Various interesting links about lighting.

[DavidCampen]

Originally Posted by isurus79

Finally, why did Philips compare their LED systems to T8 bulbs which are old technology and are less efficient than T5s? To me it seems that Philips is trying to bolster their product against a technologically less advanced version of the same product (ie. T8 vs. T5 bulb technology). Am I off base with this assumption?

I believe that T8 and T5 bulbs are comparable in efficiency. T8 may even be a bit more efficient than T5. This will also depend on operating temperature; IIRC, for T5 lamps the optimum operating temperature is a bit higher than that for T8 lamps. I use T5 fixtures because they are more compact than T8 for a given amount of light, not because of any difference in efficiency.

My purpose for using far red (>700 nm) would be to simulate long nights (by rapidly converting Phytochrome-FR to Phytochrome-R) so that short-day plants will bloom even though the lights stay long enough that they otherwise would not bloom. The increase in plant mass report is just something I stumbled across and was not my motivation for considering far red. For artificially creating long nights I would use a short period of far red at the end of the lighting period.

Most LED fixtures that use red LEDs, unless they specifically mention far red at > 700 nm, are likely using LEDs that emit at 620-660 nm

[isurus79]

Originally Posted by DavidCampen

I believe that T8 and T5 bulbs are comparable in efficiency. T8 may even be a bit more efficient than T5. This will also depend on operating temperature; IIRC, for T5 lamps the optimum operating temperature is a bit higher than that for T8 lamps. I use T5 fixtures because they are more compact than T8 for a given amount of light, not because of any difference in efficiency.

My purpose for using far red (>700 nm) would be to simulate long nights (by rapidly converting Phytochrome-FR to Phytochrome-R) so that short-day plants will bloom even though the lights stay long enough that they otherwise would not bloom. The increase in plant mass report is just something I stumbled across and was not my motivation for considering far red. For artificially creating long nights I would use a short period of far red at the end of the lighting period.

Most LED fixtures that use red LEDs, unless they specifically mention far red at > 700 nm, are likely using LEDs that emit at 620-660 nm

Great, thanks for the info!

So can you use the artificially long nights method only on more temperate plants then? I would imagine that this technique would be less effective on plants with traditionally equatorial habitats.

[DavidCampen]

Originally Posted by isurus79

So can you use the artificially long nights method only on more temperate plants then? I would imagine that this technique would be less effective on plants with traditionally equatorial habitats.

Yes, I would expect that a plant that grows at the equator would not be day length sensitive. It is known though that the flowering of some cattleyas responds to daylength. I believe that Chadwick, in his book "The Classic Cattleyas", mentions that cattleya cut flower growers, back in the day when cattleya corsages were popular, would make use of daylength manipulation to control flowering of certain cattleya species. Withner in "The Cattleyas And Their Relatives, Volume 1" also makes passing reference to daylength sensitivity of _some_ cattleyas.