Biology

Plant Transport and Physiology

2,012 Questions

Access a comprehensive set of questions on plant transport mechanisms and physiological adaptations. Topics include water movement, translocation of food, and plant responses to external stimuli. These biology questions are essential for medical entrance exams and other science competitive tests.

Xylem and phloem transportTranspiration and evaporationPlant adaptationsGeotropic and phototropic responsesWater absorption by rootsRespiration in roots

Plant Transport and Physiology Questions

Multiple choice

Which one of the following leaf modifications occur in the desert areas to inhibit water loss?

  1. Hard and waxy leaves
  2. Tiny leaves or no leaves
  3. Drip-tip leaves
  4. Thorn instead of leaves Select the correct answer using the codes given below:

  1. 1, 2 and 3

  2. 2 and 3

  3. 1, 2 and 4

  4. 1 and 4
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Desert plants adapt to conserve water by reducing leaf surface area. Hard/waxy leaves prevent transpiration, and thorns (modified leaves) reduce surface area and deter herbivores.

Multiple choice

Which of the following statements are correct/wrong?

a) A large quantity of water loss occurs through cuticleb) Lenticular transpiration is insignificant as compared to stomatal transpiration c) Stomata are minute pores found on epidermal surfaces of leaves d) Guttation occurs only in dry conditions

  1. (a) and (b) are correct

  2. (c) and (d) are correct

  3. (b) and (c) are wrong

  4. (a) and (d) are wrong
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Cuticular transpiration is minimal, not large, because the cuticle is a waxy waterproof layer. Lenticular transpiration is indeed insignificant (less than 1%) compared to stomatal transpiration (90%+). Stomata are correctly described as minute pores on leaf epidermis. Guttation occurs in high humidity/soil moisture conditions, not dry conditions - it happens when transpiration is limited but root pressure continues.

Multiple choice

When the guard cells are turgid

  1. the stoma is open

  2. the stoma is closed

  3. the stoma becomes flat

  4. it becomes a globe like structure
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When guard cells become turgid due to water uptake, their uneven thickening causes them to bend outward, creating an opening between them. This is the open stomatal pore that allows gas exchange. When flaccid, the stomatal pore closes.

Multiple choice

When the water potential of the guard cells is lower than that of the adjacent cells

  1. the stomata closes

  2. the guard cells become flaccid

  3. the stomata opens

  4. the guard cells develop kidney shaped structure
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When guard cells have lower (more negative) water potential than adjacent cells, water enters them by osmosis, making them turgid. Turgid guard cells bend outward due to uneven cell wall thickening, opening the stomatal pore. Lower water potential drives water uptake, not closure.

Multiple choice

Stomatal movement is caused by

  1. Mg++ ions

  2. Mn++ ions

  3. CI-ions

  4. K+ ions
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Potassium (K+) ion movement is the primary driver of stomatal movement. K+ ions are pumped into guard cells to open stomata (lowering water potential, causing water uptake) and pumped out to close them (raising water potential, causing water loss). Mg++, Mn++, and Cl- are not involved in stomatal mechanism.

Multiple choice

A concentration gradient of water vapour between the atmospheric air and intercellular spaces of leaves is created by

  1. the accumulation of water vapour in the intercelluar spaces of mesophyll which were created by the sun light on the surface of mesophyll cell walls

  2. the water in the cells filling the intercellular spaces of leaves

  3. the translocated water with the mesophyll cells of leaves through Xylem tissue

  4. the water present in the large intercelluar spaces and large number of stomataon the leaves
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Sunlight heats the mesophyll cell walls, causing water to evaporate into the intercellular spaces. This creates a water vapour gradient between these spaces and the external atmosphere. Option A correctly describes this mechanism, while B incorrectly states water fills the spaces (it's vapour, not liquid). C describes xylem transport, not vapour creation, and D is too vague.

Multiple choice

Turgor pressure develops in the epidermal cells of roots when there is:

  1. high water potential in the cytoplasm of cortical cells

  2. entry of water into root hair and increase in volume of cell sap

  3. a large vacuole in root hair filled with cell sap

  4. osmotic diffusion of water into the pericycle through passage cells
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Turgor pressure develops when water enters the root hair by osmosis, increasing the volume of cell sap (vacuolar contents). This influx against the cell wall creates turgor. Option A incorrectly references water potential in cortical cells. Option C describes a large vacuole but not the pressure mechanism. Option D describes pericycle transport, not root hair turgor.

Multiple choice

The loss of water in a liquid form is called _______.

  1. hydathodes

  2. transpiration

  3. diffusion

  4. guttation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Guttation is the loss of water in liquid form through hydathodes (specialized pores) usually from leaf margins. This occurs when transpiration is low and soil moisture is high, creating root pressure. Transpiration is water loss as vapor.

Multiple choice

The chief water conducting elements of ferns and gymnosperms are

  1. vessels

  2. fibres

  3. tracheids

  4. sieve elements
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Ferns and gymnosperms lack vessels (evolved in angiosperms) and rely on tracheids as their chief water-conducting elements. Tracheids are long, thin cells with tapered ends that transport water and provide structural support. Sieve elements are for food transport.

Multiple choice

Phyllode is an adaptation in some _____ plants.

  1. hydrophytic

  2. mesophytic

  3. epiphytic

  4. xerophytic
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Phyllode is a flat, expanded petiole that functions as a leaf blade. It is a xerophytic adaptation to reduce water loss while maintaining photosynthesis. Common in Australian Acacia species that grow in arid conditions.

Multiple choice

Plant cells do not burst when kept in an hypotonic solution due to the presence of

  1. vacuole

  2. plastids

  3. cell wall

  4. nucleus

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When plants are placed in water, the water enters their cells (this is because their sap has a strong solution). The water enters the plant through osmosis and fills up the cell with water to its maximum capacity. A strong cell wall stops the cells from bursting (as in animal cells) and makes the plant to become turgid (becomes rigid/stiff because of water).