The electrical penetration graph or EPG is a system used by biologists to study the interaction of

insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...

s such as

aphid Aphids are small sap-sucking insects in the Taxonomic rank, family Aphididae. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white Eriosomatinae, woolly ...

thrips Thrips (Order (biology) , order Thysanoptera) are minute (mostly long or less), slender insects with fringed wings and unique asymmetrical mouthparts. Entomologists have species description , described approximately 7,700 species. They fly on ...

, and

leafhopper Leafhopper is the common name for any species from the family (biology), family Cicadellidae: based on the type genus ''Cicadella''. These minute insects, colloquially known as hoppers, are plant feeders that suck plant sap from grass, shrubs, or ...

s with

plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...

s. Therefore, it can also be used to study the basis of

plant virus Plant viruses are viruses that have the potential to affect plants. Like all other viruses, plant viruses are obligate intracellular parasites that do not have the molecular machinery to replicate without a host. Plant viruses can be pathoge ...

transmission, host plant selection by insects and the way in which insects can find and feed from the

phloem Phloem (, ) is the living tissue in vascular plants that transports the soluble organic compounds made during photosynthesis and known as ''photosynthates'', in particular the sugar sucrose, to the rest of the plant. This transport process is ...

of the plant. It is a simple system consisting of a partial circuit which is only completed when a species such as aphids, which are the most abundantly studied, inserts its stylet into the plant in order to ''probe'' the plant as a suitable host for feeding. The completed circuit is displayed visually as a graph with different waveforms indicating either different insect activities such as saliva excretion or the ingestion of cellular contents or indicating which tissue type has been penetrated (i.e.

xylem Xylem is one of the two types of transport tissue (biology), tissue in vascular plants, the other being phloem; both of these are part of the vascular bundle. The basic function of the xylem is to transport water upward from the roots to parts o ...

mesophyll A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, f ...

). So far, around ten different graphical waveforms are known, correlating with different insect/plant interaction events.

The Circuit

The circuit connects to the insect via a 20 μm

gold Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...

platinum Platinum is a chemical element; it has Symbol (chemistry), symbol Pt and atomic number 78. It is a density, dense, malleable, ductility, ductile, highly unreactive, precious metal, precious, silverish-white transition metal. Its name origina ...

wire and to the plant via a copper electrode placed in the soil. The circuit also passes through, normally, a one gigaohm

resistor A resistor is a passive two-terminal electronic component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active e ...

and a 50x

amplifier An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It is a two-port electronic circuit that uses electric power from a power su ...

before the results are stored digitally and interpreted by a computer to calculate the final graph.

References

* Tjallingii, W.F. (1988). Electrical recording of stylet penetration activities. In: A.K. Minks & P. Harrewijn (eds.). Aphids, their biology, natural enemies and control, 95–108. * Martin, B.; Collar, J.L.; Tjallingii, W.F.; Fereres, A. (1997). Intracellular ingestion and salivation may cause the acquisition and inoculation of non-persistently transmitted plant viruses. Journal of General Virology, 78, 2701–2705. * Sauge M.H.; Lambert P.; Pascal T. (2012). Co-localisation of host plant resistance QTLs affecting the performance and feeding behaviour of the aphid Myzus persicae in the peach tree. Heredity, 108 (3), 292–301. * Giordanengo P. (2014). EPG-Calc: a PHP-based script to calculate electrical penetration graph (EPG) parameters. Arthropod-Plant Interactions, 8(2):163-169.

External links

EPG-systems

EPG-Calc
{{DEFAULTSORT:Electrical Penetration Graph Entomology equipment Phytopathology Environmental Sampling Equipment

The Circuit

See also

References

External links