Jonathan's Mistletoe Diary

May 31, 2015

Naked mistletoe!

Filed under: Mistletoe,Science — Jonathan Briggs @ 4:31 pm
Mistletoe haustorium with the bark on... the mistletoe stems are the upright ones, the horizontal piece is the host (an apple tree)

Mistletoe haustorium with the bark on… the mistletoe stems are the upright ones, the horizontal piece is the host (an apple tree)

What does mistletoe look like with no clothes on? Or, more accurately, with no bark on? Way back in the winter of 1982/83 I spent many hours decorticating (stripping bark off) African mistletoes, with some interesting results. And, having deliberately collected quite a lot of small English mistletoe haustoria (the host/parasite interface – see left) last winter I decided recently to re-visit the process.

How’s it done? You simply boil them for a couple of hours. And then, whilst they’re still hot (ouch, Ouch, OUCH!) you peel the bark off.

Back in 82/83 I operated on a small scale, in a lab, with a bunsen burner and one haustorium at a time. But, deprived of such precise facilities in a domestic environment, I decided to try processing all the specimens in just two batches – which needed a big pan…

So, off I go to find the big aluminium jam-making pan (discovered residing in the garden, moonlighting as a big plant-pot saucer). It needed a bit of a rub-down to remove the woodlice, slugs and snails, but once clean(ish) and filled with water it went onto the hob. And, when boiling, in went  the mistletoes…

A boiling jam pan full of mistletoe haustoria

A boiling jam pan full of mistletoe haustoria

I should add, at this point, that I was home-alone at the time – which is probably just as well. This is a messy process which, apart from the piles of mistletoe bits all over the kitchen surfaces, does tend to turn the kitchen into a sauna, not recommended in a family tea-time environment (but perfect for getting mistletoe naked).

Here’s a pic of the first batch on the boil, a lengthy process that seemed just a little cruel (despite the pieces all being completely dead already. It reminded me, through some obscure mental logic, of the scene in Carry On Screaming where Kenneth Williams falls into his petrifying vat. Frying Tonight!

And so what does mistletoe look like naked?

The same haustorium as the one above, but now without its bark.

The same haustorium as the one above, but now without its bark.

Beautiful – and educational. Taking the bark off helps demonstrate the way the mistletoe grows, exposing the edges of complex and convoluted haustorial interface that is 50% host and 50% parasite. The host wood shows up as smooth and relatively normal, apart from the convolutions. The mistletoe wood, by contrast, is of a much lighter construction, full of spaces between the vascular elements.

Close-up of a haustorium, showing the host wood (smooth solid surface) and the mistletoe wood (open, lattice-like surface)

Close-up of a haustorium, showing the host wood (smooth solid surface) and the mistletoe wood (open, lattice-like surface)

To properly visualise what’s going on you need to think in 3D and in time too. The mistletoe’s original point of infection is somewhere in the middle of the structure, and the host has been tricked to providing an ever-wider interface of vascular tissue as the mistletoe has grown. This is not the mistletoe physically growing into the host wood (though it may look like it) – it is the host and mistletoe growing together in a complex embrace.

Distinctive multiple strands of mistletoe griwng along the host branch

Distinctive multiple strands of mistletoe griwng along the host branch

There are hints, on nearly all the specimens, of sub-cortical spread – the mistletoe growing along the host branch, initially just under the bark but, after a few years, looking as if it is growing longitudinally through the wood itself (though actually it’s the host wood growing with it and eventually covering it).

These strands of mistletoe tissue emerge at intervals, creating peculiar dotted lines of the mistletoe’s distinctive open-weave wood structure.

There are some more photos below – click on any one of them to start a slide-show of them all.

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1 Comment »

  1. Amazing! It looks like vampire fangs.
    I am a parasitic plant lover in Japan. I am growing Japanese parasitic plants such as Aeginetia indica and Orobanche coerulescens. I enjoy your mistletoe diary.

    Comment by Kazuhiro Miyahara — July 3, 2015 @ 6:13 am | Reply


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