Plant Cuttings

Multi-purpose leaves!

Surely, it is a truth universally acknowledged is that leaves are green?
Surely, it is a truth universally acknowledged is that leaves are green?
Image: Petr Dlouhý/Wikimedia Commons.

There are few certainties in plant biology. But, surely, a truth universally acknowledged is that leaves are green, designed to engage in photosynthesis to create food for humans, and are found on the aerial parts of plants? Well, it ain’t necessarily so.

Not all leaves are green – go to the USA’s New England States in the ‘fall’ to see that notion debunked (in glorious Technicolor!). And leaves don’t just engage in food production (which, incidentally, is for the plant’s own selfish ends; only coincidentally does it benefit those creatures that feed on/off the plant’s biomass…); some leaves trap invertebrates and derive extra nourishment therefrom.

Well, combining that latter activity and a subterranean placement of those quintessential aerial organs we have Caio Pereira et al.’s study of Philcoxia minensis. Non-sensationalistically entitled ‘Underground leaves of Philcoxia trap and digest nematodes’, their study provides evidence that subterranean leaves of that genus do indeed trap and digest nematodes, and consequently the taxon should now be considered carnivorous. This behaviour was predicted on the basis of morphological and habitat similarity of Philcoxia to other carnivorous plants – and is understandable given the low nutrient status of the cerrado of Brazil where it is found. Interestingly, previous attempts to determine P. minensis’ carnivory – by Peter Fritsch et al. (Proceedings of the California Academy of Sciences, 4th series 58: 447–467, 2007) – failed to find the tell-tale signature of protease activity, suggesting it was not carnivorous. However, and presciently(?), citing ‘potential sources of error’ in their work, they did not rule out the possibility. To discover a new carnivorous plant might seem somewhat unlikely in the 21st Century (where we like to think we know practically all there is to know about everything), but – if Mark Chase et al. are correct – there are probably a lot more carnivores out there than we currently recognise. Truly, fascinating plants – as is further demonstrated in Król and colleagues’ review of the antics of those amazingly able and adept animal assimilators.

However, fascinating though the Brazilian revelation is (and it is!), I’m even more excited by the distribution pattern of Genlisea (a genus related to Philcoxia), which is shown in the image above. Is it just me, or does the ‘sticky-out bit’ on the right of South America look like it could fit into the indentation on the left of Africa? Now, I don’t know about you, but one could imagine – crazy perhaps, but bear with me – that the taxon evolved in one terrestrial location in the dim-and-distant past when the present-day continents of South America and Africa were side-by-side – maybe even joined as one ‘super-continent’ – but became dispersed to those disparate continents when that original birthplace became split asunder and different chunks of terra-not-so-firma moved apart (almost as if those continental land masses were drifting over the surface of the earth like croutons atop some sort of geological soup…). I wonder…?

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