ISA Certified Arborist Exam- Updated
Question and Answers [100% Correct]
2025/2026
What is the main pigment responsible for the green coloration in plant leaves, and what role does it play
in photosynthesis?
Chlorophyll is the primary pigment that gives leaves their green color. It plays a crucial role in
capturing light energy, which is then used during photosynthesis to convert carbon dioxide and water
into glucose and oxygen.
How does transpiration affect plants, and what specific process occurs through this phenomenon?
Transpiration is the process through which water vapor is lost from a plant's leaves and stems,
primarily through small openings called stomata. This process is essential for cooling the plant,
transporting nutrients, and maintaining water flow from roots to leaves.
What structure serves as the protective layer for the branches and trunk of a tree, and what functions
does it perform?
The bark serves as the protective layer for branches and the trunk of a tree. It shields the tree
from injury, helps prevent water loss, and defends against pests and diseases.
Describe the growth orientation found in trees with excurrent growth patterns, and how does it differ
from other types?
Excurrent growth refers to a tree's growth pattern where a central leader (main stem) dominates,
resulting in a conical or pyramidal shape. This is often observed in conifers. It contrasts with decurrent
growth, where multiple branches compete for dominance, leading to a rounder canopy.
Explain what the acronym M.A.D.HORSE represents and its relevance in botany.
M.A.D.HORSE stands for Maple, Ash, Dogwood, and Horsechestnut, which are trees with an
opposite leaf arrangement, meaning their leaves grow directly across from each other on the stem,
rather than alternating.
What does the pH scale measure, and how is it relevant to plant growth?
1
, The pH scale measures the acidity or alkalinity of a substance, ranging from 0 to 14. A pH below 7
indicates an acidic substance, a pH above 7 is alkaline, and a pH of 7 is neutral. For plants, soil pH
influences nutrient availability and root health, affecting their overall growth and vitality.
What is the characteristic growth form of trees exhibiting decurrent growth, and how does it benefit the
tree's structure?
Trees with decurrent growth exhibit a rounded or broader canopy shape due to the presence of
multiple dominant branches. This structure allows for more sunlight capture, increased leaf area, and
stability against wind.
Why are some trees described as deciduous, and what adaptive function does this serve?
Deciduous trees are those that lose their leaves in the fall. This adaptation helps conserve water
and energy during the winter months when temperatures and sunlight are lower, allowing the tree to
survive in challenging conditions.
What role does respiration play in plants, and how does it support their survival?
Respiration is the metabolic process by which plants convert stored food (glucose) into usable
energy. This occurs continuously, supplying the energy necessary for growth, reproduction, and repair of
plant tissues.
What is the function of stomata in plant leaves, and how do they contribute to water regulation?
Stomata are small openings on the surface of leaves that can open and close to regulate the
exchange of gases and water vapor. They play a critical role in photosynthesis by allowing carbon dioxide
to enter and oxygen to leave while controlling water loss through transpiration.
How does the xylem function in water and nutrient transport within a tree?
The xylem is a specialized tissue responsible for transporting water and dissolved minerals from
the roots throughout the tree. This upward movement of water is vital for nutrient distribution,
structural support, and overall plant health.
What role does the phloem play in a plant's nutrient transport system?
The phloem conducts carbohydrates, such as sugars produced during photosynthesis, from the
leaves to other parts of the plant, providing energy for growth and repair.
2
