OldBasilisk

Phytochrome-mediated effects of near-ultraviolet radiation in the induction of flowering in etiolated Lemna paucicostata T-101, a short-day plant

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Takeshi Ohtani1 and Tadashi Kumagai1(1) Institute for Agricultural Research, Tohoku University, 980 Sendai, Japan


Received: 15 June 1980 Accepted: 14 September 1980
Abstract Induction of flowering of etiolated Lemna paucicostata Hegelm. T-101, a short-day plant, was inhibited by far-red (FR) or blue light (BL) applied at the beginning of a 72-h inductive dark period which was followed by two short days. In either case the inhibition was reversed by a subsequent exposure of the plants to near-ultraviolet radiation (NUV), with a peak of effectiveness near 380 nm. Inhibition by BL or FR and its reversion by NUV are repeatable, i.e., NUV is acting in these photoresponses like red light although with much lower effectiveness. Thus, it is considered that NUV acts through phytochrome and no specific BL and NUV photoreceptor is involved in photocontrol of floral induction on this plant.

Key words Flower formation - Lemna - Phytochrome - Ultraviolet (near)
Abbreviations BL blue light - FR far-red light - NUV near ultraviolet radiation - P red-absorbing form of phytochrome - Pfr far-red absorbing form of phytochrome - R red light

Planta Journal
Springer Berlin / Heidelberg
Volume 153, Number 6 / December, 1981
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If UV does not interrupt flowering & cancels out the effects of both blue and red light, UV should be administered at night, not under heat.

ioneyesus

The sun seems to agree...

OldBasilisk

There is only little light at night. But compared to daylight, the colour spectrum is shifted towards short, UV-wavelengths.

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Daily and circadian variation in survival from ultraviolet radiation in Chlamydomonas reinhardtii

During the day, organisms use a variety of strategies to protect themselves from deleterious ultraviolet (UV) wavelengths of sunlight. Among those strategies could be timing of UVsensitive cellular processes to occur at night to avoid UVinduced damage. We tested whether the unicellular alga Chlamydomonas reinhardtii uses this strategy by measuring the survival of cells following exposure to LTV radiation at different phases of the day. Chlamydomonas cells displayed a rhythm of survival from UV radiation where the most sensitive phases occurred during the end of the day and at the beginning of the night. This phase of sensitivity corresponds to the time of nuclear division. The rhythm continues in constant light indicating control by a circadian clock. The results presented here suggest a hypothesis of how circadian clocks may have evolved; a temporal program whereby light-sensitive processes are timed to avoid sunlight-induced damage would be advantageous and therefore selected.

the daily cycle of UV radiation may have created a selective pressure favoring the evolution of circadian clocks. This hypothesis dovetails with the recent discovery of a role for cryptochromes in circadian systems. Cryptochromes are pigmented photoreceptors that are involved in blue-light mediated photomorphogenesis (42) and photoperiodism (43) in plants. Cryptochromes share sequence homology to another blue-light activated protein, DNA photolyase, which uses blue-light energy to catalyze the photochemical reversal of pyrimidine dimerization caused by UV radiation (44).

Photochemistry and Photobiology, Jun 2000 by Nikaido, Selene S, Johnson, Carl Hirschie

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UV radiation from the atmosphere: Results of the MSU “Tatiana” satellite measurements
Abstract

In the space experiment a near visual UV radiation (NUV) from the Earth atmosphere was measured during the moon month. At moonless local nights the results of previous measurements are confirmed: NUV intensity is in limits of 3 × 107–108 photons/cm2 s sr. At the background of natural NUV light the light from big cities was registered. In a detector FOV (the corresponding diameter of the observed atmosphere area is 250 km) the brightest cities radiate NUV comparable with the natural level. At moon nights the NUV intensity depends on the moon phase, the moon local zenith angle and cloud cover. Monitoring of the average NUV intensity shows that only in 1/4 of the moon month the average intensity is over 109 photons/cm2 s sr. The method of digital oscilloscope was applied for searching and registering the short NUV flashes (from 1 to 10 ms). The trigger system selects the brightest flash in one satellite circulation. In the registered NUV flashes the energy radiating in the atmosphere in 1–10 ms is of the order of 1011–1013 erg. Those energetic flashes are found to be concentrated in the Earth equatorial region.

G.K. Garipova, B.A. Khrenova, , , M.I. Panasyuka, V.I. Tulupova, A.V. Shirokova, I.V. Yashina and H. Salazarb
aDepartment of Super High Energy Particles, D.V. Skobeltsyn Institute of Nuclear Physics, Moscow State University, Vorobjevy Gory 1, Moscow 119992, Russia
bDepartment of Physics and Mathematics of University of Puebla, Puebla, Mexico
Received 21 June 2005; revised 31 August 2005; accepted 6 September 2005. Available online 27 September 2005.
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ioneyesus

Hey thanks for the reply. But it still stands as a criticism:

these studies can show whatever they want. Remember though, there is no practice in theory and you'll never get sunburned at night.

We're not some unlimited resource university lab where we can check a pool of a hundred plants under six different UV timings and spectrums. Unless you have excessive resources (not many of us do) administer it during the day.

There is theory in practice, and that's been the practice.

OldBasilisk

Mostly just some info to stir the juices.

I decided to be a guinea pig in this, so I'm implementing UV treatment at night.
I'm running ~50+ microwatts/cm2 of UVB & 900+ uW/cm2 of UVA, and it hasn't seemed to affecting the flowering period yet. The plants are doing their thing.

ioneyesus

That's great!

Thanks for the info, please let us know how it goes.

You're using led's then, or which type?

old_greg

I'm planning to add UVB to my grow, just cycle it 12/12 with my HPS light. Will be glad to report what if any difference it makes..

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Freakshow68

I'll be running Uvb in my grow as well. I have a Reptisun 10.0 26 watt bulb, just for the record.

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snwbrdr

interesting, but honestly some of the best grows i have ever seen never used UVb supplement just MH(which i just found out contain a lil UVb)and HPS lights.

im curious though like everyone else.

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Current Grow journal!

OldBasilisk

Im not using LEDs, I'm using this bulb:
UV Lighting for Reptiles: Mercury Vapour Lamps

The 60w Externally ballasted. It's interchangeable with the 60watt Zoo version (much more powerful) but I wanted to start off just shy of overkill...

I will keep you all posted