Chemo Defenses In Plants
Chemo defenses in plants are induced by chemical inducers. Nitrogen-containing alkaloids are a diverse group of bitter-tasting nitrogenous plant compounds that are produced by a wide range of vascular plants to provide defense against pests and diseases.
Nitrogen-containing Alkaloids are a broad family of bitter-tasting nitrogenous plant chemicals inducers, present in many vascular plants for defense. It is composed of aspartate, lysine, tyrosine, and tryptophan, and has significant impacts on animal physiology. Caffeine is an alkaloid present in coffee, tea, and cocoa plants (Theobroma cacao). It kills insects and fungus.
Caffeine-generated chemo defenses by coffee seedlings may actually hinder the germination of other seeds nearby, a process known as allelopathy. Allelopathy enables one plant species to “defend” itself against competitors for growth space and nutrients.
The nightshade (Solanaceae) family produces many alkaloid chemicals. Nicotine is an alkaloid generated in tobacco roots (Nicotiana tabacum) and stored in vacuoles in the leaves. Herbivores grazing on the leaves tear open the vacuoles. Deathshade produces a neurotoxic and heart stimulant called atropine (Atropa belladonna).
Although it is hazardous in high doses, it has been used medicinally in small doses to dilate pupils and treat nerve gas poisonings. Capsaicin and related capsaicinoids are the active ingredients in chilli peppers that provide the burning sensation in hot, spicy meals.
Chemo defenses in plants through Cyanogenic glycosides
Chemical inducers like HCN, a deadly molecule that halts cellular respiration in aerobic species, is produced when cyanogenic glycosides (CG) are broken down. They are kept in distinct compartments or tissues inside the plant and when herbivores eat on these tissues the enzymes and substrates combine and generate deadly hydrogen cyanide. To break down glucosinolates (mustard oil glycosides), enzymes called thioglucosidases generate cyanide gas.
Proteins and Enzymes
A large number of plants and seeds have proteins that selectively inhibit disease and pest enzymes by blocking active sites or altering enzyme conformations. These proteins are tiny and contain a lot of cysteines. Inhibitors of amylase, lectin, and proteinase are examples.
Proteins, unlike terpenoids, phenolics, and alkaloids, take a lot of plant resources and energy to generate, thus they are only produced in large amounts following a disease or pest assault. Defensive proteins and enzymes suppress fungus, bacteria, nematodes, and insect herbivores once triggered.
Chemo Defenses by Defensins
Defensins are tiny cysteine-rich proteins that have wide antimicrobial action (Triticum aestivum). They are widespread and found in most plants. Plant tissues that contain defensins include leaves, pods, and tubers. They are also present in flowers and roots. They have a broad variety of biological actions that limit fungus and bacteria development.
Some defensins also impede herbivore digestion. The methods by which plant defensins suppress fungus and bacteria are yet unknown, although they seem to target molecular targets in pathogen plasma membranes. Inhibiting pre-existing ion channels or creating new membrane holes disrupts cellular ion homeostasis.
Digestive enzyme inhibitors chemo defenses in plants
Digestive enzyme inhibitors are proteins that prevent herbivores from digesting and absorbing nutrients normally. Alpha-amylase inhibitors attach to amylase enzymes and prevent starch digestion. Agglutination of blood cells is one of the many activities of lectins, which are non-enzymatic proteins and glycoproteins that bind to carbohydrates. Castor bean ricin is a potent poison (Ricinus communis). An N-glycoside hydrolase that penetrates animal cells and suppresses protein synthesis. Ricin is a very toxic toxin with a fatal dosage of just 0.2 mg in humans.
Protease inhibitors based chemo defenses in Plants
Protease inhibitors block digestive enzymes including trypsin and chymotrypsin, which are attacked by herbivores. It is known that they are found in legumes, solanaceous plants, and grasses. Herbivore feeding frequently initiates a cascade of molecular signaling events that promote the systemic synthesis of these chemicals in distant tissues, helping to shield unharmed plant sections against herbivore pest assaults.
Some plants generate hydrolytic enzymes in reaction to infections, which concentrate in extracellular areas and destroy pathogenic fungal cell walls. Chitinases are enzymes that degrade chitin, a polymer with a backbone similar to cellulose found in real fungi’s cell walls.
Glycosylated links in glucans, a type of polymers related to cellulose, are degraded by glucanases (water molds). These chemicals are anti-fungal in nature, and transgenic plants producing large amounts of these enzymes are resistant to a broad variety of foliar and root diseases. Enzymes that hydrolyze bacterial cell walls.