Biology, HSSC-Punjab First Year. This chapter is split into 33 topics and has
770 practice questions. The topics covered are listed below, followed by
10 free sample questions from the chapter.
Topics in this chapter
Water potential and water movement in cells25 questions
Secondary growth, cambium and annual rings25 questions
Movements in plants: tropic and nastic movements25 questions
Plant nutrition: macro and micronutrients25 questions
Photoperiodism and vernalisation25 questions
Support in plants: turgor and supporting tissues25 questions
Transport of water through roots and xylem25 questions
Translocation of food in plants: phloem25 questions
Growth in plants: primary growth25 questions
Plant growth regulators25 questions
Gas exchange in plants: stomata and transpiration25 questions
Osmoregulation and thermoregulation in plants25 questions
Chapter 8 learning outcomes: verbs and content25 questions
Chapter 8 section numbers and figure index28 questions
Nutrients and macronutrients: roles in detail25 questions
Micronutrients: roles and deficiency patterns21 questions
Insectivorous plants: traps and digestion in detail23 questions
Leaf structure and the gas exchange pathway (Figures 8.4 and 8.5)20 questions
Water potential: worked numericals25 questions
Supporting tissues: Figure 8.6 and comparisons20 questions
Root pathways and xylem structure (Figures 8.7 and 8.8)22 questions
TACT mechanism and Figure 8.9: reasoning questions21 questions
Phloem: structure details, Figures 8.10 and 8.11, pressure-flow reasoning23 questions
Meristems and growing points: details and Figure 8.1220 questions
Growth zones, Figures 8.13 to 8.15 and annual rings: detail and reasoning21 questions
Plant growth regulators: further effects in detail25 questions
Plant growth regulators: comparisons across the five groups20 questions
Osmoregulation, Figure 8.16 and hydrophyte adjustments24 questions
Mesophytes, xerophytes and halophytes: habitats and adaptations in detail21 questions
Temperature stress and tropic movements: further detail20 questions
Photoperiodic classes: Table 8.2 examples and night-length numericals21 questions
Phytochrome, florigen and vernalisation: reasoning questions22 questions
Chapter 8 exercise: question numbers and prompts23 questions
Sample questions: Plant Physiology
10 sample questions with the correct answer and an explanation. Try to answer each one before reading the explanation.
Q1. Compared with marine hydrophytes, freshwater hydrophytes typically have:
A. thick cuticles that reduce water loss from the leaves
B. specialized salt glands for excreting excess salts
C. fleshy stems that store water for use in dry periods
D. thin or absent cuticles and reduced root systems, relying on direct nutrient and water absorption(correct answer)
Answer: D.Freshwater hydrophytes have thin or absent cuticles that facilitate water exchange and often have reduced root systems, relying on direct nutrient and water absorption; thick cuticles are characteristic of marine hydrophytes.
Q2. A biennial plant is kept warm, except that its leaves are chilled to 4 °C for several weeks. Will it be induced to flower, and why?
A. No, because vernalisation requires high temperature treatment instead
B. No, because the low temperature stimulus is received by the shoot apex of a mature stem or the embryo of the seed, not by the leaves(correct answer)
C. Yes, because the leaves perceive the low temperature stimulus for vernalisation
D. Yes, because vernalisation only requires a drop in temperature in any part of the plant
Answer: B.The low temperature stimulus of vernalisation is received by the shoot apex of a mature stem or the embryo of the seed, not by the leaves (as in photoperiodism); therefore chilling only the leaves will not induce flowering.
Q3. Which of the following best distinguishes vernalisation from photoperiodism?
A. Vernalisation is a response to low temperature, whereas photoperiodism is a response to the length of day and night(correct answer)
B. Vernalisation occurs only in day-neutral plants, whereas photoperiodism occurs in biennials and perennials
C. Vernalisation requires the dark period to be interrupted by light, whereas photoperiodism requires a cold shock
D. In vernalisation the stimulus is perceived by the leaves, whereas in photoperiodism it is perceived by the shoot apex
Answer: A.Vernalisation is the stimulation of flowering by low temperature, while photoperiodism is the response of plants to the length of day and night; in vernalisation the stimulus is received by the shoot apex or embryo, not the leaves.
Q4. Assertion (A): At high temperature, when leaf cells start wilting, stomata close even in the presence of light. Reason (R): Abscisic acid released by mesophyll cells stops the active transport of K+ into guard cells.
A. Both A and R are true, and R is the correct explanation of A(correct answer)
B. A is false but R is true
C. Both A and R are true, but R is not the correct explanation of A
D. A is true but R is false
Answer: A.When leaf cells start wilting at high temperature, mesophyll cells release abscisic acid, which stops the active transport of K+ into guard cells, overriding the effect of light and CO2 concentration; K+ pumping stops and stomata close.
Q5. Which of the following correctly matches a phloem component with its described role?
A. Phloem fibres — communicate with sieve tubes via plasmodesmata
B. Companion cells — store latex and mucilage
C. Sieve tube elements — transport sugars and other organic material throughout the plant(correct answer)
D. Phloem parenchyma — conduct sucrose over long distances
Answer: C.Sieve tube elements are the phloem cells that transport sugars and other organic material; latex and mucilage are stored by phloem parenchyma, companion cells supply ATP and proteins, and plasmodesmata connect sieve tubes with companion cells.
Q6. Which of the following sequences correctly describes the steps of the pressure-flow mechanism from source to sink?
A. Sugar is unloaded at the sink → sucrose is loaded at the source → water enters by osmosis → the solution flows toward the sink
B. Water enters the sieve tubes → sucrose is loaded → the solution flows toward the sink → sugar is actively unloaded
C. The solution flows toward the sink → sucrose is loaded → water enters by osmosis → sugar is unloaded
D. Sucrose is loaded into the sieve tubes → water enters by osmosis → a difference in water potential develops between source and sink → the solution flows toward the sink and sugar is actively unloaded(correct answer)
Answer: D.The pressure-flow theory follows the order: loading of sucrose into the sieve tubes, entry of water by osmosis, development of a higher water potential at the source than at the sink, bulk flow of the solution to the sink, and unloading at the sink.
Q7. Assertion (A): In the pressure-flow mechanism, water along with the dissolved sucrose moves from the source end to the sink end of the sieve tubes. Reason (R): There is a higher water potential at the source end and a lower water potential at the sink end, and this difference causes water to flow from source to sink.
A. Both A and R are true, and R is the correct explanation of A(correct answer)
B. Both A and R are true, but R is not the correct explanation of A
C. A is true but R is false
D. A is false but R is true
Answer: A.The textbook states that there is a higher water potential at the source end while a lower water potential at the sink end, and that this difference causes water to flow from source to sink, carrying the dissolved sucrose along.
Q8. A plant is treated with a chemical that blocks the active transport of sucrose into the companion cells of the phloem at the source (leaf). What is the most likely direct effect on translocation to the sink?
A. Translocation continues at the same rate because sucrose can quickly enter the sieve tubes by diffusion instead
B. Water enters the sieve tubes more rapidly, so translocation speeds up
C. Sucrose entry into the sieve tubes is reduced, decreasing the difference in water potential and reducing the mass flow toward the sink(correct answer)
D. The xylem begins to transport sucrose to the sink in place of the phloem
Answer: C.Loading sucrose into the sieve tubes is the step that raises the solute concentration and draws water in by osmosis; if loading is blocked, the water potential difference that drives mass flow is reduced, and diffusion is far too slow to substitute.
Q9. A scientist studies the ring patterns of ancient trees to reconstruct rainfall and temperature of past centuries. This application is possible because annual ring formation is:
A. Restricted to herbaceous plants
B. Caused by apical meristems at the root and shoot tips
C. Completely independent of the environment
D. Influenced by environmental factors, so rings provide information about conditions experienced during each growing season(correct answer)
Answer: D.Annual ring formation is influenced by environmental factors, and the rings provide valuable information about the age of the tree and the environmental conditions experienced during each growing season, which makes dendrochronology useful for studying long-term climate variability.
Q10. Assertion: Abscisic acid is antagonistic to gibberellins in flowering.
Reason: Abscisic acid promotes flowering in short-day plants and inhibits it in long-day plants, while gibberellins promote flowering in long-day plants and inhibit it in short-day plants.
A. Both Assertion and Reason are true and the Reason is the correct explanation of the Assertion(correct answer)
B. Both Assertion and Reason are true but the Reason is not the correct explanation of the Assertion
C. Assertion is true but Reason is false
D. Assertion is false but Reason is true
Answer: A.ABA promotes flowering in short-day plants and inhibits it in long-day plants, and the text explicitly notes it is antagonistic to gibberellins, which promote flowering in long-day plants and inhibit it in short-day plants.