LED Lights for Improved Conifer Growth

By Website Editor

Find out about the illuminating discoveries of blue light on conifer growth.

The light table
The light table

The new propagation model at Hidden Lake Gardens continues to be quite an illuminating experience, in every sense of the word. With 2017 behind us and 2018 chilling us with its winter winds, we have discovered new questions about plant propagation. We are diving into an expansion of our original model, feeling some trepidation and even some fear of failure. In order to succeed, our quest is to put together the missing pieces; it is much like seeing the pieces of a jigsaw puzzle spread out before us and then solving the puzzle. The pieces of information are there. They just await discovery.

Leonardo da Vinci had once said: “It had long since come to my attention that people of accomplishment rarely sat back and let things happen to them. They went out and happened to things.” Over the years, I have begun to grapple with the molecular machinery of conifers. A conifer is so finely tuned down to the quantum level that, first and foremost, we must allow ourselves to experience the awe and wonder of what has been created and also what is hidden from eyesight. The more we work at it, the more, piece by piece, the puzzle begins to reveal itself.

Light3

Our sun is by far the largest object in our solar system. As we gaze into the sky, we should marvel at its splendor and life-giving energy. Without the sun, all life on earth would cease to exist. It is often said that the sun is an ordinary star; however, for our earth and our existence, it is anything but ordinary!

The sun’s light, which is an electromagnetic spectrum, takes exactly eight seconds as both a particle and wave to travel 93 million miles to reach earth. In a stream of constant photons, the spectrum of the sun’s light envelops the earth day after day. Sunlight consists of 50% infrared, 40% visible, and 10% ultraviolet light. As a vital source of energy, sunlight is one of the factors that significantly influences the development of plants.

Theophrastus, a 300 BCE Greek native of Athens, was the successor to Aristotle and is considered to be the father of botany. Many of his words are still valid today. He said: “We must consider the distinctive character and the general nature of plants from the point of view of the morphology, their behavior under external condition, their mode of generation, and the whole course of their life.”

So why the blue wavelength?

Jon Genereaux and his new light table
Jon Genereaux and his new light table

Conifers and its Propagation with LED

Conifers acquire and use the electromagnetic radiation from millions of miles away to carry out various functions of life in complex reactions in every cell. Conifer needles convert photons of light energy in their chloroplast-absorbing wavelengths of light to stimulate the electron transport chain. When sunlight strikes the chlorophyll molecule, the energy excites the electrons passing from one molecule to the next, doing the necessary work of life.

In common nursery practice, we propagate conifer species vegetatively. Propagations of these cuttings are generally performed during winter months after a minimum of 350 hours of vernalization (cooling). I have found that these woody cuttings do not thrive well in light values that are too low; they lose carbohydrates, especially glucose, too quickly, and also lose auxin before many can produce a sufficient number of roots to survive.

Light-emitting diodes (LED) are changing the future of propagation at Hidden Lake Gardens. The complicated nature of light has brought innovation in artificial lighting which has created sufficient irradiance to the root growth chamber, which we like to call the “photon molecular chamber."

Plants absorb certain wavelengths of light. Photosynthesis is fueled by blue and red wavelengths of visible light, 450 nm blue and 660 nm red. This is where photomorphogenesis begins and cellular expansion promotes stem cells to become root cells and produce roots where none existed before at an accelerated rate.

The sneak peak shot of the light table
The sneak peak shot of the light table

Using LED to Induce Early Growth in Conifers

As I wrote in the Fall Conifer Quarterly article, the purpose of this propagation experiment at Hidden Lake Gardens was to induce cellular division to initiate root primordia, callus, and new roots within 30 days. We succeeded on day 21! The pigment cryptochrome is sensitive to the ratio blue. Blue light acts as an environmental sensor.

Under predominately blue light only, we are turning on a switch to make molecular changes to produce root primordia at the earliest stages of development. By introducing carbon dioxide gas, we keep the stomata open to allow carbon and oxygen to enter into the cuttings, in order then to drive the nonphotosynthetic cells to produce auxin.

Our recent experiment at Hidden Lake Gardens has shown real promise, and I have not formed my opinion totally, as of yet, because we are still learning, and our knowledge is not complete. However, this is a new season. We have begun a journey to find the optimal illumination and then to set in motion, with cutting edge ideas, all with a childlike sense of wonder. The truth is, they’re just beyond our reach, awaiting discovery.

Text and photographs by Jon Genereaux.

This article was originally published in the Winter 2018 issue of Conifer Quarterly. Join the American Conifer Society to access our extensive library of conifer-related articles and connect to a nationwide group of plant lovers! Become a member for only $40 a year and get discounts with our growing list of participating nurseries in our Nursery Discount Program.

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