Red leaf chemical: Anthocyanin

Greetings all, I have a question about red maple leaves and their herbicidal behaviour.

A Toronto Star article says that the red leaves contain anthocyanin, which is produced in the fall. When the chlorophyll breaks down, the yellow colours emerge. But the reds are caused by the production of anthocyanin - which also turns out to be a natural herbicide. (Pg F4 of Oct. 23rd issue for folks who read it, sorry I couldn't find it online for every one else.)

Tests were performed using 4 different types of leaves green beech, yellow beech, green maple and red maple leaves. Lettuce seedlings came into contact with green and yellow leaves sprouted fine, however the seedlings that came in contact with the red maple leaves were inhibited. The theory is that Maple leaves stop growth of other plant seedlings and saplings, so it's own will have an advantage.

My questions:
1) When the red leaves dry up and turn brown - do they lose the anthocyanin?
2) If not - at what point is maple leaf content in a backyard leaf mulch going to cause risk to flower bed seedlings and saplings?

Thanks for your thoughts.

 

Excellent question--I look forward to the answer. The qestion might be related to how much is required? You might try to post this or link it in the soils and fertilizers fourm--it is as close to composting as I could find.

MJH

 

Thanks MJH, I couldn't figure out how to 'link" so i re-posted in Soils and Fertilizers.

 

Hello
I posted this in the soild but came across it again in maples sorry if you have read it twice!!


just some thoughts ...

There is a great deal of interest again in anthocyanins and their related compounds flavonoids. both are bioactive and have been used recently as a health food fad!! reluctantly without much thought as to why the plant needs them or uses them. They were thought to be secondary compounds that the plant did not need and so were good deposits of wastes and other unwanted things in the vacuole of the plant cell. there is a great deal of information out there by Jeffery Harborne at Reading University in England and Bruce Bohm and the late Neil Towers at UBC in Vancouver. Both Professors were looking not only at the activity of these anthocyanins but their building blocks and their related compounds and their relationships to the plant as a species.

it is unlikely the anthocyanins alone are responsible for the suppression of the seelings. The common flavonoid "Rutin" is known to have anti-fungal characteristics. But ... both are water soluable and unstable in an acid or a basic solution for any length of time as they are never found in their pure state.

to answer the question
1) When the red leaves dry up and turn brown - do they lose the anthocyanin?

yes it is most likely degraded into the basic building blocks of a cinnamic acid and a coumarin both of which can be bioactive in anti bacterial and anti fungal senses. these are also water soluable, colourless and so do not hang around for any great length of time. therefore the plant looses the red colouring!! you should also know the anthocyanins fluoresce in Ultra violet light and suppress UVA & UVB damage to the internal organs of the plant. the compounds that are left in a brown leaf are the terpenoids and the things that make Tea and coffee that wonderful taste and colour ... the tannins. an overdose of all of these compounds in a concentrated area will suppress growth due to their combined actions.


to answer the second point
2) If not - at what point is red maple leaf content in a backyard leaf mulch going to cause risk to flower bed seedlings and saplings? (HOw much is too much?)

you should be putting the leaves in to your compost and letting the good fungus and good bacteria break down the tannins and organic materials left over a long period of time. the heat generated will also degrade any compounds in the leaves. Obviously do not make your compost out of only one plant as this will result in an nutrient imbalance. mix it in with the normal green matter and vegetablke waste in order to produce a balanced compost.

I hope this helps

Pierrot

 

Hello Vcallinan, fascinating topic.

We have this conversation going in two threads now, so I am going to close this one, but please take up the conversation in the Soils forum:
http://www.botanicalgarden.ubc.ca/forums/showthread.php?t=10265

Vcallinan,

To link to another thread is like any other link, just go to the forums page and copy the url from you browser and post it. If you want to use some text in your post as the link, just highlight it, then click the link icon on the editor (the earth with chain links) to fill in the URL.

I found the article. I will post links to it in Soils.