Biology and Physiology Flashcards

What is the primary function of lenticels on a tree's bark?

Answer: Gas exchange between inner tissues and atmosphere

Lenticels are porous openings in bark that allow oxygen and carbon dioxide to pass between the atmosphere and the living cells beneath.

Which vascular tissue is responsible for transporting sugars produced by photosynthesis downward through the tree?

Answer: Phloem

Phloem conducts photosynthates (sugars) from leaves to roots and other non-photosynthetic tissues through sieve tube elements.

In trees, what is the zone called where new xylem and phloem cells are produced?

Answer: Vascular cambium

The vascular cambium is the meristematic layer that divides to produce secondary xylem (wood) inward and secondary phloem outward.

What happens to a tree's stomata during periods of drought stress?

Answer: They close to reduce water loss

Guard cells lose turgor pressure during drought, causing stomata to close and reducing transpiration, though this also limits photosynthesis.

Which anatomical feature distinguishes hardwood (angiosperm) trees from softwood (gymnosperm) trees under a microscope?

Answer: Presence of vessels (pores)

Hardwoods contain vessels (large-diameter pores) for water conduction, while softwoods rely solely on tracheids for this function.

What is the primary role of mycorrhizal fungi in association with tree roots?

Answer: Extending root surface area for water and nutrient absorption

Mycorrhizal hyphae dramatically increase the absorptive surface area of roots, improving uptake of phosphorus, water, and other minerals.

What process describes water movement upward through xylem vessels driven by evaporation from leaves?

Answer: Transpiration-cohesion-tension

The transpiration-cohesion-tension mechanism uses evaporative pull at leaves, water's cohesive properties, and negative pressure to move water from roots to canopy.