Transport in Plants MCQs

Examine these statements about measuring transpirational water loss:

I. Transpirational water loss can be demonstrated by placing a dry cobalt chloride paper strip on a leaf surface.
II. Cobalt chloride paper is a chemical indicator that changes color from blue to pink upon absorbing water molecules.
III. In dorsiventral (dicot) leaves, the cobalt chloride paper changes color much faster on the upper epidermis than the lower epidermis.
IV. This test shows that water loss occurs primarily through stomata, which are more abundant on the lower leaf surface in dicots.

Which of the above statements are correct?

Consider the following statements regarding stomatal function:

I. Stomatal apertures are the principal sites for both transpirational water vapor loss and photosynthetic gaseous exchange (CO₂ and O₂).
II. Stomata are normally open during the night and remain tightly closed during the day to maximize photosynthesis.
III. The immediate cause of stomatal opening is a change in the turgidity of the flanking guard cells.
IV. The opening and closing of stomata is regulated by active solute potential shifts in guard cells.

Which of the above statements are correct?

Study these statements regarding the forces that maintain the continuous xylem water column:

I. Cohesion is the mutual physical attraction between individual water molecules.
II. Adhesion is the attraction of water molecules to polar surfaces, such as the walls of tracheary elements.
III. Surface tension attracts water molecules to each other more in the gas phase than in the liquid phase.
IV. High tensile strength and capillarity allow water to withstand pull forces and rise in narrow conduits.

Which of the above statements are correct?

Examine these statements about the physiological purposes of transpiration in plants:

I. Transpiration supplies the water needed for photosynthetic carbon reduction reactions.
II. Evaporative cooling from transpiration can cool leaf surfaces by 10 to 15 degrees Celsius.
III. Transpiration maintains cell turgidity, keeping herbaceous organs and leaves erect.
IV. Transpiration hinders mineral absorption because the constant upward movement of water dilutes soil minerals.

Which of the above statements are correct?

Review the photosynthetic adaptations of plants with respect to transpiration:

I. C₄ plants have evolved metabolic and anatomical adaptations to maximize carbon dioxide uptake while minimizing transpiration.
II. C₄ plants are twice as efficient as C₃ plants in terms of carbon fixation (sugar synthesis).
III. A C₄ plant loses twice as much water as a C₃ plant for the same amount of carbon dioxide fixed.
IV. The evolution of the C₄ system is a strategic adaptation designed to handle arid, water-limiting environments.

Which of the above statements are correct?

Study the following statements regarding the movement of water within leaf tissues during transpiration:

I. As water evaporates from the substomatal cavity into the atmosphere, a water potential gradient is set up across the mesophyll cells.
II. The evaporation of water from leaf cell walls creates a continuous pull that transmits tension directly into the water-filled xylem of the leaf vein.
III. The pull of water molecules into leaf parenchyma cells from xylem conduits occurs molecule by molecule due to the cohesive properties of water.
IV. The concentration of water vapor in the atmosphere is typically much higher than that in the substomatal cavity, driving water inward.

Which of the above statements are correct?

Consider the surgical removal of tissue during a classic girdling experiment:

I. Girdling removes the outer bark of a tree trunk down to the depth of the vascular cambium and phloem.
II. In the weeks following the girdling, the root system is the first organ to show signs of starvation and death.
III. The portion of the bark situated directly above the girdled ring becomes visibly swollen due to the interruption of downward organic solute translocation.
IV. The continuous upward translocation of water and minerals in the xylem is immediately halted when the bark is girdled.

Which of the above statements are correct?

Examine the modern physiological view of solute transport within plant vascular tissues:

I. Material exchange never occurs between adjacent xylem and phloem conduits.
II. Chemical analysis of xylem exudate demonstrates that nitrogen is transported both as inorganic ions and organic forms like amino acids.
III. Phosphorus and sulfur are transported exclusively as inorganic ions within the xylem stream.
IV. The traditional concept of a strict functional division where xylem carries only inorganic nutrients and phloem carries only organic solutes is incorrect.

Which of the above statements are correct?

Analyze these statements concerning the translocation of plant growth regulators (hormones):

I. Hormones and other chemical stimuli are transported through vascular tissues in extremely massive quantities.
II. Polar or strictly unidirectional transport is exhibited by certain plant growth regulators from their site of synthesis.
III. Growth regulators are translocated over long distances solely through passive simple diffusion.
IV. In a flowering plant, there is a complex but highly orderly traffic of compounds moving in different directions.

Which of the above statements are correct?

Study the physical laws governing diffusion in different states of matter:

I. Diffusion is a rapid process in solids, allowing molecules to move several meters in a few minutes.
II. In plants, passive diffusion is the only physical mechanism available for gaseous movement within the plant body.
III. Diffusion is highly obvious in gaseous and liquid systems.
IV. For plant tissues, diffusion in solids rather than of solids is the more likely physical phenomenon.

Which of the above statements are correct?