A Deciduous Friendship (and the science of how leaves change their colour)
Hands down, autumn is my favourite season of the year. Although a harbinger of winter, fall is the time of cosy throw covers, warm fireplaces and the anticipation of holiday celebrations. As the last days of October transition into November, Toronto has a chill in the air, darkening early evenings, and spectacular landscapes painted with hues of orange, yellow and red.
On an early morning walk with Madeline (also known as #Writer’sBlock), I noticed that the trees had hit their peak in colour change, and many were dramatically shedding their colourful bounty, decorating the ground below. Marvelling at the colours, I realized how little I knew about why leaves change their colour.
I’m sure I must have learned it at some point during a university botany class, but as Madeline and I walked through the park, the details escaped me. I guessed it was the temperature change. Cold weather killing off the leaves made sense.
As I dug deeper into the science of autumn leaf transformation, I learned temperature was only part of the story. Surprisingly, my search for answers would also lead to an insight into a friendship that was troubling me.
There are two main types of trees: deciduous and coniferous. Deciduous trees have leaves that fall off yearly, while coniferous trees, such as the evergreens, have needles or scales that remain intact year-round.
I’d assumed the leaves changed colour as the temperature dropped when, in fact, it’s the gradual decrease in daylight that triggers molecular changes within the cells of the tree leaves. To survive, the tree uses photosynthesis to generate energy by harnessing sunlight to convert carbon dioxide in the air into a usable power source — sugars. In mammals, the power generators of the cell are mitochondria, while plants rely on spheroid structures called chloroplasts. If you were to put a plant leaf under the microscope, you would see thousands of oblong green discs embedded within each plant cell. The abundant chloroplasts are what gives the leaf its green colour, masking the true colour of the tree’s foliage.
Microscopic view of plant cells. Green = chloroplasts. Note hints of red in each cell, in fall this leaf likely turns red.
As the amount of sunlight decreases in the fall, the process of photosynthesis begins to fade, just like the leaves. Each year the leaves don’t actually change colour. Instead, the sunlight-reliant green colour from chloroplasts fades to reveal each deciduous tree’s unique natural pigments. The dazzling hues of yellow, orange and red were always there, the robust green colour of chlorophyll just overshadowed them.
As autumn approaches, without enough sunlight, the deciduous tree can no longer create the energy it needs to survive if it were to carry on, business as usual. Suddenly, the thousands of fading leaves on the tree’s branches are a massive energy liability.
Instead, to conserve and store energy to survive the winter months, the tree closes off the connection to the leaves in a process called abscission. A good gust of wind and the leaf spirals away into the breeze.
As I considered the tree’s struggle to conserve its energy by severing the connection to its leaves, I thought of a friendship that left me struggling. Over the years, the differences between my friend Joseph and I began to overshadow what we had in common. I’d gotten far too comfortable with his constant negativity, but when he returned to lying and deceitful behaviour, I made my decision. I didn't have the energy to keep Joseph in my life. Like the deciduous tree that cuts off the connection to its leaves in the dwindling autumn sunlight, I too needed to sever my connection to Joseph to save my own energy balance. For my mental well-being, I also needed to try a little abscission.
In shedding my friendship with Joseph, I realized I was no longer prepared to settle for a deciduous friendship.
I want evergreen friendships.
credits: Three trees: ©mirifadapt (via Adobe Stock); chloroplasts: ©tonaquatic (via Adobe Stock); diagram: generated using assets from ©sudowoodo and ©bokasana (via Adobe Stock); evergreens: ©Ioan Panaite (via Adobe Stock).