IB Biology HL B3.1.7 Leaf Gas Exchange Adaptations Questions

Explore how stomata and guard cells regulate gas diffusion while mesophyll air spaces, veins and the cuticle balance photosynthesis with water conservation in IB Biology HL B3.1.7.

Exam points

Explain how stomata and guard-cell turgor control diffusion of carbon dioxide, oxygen and water vapour.
Use daily stomatal-opening patterns to infer plant adaptation to water loss or desert conditions.
Relate mesophyll air spaces, veins and the waxy cuticle to gas diffusion while limiting water loss.

[Maximum number: 2]

The micrograph shows part of a lilac (Syringa vulgaris) leaf in vertical section.

Figure for Question IB Biology HL B3.1.7 Leaf Gas Exchange Adaptations Questions question 1 — IB Biology HL

Explain the roles of two leaf structures that help with the process of gas exchange in the leaf.

a. spongy mesophyll provides a large/moist/permeable surface area (for gas exchange);
b. guard cells form pores/stomata (through the epidermis) / open and close stomata OR stomata are pores (through the epidermis that) allow $\mathrm{CO}_{2} / \mathrm{O}_{2} /$ gases to enter/exit the leaf/to pass through the epidermis;
c. (air) spaces for diffusion/movement/transfer of gases (to/from spongy mesophyll cells and stomata);
2 max

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IB Biology HL B3.1.7 Leaf Gas Exchange Adaptations Questions question 1