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Plant ECG – when plants sound the alarm
Although plants do not have a nervous system, they are nevertheless able to transmit and
process electrical signals in the organism. The signals are generated in relation to catching
prey and fending off enemies as well as in the production and release of fragrances that the
plants use to communicate with each other. Lehner GmbH, based in Kirchheim, develops
sensor systems for use in plant cultivation that are able to detect specific electrical signals.
The plant ECG can be used to detect mildew infestation on grapevines. © Lehner GmbH
Lehner Jr. is a biotechnology specialist who did his doctoral thesis on circadian rhythms in
plants (roughly 24-h cycle). The thesis was partially financed by the DFG and Lehner's
supervisor was Prof. Dr. Edgar Wagner, a leading light in chronobiology. Wagner examined the
day- and night rhythms in Chenopodium (goosefoot). At night, the plant's leaves are closed
(night position) and during the day they open up (day position). "We found that longitudinal
growth happens at defined periods of time. Different daylight periods affect the formation of
flowers and the plants' longitudinal growth. It is also known that the onset of flower formation
is influenced by the duration of daylight as sensed by the leaves. The phenomena of growth,
leaf position and onset of flower formation are closely linked," explained Lehner.
These findings led to new questions: if the leaf position and the longitudinal growth of the
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stem function are indicators of the onset of flowering, how are these two processes linked? “We
wanted to know whether electrical signals played a part in this phenomenon. Although
electrical signals in plants have been known for quite some time, they have not been
specifically analysed,” said Lehner going on to add that this approach required the
development of a system that enabled long-term measurements without damaging or
affecting the plant in any way. “Any damage to the plant triggers signals that can falsify the
measurement results. That is why we had to find a very gentle method,” said Lehner.
And so the plant ECG was born. Just like human ECG systems, the plant ECG has electrodes
that are attached to the plants. Different versions of electrodes have been developed in order
to avoid using invasive methods. “For goosefeet, we use the same contact gels that doctors use
for ECGs. However, these contact gels do not work with Arabidopsis and a number of other
plants,” said Lehner explaining that the contact agents used need to be adapted to the
requirements of individual plant species. However, as he pointed out, the registration of signals
and the principle of signal analysis are the most difficult processes. “We have to prepare a
specific electrophysiogramme for each individual plant species, containing the characteristic
signalling patterns of the different plant states. The fact that electrical signals in plants follow
their own regularities needs to be taken into consideration. In goosefeet, it takes up to five
minutes before an action potential is generated.”
The perfect early warning system
This sensor system is used to register electrical signals on a grapevine. © Lehner GmbH
Lehner finally managed to register action and variation potentials and characterise their
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distribution throughout the day. He was also able to show that certain signalling patterns
correlated with the onset of flowering induction in goosefeet. "This means that
electrophysiogrammes can be used to assess the onset of flowering and fruit formation, long
before the flowers are visible." The researchers are now aware of a broad range of specific
signalling patterns that occur as a result of certain environmental stimuli such as water
shortage: "Extreme water stress leads to a high-frequency series of action potentials," said
Lehner.
Signalling patterns related to the infestation of the plants by pests are of great interest for
commercial plant cultivation. The infestation of grapevines with mildew leads to characteristic
action potential patterns. It may be just a distant dream, but perhaps one day vineyards will be
equipped with sensor systems that sound an alarm when the dreaded fungus appears. The
great advantage of systems like these is that the winegrowers would be able to treat the
affected plants, thus preventing the fungus from spreading to other plants. The ideal-case
scenario would be the attachment of the sensor system to a radio network, which would send a
text message to the winegrower as soon as a pest makes its first devastating move. Lehner
GmbH is currently developing measurement systems for such applications that it hopes to
launch in 2010. Lehner estimates that the systems will cost a few hundred euros, "when used
for a homogeneous area the size of a football field where ten plants are equipped with a
measurement unit." The plants that are thus equipped would serve as indicators for the state
of all plants on a particular area.
Controlling the onset of flowering –without the help of genetic
engineering
Lehner is already thinking far beyond these alarm systems, in the belief that the ability to
measure electrical signals also means that the signals can be manipulated. “We are already
able to trigger the onset of flowering using specific electrical stimulations. In order to do this,
plants have to be at a particular stage in their development. We assume that in addition to
stimulating the onset of flowering, we will also be able to delay the formation of flowers by
applying certain disturbing signals,” said Lehner. One interesting application for Lehner’s
system might be to delay the onset of flowering until weather conditions are more favourable,
for example when there is no frost.
Lehner’s vision: electrophysiogramme databases for all plant species to help users trigger or
delay the onset of flowering and collect information about the physiological state and
requirements of their plants.
Help for self-help
Another project Lehner and one of his new partners are hoping to focus on is the defence
against herbivores, for example in crops such as corn. Over the last few years, the Western corn
rootworm from the Balkans has become a serious problem for German corn growers. These
insects feed on the corn plants and destroy entire harvests. “Western corn rootworm
infestations are expected to result in a very special signalling pattern, because when
rootworms feed, considerable tissue damage occurs,” said Lehner who is not only considering
the development of an alarm sensor. He also believes that the best prophylaxis would be to
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electrically trigger healthy plants to produce a signalling substance that attracts the
rootworm’s enemies. We are aiming to find a way to imitate the electrical triggers and transmit
them to healthy plants,” said Lehner explaining that this helps the plants to defend
themselves – in the ideal-case scenario this would be entirely without the use of chemicals.
Further information:
LEHNER GmbH Sensor Systeme
Dr. Lars Lehner
Kruichling 31
73230 Kirchheim/Teck
Tel.: +49 (0)7021 97013-21
E-mail: lars.lehner[at]lehner-gmbh.com
Article
15-Mar-2010
leh
BioRegio STERN
© BIOPRO Baden-Württemberg GmbH
The article is part of the following dossiers
Signal transduction - exciting research with huge potential for the future
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