Transcriptomic analysis of CDL-gated photoperiodic flowering mechanisms in cannabis and their responsiveness to R: FR ratios in controlled environment agriculture

Ashley Manning
May 29
2 min read

Authors: Samuel R. Haiden, Nathan Johnson & Gerald A. Berkowitz

What this research is about (simplified):

Transcriptomic analysis means they looked at the cannabis plant’s genes and how they are turned on or off (gene expression) during flowering.
CDL-gated photoperiodic flowering means the study focuses on how the Critical Day Length (CDL) the exact amount of daylight needed controls when cannabis plants start flowering.
They also studied how the plants respond to Red to Far-Red light ratios (R:FR) different types of light wavelengths that affect flowering signals.
All this was done in (CEA) controlled environment agriculture, like indoor growing with precise light and environment controls.

Summary & Key Findings

This research studied how cannabis plants decide when to start flowering based on day length and light quality. They looked at the plant’s genes (transcriptomics) to see how flowering is triggered by the Critical Day Length (CDL) the specific amount of daylight needed and how the ratio of red to far-red light (R:FR) influences this process.

What you need to know as a grower:

Cannabis plants sense when days get shorter (or nights get longer) to start flowering.
Flowering is controlled by certain genes that turn on or off at the right time.
The balance of red light and far-red light affects how the plant perceives day length and when it flowers.
By adjusting both the length of light exposure and the red:far-red light ratio, you can control when your plants flower more precisely.
This knowledge helps you optimize flowering time and yields, especially indoors where you control the light environment.

Implementation Steps for Your Grow

1. Understand Your Strain’s Critical Day Length (CDL)

Learn or test how many hours of light your cannabis strain needs before it switches to flowering.
For many strains, flowering starts when day length falls below about 12-14 hours, but it varies.

2. Control Light Duration

Use timers to set consistent light schedules.
When ready to flower, reduce light hours to the strain’s CDL or less (typically 12 hours light / 12 hours dark).
Keep dark periods completely uninterrupted for best results.

3. Adjust Red to Far-Red Light Ratio (R:FR)

Use LED or grow lights that allow you to tweak the red and far-red light levels.
Increasing far-red light (or lowering R:FR ratio) during the day or at the end of light cycles can encourage earlier flowering.
Conversely, higher red light (higher R:FR ratio) can delay flowering or promote vegetative growth.

4. Monitor Plant Response

Watch for early signs of flowering like pistil formation.
Adjust light quality or duration slightly if flowering is too slow or too fast.

5. Optimize for Yield and Quality

Use this precise control over flowering to time harvests better.
Experiment with light spectra for your specific strain to maximize bud development and cannabinoid profiles.

6. Consider Breeding or Selecting Strains Based on Flowering Traits

Use knowledge about genes controlling flowering to choose strains that fit your grow environment.
Breeding for strains that respond well to your light setup can improve consistency and performance.

In short:By managing how long your plants get light and the color spectrum of that light (especially red and far-red), you can take charge of when your cannabis flowers, helping you grow better, faster, and more predictably.