Plant_secondary_metabolites - Ioana Dobre Plant secondary...

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Ioana Dobre Plant secondary metabolites The insect sequesters compounds from the plant and uses them for protection against its own predators - Advertises its toxicity with its blue coloration Communication for lower life forms is largely through chemicals i.e secondary metabolites - These are not needed for photosynthesis, nitrogen metabolism etc - They are only used in chemical ecology - They are the typical medicinal compound of plants Chemical ecology of plant secondary metabolites (PSM) - Chemical ecology is the study of chemically mediated interactions between organisms PSM’s provide: 1) Protection against insects as feeding deterrents or “antifeedents” as well as growth reducers, toxins, etc. - In an insect or large herbivore comes around, they need to defend themselves through chemical warfare - They are endowed with exquisitely toxic chemicals - In evolutionary terms, insects have put much more pressure on plant biology than other organisms 2) Create biochemical interference with other plants “allelopathy” -they direct phytochemical defenses against plants that they are competing with 3) Provide protection against fungi, especially as inducible anti-fungals called “phytoalexins” - These toxins can also be directed against pathogens like fungi, viruses, bacteria 4) May provide positive communication in legume nodulation or pollination ( flower scent), natural enemies - Some secondary metabolites may not have a negative effect on other organisms may provide positive communication e.g pollination - Flowers may communicate with their pollinators through delightfully scented compounds, or beautiful colors - May also send out volatile compound to bring in natural enemies of the caterpillars that are attacking them
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Ioana Dobre Antifeedant effect of pure compound - Insects are completely deterred by the anti-feedant compound - They starve to death rather than feed on the leaves In situ avoidance of toxin in Gland on leaf edge of St. John’s wort - This plant contains toxic compounds but the insect does not eat all the leaf. It only eats the parts that do not consists of the toxic glands which have light activated toxins - They preferentially eat between the veins where there are fewer glands available - Other insects that eat the whole leaf, die intoxicated Black – eyed susan or brown daisy - Contains light-activated toxins (substances that become active upon light stimulation) Crispy critters: - The larvae were fed thiophene from the black eyed susan and then placed in the sun light for a few minutes - A few minutes later, the chemicals become activated and the insects become barbequed Allelopathy in California chaparral: (cyclic) - Sage is a very aromatic bush
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Plant_secondary_metabolites - Ioana Dobre Plant secondary...

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