chemistry

Phytoncide

Phytoncide is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Phytoncide rather than just read about it. In short: Phytoncides are antimicrobial and insecticidal volatile organic compounds derived from plants. The word, which means "exterminated by the plant" (from the Greek φυτόν "plant" and the Latin caedere "to kill"), was coined in 1928 by Boris P.

Key takeaways

Phytoncide belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Phytoncide to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Phytoncide from memory before moving on to harder problems.

Reference excerpt

Phytoncides are antimicrobial and insecticidal volatile organic compounds derived from plants. The word, which means "exterminated by the plant" (from the Greek φυτόν "plant" and the Latin caedere "to kill"), was coined in 1928 by Boris P. Tokin, a Soviet biochemist then studying at Moscow State University. He found that some plants give off very active substances that help to prevent them from rotting or from being eaten by some insects and animals. Phytoncides are a biologically active substance of plant origin that kills or inhibits growth and development of bacteria, microscopic fungi, and protozoa. Phytoncides play an important role in plant immunity and in the relationships between organisms within an ecosystem. The ability to produce phytoncides is a quality common among plants. The release of phytoncides increase when a plant is injured. Phytoncide compound compositions vary depending on whether the compound is considered a glycoside, terpenoid, or other secondary metabolites.

Categories There are two categories of phytoncides: 1) nonexcretory phytoncides (found in the protoplasma of cells) and 2) volatile phytoncides (released into the atmosphere, soil and water). Examples of plants with nonexcretory phytoncides are onion, garlic, and horseradish. Examples of plants with volatile phytoncides are pine, oak, eucalyptus, and members of the Sophora genus. More than 5,000 volatile substances defend plants that protect them from bacteria, fungi, and insects. Phytoncides work by inhibiting or preventing the growth of the attacking organism.

Function

Some phytoncides affect only insects feeding on the plant, acting on the insect's autonomic nervous system. Other phytoncides target mainly microbes. The antimicrobial potency and range of phytoncides vary greatly among species. Some can kill many types of protozoa, bacteria, fungi, and insects within minutes or seconds, while others may take hours or only harm the pest. In addition to acting as a "plant protector", phytoncides can also impede the reproduction of pests.

Occurrence Cedar, garlic, locust, oak, onion, pine, tea tree, many spices, and many other plants give off phytoncides. Garlic contains allicin and diallyl disulfide. Pine contains alpha-pinene, carene, myrcene, and other terpenes. Sophora flavescens contains sophoraflavanone G.

Uses

Environment One hectare of pine forest releases approximately 5 kg of volatile phytoncides into the atmosphere daily, reducing the population of microflora in the air and essentially sterilizing the forest atmosphere, which contains only about 200-300 bacterial cells/m3. This effect is found more commonly in coniferous forests than deciduous forests.

Other Because of the antimicrobial properties of phytoncides, research has investigated potential use in medicine, as a plant protector in greenhouses, and in the shipping and storing of perishable fruits and vegetables. One volatile phytoncide, sophoraflavanone G, is of particular interest due to its potential for use against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus bacteria. Phytoncides are used in Ukrainian, Korean, Chinese, and Japanese traditional medicine, as well as in alternative medicine, aromatherapy, and veterinary medicine.

See also Plant defense against herbivory § Chemical defenses Allelopathy

References

Worked examples

Example 1 — a first encounter with Phytoncide

Start with the simplest possible case. Write down what Phytoncide claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Phytoncide before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Phytoncide ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Phytoncide

In research: Phytoncide appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Phytoncide in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Phytoncide is common in secondary-school and first-year university syllabi. It links to neighbouring topics Biologically based therapies, Phytochemicals, so understanding it makes those chapters shorter.
In everyday life: Look for Phytoncide outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Phytoncide in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Phytoncide means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Phytoncide out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Phytoncide in simple terms?

Why does Phytoncide matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Phytoncide?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Phytoncide.