Too much fluorescent light?

[isurus79]

Originally Posted by DTEguy

I think I noticed stunted leaf span on a phal. and on my B. cucullata from very high light (don't have enough experience in growing to confirm that). If my observation is correct than perhaps the phals you saw have larger leaves from less than optimal light which equals to more storage to compensate (or actually more beneficial) for high photosynthetic rate in higher light?

You can burn the Phal pretty easily, but burning the B. cucullata is pretty hard to do.

Originally Posted by DTEguy

I had a B. nodosa about 2 feet away from the light but was turning very purple (about 1000fc for 14 hours).

Wow, that is some intense light!! Now I see why you were worried about the cucullata! lol

Originally Posted by DTEguy

I was also curious if too much anthocyanin would actually result in lower photosynthetic rate.

Alan Koch of Gold Country Orchids talked about this. He said that too much light can inhibit flowering, however when I grew my plants in Hawaii, many of them were in full sun all day and flowered very profusely. I think it really depends on the species.

[DTEguy]

Hi Steve,

Since Catts can take > 3000 fc, 1000 is still lower than the recommended the 42% guideline for constant light. Which actually makes me feel that there's something fishy about T5H0s --prolly has a biased-maxed out blue wavelength or something like that.

Originally Posted by isurus79

Alan Koch of Gold Country Orchids talked about this. He said that too much light can inhibit flowering, however when I grew my plants in Hawaii, many of them were in full sun all day and flowered very profusely. I think it really depends on the species.

Yeah I read and seen pictures of those purple Barney orchids in full sun and bloom their head off. I agree it's depending on species. The scientist in me wants to put an algorithm to it....but I now realize there is no shortcut and only ONE way to get better at this:


KILL MORE FRIGGIN ORCHIDS!!!



However, magnus brought up a very very good point, emergence of anthocyanin might not mean optimal light especially when it's from a sudden highlight shock.

Sorry for the many questions folks....I love learning new things . Many thanks again for the replies.

[isurus79]

Originally Posted by DTEguy

Hi Steve,

Since Catts can take > 3000 fc, 1000 is still lower than

Ahhhh!!!! I read 10000k!!

I figured that was why the nodosa turned purple!! No, 1000fc should not make your nodosa get dark unless it was suddenly thrust under the lights. You can see the same effect from new growths on Cattleya. Under high light (or even moderate light, depending on the species) new growths will come out red or purple and then turn green once they "harden." This is another way to see if your green Catt is getting enough light, even though the adult growths are green and not red/purple.

Honestly, I would just move the plants farther away or closer, depending on what you are growing. Or take out a bulb. That works to lower light levels as well!

[Magnus A]

Originally Posted by isurus79

Alan Koch of Gold Country Orchids talked about this. He said that too much light can inhibit flowering, however when I grew my plants in Hawaii, many of them were in full sun all day and flowered very profusely. I think it really depends on the species.

The filtering effect by anthocyanins of the wavelengths used by photosynthesis is not very significant. But at those light levels the photosystem II (PSII) has inhibit itself, and it is then it get really sensitive for light radiation damage.

The scientific explanation is that the proton gradient over the thylakoid membrane, where PSII is located, get to high after a while and prevent the possibility for PSII to use water as an electron source.(Water can no longer be converted to oxygen) This happen in the northern hemisphere pine forests at about 10-11 am during a normal summer day.

[DTEguy]

Originally Posted by Magnus A

The filtering effect by anthocyanins of the wavelengths used by photosynthesis is not very significant. But at those light levels the photosystem II (PSII) has inhibit itself, and it is then it get really sensitive for light radiation damage.

The scientific explanation is that the proton gradient over the thylakoid membrane, where PSII is located, get to high after a while and prevent the possibility for PSII to use water as an electron source.(Water can no longer be converted to oxygen) This happen in the northern hemisphere pine forests at about 10-11 am during a normal summer day.

I read that PSII system will be damaged regardless of the light intensity and is rapidly repaired. I was thinking even if the rate of damage is higher than rate of repair (in high light), the job is done and the photosynthesis yield would have been optimal (unless there are some irrerversible damage). However, photosynthesis rate was actually lower in a research on catts. in high light versus the one in intermediate light.

edit: Just read that excessive free radical oxygen from high light inhibit the repair mechanism. That makes sense now.

I guess the best thing to do is to use the reported fc as a guide and figure out that threshold. The tip that you gave me on how to observe the level of anthocyanin as you acclimatize it slowly will be very useful. Thanks.

---------- Post added at 12:21 AM ---------- Previous post was at 12:19 AM ----------

Originally Posted by isurus79

Under high light (or even moderate light, depending on the species) new growths will come out red or purple and then turn green once they "harden." This is another way to see if your green Catt is getting enough light, even though the adult growths are green and not red/purple.

Thanks for the tip!!

[Magnus A]

Originally Posted by DTEguy

I read that PSII system will be damaged regardless of the light intensity and is rapidly repaired. I was thinking even if the rate of damage is higher than rate of repair (in high light), the job is done and the photosynthesis yield would have been optimal (unless there are some irrerversible damage). However, photosynthesis rate was actually lower in a research on catts. in high light versus the one in intermediate light.

edit: Just read that excessive free radical oxygen from high light inhibit the repair mechanism. That makes sense now.

Yes you are right, The D1 protein in PSII has a general lifetime of 30 minutes and it is the repair cycle that need to keap up. The D1 protein is believed to be damaged by radical oxygen species and if the repair cycle is inhibited by oxygen radicals it make sence, that at high light levels the repair mechanism can´t keap up and you get bleaching.
Furthermore the buildup of the proton gradient over the thylakoid membrane inhibit the PSII to use water as electron source and you have a higher probability to generate free oxygen radicals in the system.