Far red lighting and inducing flowering

Hey ther RIU! Just came across two articles in particular that I thought I should share

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The relationship between red and far-red light on flowering of the long-day plant, Lemna gibba

1. Yoshio Ishiguri and
2. Yoshiharu Oda

+Author Affiliations

1. Institute for Agricultural Research, Tohoku University Sendai, Japan

• Received July 17, 1971.

Abstract
Lemna gibba, a long-day duckweed, can be induced to flower when the 10 hr white photoperiod is extended with red or far-red light. The 10 hr red photoperiod is also effective in inducing flowering when followed by a far-red extension, but a red extension is ineffective.

When 2 hr of far-red light are given immediately after the 10 hr red photoperiod, the following red as well as the far-red extension can induce flowering, indicating that the 2 hr far-red light plays an important role as a starting factor for induction. This red or far-red extension is effectively replaced by a red break given at a proper time in the darkness which follows the 2 hr far-red light as the starting factor. The effect of the red break in not cancelled by subsequent exposure to far-red, which synergistically promotes flowering.

However, a red break given immediately after a proper period of far-red extension further promotes flowering. The phase sensitive to the red break coincides with that sensitive to the red break given in darkness. The effect of the red break is reversed by subsequent exposure to far-red, contrary to the effect of the red break in darkness.

Using these results, relation between red and far-red light on flowering in L. gibba is discussed.
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AND....
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Plants use a phytochrome system to sense the level, intensity, duration, and color of environmental light to adjust their physiology.

LEARNING OBJECTIVE[ edit ]

• Explain the response of the phytochrome system to red/far-red light
  

• • Exposure to red light converts the chromoprotein to the functional, active form (Pfr), while darkness or exposure to far-red light converts the chromophore to the inactive form (Pr).
  • Plants grow toward sunlight because the red light from the sun converts the chromoprotein into the active form (Pfr), which triggers plant growth; plants in shade slow growth because the inactive form (Pr) is produced.
  • If seeds sense light using the phytochrome system, they will germinate.
  • Plants regulate photoperiodism by measuring the Pfr/Pr ratio at dawn, which then stimulates physiological processes such as flowering, setting winter buds, and vegetative growth.

• photoperiodism
  the growth, development and other responses of plants and animals according to the length of day and/or night
  
  
• phytochrome
  any of a class of pigments that control most photomorphogenic responses in higher plants
  
  
• chromophore
  the group of atoms in a molecule in which the electronic transition responsible for a given spectral band is located
  

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Interesting..

Not quite sure how they arrived at 2 hours. I've used far red for just a few minutes at end of day and successfully shortened flowering.

Little hard to follow, almost needs a visual aid to go with the reading..

^^^^ yes, agreed

HappyMan420 said:

Plants grow toward sunlight because the red light from the sun converts the chromoprotein into the active form (Pfr), which triggers plant growth; plants in shade slow growth because the inactive form (Pr) is produced.

Click to expand...

I thought it was the other way around. Plants in the shade grow more to get to where the light is and that is why far red promotes stretching?

,...cannabis is a short day plant, less light(12x12) means it flowers on the short days

Red light promotes node growth and flowering but not by itself. In shade, the ratio of far red to red light is increased because far red is transmitted through the leaf more than red light. The increase in far red promotes stem elongation to stretch the node into the light from the shade. Although stem elongation is growth, it is not node or flower growth. Red light as well as blue and far red all work together to help regulate growth, but not all growth is the same.