Certified Arborist Practice Test

Photosynthesis is the process that occurs in the leaves of trees and many other plants to produce food. During this process, chlorophyll in the leaves captures sunlight and uses it to transform carbon dioxide from the air and water absorbed by the roots into glucose, a type of sugar that serves as food for the plant. This process also releases oxygen into the atmosphere as a byproduct, which is essential for the survival of many living organisms.

In contrast, transpiration refers to the movement of water vapor from the inside of the leaves to the atmosphere, which regulates water levels in the plant but does not contribute to food production. Respiration is a process where plants convert glucose and oxygen into energy, which is essential for growth and metabolic functions but does not produce food. Decay is the breakdown of organic matter and does not relate to the food production processes of trees. Therefore, photosynthesis is the correct answer as it directly relates to how trees create their own food.