On Bean Leaves, Bedbugs, And The Sugar “Internet” In Plants

Jatropha hybrid - Leaf detail (129 DAS)

Jatropha hybrid – Leaf detail (129 DAS) (CC BY-SA 2.0) by Ton Rulkens

One Thing Leads To Another….

You’ve probably already read the New York Times article about how bean leaf surfaces can entrap bedbugs (the trichomes on the leaf surfaces are microscopic velcro-like hooks, ensnaring the bedbugs). If you haven’t yet, it’s certainly worth checking out.

This NY Times story is about a paper (see Ref. 1 below) that was recently published online in The Journal of the Royal Society Interface, which, I must admit, is a journal I don’t read very often…(well, to be honest, I’ve never read it.)

Briefly, this paper shows that the bedbugs can be trapped pretty effectively on the surface of bean leaves, but a synthetic material mimicking the bean leaf surface doesn’t work so well.

But while perusing the current contents of The Journal of the Royal Society Interface, I spotted another paper (see Ref. 2 below) which looked interesting. (You can read brief summaries of this paper here and here.)

This paper is about the nature of sugar transport in the phloem, which I liken to the internet because, after all, the phloem really is just a series of tubes.

Anyway, some scientists at Harvard University were curious about what is the optimal sugar (mostly sucrose) concentration in the phloem for sugar transport in plants.

For example, if the sugar concentration was too low, then not much energy could be effectively supplied from the leaves to the other parts the plant. But if the sugar concentration was too high, then it would be very viscous, and this high viscosity would serve as a drag to efficient transport.

So, what these researchers did was simply go back into the literature and look at what other people had measured for the sugar content in the phloem from at least 40 different plant species.

What the data showed was “…an average concentration in the range from 18.2 per cent (all species) to 21.1 per cent (active loaders), suggesting that the phloem vasculature is optimized for efficient transport at constant pressure and that active phloem loading may have developed to increase transport efficiency.” (from Ref 2 below)

In other words, these investigators calculated that the optimal sugar concentration would be around 23.5% (presuming phloem pressure is constant). What they discovered from the old data is that most plants apparently do indeed maintain nearly this optimal sugar concentration in the phloem. In order to do this, however, the plants must expend energy to actively pump sugars into the phloem (“phloem loading”) at the sources (the leaves).


1. Szyndler, M. W., K. F. Haynes, M. F. Potter, R. M. Corn and C. Loudon (2013) “Entrapment of bed bugs by leaf trichomes inspires microfabrication of biomimetic surfaces.” The Journal of the Royal Society Interface, (published online 10 April 2013). (Abstract)

2. Jensen, K. H., J. A. Savage and N. M. Holbrook (2013) “Optimal concentration for sugar transport in plants.” The Journal of the Royal Society Interface, (published online 20 March 2013). (Abstract)

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