Measuring Plant Defense and Leaf Wounding Reactions Using PTR-MS

Reactions in nature frequently take place at a rapid pace. The current techniques used to analyze compounds released when damage occurs to leaves are not able to monitor plant reactions in a sufficiently high time resolution to allow for the identification of underlying reaction sequences.

As a result, these fascinating relations remain a mystery, and scientists are denied the opportunity to investigate further. Instrument response times are responsible for limitations in the ability to study the interesting realm of interactions between plants and animals.

The Real-Time Monitoring Solution

Boasting extremely sensitive online measuring solutions, Ionicon Analytik empowers research groups across the globe to detect and quantify reactions occurring in nature. It is thus possible to carry out real-time analysis of leaf wounding, and the resultant interactions between animals and plants, without losing vital information in the finer details.

Analysis of VOC emission following leaf cutting has been carried out using PTR-MS measurement. A variety of plants have been found to emit similar compounds, including "greenleaf volatiles," alcohols, terpenoids, C6-aldehydes, and phenolic compounds. These can been seen in Figure 1.

Leaf wound reactions after cutting. Under nitrogen atmosphere and later when in contact with air.

Figure 1. Leaf wound reactions after cutting. Under nitrogen atmosphere and later when in contact with air.

Real-Time Monitoring of Plant Defense Reactions with PTR-MS

There are a number of difficulties to overcome in the online measurement of compounds released from leaf wounds, particularly where there is a need to quantify the reactions from plants immediately after the attack, making PTR-MS the only appropriate method.

Researchers are best able to monitor leaf reactions in real-time where an extremely short reaction time appears in combination with a detection limit in the pptv-range.

Results

As a result of their numerous adversaries in the natural world, plants have gradually developed defense mechanisms. Aside from direct methods of defense, including toxins and digestibility reducers amongst others, there are also a number of indirect processes in existence which relate to the third trophic level: signaling herbivore attack through the production of volatile organic compounds (VOCs).

It has been demonstrated by scientists* that plants being attacked by caterpillars emit volatile organic compounds (VOCs). Volicitin, found in caterpillar saliva, activates defense genes, resulting in the production of indole and other VOCs, attracting wasps. The wasps then assist the plants by utilizing the caterpillars in their reproduction cycle. This can be seen in Figure 2.

Schematic drawing of plant defense mechanism. Source: Alborn et al. (1997). Science 276: 945-949.

Figure 2. Schematic drawing of plant defense mechanism. Source: Alborn et al. (1997). Science 276: 945-949.

When caterpillars ingest maize, indole production is stimulated and can be identified online using PTR-MS. This can be seen in Figure 3.

Plant reactions under attack from caterpillars. Indole (designated by the blue crosses) is released when a leaf wound (as indicated by the primary VOCs, designated by the blue diamonds and the red squares) has contact to caterpillar saliva.

Figure 3. Plant reactions under attack from caterpillars. Indole (designated by the blue crosses) is released when a leaf wound (as indicated by the primary VOCs, designated by the blue diamonds and the red squares) has contact to caterpillar saliva.

Wasps are attracted by VOCs, released by plants as a reaction to caterpillar attacks. Picture: Held.

Figure 4. Wasps are attracted by VOCs, released by plants as a reaction to caterpillar attacks. Picture: Held.

Reference

*Dr. Ted Turlings, Dr. Matthias Held, Université de Neuchâtel, Tél. +41 32 718 3161, [email protected]

About Ionicon Analytik Ges.m.b.H.

IONICON Analytik was founded 1998 as a spin-off company of the University of Innsbruck, Austria commercializing an innovative technology called Proton Transfer Reaction - Mass Spectrometry.

Since then they have been improving this leading-edge technology resulting in the development of several types of ultra sensitive high resolution online mass spectrometers for monitoring and quantification of volatile organic compounds (VOCs) in sub-pptv level concentrations.

Today they are the world’s leading producer of trace gas analyzers with market-leading, real-time, single-digit pptv-level detection limits using the unique Proton Transfer Reaction – Mass Spectrometry (PTR-MS) and Selective Reagent Ionization – Mass Spectrometry (SRI-MS) technology.

Their product portfolio includes quadrupole MS and time of flight MS based instruments, industrial VOC monitoring solutions and custom built instrumentation, complemented by their own range of trace calibration devices and accessories.

Since 1998, they are serving their customers in many different application areas including atmospheric chemistry, environmental research and trace gas analysis (e.g. emissions in urban and remote areas, indoor spaces, vehicles), food and flavor science (e.g. analysis of coffee, olive oil, butter, cheese, wine, herbal extracts and aromas), industrial VOC monitoring (e.g. in waste incineration plants, chemical factories and production sites of the semiconductor industry) and illicit substances detection (Explosives, CWAs, TICs).

A special focus was given to medical and biotechnological applications where real-time monitoring of industrial fermentation processes, of synthetic gas production processes in the petrochemical industry and real-time breath gas analysis in clinical settings are carried out.

They also offer analytical services and are an active contributor to numerous international scientific research and training projects.

In 2016 they proudly celebrated 300 PTR-MS instruments sold. They manufacture their precision instruments at their company site located in Innsbruck, Austria.


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Last updated: Feb 18, 2019 at 4:42 AM

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