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Reborn Dandelion Quadriptych

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#1 Mark

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Posted 16 March 2017 - 01:10

Back in January I took a business trip overseas. I was away for just over three weeks, during which time my dandelion dried up and died. Although just before leaving I did attempt a last minute watering scheme to keep my dandelion alive in my absence, it wasn't enough. Upon my return I found the brittle, dried leaves of a plant that deserved better.

Considering how hardy dandelions are - seemingly impossible to get rid of otherwise - I decided to soak the soil, and proceeded to keep it moist for days. Days which turned to weeks. Then, one morning I noticed a small green leaf reaching up from the carcass of the plant I had slain. Success! After much waiting, it had managed to come back to life.

At this point it seems to be doing quite well and on its way to full recovery. Though I have noticed it just isn't its old self. Something is different. Its leaves are no longer broad, but rather slim and spiky. It seems to have a bad attitude, and I don't blame it. Maybe I can flatter it with a photo shoot...

Here it is, smaller still than when I first posted it back in December (http://www.ultraviol...__fromsearch__1):
(clockwise from top left = VIS, UVIVF, UV, IR)
Attached Image: 03-14-2017_19-42-32.jpg

I hope it soon returns to its former, fuller, healthy self. More to the point, I hope it blooms soon! I've been waiting all winter for a shot of this target! (the flower head)

Camera
- Nikon D750 [broadband] + 78 mm quartz lens + 12 mm extension tube
Lens filters

- VIS: 425 nM longpass + GG435 longpass + KolariVision IR-block stack
- UVIVF: 2" Baader UV/IR block
- UV: Asahi ZRR0340
- IR: 1000nm longpass + XNite830 stack

Illumination/Irradiation
- VIS & IR: Sigma EF-500 DG super

- UV & UVIVF: 4x18" T8BL-B + FL-02 glass

#2 Andrea B.

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Posted 17 March 2017 - 01:06

I'm happy to see the Dandelion is back in business!
Maybe those are its mature leaves and it's ready to bloom?
Andrea G. Blum
Often found hanging out with flowers & bees.

#3 aphalo

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Posted 17 March 2017 - 02:43

Very interesting! It is known that such changes in leaf shape in Dandelion can be induced by the light spectrum in the growth environment. This kind of narrow leaves with deep teeth can be induced by a high red:far-red ratio in the growth environment (a cue of absence of nearby vegetation) and almost entire blades with low red:far-red photon ratio (a cue of shade or nearby green plants). The usual interpretation is that the "sun leaves", similar to those in your recovering plant are "better" in a dry and hot environment as cooling is more effective because of the different aerodynamic properties. However the induction of such a change in morphology by drought itself is a phenomenon I haven't earlier been aware of. This is interesting indeed!

#4 nfoto

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Posted 17 March 2017 - 12:24

Also quite depressing news to those eager taxonomists describing new 'micro'species of Taraxacum based amongst other criteria, the leaf shape :D
Bjørn Birna Rørslett

#5 Andrea B.

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Posted 17 March 2017 - 15:49

The leaf shape varies so widely! And it is different the first year while still in non-blooming rosette form.
Andrea G. Blum
Often found hanging out with flowers & bees.

#6 Mark

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Posted 17 March 2017 - 20:48

That red:far-red ratio effect is interesting. Consider, I initially took this dandelion in near the end of last summer, from an open/unshaded area in my yard. I now have it under an LED grow light which consists of nine red LEDs and three blue LEDs. I'm not sure how to relate this lighting to the high-red:far-red ratio, since its basically just red (and a little blue).

#7 aphalo

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Posted 18 March 2017 - 04:21

R:FR photon ratio in direct sunlight is about 1.15, in shade it can be less than 0.1, a blue + red LED is likely to give a ratio of 20 or more depending on other light sources in the room/window. The response is not linear so the effect going from 1.15 to >20 or so usually is not very large. The R:FR before darkness can be decisive in some cases. In recent years some sort of consensus has developed recognising a role of green light in plant morphogenesis, but different species seem to respond quite differently. In some cases it has been shown that a high blue:green ratio is a cue of open space/no shade. I do not know of any studies on the effect of green light or lack of it on dandelion.

I looked up the old papers I had in mind in relation to R:FR.

Sánchez, R. A.
Some observations about the effect of light on the leaf shape in Taraxacum officinale L
Mededelingen Landbouwhogeschool, Wageningen, 1967, 67, 1-11


Sánchez, R. A.
Phytochrome involvement in the control of leaf shape of Taraxacum officinale L
Experientia, 1971, 27, 1234-1237


Sánchez, R. A. & Cogliatti, D.
The interaction between phytochrome and white light irradiance in the control of leaf shape in Taraxacum officinale
Botanical Gazette, 1975, 136, 281-285


However, as Andrea wrote above, light spectrum is only one of many things that controls leaf shape in these species (seeds are mostly by apomixis). Over the years Taraxacum officinale has been split into different species, so I am not sure if the species used in these papers would nowadays be called Taraxacum officinale.