How Leaves Breathe and Make Food

An article about how leaves breathe and how they make their own food. A fascinating insight by gardener, herbalist, and aromatherapist Sharon Falsetto Chapman.

Leaves are vital to a plant’s existence and come in many shapes and sizes; they have one of the most important functions, that of producing food for the plant. Many essential oils and hydrosols are extracted from leaves, so it is important that an aromatherapist understands the nature and function of this vital plant part, to grasp a better understanding of where oils and hydrosols originate from.

The majority of plants are capable of making their own food, an ability which animals and humans do not have; leaves are vital to this process. Food is produced in a plant by a simple process called photosynthesis, the act of collecting energy from light and converting it to chemical energy. This energy is then stored in the bonds of sugar; sugar helps the plant to live and grow.

How a Leaf Makes Food

The leaf captures the energy from light with the help of chlorophyll, a green pigment in the plant; chlorophyll looks green to the human eye because it absorbs the red and blue light wavelengths and reflects the green. As the green light is not absorbed by the plant and the red and blue light is, it is actually the red and blue light, which is used in photosynthesis, even though the leaf appears green.

The process of photosynthesis involves the addition of water and carbon dioxide, but it is the captured light which is important in converting the energy to chemical energy. The chemical energy is stored within the leaf in the sugars, the bonding of the chemicals to the sugars results in a similar molecule to the building blocks of human DNA. Photosynthesis takes place in the chloroplasts of the leaf.

How Leaves Breathe

A plant is a living thing and as such needs to breathe; a leaf has minute slits like a mouth which are called stomata (single stoma), a name derived from the Greek word for mouths.  The stomata can be found on the underside of a leaf and allow water vapor and gases to pass in and out of the leaf.

The rate at which a plant loses water is controlled by the stomata, a process called transpiration. Air enters the plant through the stomata, thus allowing it to breathe; the air contains carbon dioxide which is used in the photosynthesis process. Oxygen, as a by-product of photosynthesis, is dispersed from the leaf through the stomata.

How Desert Plants Differ

Certain species of plants, in particular desert plants, open their stomata at night, not during the day. These plants belong to a group known as the CAM plants (Crassulacean Acid Metabolism, after the plant family Crassulaceae); water evaporates more slowly in the cooler desert night than throughout a hot, dry desert day when a plant needs to conserve its water. The following day, carbon dioxide is released when the stomata are once again closed. Plants which do this include cacti and pineapple.

Leaf Features

Leaves come in various shapes and sizes. Some leaves possess special features; cacti leaves, for example, need to conserve water from a hot, dry climate and have narrow spines to do this.  Plants in strong sunlight and situated in high mountains have furry leaves to protect them.

Water plants have thick, waxy leaves, which water easily runs off, and prevents the plant from being overcome by water, such as those in rain forests. Deciduous trees lose their leaves in fall whereas evergreens do not.

Leaves in Aromatherapy

A leaf is without doubt an important part of a plant, from how leaves breathe and make food, to their importance in herbalism and aromat. Some essential oils which are extracted from leaves include many from the Lamiaceae plant family such as sage (Salvia officinalis), melissa (Melissa officinalis) and peppermint (Mentha × piperita). Many of the evergreen trees, such as pine (Pinus sylvestris) and black spruce (Picea mariana), are also extracted for essential oils and hydrosols.

If you enjoyed this article and would like to learn more, including how leaves breathe and make food, enroll in our Certificate in Community Aromatherapy Program and discover how plants can heal us on a daily basis!

About the Author:

The author of this article has been working in the health care industry since the 1990’s and in the aromatherapy industry since the 2000’s. She is UK-certified aromatherapist, a NAHA Certified Professional Aromatherapist®, a gardener, and a certified herbalist with several years of study. She is also a botanical perfumer, working on launching her first fragrance line.

Sharon is both a published author and editor in aromatherapy, a consultant, and custom blend formulator. She is the author of Authentic Aromatherapy and the current chief editor of the NAHA Aromatherapy Journal. Sharon works from her garden studio in Sedona, Arizona, where she gardens and distills plants from her own aromatic gardens, surrounded by natural fauna and flora on an original pioneer homestead property.