Epson salts and high light plants

[DirtyCoconuts]

So my plants that are reddish but are still growing and blooming, are they deficient and should be moved to less light?

[rbarata]

Originally Posted by DirtyCoconuts

So my plants that are reddish but are still growing and blooming, are they deficient and should be moved to less light?

Nope...consider it the same as tanning in humans. After that comes sunburn, if light levels are higher.
That's a good sign because it gives you an indication that the plant is reaching the threshold point I was refering to.

[neophyte]

Originally Posted by rbarata

So, the question that motivated this thread is: considering Mg is used by plants to produce chlorophyll, if we increase it in watering would it help plants to cope better with light levels beyond that threshold point?

I don't think it would. Magnesium doesn't exactly help a plant produce chlorophyll, it's simply a component of the chlorophyll molecule. When the plant is bleached, it's not losing the magnesium; it's just that the magnesium can't stay in the chlorophyll and has to go elsewhere. So adding more won't really make a difference because there is no deficiency.

Here's a weird analogy: if you're trying to store water in buckets and the buckets disappear, it won't help to get more water because the buckets are gone; you need to buy more buckets. Similarly, supplementing with extra Mg doesn't reduce bleaching because the Mg won't end up in chlorophyll. In fact, overdosing on Mg can actually lead to more damage (due to toxicity).

Of course, if the plant is showing signs of chlorosis for reasons not due to harsh light, then a Mg supplement might solve the issue. However, when a plant is already healthy and is simply lacking chlorophyll due to harsh light, then the best solution is to provide some shade.

[rbarata]

So, am I correct to say that an heathy plant always has the optimal chlorophyll levels for the light levels in their environment?
If these levels are increased, because the plant doesn't need that much chlorophyll, it starts to get lighter green leaves. This is not bad only if light levels are stationary and don't go up to the point of destroying the remaining chlorophyll.

[SouthPark]

This paper seems to be quite ok .... here.

Also roughly summarised here.

It says something about a mechanism that occurs in plants for protecting themselves - the chlorophyll - to some point - in the presence of relatively high light level/intensity.

Something about - if light levels become high enough, the plant forms carotenoids, which can then interact with the chlorophyll (by combining -- ie. chlorophyll combining with the carotenoid), expelling heat energy from the chlorophyll in the process ...... I assume heat energy transferred to somewhere else in the leaf or plant, which then goes into the atmosphere (eg. maybe cool breeze, wind, air-movement).

So - maybe, to prevent leaf burn - might need to up the air-flow (or cool air-flow). Compensation. Either that --- or have some system that automatically provides more shading of the plant if light intensity or levels reach an estimated 'unsafe' level.

One nice thing is - if an orchid can push through season after season with some leaf burn, but not enough to wipe out the orchid - and the orchid appears to always recover well, or 'shrugs it off', then that's not such a bad thing.

As for the combining of chlorophyll with carotenoid ----- haven't yet seen any details about what happens later, such as --- can they de-combine and get back to the regular state?

[Ray]

Originally Posted by neophyte

I don't think it would. Magnesium doesn't exactly help a plant produce chlorophyll, it's simply a component of the chlorophyll molecule. When the plant is bleached, it's not losing the magnesium; it's just that the magnesium can't stay in the chlorophyll and has to go elsewhere. So adding more won't really make a difference because there is no deficiency.

Here's a weird analogy: if you're trying to store water in buckets and the buckets disappear, it won't help to get more water because the buckets are gone; you need to buy more buckets.

Yes, and adding more water doesn’t create buckets!

Similarly, supplementing with extra Mg doesn't reduce bleaching because the Mg won't end up in chlorophyll. In fact, overdosing on Mg can actually lead to more damage (due to toxicity).

I’m going to have to temper that statement. Mg toxicity is very rare. Mg is very loosely bound, so damned near every other cation out-competes it for uptake and placement in tissues and excesses are very easily dumped by the plant. I have applied as much as two tablespoons/gallon without issue.

[neophyte]

Originally Posted by rbarata

If these [light] levels are increased, because the plant doesn't need that much chlorophyll, it starts to get lighter green leaves. This is not bad only if light levels are stationary and don't go up to the point of destroying the remaining chlorophyll.

I'm not sure about the first part... that would probably explain why leaves tend to be really dark green under low light and bright green under normal light, so it makes sense (of course, some part of it still has to do with the fact that more light just makes everything look a bit brighter). But I can definitely affirm that bright light is good up until the point where chlorophyll starts getting damaged. I think under normal conditions chlorophyll will "wear out" after a while, but harsh light will definitely accelerate the process.

Originally Posted by Ray

I’m going to have to temper that statement. Mg toxicity is very rare. Mg is very loosely bound, so damned near every other cation out-competes it for uptake and placement in tissues and excesses are very easily dumped by the plant. I have applied as much as two tablespoons/gallon without issue.

Thanks for the correction.