Understanding phytochrome, this biological receptor, makes it possible to fully exploit the potential of agricultural sciences adapted to cannabis
Phytochrome is a pigment found in the leaves of all plants, including cannabis. The role of this pigment is to detect light and then allow the plant to grow according to the season or the weather to induce flower production. When light hits the surface of a leaf, two types of light sensors are at work: one that detects blue light and the other red light. The one designed to detect red light is the phytochrome.
How does phytochrome work?
Depending on the intensity and type of light, the plant can trigger certain biological processes.
When a plant performs photosynthesis, a chain reaction occurs. The plant absorbs carbon dioxide and light and in turn produces sugars for food. Light is the biological signal for activating photosynthesis, and the way light is used can determine seed germination, stem elongation, chlorophyll synthesis, and flowering induction.
The phytochrome system consists of two parts, defined as Pr and Pfr. Understanding the wavelength needs of plants has been a topic lighting companies have been working on for years to find out how nature programs itself with a 24-hour body clock known as the circadian rhythm.
Phytochrome: Pr - Pfr
Phytochrome exists in two forms. The transition from one shape to another is caused by the perceived wavelength (photoreversibility):
- Pr (for " red ”): the inactive form, whose absorption maximum is located at 660 nm (red).
- Pfr (for " far red ”): the active form, whose absorption peak is located at 720 nm (far red).
Pr : Technically this wavelength of light is classified as red light and during this time red light changes phytochrome to its biologically active form. Plants that are dark green and usually with short internodal spaces are an expression of the Pr range used.
Pfr : It sounds complicated and what the relevance of each does can be difficult to understand, however the phytochrome Pfr is responsible for inducing flowering as it corresponds to the amount of light or shade available. Phytochrome plays a role in the control of gene expression and may cover factors of stem elongation, stomatal function, and light sensitivity in terms of flower production and plant metabolism.
The circadian rhythm
Just as humans, animals and fungi have a natural body clock, so do plants, and throughout the year they are dependent on specific lighting conditions. When growing cannabis, plants will react chemically to a period of reduction in light or darkness which can trigger hormones and induce pre-flowering, flowering and ultimately maturation of cannabis buds.
There may be consequences that can lead to genetic problems duringa change in the circadian rhythm and that is why cannabis plants use two types of phytochrome.
The light cycles used during the growing cycle usually vary from 16 to 18 hours of light and plants at this time will respond to periods of darkness or shade of 6 to 8 hours. Naturally, a cannabis plant growing outdoors will grow with narrow internodal spacing and can be trained to grow more in width than in height. When flowering is induced in a cannabis plant, it means that hormonal changes have occurred in the plant. Indoor cultivation can then be difficult. Receiving only 12 hours or less of light, the plant will respond to what it believes to be the change of seasons.
Studies have shown that the stretch period that growers experience when inducing flowering can be controlled and manipulated to allow the cannabis plant to stay shorter rather than grow taller. Research has shown that plants treated with far red light focus their energy on root development and growth.
By eliminating the need for the plant to stretch to the highest point, it can focus on vigor and the development of new shoots, stems and flower beds. Chlorophyll production will be higher, and therefore darker leaves will attract more sunlight than lighter green plants.
Blue light has a spectrum of 6400k, which is what plants need to grow well. This is a soft blue light that can be found in most types of fluorescent lighting.
The process of phytochrome can destroy plants by sending the wrong biological signals at the wrong time. These could be accidental mistakes, but they can cause enough stress and trauma for the plant to become hermaphroditic or experience serious metabolic and functional problems, especially if the circadian rhythm is disturbed.
By understanding the red light spectrum and the needs of plants, you will understand how the phytochrome system works to start the genetic clock in cannabis plants and better control it.
There is a fine balance between plant absorption, lighting and shade. The results and variables associated with this natural balance can vary the performance of the plant.