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I was recently visiting Fremantle in Western Australia and noticed a large Morton Bay Fig tree in Kings square in the centre. Apparently the health of this tree had been declining, but they hope that recent treatment will lead to an improvement.

The notice by the tree said this was by “injection of a tree enzyme”. I also found the following quote on the City of Fremantle FB page:

To improve the tree’s absorption of nutrients which will help it grow stronger, the bioscientist has given it a ‘booster’ enzyme injection. This enzyme naturally occurs in trees and is an additional boost that will hopefully help the fig tree recover and flourish again this spring.

Well trees have enzymes like any other living thing, but I find it difficult to imagine what enzyme injected into a tree would get transported through its system and help it heal. Is there anyone in silviculture (or WA) who has any idea what this was?

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So eventually I decided to email the City of Fremantle, who put me in contact with their Parks Department, who gave me the name of the company who had handled the tree, who replied with a most informative letter.

And the answer is…

Glutathione

Structure of Glutathione

Most animal biochemists, like me, will be more familiar with the importance of glutathione (reducing sulphydryl group highlighted in yellow, above) as a reducing agent in erythrocytes, the constituents of which are subject to oxidation damage.

What was wrong with the tree?

“…the figs in Kings Square… had quite elevated levels of heavy metals Cd, Cr, and metalloids Hg and As. We traced this back to the colonial past, where in the 1830s – 1840s, when gold had been discovered south east of Fremantle, a battery operated (by the Crown) in Fremantle. In those days, gold was commonly lixiviated using mercury. Kings Square had a pit cut earlier for mining limestone. A good place to dispose of battery mullock is a pit.The earliest gold deposits were mafic ores, so often contained Cd and Cr.”

Why use glutathione to treat the trees?

Firstly, it stimulates the jasmonate pathway, thereby alters transpiration and root growth.

Secondly, it assists in the isolation and immobilisation of heavy metals.

Thirdly, if assists in the breakdown of triazine herbicides by ring cleavage…”

And my correspondent kindly provided a review by Hossain et al. in the Journal of Botany, which elaborates on the second point.

And why the “tree enzyme” business?

This did not come from the company that handled the treatment, but from someone (unknown or nameless) who was handling the public relations, and who wished to provide reassurance that the treatment was ‘natural’:

“I guess in the world of snake oil, “enzymes” are benign, natural things, rather than usually ephemeral catalytic proteins.”

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  • $\begingroup$ I admit that, depending on a personal letter, the answer does not totally conform to the criteria of testability. (I did not think it appropriate to name my correspondent.) However the background details and the literature reference do provide strong support. In any case, as there had been some interest in the question, I thought I should do some work myself and then post an answer. $\endgroup$ – David Feb 26 '18 at 16:13
  • $\begingroup$ Interesting answer. $\endgroup$ – canadianer Feb 26 '18 at 20:11

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