Reducing stretch with DIF technique

[obliterated]

Hi guys,

Some people are always looking to reduce their "stretch" period of flower.
Extra light, light spectrum, lowered N levels etc. and sometimes even pgrs...

Just stumbled upon this article the other night... thought it may add good food for thought/discussion on the viability of this technique
 

 

DIF

DIF Temperature Control By now most growers have heard of the DIF technique of temperature control developed by Dr. Royal Heins and colleagues at Michigan State University. In fact, some growers in our area are using some form of DIF on a regular basis. DIF is defined as the difference between day temperature (DT) and night temperature (NT). Stem elongation is promoted by warmer days than nights (+ DIF) and inhibited by warmer nights than days (- DIF). Plants become taller as DIF becomes more positive and plants become shorter as DIF becomes smaller or more negative.

Significant height control and reduction in PGR use is possible by reducing the difference between DT and NT as much as possible. Another approach to using DIF is the "cool morning pulse." A cool morning pulse is created by reducing the greenhouse temperature 5-10 F lower than the NT for 2- 3 hours at dawn. This approach reduces plant height as much as a negative DIF and may be the most easy DIF treatment to make.

DIF seems to be effective on most greenhouse plants, but research continues with many different species. Some responsive and non-responsive species are listed in Table 1. DIF, like a PGR, has its greatest effect on height during the period of most rapid stem elongation. DIF does not have to be applied continuously throughout a crop cycle to be effective, but rather only during the period of most active vegetative growth.

And the full article which you should also read...

http://extension.umass.edu/floriculture/fact-sheets/controlling-plant-height-without-chemicals

A cold blast for 2hr upon lights on....?

What are your thoughts...?

Peace!

 

[Frank Reynolds]

I know, it is a method with seedling production to elongate/keep them squat, I'm not sure how widespread its use is within the nursery industry.

 

in regards to nutrition and stretch, plants will need lots of N, drop that phosphorus!!!

 

Otherwise, in reality geneics have a big role, picking the right genetics for your space is king

[obliterated]

Funny you speak of nutients and their relation to gillberins
Not related directly to DIF, but an abstract from a paper I was also reading:

 

 

Inhibition of gibberellin biosynthesis by nitrate Abstract 

Gibberellin production in Gibberella fujikuroi starts upon exhaustion of the nitrogen source. To determine the role of nitrate and ammonium in the regulation of gibberellin biosynthesis we have isolated mutants that cannot use nitrate as a nitrogen source. Nitrate inhibited partially the production of gibberellins in mutants devoid of nitrate reductase activity. The inhibition occurred whether nitrate was added before or after the onset of gibberellin production. Addition of tungstate to the wild type mimicked the results with nitrate reductase mutants. We conclude that nitrate inhibits gibberellin biosynthesis by itself, independently of the intracellular signal that conveys nitrogen availability.

 

I enjoy looking into other aspects of a plants cycle other than "getting massive budz"
Peace!

[nibbler909]

Interesting how the difference between red and far red light induces such physiological changes. So does this mean its the far red light that we can't see in a hps causes the stretch, and I wonder what using a far red filter would do?