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Lights, darkness and flowering. What's the story?

in Beginners Starting out Mon Nov 25, 2013 12:50 am
by ozzydiodude • The Weird One | 2.453 Posts | 11438 Points

Lights, darkness and flowering. What's the story?
When light within a certain spectrum hits the surface of the plants chlorophyll receptors, it prompts a hormone called florigen to be produced.

Another hormone named antiflorigen is produced by flowering plants. The ratio between these two hormones is what causes a plant to flower or not.

In the plants leaves, another chemical named phytochrome that is necessary to react with florigen to produce flowers.

When the phytochrome within the leaves of a plant receive a duration of light that would be considered "short day light" by that exact plant, then the antiflorigen is repressed and the florigen is increased, thus causing the plant to start flowering.

If the duration of light of correct spectrum and intensity is interrupted from a "short day", anywhere within the "dark cycle", it causes the plant to again start producing antiflorigen. The ratio between the florigen and antiflorigen is altered and flowering will decrease or stop.

This switch between ratios of florigen and antiflorigen is stressful to the plant and can cause a sexual reversal from female to male or male to female.

The result in this light hormonal stress is usually seen as Hermaphrodites. The entire plant doesn't change sex, only part of it. It will be the part of the plant that has the largest response to the florigen/antiflorigen ratio alteration.

All flowering plants use this exact system of hormones and ratios in regard to flowering.

The amount of phytochrome within the leaves of a plant determine it's reaction to light. Some plants have more, some less. The health of the plant, nutrients and humidity all are factors that determine how much phytochrome exists.

If you take all of this information and relate it to each of your plants, you'll see that in regards to light interrupting a darkness cycle, many factors come into play.

Brief interruptions of low intensity may not be sufficient to cause the florigen/antiflorigen ratio to change enough to change the plants flowering in any visible way. It can however, cause a slowing of flower growth.

The best way to not affect this ratio of florigen/antiflorigen is to leave the flowering room completely dark for the entire darkness cycle. This makes it foolproof.

Any light of sufficient strength to be "seen" by the phytochrome receptors in the leaf will have an effect on the flowering.

Low light levels of the green spectrum may be low enough to NOT be received by the phytochrome receptors in any appreciable amount that would cause a negative alteration of the ratio between the florigen and antiflorigen.

If you have a plant that doesn't react to low level green light, then you've found a winner in the pot growing family. Of course, it may be slowing the flowering to a degree without you noticing without another test group to observe.

Here is a very good article about this subject from Botany Online:

Photoperiodism and Stimulation of Flowering


Let's help each other, by spreading our knowledge of the plants we love
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