Botanysecondary metabolismA class of organic compounds with a wide variety and generally less content, also known asSecondary metabolites。It is mainly divided into nitrogen containing organic matterTerpenoidandPhenolic compoundsThree categories, such aspigment, alkaloidsTerpenoids, antibiotics, etc.They are different from the primary metabolites in terms of distribution and function in addition to their different ways of production.The distribution of secondary substances is limited, only appearing in certain species, organs, tissues or cells.In terms of function, some secondary substances such as plant hormones, as regulators of growth and development, have become important substances of life;Some actionsAttractant、Repellent、AntifeedantAnd antimicrobials are of great ecological significance.
exceptSugar、Fat、nucleic acidandproteinEquibasicorganic compoundoutside,Plant bodyThere are many other organic substances in theTerpenoids、PhenolsandalkaloidThey are composed of sugars, fats, amino acids and other organic substancesmetabolizeThe derived substance is therefore calledsecondary plant substance 。[1]The so-called secondary plant substances refer to a variety of organic substances that exist in plants and have no direct relationship with the growth and development of plants, but play an important role in plant adaptation to adverse environments or resistance to pathogens, as well as plant metabolic regulation, also known as secondary products or natural compounds.Secondary plant substances are different from primary metabolites such as amino acids, nucleotides, sugars and membrane lipidsphotosynthesis、Respiration, assimilate transport, growth and differentiation and other physiological processes, there is no direct or obvious role.In addition, the production and distribution of secondary plant substances are often limited to one or several plant species that are similar in taxonomyprimary metabolite It exists in all plants.Secondary plant substances stored in vacuoles or cell walls are the final products of metabolism. Except for a few, most of them no longer participate in metabolic activities.
Role of secondary plant substances
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Organic compounds produced in plants but not essential in their growth, development, reproduction and other life activities;Mainly divided intoNitrogenous organic matter、TerpenoidandPhenolic compoundsThree categories, including nonProtein amino acid、amine , alkaloidsPhenols, benzenepropaneAcidsCoumarins、Flavonoids、Cyanogenic glycoside、lipid、Terpenoids、anthraquinoneAnd glucosinolates.Its production and distribution are limited, that is, certain secondary substances only appear in specific species, organs, tissues or cells, as well as in specific growth and development periods, and the amount produced is strongly affected by environmental conditions.It plays an important role in the survival and development of plants.[1]
Some are used as growth regulators, such as plant hormones andGrowth inhibitor；Some actionsAttractant、Repellent、AntifeedantAnd antimicrobials are of great ecological significance.Some secondary substances have great application value in industry and medicine, such as rubber, ginsenoside, etc.Plant secondary substancesThere are many varieties with different chemical structures, but they all originate from a few precursors, such asacetic acid、Shikimic acidandIsopentene pyrophosphateEtc.These precursors are often found inprimary metabolism The critical branch point position in.[1]
Factors affecting the formation of secondary plant substances
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The formation of plant secondary substances is not only related to the growth and development of plants, but also strongly affected by environmental conditions such as light, temperature, rainfall and nutrients.Therefore, in different latitudes, altitudes, climates and soil conditions, the content of secondary substances in plants varies greatly.For example, the content of alkaloid quinine in the bark of Cinchona is up to 15%, while in rainy seasonsoil moistureHigh hourcinchonaIt does not produce quinine.In alpine plantsFlavonoidsThe content of substances is much higher than that of the same kind of plants on the flat land.Proper application of nitrogen fertilizer can improvelupinandbarleyAlkaloid content in.Ammoniacal nitrogenrelativelyNitrate nitrogenIt is more conducive to the formation of alkaloids in Ligusticum ligusticum.In recent years, there have been many successful cases of using plant tissue culture technology to produce secondary biomass.Through the regulation of the culture environment, some have increased the content of secondary biomass, and some have changed the type of secondary biomass.in China,Ginseng、three seven、Lithospermum, Coptis chinensis and other medicinal plantscell cultureAll have achieved success.Such as Lithospermum cellsuspension culture GeneratedNaphthoquinones The content of pigment is 8 times higher than that of the original plant.[1]
Significance of secondary plant substances
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On the surface, plants can not move and will not take the initiative to fight back. They have a long life cycle and are at a disadvantage in the relationship with insects. However, insects are small in size, short in life cycle and high in reproduction rate. They can quickly adapt to the changing environment. Moreover, insects have wings and can migrate from far places and find food resources.However, plants are still lush, covering most of the land surface.Obviously, plants have effective physical, chemical and developmental resistance mechanisms.The mechanism of chemical resistance mainly depends on plant secondary substances: understanding plant secondary substances is a key to study the relationship between insects and plants.
Although Julus Von Liebig pointed out in 1858Plant secondary substancesstayPlant resistanceHowever, some botanists insist that plant secondary substances are only wastes of plant metabolism;It was not until the second half of the 20th century that people unified their understanding and gradually realized the significance of plant secondary substances (Mothes 1995).Fraenkel (1959) further emphasized the role of plant secondary substances in defense against insects and other natural enemies.The secondary substances of plants are more important and effective than any other single natural factors in resisting the invasion of diseases and pests.Not only that, plant secondary substances also play an important role in resisting adverse physical and chemical environment.
It is generally believed that the chemical composition of different parts of plants and between plants are similar (i.e. homogeneous).In fact, the chemical composition of plants is different in space and time, that is, heterogeneous.This heterogeneity in chemical composition and structure of the plant world has formed a huge resistance barrier against insect damage.Here, resistance refers to the characteristics of plants that can avoid or reduce the damage of plant eaters.Resistance and defense are not synonyms, because "defense" means the purpose of evolution, while "resistance" is more neutral, so most people tend to use the word "resistance".[2]
A class of nitrogen-containing alkalinitynatural product。More than 5500 alkaloids are found in about 4000 plants, mainly distributed inDicotyledonMedium.Alkaloids are divided into three categories: true alkaloids contain nitrogenHeterocycleNuclear, e.gIsoquinoline alkaloidClass;The original alkaloids do not have heterocycles and are usually simple amines, such as cactus alkaloids and ephedrine.Both true alkaloids and protoalkaloids are derivatives of amino acids, and some protoalkaloids may be precursors of true alkaloids;Pseudoalkaloids are not derivatives of amino acids, but are derived fromTerpenoids、purineandSterolsMaterial production,PseudoalkaloidincludeTheobromineAnd caffeine, bothMethylationPurine.Most alkaloids are bitter and toxic, and have strong and specific effects on human nerve centers.asmorphine、atropine、berberine、vincristine、quinineandHyoscyamineAnd so on are important drugs.Some alkaloids can protect plants from animals.The phenomenon that insects choose to invade one or a few plants may be related to the effect of alkaloids.[1]
Non protein amino acids
About 400 species have been identified, which are rich in some legume seeds, most of which are toxic.Because their structures are similar to protein amino acids, they can be wrongly mixed into proteins to form toxic proteins, which affect the normal metabolism of organisms and cause deathAntimetabolite。asLily of the valleyAmmonia can interfereprolineSynthesis or utilization of.wrongProtein amino acidIt can protect plants themselves.asOil hemp vinePlant seeds containTyrosineStructurally similarL-dopaIt is toxic to insects and can protect seeds from insects.But this substance is non-toxic to mammals and can be used as a treatmentParkinson's diseaseDrugs.[1]
amine
About 100 kinds of amine secondary substances have been identified.stayseed plantIt is widely distributed in the middle part of the plant and often exists in flowers. It has a foul smell and can repel animals and attract some insectspollination。Some amines have hallucinogenic effects.[1]
seed plantIt can form various terpenoids andSteroid。About 3500 structures have been identified.They are composed of isopentene unit, which is formed by acetic acid -MevalonatePathway biosynthesis.By twoIsopentene(C5) Unit synthesisMonoterpene, such as myrceneLimonene、menthol 、camphorAnd so onvolatile oilComposition;Synthesis from three isopentene unitsSesquiterpene, such as plant hormoneabscisic acid, Intestinal ParasiticsYamato YearEtc., found in recent yearsCompositaeContains multiple sesquiterpeneslactone, has anti-cancer and sensitization effects;Diterpenoids are composed of four isopentene units, such as plant hormonesgibberellin、anticatarrhalsAndrographolideEtc;Synthesized from 5 isopentene unitsBisquiterpeneThere are few in nature, such as amperocoelin from fungi and spongin isolated from sponges;Consists of 6 isopentene unitsTriterpene，GinsengThe main components ofTriterpene saponin, someCardiac glycosideThis is also true;8IsopenteneThe unit forms terpene, such asCarotene; It is composed of multiple isopentene units, such as rubber.SteroidsThey are not true triterpenes, but have C27-C29 skeletons rather than C30 skeletons.Because their biosynthetic precursors are all C30Spinalene, so it is often considered together with triterpenes.SteroidalcholesterolAnd its esters are important components of biofilm.Cholesterol is also the raw material for biosynthesis of steroid hormones, which is synthesized in many plantsEcdysoneOfSteroid hormone。Ecdysone can affect insect metamorphosis, and can be used to control the development and behavior of silkworm in agriculturePollution-free pesticidePest control.[1]
A large category of benzeneChromonePlant based on environmental systemnatural product。PressPyran ringThe oxidation degree of can be divided intoAnthocyanin、flavone、isoflavoneandFlavanoneFour categories.FlavonoidsIt is water-soluble, and is usually associated withPentoseorHexose(sometimes with disaccharides orTrisaccharide）ChengGlycosideForm exists.FlavonoidsThere are many kinds. The yellow, orange, red, blue and other pigments of plant flowers, leaves, fruits and other parts are mainlyFlavonoids。Some flavonoids are associated withauxin(Indole acetic acid）Control of activity, e.gQuercus barkKetogenic inhibitionIndoleacetic acid oxidaseActive, while 4, 5, 7-TrihydroxyflavoneAlcohols can promote the activity of this enzyme.Some isoflavones arephytoalexins , such as the tincture to avoid killing accumulated after pea tissue is infected by bacteria.Some isoflavones have similarestrogenActivity.SomeflavonoidIt is highly toxic to some animals, such asrotenone。Most flavonoids and isoflavones are non-toxic to mammals, and some can be used for medicine, such asVitamin Pandrutin。SomeFlavonoidsIt is unique to some plant groups and can be used as a basis for plant classification.[1]
Quinones
By benzene or morecyclic hydrocarbonAromatic dioxides derived from hydrocarbons (such as naphthalene, anthracene, etc.).According to its ring system, it can be divided intoBenzoquinone、NaphthoquinoneandAnthroneEtc.Quinones are widely found inbiological groupMedium.With longIsoprenoidSide chain quinones, such asPlastoquinone、UbiquinoneAnd quinones participate in basic life activities such as photosynthesis and respiration.Quinones are yellow, orange or red, which is also the reason why plants are colored.[1]
