Do Plant Roots Talk to Leaves?

Arabidopsis thaliana
Arabidopsis thaliana (Wikipedia)

Surrounded by material excreted (exudate) by their own root border cells, the growing root tips (apical region) of plants move through soil regions where important biological interactions occur with a community of soil microbes. This exudate not only helps define the soil microbiome (microbial community), but also changes the physical and chemical characteristics of rhizosphere soil.

Root tip (100×) 1. Meristem 2. Columellae 3. Lateral part of the tip 4. Dead cells 5. Elongation zone (Photo: SuperManu – Clematis)

Hiltpold et al (2011) provided evidence of  systemic, volatile signals in maize roots in response to herbivore attack. From 2013 research on Arabidopsis suggests that soil microbes can alter plant leaf chemistry to inhibit insect feeding. They posited a role for microbial-derived volatile organic compounds acting as a deterrence signal, and noted the presence of Actinobacteria, Firmicutes and Proteobacteria in soil and within Arabidopsis root tissue.In a 2013 Tansley Review, Turnbull and Lopez-Cobello noted that despite localized cellular communication found in the root apical meristem, communication via vascular transport to the rest of the plant did not seem to occur. That left me wondering how plant roots communicated changes throughout the entire plant (systemic).

Those microbes are often associated with “soil odors”. On a sensorial level,  “smelling” the earth may help us appreciate the complex, unseen communication happening under foot.

Are All Plants Carnivores?

Fungal species of the Metarhizium genus colonize most land plants and help provide nitrogen to the plant root. The nitrogen source is unique – insects that the fungus has pathogenized and killed using enzymatic degradation of the insect’s shell.

Insect infected with Metarhizium spp.

Mike Bidochka of Brock University investigated the phenomena by injecting labelled nitrogen into Galleria mellonella larvae (moth). They buried the larvae in soil and separated the larvae from either beans (Phaseolus vulgaris) or switchgrass (Panicum virgatum) plants using a screen with pores large enough for fungal mycelium to grow through but small enough to prevent plant root growth.

Fourteen days later, they found labelled nitrogen made up more than a quarter of nitrogen found in plant root tissue. Insects Larvae with labelled nitrogen not infected by the fungus did not act as nitrogen sources for the plant.

Good evidence for an ecosystem rich in biota, rather than one where selective human inputs alters it into a simpler set of relationships. In most cases, the soil environment becomes less sustainable.

Are you a Renegade?

The renegade, or wild thing, in my heart is a man that loves to play.

I was cheerfully reminded of my need for play at a men’s retreat, how a water balloon and squirt gun fight, with little or no rules, can lift my heart and mind. I’ve been in play deficit, probably for some time. My inner grown up has been in charge much too long.  Although I consider the craft of writing, both science and poetry, a form of play, rarely do I experience physical play. Working out is not really play, but it can be – see Go Animal.

My girls claim I play like a boy, a bit too wild. When I was playing pickup soccer, or actively studying martial arts or dance I played daily. Stuart Brown at the National Institute for Play presents research in a TED Talk from 2008. Take a minute and review your own life. Are you playing enough?

I do play using my mind quite frequently, my inventive creativity a strength. I firmly trust the concept of Beginners Mind, as espoused by Shunryu Suzuki. I find in mentoring herbalists and researchers the freedom to play is a great asset that few have learned. This is especially true in multi-disciplinary environments. Here’s an example I ran across recently about the power of trusting in play.

Justine Musk’s blog discusses the Innocentive problem solving website started by Alpheus Bingham, a vice president at Eli Lilly. He asked the public to solve some of the company’s hardest scientific problems by offering a financial reward to anyone who proposed a solution.

When solvers “rated the problem as outside their own domain”, Alpheus noted that they were more likely to stumble upon solutions. They were “bridging knowledge fields” – taking ideas from one domain and introducing them into a different domain. They reframed problems, combined and recombined ideas, and opened up new lines of thinking.

This message echoed my own experience. Pursue your passions outside the explicit area in which you “work”. Embrace your inner renegade. And don’t back down from throwing unusual ideas into the conversation. Have faith in your own unique perspective. You never know when creative people in your sphere of influence will “run with it”.

I want to give a shout out to my best bud, Chas Murray. Whenever we are together, we play. Let me share what I miss the most. He was living in Norfolk and when I’d visit we inevitably ended up at the beach. Our favorite game was to take a ball or a Frisbee and play catch with a twist. The  player without the ball ran into the surf at full speed and the thrower tried to lead them into a full layout just as a cresting wave arrived. You had to trust in what would unfold and that your commitment to the moment was a joyful act in and of itself!

Not knowing is the most intimate thing (Zen Master Jizu).