Exam I - Plant Chemical Ecology I. Plant Metabolism a....

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Plant Chemical Ecology I. Plant Metabolism a. Primary Metabolism i. Involved in the biosynthesis of compounds that are essential for plant cell division and growth ii. Most compounds common to other organisms b. Secondary Metabolism i. Compounds that are not essential for plant cell division and growth ii. Diverse array of compounds, many unique to plants iii. Role of Secondary Metabolites 1. Metabolic “Wastes” a. No functional purpose b. Metabolic inefficiencies – trash c. Nitrogen overflow d. Excrement 2. Mediate Ecological Relationships a. Serve role in increasing fitness of plant b. Clear biological activities II. “The Good” – Beneficial Interactions a. Attraction for Pollinators i. Food 1. Floral Nectar a. Nectar as sweet reward b. Nectars vary in sugar content and composition c. Nectar contain amino acids and vitamins d. Symbiosis – Ants ii. Colors 1. flowers are most common plant anatomical structures that use color to attract insects and animals 2. important long-distance cue 3. less important for night pollinators, therefore often white 4. certain flowers try to resemble smells and colors that attract pollinators 5. Insect UV Light Perception a. Insects perceive broader spectrum of light, particularly UV range b. Plants use chemicals that emit/absorb in UV range to provide clues for where nectar/pollen’s location iii. Fragrances 1. “Sweet” Smells Attract: bees, birds, beetles, moths, and bats 2. “Putrid” Smells Attract: flies and beetles iv. Pheromones 1. Pheromones – small molecule chemicals that are sexual attractants 2. some plants synthesize very similar compounds as 2’ metabolites and thus attract insect pollinators v. Mimicry 1. orchids combine pheromones with flower structures that mimic female insect – pseudo-copulation and transfer of pollen III. “The Bad” – Defensive Interactions a. Animals as Electricians, Plants as Chemists i. Animals – “fight or flight”, systems used to defend and protect (muscles, sight, hearing, etc) ii. Plants – use chemical and mechanical methods of protection
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b. Chemical Defenses: i. Mechanical 1. thorns 2. sticky glandular hairs ii. Digestibility Reducers 1. cellulose, hemi-cellulose, and pectin 2. lignins (cellulose) and tannins (proteins) – make them indigestible 3. protease inhibitors to block digestive enzymes iii. Toxins 1. Amino Acid Analogs a. A.A. as 1’ metabolites b. Analogs as 2’ metabolites c. Incorporate into proteins and cause misfolded non-functional proteins d. Effective against plants and animals 2. Alkaloids a. Broad class of compounds with nitrogen-containing ring structure b. Usually very bitter taste and toxic c. Ex: caffeine, morphine, nicotine, quinine, cocaine 3. Cyanogenic Glycosides a. Synthesized as cyanide chemically linked to sugars (inert until glycoside is broken) b. Plant also synthesizes a glucosidase enzyme to cleave bond during herbivory c. Glucosidase and glycoside compartmentalized separately d. Cyanide disrupts respiration
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This note was uploaded on 03/29/2008 for the course PPWS 2104 taught by Professor Jelesko during the Spring '07 term at Virginia Tech.

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Exam I - Plant Chemical Ecology I. Plant Metabolism a....

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