Upon stimulation, plants elicit electrical signals that can travel within a cellular network analogous to the animal nervous system. It is well-known that in the human brain, voltage changes in certain regions result from concerted electrical activity which, in the form of action potentials (APs), travels within nerve-cell arrays. Electro- and magnetophysiological techniques like electroencephalography, magnetoencephalography, and magnetic resonance imaging are used to record this activity and to diagnose disorders. Here we demonstrate that APs in a multicellular plant system produce measurable magnetic fields. Using atomic optically pumped magnetometers, biomagnetism associated with electrical activity in the carnivorous Venus flytrap, Dionaea muscipula, was recorded. Action potentials were induced by heat stimulation and detected both electrically and magnetically. Furthermore, the thermal properties of ion channels underlying the AP were studied. Beyond proof of principle, our findings pave the way to understanding the molecular basis of biomagnetism in living plants. In the future, magnetometry may be used to study long-distance electrical signaling in a variety of plant species, and to develop noninvasive diagnostics of plant stress and disease.
According to their research, published Sept. 23 in Current Biology, plants actually do have a way of talking to each other. Their messages come embedded in the form of airborne chemicals known as volatile organic compounds (VOCs), which transfer information among plants.
The big finding in the study is what Kessler calls “open-channel communication.” Based on their genotypes, different plants have different smells. But when plants come under attack from pests like the goldenrod leaf beetle, their smells – carried by VOCs – become more similar.
“So they kind of converge on the same language, or the same warning signs, to share the information freely,” Kessler said. “The exchange of information becomes independent of how closely related the plant is to its neighbor.”
The research found that neighboring plants pick up on warning VOCs and prepare for the perceived threat, such as an oncoming insect pest. Said Kessler: “A (VOC) emitted by one plant can be picked up by another plant, and they can either ready their defenses or they may actually directly induce those defenses.”
However, their goodwill toward plant neighbors only works on an if-you-see-something-say-something basis and when, as a result of the communication, pest pressure is equally distributed across the plant population. Plants in populations without herbivores do not freely share information with their neighbors. Instead, they maintain a private channel with their closest kin through VOC emissions that induce resistance – but only in those relatives or plant parts distant from the damage site on the same plant.
“We code our language if we want to keep it private, and that’s exactly what happens there, but on a chemical level,” Kessler said. “That analogy is striking and not what we expected.”
In the next month or so, orange trees across Florida will erupt in white blossoms, signalling the start of another citrus season. But this year, something different will be blowing in the winds. Farmers are preparing to spray their trees with hundreds of thousands of kilograms of two common antibiotics to combat citrus greening, a bacterial disease that has been killing Florida citrus trees for more than a decade.
The US Environmental Protection Agency (EPA) is in the process of allowing growers to use streptomycin and oxytetracycline as routine treatments, spraying trees several times per year, beginning with the ‘first flush’ of leaves this spring. Growers in the state could end up using as much as 440,000 kilograms of the drugs. Although the compounds, which are both used in human medicine, have been sprayed on other crops in the past and applied in limited amounts to citrus groves, the scale of this application has researchers and public-health advocates alarmed.
“They are doing a huge experiment with limited monitoring,” says Steven Roach, a senior analyst in Iowa City at Keep Antibiotics Working, a coalition of research and advocacy groups that has formally objected to the plan with the EPA.
( read more at Nature )
Surprisingly, dandelion seeds use a method of flight previously thought impossible.
Wind-dispersed plants have evolved ingenious ways to lift their seeds1,2. The common dandelion uses a bundle of drag-enhancing bristles (the pappus) that helps to keep their seeds aloft. This passive flight mechanism is highly effective, enabling seed dispersal over formidable distances3,4; however, the physics underpinning pappus-mediated flight remains unresolved. Here we visualized the flow around dandelion seeds, uncovering an extraordinary type of vortex. This vortex is a ring of recirculating fluid, which is detached owing to the flow passing through the pappus. We hypothesized that the circular disk-like geometry and the porosity of the pappus are the key design features that enable the formation of the separated vortex ring. The porosity gradient was surveyed using microfabricated disks, and a disk with a similar porosity was found to be able to recapitulate the flow behaviour of the pappus. The porosity of the dandelion pappus appears to be tuned precisely to stabilize the vortex, while maximizing aerodynamic loading and minimizing material requirements. The discovery of the separated vortex ring provides evidence of the existence of a new class of fluid behaviour around fluid-immersed bodies that may underlie locomotion, weight reduction and particle retention in biological and manmade structures.
Dandelion seeds fly using ‘impossible’ method never before seen in nature
Nature, Revealed: the extraordinary flight of the dandelion
Paper, A separated vortex ring underlies the flight of the dandelion
Research Gate project, The form and function of the dandelion fruit
Citrus canker is a disease that affects all citrus species and varieties. It is caused by Xanthomonas citri, a bacterium originally from Asia, where it is endemic in all citrus-producing countries. Although the bacterium can be combated in several ways, none is sufficient to eradicate the disease. Therefore, new chemical or biological methods of protecting citrus groves have to be pursued.
In an article published in Letters in Applied Microbiology, a team led by Daiane Cristina Sass, Lara Durães Sette and Henrique Ferreira, professors in São Paulo State University’s Bioscience Institute (IB-UNESP) in Rio Claro, Brazil, identify 29 fungi with proven action against X. citri. The origin of the fungi is surprising. They were isolated from samples of soil and marine sediment collected in Antarctica. read more…
Terrestrial and marine Antarctic fungi extracts active against Xanthomonas citri subsp. citri
Biotechnological potential of secondary metabolites from Antarctica fungi with activity against plant pathogenic bacteria