Consequences of too much light? (not sunburn, though)

[astrid]

Hey everyone!!

I have caught tidbits here and there discussing the consequences of too much light on orchids - delayed or lessened flowering, slow growth, and so on.

However, I am not too clear on these issues and would love clarification. A nice, bulleted list would be great!

So, obviously, midday summer sun on an orchid that has been wintering in the shade is going to burn the plant half to death or worse.
This is not the excessive sunlight I mean! I am asking more about light that's maybe 30% too much, but not enough to visibly damage the plant.

What will happen?
Thanks, everyone!

[hanzy08]

In my opinion it's the red tinging of the leaves that indicates that the plant is getting the maximum light it can take and anything more than that will burn the leaves. I always try to aim for this and adjust as needed cause sometimes culture sheets gives you a range of light requirments specially for hybrid plants.

[astrid]

Originally Posted by hanzy08

In my opinion it's the red tinging of the leaves that indicates that the plant is getting the maximum light it can take and anything more than that will burn the leaves. I always try to aim for this and adjust as needed cause sometimes culture sheets gives you a range of light requirments specially for hybrid plants.

I am not asking how to tell if my plant is getting enough light.

I am asking the consequences of constantly providing too much light to the plant. Not lethal amounts, but just overly high amounts of light.

I seem to have read that too much light will stress a plant and cause the plant issues, but I am not sure what those issues are.

[Greystar]

I had a look around on google but can't seem to find a definitive piece of information about the negatives of constant exposure to high amounts of light. There was a page I found a short while back that may have explained it and I've been desperately trying to find it again but until then...

I don't think it adequately answers the question but the main point I'm plucking out is:
"Over-excitation (by light) manifests itself as a repression of photosynthesis, phenomenon called photoinhibition (Long et al., 1994). Chronic photoinhibition can significantly reduce productivity and may have a negative effect on survival (Ball et al., 1991).
Photoinhibitory conditions may lead to the formation of reactive oxygen species, which in turn cause photodynamic bleaching and perturbation of cellular metabolism (Foyer et al., 1994)."

[dbarron]

Hmm, and I'm like hanzy08's comment, I thought the consequences of giving plants as much as they could take without damage was strong growth and flower bud formation. I'll be watching this thread, good question Astrid.

[Bulbofett]

I guess I will let you know what the consequences are lol

[NYCorchidman]

Long-term effect of too much light on plants are, as mentioned above, less than optimum performance in general including growth (may be slow or stunted in severe case) and flowering (poor to no-flowering) when stressed too much by too much light, and decline of other physiological function such as more prone to disease or bug attack, especially mites.

Too much light comes with heat stress and dehydration of the plant, so it is a rather complex issue.
Depending on the type of plants, as long as humidity and water available at the roots and temperature are kept optimum, then the negative effect might be minimal, although too much light usually comes with too much heat.

Purple tinge on the leaves is not a sign of too much light, and it is only exhibited by certain plants.

Overal yellowing (still showing green but predominantly yellowish) is a sure sign and this happens over a period of time, and plants should moved to a more shaded area and less heat.

Ok, I reread your original post and I realize that my comment is probably way off as I mentioned the effect of too much light, too much enough to cause harms.
Ignore it.

A bit more than optimum light may not hurt plants, but again, it is related to humidity, watering, and temperature.
Most plants should take it fine, although they won't be happy.

Another thing, which is also mentioned, maximum light a plant can take without causing ill effect seem to bring out the best flowering in many orchids I grow. Phals, dendrobiums, cymbidiums, paphs, oncidiums, and others.
Then, once you go over this limit, then plants will suffer.
I can't tell you exact figure, but you can find out through trial and error in your own unique growing conditions.

My cattleyas for example look horrible and yellow during the summer because I let them sit in the sun by the window without any protection, but I just don't care.
They happen to be in the window that I just do not want to negotiate with plants. I want to have at least some windows clear of curtain to enjoy the city view. lol
So I have been tossing my cattleyas and replace them with Brassavola nodosa and its hybrids. These seem to be very happy in the sun without curtain. So we are both happy. hahaha

[Orchid Whisperer]

It really depends on the plant, I think.

The "mule-ear Oncidiums" (Trichoglossum) frequently seem to prefer all the light that they can get, short of burning; the best-blooming plants always seem to have some red in the leaves. High light levels also seem to work for Brassavola . I would be less inclined to try to grow Paphiopedilum and Phalaenopsis the same way.

[astrid]

Originally Posted by NYCorchidman

Long-term effect of too much light on plants are, as mentioned above, less than optimum performance in general including growth (may be slow or stunted in severe case) and flowering (poor to no-flowering) when stressed too much by too much light, and decline of other physiological function such as more prone to disease or bug attack, especially mites.

Too much light comes with heat stress and dehydration of the plant, so it is a rather complex issue.
Depending on the type of plants, as long as humidity and water available at the roots and temperature are kept optimum, then the negative effect might be minimal, although too much light usually comes with too much heat.

Purple tinge on the leaves is not a sign of too much light, and it is only exhibited by certain plants.

Overall yellowing (still showing green but predominantly yellowish) is a sure sign and this happens over a period of time, and plants should moved to a more shaded area and less heat.

Ok, I reread your original post and I realize that my comment is probably way off as I mentioned the effect of too much light, too much enough to cause harms.
Ignore it.

A bit more than optimum light may not hurt plants, but again, it is related to humidity, watering, and temperature.
Most plants should take it fine, although they won't be happy.

Another thing, which is also mentioned, maximum light a plant can take without causing ill effect seem to bring out the best flowering in many orchids I grow. Phals, dendrobiums, cymbidiums, paphs, oncidiums, and others.
Then, once you go over this limit, then plants will suffer.
I can't tell you exact figure, but you can find out through trial and error in your own unique growing conditions.

My cattleyas for example look horrible and yellow during the summer because I let them sit in the sun by the window without any protection, but I just don't care.
They happen to be in the window that I just do not want to negotiate with plants. I want to have at least some windows clear of curtain to enjoy the city view. lol
So I have been tossing my cattleyas and replace them with Brassavola nodosa and its hybrids. These seem to be very happy in the sun without curtain. So we are both happy. hahaha

This! This is exactly what I was looking for- thank you!

My brassavola nodosa likes to hang in the bright, bright window. I have little thin plastic on the window to slightly diffuse the light, but in a few weeks, I think the plant could handle direct sun. Mine just gets little black spots from the sun that spread out and then fade back to green.

I guess it's a fine balance. I'm trying to acclimate most of my dens to bright light and mildly filtered sun.
Thanks so much!

[NYCorchidman]

So what do I get for the right answer?
Just kidding. lol

Regarding B. nodosa, I saw a HUGE clump, I really mean huge, covered with hundreds of flowers in Honolulu in October. It is a bit higher elevation, but still, it was growing outside on a tree and exposed to full sun. All the leaves were green.

Speaking of purple spots or tinge, I am not sure if it is due to bright light. It can also be due to cold or magnesium deficiency. I'm not really sure.
Certain ondiciums or miltoniopsis, when they get a lot of light, they develop purple tinge but they do not go away unless they are moved to lesser light.

Dendrobiums- nobile hybrids (you said you don't like the smell of their flowers?) take full sun fine, but your recent purchase type, they will definitely be cooked. Just a word of warning.