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Why Magnesium is important to our plants....

2118 Views 6 Replies 4 Participants Last post by  plantbrain

Chlorophyll B

Here are some others that don't require Mg but are related to the above two:


More fun with chemical structures to come!
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Excuse the oversimplification, but from the diagram...Is Mg the "glue" that holds Chlorophyll together, as both diagrams place Mg at the center.

Technically, the Carbon-Carbon bonds signfied in the diagrams by the straight lines between points without a designator are the glue. However, Magnesium is essential to Chlorophyll simply because it's the central unit of the molecule. Interestingly, that large structure is a substituent of a very long hydrocarbon chain which can be seen in the bottom left (H39C20) making Chlorophyll a lot larger molecule than most of us may think.

Looking at the middle MN4 group it's pretty easy to see why our plants go green when they get Nitrogen or Magnesium deficiencies. Notice there's no Iron or Potassium in the molecule.

One of my hypotheses on red coloration and Nitrogen deficiencies is that the plants have the red pigments already but they're covered up by the Chlorophylls. When the plant is N deficient and has to resort to breaking down Chlorophyll to get at the Nitrogen it needs the red, orange, and yellow pigments come out from hiding and can be seen. Since these Carotenoid pigments are less effective than Chlorophyll higher light is needed to obtain the same amount of sugars, hence red plants needing higher light.

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Great post, Phil - thank you!

So, are you saying for nice, bright reds, deprive them of Nitrogen and provide plenty of Magnesium?

It's worth a try to find out. I actually had the idea at the CAPE meeting at Neil's house. His plants were the brightest red I've ever seen and he said that he doesn't fertilize much of anything. I wouldn't do it with your prized species, but Ludwigia repens would be a really good test subject because of its green and red characteristics. Just be careful, they still need these chemicals for other things too. Don't totally deprive them of N and Mg. Actually, you've on well water, aren't you? It's going to be really hard to not give them enough Mg.

I probably wouldn't want to do a real test as I absolutely hate testing :( So, I rarely do much of it. I don't fert much either, although I do from time to time use some epsom salts and calcium carbonate, and Kent Bontanic Grow, because my well water is extremely soft (1kh, 1gh). I do have Equilibrum, but have only used it once. I use the normal Flourish for my 55 but not my shrimp tank because of the copper.

My absolute easiest tank, however, is my 29 gallon shrimp tank, and I'm actually less happy with it since I raised the kh to 3. I'm letting it go back down as my Toninas are much happy with the lower kh.

However, I will dose some more epsom salts now just to see if it will increase reds as an informal kind of experiment :)
So Phil, will you draw me the D1 protein for Mn2+?

You may find it interesting to replace the Mg with Fe and remove the conjugated tail, what do you think you'll have then?

It's red...........

See Figure 4, note the ring structure.

Pretty cool that plants and people's blood are fairly close in structure and formation of the basic parts and enzymes.

So Phil, we might be about to call your plant blood somewhat human in some sense.

But that's not why plants are red:) they don't have Fe boold, some algae, BGA's have heme like O2 removers for N2 fixation(this process needs anaerobic conditions) which are similar to hemoglobins.

Tom Barr
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