Question

question 43 (1 point)
what role do guard cells have in plants?
o a they store food for the embryo
o b they protect against insects that eat plants
o c they transport oxygen through the plant
o d they control the size of stomata

question 44 (2 points)
which adaptation helps reduce water loss in terrestrial plants? select all that apply
o a cuticle
o b flowers
o c phloem
o d guard cells
o e cells that perform photosynthesis

Explanation:

• Question 43: Guard cells are specialized cells in plant leaves. Their main function is to regulate the opening and closing of stomata (pores on the leaf surface). By changing their shape (due to turgor pressure changes), they control the size of stomata. This is crucial for gas exchange (e.g., intake of \(CO_2\) for photosynthesis and release of \(O_2\)) and water - vapor loss (transpiration).
• Option a: Storing food for the embryo is typically the role of structures like cotyledons (in seeds), not guard cells.
• Option b: Protection against insects is more related to structures like thorns, trichomes, or chemical defenses (e.g., secondary metabolites), not guard cells.
• Option c: Transport of oxygen (and other substances like water and nutrients) through the plant is mainly the function of vascular tissues (xylem and phloem), not guard cells.
• Question 44:
• Cuticle: It is a waxy layer on the surface of leaves (and other aerial plant parts). This waxy layer acts as a barrier, reducing the rate of water loss through evaporation from the plant surface.
• Guard Cells: As explained in question 43, by controlling the size of stomata, they can limit the amount of water vapor that escapes from the plant during times when water conservation is necessary (e.g., in dry conditions). When stomata are closed (due to guard - cell action), water loss via transpiration is reduced.
• Phloem: Its main function is to transport organic compounds (e.g., sugars produced during photosynthesis) throughout the plant. It has no direct role in reducing water loss.
• Flowers: Their primary functions are related to reproduction (e.g., attracting pollinators, housing reproductive organs). They do not play a role in reducing water loss in the context of the whole plant's water - conservation mechanisms.
• Cells that perform photosynthesis: Their main function is to convert light energy into chemical energy (sugars) using \(CO_2\) and water. While they use water in photosynthesis, they do not have a direct role in reducing water loss from the plant.

Answer:

• Question 43: d. They control the size of stomata
• Question 44: a. Cuticle, d. Guard Cells