germination photoeffects
- To: "Propagation List"
- Subject: germination photoeffects
- From: M* S*
- Date: Thu, 11 Nov 1999 10:19:30 +0100
Thought this might be interesting:
Under natural conditions fresh Lactuca (lettuce) seeds need light to
germinate,
however there are techniques you can use to overcome these photoeffects and
germinate lettuce seeds in the dark - most commercial lettuce seed will
have been dry stored (this helps - fresh lettuce seed will not germinate in
the dark - dry storage removes the inhibition to germinate) a cold
pretreatment of 3 months in the fridge is also encouraging. GA-3
(gibberellic acid) treatment will often take away the need for light.
It will probably be found that lettuce seeds will germinate better at
different temperatures depending on the light.
The type of light is also important green plants are green because the
chlorophyll absorbs most of the red light and reflects most of the
blue/yellow light.
Allied with the chlorophyll is "Phytochrome" which detects information about
the plant's light environment.
Phytochrome exists in 2 main forms, one sensitive to red light (known as the
active form - "Pfr") and one to "far-red" light (the inactive form - "Pr").
Normal unfiltered sunlight is considered to have the balanced proportions of
red:far-red needed to encourage the active Phytochrome Pfr (and therefore
growth).
The filtered light underneath plants is more green (most of the red having
been absorbed by leaves) and there is also a higher proportion of the
"far-red" light - promoting the inactive Phytochrome Pr and repressing
growth.
Best wishes,
Matthew Sleigh
B & T World Seeds
Paguignan
34210 Olonzac
France
fax:00 33 4 68 91 30 39
ph: 00 33 4 68 91 29 63
m@b-and-t-world-seeds.com
http://b-and-t-world-seeds.com/
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