roots and developing seeds). Other mature leaves make their own sucrose, so they do not import it.
2. A marram grass leaf rolls up in dry conditions, with its stomata on the inner surface. Why does this reduce transpiration?
A
it closes the xylem vessels in the midrib, so less water reaches the mesophyll cells
B
it thickens the cuticle, which makes the leaf waterproof
C
it lowers the temperature of the leaf, so that water no longer evaporates from the mesophyll cell walls
D
humid air is trapped in the roll, reducing the water potential gradient out of the leaf
Show answer
Answer: D. Water vapour builds up inside the roll, so the air there is humid and water vapour diffuses out more slowly.
3. What is the effect of the Casparian strip in the endodermis?
A
it pumps water into the xylem by active transport, creating the pressure that pushes sap upwards
B
it lets mineral ions bypass the cell membranes and enter the xylem directly through the walls
C
it blocks the symplast pathway, so water has to pass through the cell walls to reach the xylem
D
it blocks the apoplast pathway, forcing water to cross a cell membrane into the symplast
Show answer
Answer: D. The waterproof strip in endodermal cell walls blocks the apoplast, so water and ions must cross a cell membrane and enter the symplast.
4. Which feature of a mature phloem sieve tube element reduces resistance to the flow of sap?
A
it has a large central nucleus that controls the flow of sap through the sieve plates
B
it has no nucleus and very few organelles, with only a thin layer of cytoplasm
C
its walls are thickened with lignin so the tube does not collapse under pressure
D
it contains many chloroplasts that make sucrose inside the tube
Show answer
Answer: B. With almost no contents in the lumen, sap flows easily; the cell stays alive with support from its companion cell.
5. Which feature of xylem vessel elements allows water to flow in an unbroken column?
A
they are joined to companion cells by plasmodesmata
B
they are dead cells with no cytoplasm and no end walls
C
they have many mitochondria to supply ATP for pumping water upwards
D
they have sieve plates between cells that let sap pass through
Show answer
Answer: B. Mature vessel elements are empty dead tubes with end walls lost, giving a continuous column with little resistance.
6. A student draws a plan diagram of a stem in transverse section. On the drawing the whole stem is 60 mm across and the xylem region is 12 mm wide. The real stem measured 4.0 mm across. What is the real width of the xylem region?
A
0.2 mm
B
0.8 mm
C
3.2 mm
D
8.0 mm
Show answer
Answer: B. The magnification is 60 ÷ 4.0 = ×15. Real width = drawing width ÷ magnification = 12 ÷ 15 = 0.8 mm. Using 12 ÷ 60 alone gives 0.2, and subtracting gives 3.2.
7. How does cohesion help water move up the xylem?
A
water molecules form ionic bonds with each other so the column cannot break
B
hydrogen bonds between water molecules let the column be pulled up as one unit
C
active transport of water by cells around the vessels pushes the column upwards
D
water molecules are attracted to the cellulose in the vessel walls, which pulls the column upwards
Show answer
Answer: B. Hydrogen bonds between water molecules hold the column together, so water lost at the top pulls the whole column upwards (cohesion-tension).
8. What are the functions of lignin in the walls of xylem vessels?
A
it makes the walls permeable so water can pass freely into the vessel from the cortex
B
it supplies the energy for water to move up the vessel
C
it stores water in the vessel walls so the vessel stays filled at night
D
it stops the vessels collapsing under tension and makes the walls waterproof
Show answer
Answer: D. Lignin strengthens walls against the negative pressure (tension) in the xylem and waterproofs them. Pits allow sideways movement.
9. What is the role of adhesion in the movement of water in the xylem?
A
water molecules form ionic bonds with the cellulose in the vessel walls, which holds the column in place
B
hydrogen bonds between water molecules hold the column together so that it can be pulled
C
water molecules form hydrogen bonds with the cellulose in the vessel walls
D
water molecules stick to starch grains in the xylem, which stops the column falling back
Show answer
Answer: C. Adhesion is attraction between water and the walls; together with cohesion it helps water move up narrow vessels.
10. Which describes transpiration?
A
water evaporates from the surface of the xylem vessels in the leaf and is lost by mass flow through the stomata
B
water evaporates from the surfaces of mesophyll cells, then water vapour diffuses out through stomata
C
guard cells pump water out of the leaf through the open stomata by active transport
D
liquid water moves out of the leaf through the cuticle and evaporates from its outer surface
Show answer
Answer: B. Evaporation happens from the wet internal surfaces of leaf cells; the vapour then diffuses down a water potential gradient to the air outside.
24, each with the answer and a short explanation, across 2 topics: Structure of transport tissues, Transport mechanisms. Every chapter test draws ten of them, so you can take it many times.
Is the AS Level Biology chapter 7 test free?
Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.
How is the chapter test marked?
The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.
