Image: Stan Shebs/Wikimedia Commons.
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By the pricking of my thumbs…

Can cacti help us harness water from the air in hostile environments?

Image: Stan Shebs/Wikimedia Commons.
Image: Stan Shebs/Wikimedia Commons.

Cacti live in some of the driest places on the planet. The fact that they survive there means they must get sufficient water to grow and sustain vital processes. Although they usually have roots (few plants choose a tumbleweed, rolling-stone, lifestyle), they have other ways of obtaining life-giving moisture. For example, using spines and trichomes on its stem Opuntia microdasys (bunny ears cactus) exploits an efficient fog (‘liquid water droplets or ice crystals suspended in the air’) collection system, whose mechanism has been uncovered by Jie Je et al.

The team demonstrate that each spine of a conical cluster contains three integrated parts, each with different roles in the fog-collection process according to their surface structural features. Whilst we might rightly marvel at this vegetable’s mastery of physics and exploitation of such phenomena as the Laplace pressure gradient (‘pressure difference between the inside and the outside of a curved surface’), the more ‘plants-as-a-resource’ oriented amongst the paper’s authors muse that investigations of this system’s structure–function relationship may help us to design novel materials and devices to collect water from fog with high efficiencies. Maybe so we humans might survive a little better in such hostile environments?

But you won’t get far in your dissection of the biology of the system without an appreciation of the underlying molecular-genetic basis. However, have you ever tried to get DNA out of such a botanical hedgehog? No, neither have I because I imagine it’s far too pricklesome and needlessly self-perforating! However, fear not, in timely fashion Shannon Fehlberg et al. report ‘a novel method of genomic DNA extraction for Cactaceae’ (such as O. microdasys). Firmly grasping the nettle – so to speak – their procedure actually uses the spines themselves to provide the requisite molecular sample. Modestly, the team say this is to avoid complications from presence of polysaccharide-based mucilage and other secondary compounds in DNA samples from elsewhere in the plant. But we can reveal the real reason for going straight to the pointy end: botanists are ‘well ‘ard’ and not afraid to go where other lesser mortals – e.g. zoologists – would fear to tread! Power to the prickly procedure people! Try DNA? Tri-chology!

[Hair-raising rumours that over-sampled individuals of the cacti are being sold on eBay as var. braziliensis are probably groundless – Ed.]

Nigel Chaffey

I am a Botanist and former Senior Lecturer in Botany at Bath Spa University (Bath, near Bristol, UK). As News Editor for the Annals of Botany I contributed the monthly Plant Cuttings column to that international plant science journal for almost 10 years. As a freelance plant science communicator I continue to share my Cuttingsesque items - and appraisals of books with a plant focus - with a plant-curious audience at Plant Cuttings [] (and formerly at Botany One []). In that guise my main goal is to inform (hopefully, in an educational, and entertaining way) others about plants and plant-people interactions, and thereby improve humankind's botanical literacy. I'm happy to be contacted to discuss potential writing - or talking - projects and opportunities.
[ORCID: 0000-0002-4231-9082]

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