SECTION 1: MULTIPLE CHOICE QUESTIONS

PLANT PHYSIOLOGY

1. Process by which water evaporates from surface of leaf primarily through stomata:

(a) Transpiration (b) Guttation (c) Imbibition

Correct Answer: (a) Transpiration

Explanation: Transpiration is the evaporative loss of water from plant surfaces, mainly through stomata in leaves, which drives water uptake from roots and maintains turgor. Guttation involves liquid water excretion via hydathodes, and imbibition is water absorption by colloids without evaporation.

2. Through which structure does most of transpiration occurs?

(a) Root hairs (b) Phloem (c) Xylem

Correct Answer: (c) Xylem

Explanation: Transpiration pulls water upward through the xylem vessels and tracheids from roots to leaves, where it evaporates. Root hairs absorb water, but phloem transports sugars, not water for transpiration.

3. The TACT theory primarily explains

(a) The movement of nutrients in the plants (b) The transport of water in plants (c) The absorption of minerals (d) The process of photosynthesis

Correct Answer: (b) The transport of water in plants

Explanation: TACT (Transpiration, Adhesion, Cohesion, Tension) theory describes the ascent of sap in xylem, where transpiration creates tension, and cohesion/adhesion of water molecules pulls it upward against gravity. It does not relate to nutrient movement (phloem), mineral absorption, or photosynthesis.

4. Which of the following is not a function of xylem?

(a) Transport of water (b) Transport of minerals (c) Transport of food (d) Mechanical support

Correct Answer: (c) Transport of food

Explanation: Xylem conducts water and minerals upward and provides mechanical support via lignified walls, but food (organic solutes like sugars) is transported via phloem. Cohesion is a property aiding xylem function, not stomata (which are for gas exchange).

5. Which of the following has a perforated cell wall?

(a) Vessel (b) Fibre (c) Tracheid (d) Sclereid

Correct Answer: (a) Vessel

Explanation: Vessels in xylem have perforated end walls (perforation plates) allowing efficient water flow. Tracheids connect via pits, while fibres and sclereids are supportive with thick, imperforate walls.

6. Exposure to low temperature stimulates the process of flowering in biennial or perennial plants:

(a) Dormancy (b) Photoperiodism (c) Vernalization

Correct Answer: (c) Vernalization

Explanation: Vernalization is the promotion of flowering by prolonged cold exposure in biennials/perennials, accelerating reproductive development. Photoperiodism involves day-length responses, and dormancy is a resting phase.

7. Plants that are adapted to survive in dry conditions:

(a) Xerophytes (b) Hydrophytes (c) Mesophytes (d) Halophytes

Correct Answer: (a) Xerophytes

Explanation: Xerophytes have adaptations like thick cuticles, sunken stomata, and reduced leaves to minimize water loss in arid environments. Hydrophytes are aquatic, mesophytes temperate, and halophytes saline-tolerant.

8. When sugar content in a cell increases the concentration of solute increases, what happens to the water potential?

(a) Raises (b) Drops (c) Unchanged

Correct Answer: (b) Drops

Explanation: Water potential (ψ) decreases with higher solute concentration due to solute potential (ψs) becoming more negative, making water less likely to enter the cell osmotically.

9. In higher plant, transport of food materials occurs through;

(a) Companion cells (b) Sieve tubes (c) Vessel elements (d) Tracheids

Correct Answer: (b) Sieve tubes

Explanation: Sieve tubes in phloem, aided by companion cells, conduct sugars and organic nutrients from source (leaves) to sink (roots/storage). Vessels and tracheids are for water in xylem.

10. The plant hormone which inhibits the stem and root growth is

(a) Auxin (b) Ethylene (c) Cytokinin (d) Gibberellin

Correct Answer: (b) Ethylene

Explanation: Ethylene is a gaseous hormone that promotes fruit ripening and inhibits elongation in stems/roots, causing dwarfing. Auxin, cytokinin, and gibberellin generally promote growth.

11. The leaves of some hydrophyte float on the surface of water. In such a leaf, stomata are found in;

(a) Lower epidermis (b) Upper epidermis (c) Sides of leaf (d) Deep depressions in leaf

Correct Answer: (b) Upper epidermis

Explanation: In floating hydrophyte leaves (e.g., water lily), stomata are restricted to the upper epidermis, which is exposed to air, while the lower side contacts water and lacks stomata to prevent water entry.

12. Mesophytes are adapted to survive in:

(a) Moderate environments (b) Dry conditions (c) Water environments (d) All of above

Correct Answer: (a) Moderate environments

Explanation: Mesophytes thrive in temperate, moist habitats with balanced water availability, unlike xerophytes (dry), hydrophytes (wet), or halophytes (saline).

SECTION 2: SHORT QUESTIONS

PLANT PHYSIOLOGY

1. Differentiate between macronutrients and micronutrients?

Macronutrients are essential elements required in large quantities (>0.1% dry weight) for plant growth, such as nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S); they form major structural components like proteins and chlorophyll. Micronutrients are needed in trace amounts (<0.01% dry weight), including iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), molybdenum (Mo), boron (B), and chlorine (Cl); they act as cofactors in enzymes and metabolic processes.

2. What is water potential?

Water potential (ψ) is the measure of the potential energy of water in a system relative to pure water, determining the direction of water movement. It is the sum of solute potential (ψs, due to solutes) and pressure potential (ψp, due to turgor), expressed in megapascals (MPa); water moves from higher ψ to lower ψ.

3. What are the main three pathways for the movement of water between plant cells?

The three pathways are: (i) Apoplast pathway (water moves through cell walls and intercellular spaces without crossing membranes, fastest but can be blocked by Casparian strip); (ii) Symplast pathway (water moves via cytoplasm through plasmodesmata, regulated and energy-dependent); (iii) Transmembrane pathway (water crosses plasma membranes via aquaporins, selective and slower).

4. Differentiate between hypertonic and hypotonic solution?

A hypertonic solution has higher solute concentration (lower water potential) than the cell, causing water to exit the cell by osmosis, leading to plasmolysis. A hypotonic solution has lower solute concentration (higher water potential) than the cell, causing water to enter, resulting in turgor and potential cell swelling or lysis.

5. What are halophytes?

Halophytes are plants adapted to grow in high-salinity environments (e.g., salt marshes), with features like salt-excreting glands, succulent tissues for dilution, and specialized ion uptake to maintain osmotic balance without toxicity.

6. Differentiate between long day plants and short day plants?

Long-day plants (e.g., wheat, spinach) flower when day length exceeds a critical period (usually >12 hours), promoted by phytochrome in far-red light. Short-day plants (e.g., rice, chrysanthemum) flower when day length is shorter than the critical period (<12 hours), inhibited by long exposures; both respond to night length primarily.

7. Write down the phases of plant growth?

The three phases are: (i) Lag phase (initial slow growth with cell division starting); (ii) Exponential (log) phase (rapid growth via meristematic activity and elongation); (iii) Stationary (maturation) phase (growth slows as cells differentiate and resources limit further division).

8. Differentiate between Vernalin and Florigen.

Vernalin is a hypothetical glycoprotein pigment synthesized in leaves during vernalization (cold treatment), which travels to the apex to induce flowering competence. Florigen is a mobile flowering hormone (identified as FT protein) produced in leaves under photoperiodic conditions, signaling the shoot apex to initiate floral development.

9. Differentiate between Thigmotropism and Geotropism.

Thigmotropism is directional growth in response to touch or mechanical stimuli (e.g., tendrils coiling around supports). Geotropism (gravitropism) is growth response to gravity (e.g., roots growing downward positively, shoots upward negatively).

10. How intercalary meristem is different from apical meristem?

Intercalary meristem is located at the base of leaves, internodes, or stems (e.g., in grasses), enabling elongation growth after the tip and accommodating grazing damage. Apical meristem is at the shoot/root tips, responsible for primary growth in length and width, establishing the plant body pattern.

SECTION 3: LONG QUESTIONS

1. Describe osmoregulation in Hydrophytes and Halophytes?

2. Describe the Physiological adaptation of plants to extreme conditions. How do plants adjust their cell membrane composition and protein structures to survive high and low temperatures?

3. What is the role of meristem in the growth of plants?

4. Describe the mechanism of opening and closing of stomata?

5. Explain the concept of photoperiodism and its influence on plant flowering. How do short-day, long-day and day-neutral plants differ in their flowering responses, and what role does phytochrome plays in this process?

INQUISITIVE QUESTIONS

1. Can you explain the hypothesis regarding the opening and closing of stomata?

The primary hypothesis is the potassium ion (K+) pump theory: During opening, guard cells actively pump K+ ions inward via ATP-driven pumps, increasing solute concentration, lowering water potential, and drawing in water osmotically, causing turgor and stomatal aperture widening. For closing, K+ efflux occurs, water exits, and turgor decreases. An alternative sugar-based hypothesis involves starch-sugar interconversion, but K+ mechanism is more supported.

2. What mechanisms enable carnivorous plants to supplement their nutrient uptake despite being autotrophs?

Carnivorous plants (e.g., Venus flytrap, pitcher plants) inhabit nutrient-poor soils (low N/P), so they supplement via traps: adhesive mucilage or snap mechanisms capture insects, digestive enzymes (proteases, phosphatases) break down prey externally/internally, and specialized glands absorb released nutrients like nitrogen as amino acids/ammonium, enhancing growth without relying solely on root uptake.

3. How can you say that parenchyma and schlerenchyma provide support to plants?

Parenchyma provides turgor pressure support through thin-walled, living cells filled with water, maintaining herbaceous plant rigidity (e.g., in pith). Sclerenchyma offers mechanical support via thick, lignified, dead cells with secondary walls that resist tension/compression (e.g., fibres in vascular bundles, sclereids in nutshells), enabling woody strength and flexibility.

4. How do the annual rings depict climatic variability?

Annual rings form from seasonal xylem growth: Spring wood (wide, light cells) reflects moist, warm conditions favoring rapid growth; autumn wood (narrow, dark cells) indicates dry/cold stress slowing growth. Ring width/thickness patterns reveal wet/dry years, temperature fluctuations, or droughts, allowing dendrochronology to reconstruct past climates over centuries.

5. How does Pressure Flow Theory explain the movement of sugars through a plant?

Pressure Flow Theory (mass flow) posits sugars load into phloem sieve tubes at the source (leaves) via active transport/companion cells, increasing solute concentration, lowering water potential, and drawing water in osmotically to create high turgor pressure. This pressure gradient drives bulk flow of sugar solution to sinks (roots/fruits) where sugars unload, water exits, and pressure drops, maintaining continuous translocation.

6. What strategies would you adopt to induce flowering in a plant?

Strategies include: (i) Manipulate photoperiod (extend/shorten days for long/short-day plants using lights); (ii) Apply vernalization (cold treatment for biennials); (iii) Use hormones like gibberellins to bypass environmental cues; (iv) Grafting onto induced scions for florigen transfer; (v) Chemical inducers (e.g., paclobutrazol to stress plants); ensure optimal nutrition/light to avoid delays.

Plant Physiology Interactive Quiz