ISA Tree Biology and Physiology 3

Question 1

What is the CODIT model and who developed it?

Accepted Answer

The Compartmentalization of Decay in Trees model, developed by Dr. Alex Shigo

Answer

A computer model for predicting tree growth, developed by the US Forest Service

Answer

A classification system for tree diseases, developed by the International Society of Arboriculture

Answer

A computer-based diagnostic tool for identifying insect pests

Question 2

What is the primary function of the vascular cambium in a tree?

Accepted Answer

Producing new xylem (wood) cells inward and phloem (inner bark) cells outward, enabling secondary growth

Answer

Storing food reserves during winter dormancy

Answer

Transporting water from roots to leaves

Answer

Protecting the tree from insect attack

Question 3

How do deciduous trees prepare for winter dormancy at the cellular level?

Accepted Answer

They increase sugar concentrations in cells, lower the freezing point of cytoplasm, and move water from cells to intercellular spaces where ice formation is less damaging

Answer

They produce antifreeze proteins that prevent all cell freezing

Answer

They completely dehydrate their tissues to eliminate any freezable water

Answer

They increase respiration rates to generate metabolic heat within tissues

Question 4

What is the cohesion-tension theory and what process does it explain?

Accepted Answer

How water moves from roots to the top of tall trees through continuous water columns in the xylem, driven by transpiration pull

Answer

How tree branches resist wind forces through flexible wood fibers

Answer

How roots absorb minerals from the soil through ion exchange

Answer

How phloem transports sugars from leaves to roots

Question 5

What is the difference between heartwood and sapwood in terms of function?

Accepted Answer

Sapwood is the physiologically active outer wood that conducts water and stores reserves; heartwood is the non-conducting inner wood that provides structural support

Answer

Heartwood is living tissue that stores food; sapwood is dead structural tissue

Answer

Heartwood conducts water faster than sapwood due to larger vessels

Answer

There is no functional difference; they differ only in color

Question 6

What role do auxins play in tree growth and development?

Accepted Answer

They regulate apical dominance, promote cell elongation, stimulate cambial activity, and influence root initiation

Answer

They promote root growth exclusively and have no effect on shoots

Answer

They are primarily responsible for leaf abscission in autumn

Answer

They function only as defense chemicals against herbivores