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Plant defense against herbivory or host-plant resistance is a range of adaptations evolved by plants which improve their survival and reproduction by reducing the impact of herbivores. Many plants produce secondary metabolites, known as allelochemicals, that influence the behavior, growth, or survival of herbivores. These chemical defenses can ...
Chemical defense is a strategy employed by many organisms to avoid consumption by producing toxic or repellent metabolites or chemical warnings which incite defensive behavioral changes. [ 1 ] [ 2 ] The production of defensive chemicals occurs in plants, fungi, and bacteria, as well as invertebrate and vertebrate animals.
Some chemical defenses once thought to be produced by the plant have since been shown to be synthesized by endophytic fungi. The chemical basis of insect resistance in endophyte-plant defense mutualisms has been most extensively studied in the perennial ryegrass and three major classes of secondary metabolites are found: indole diterpenes, ergot alkaloids and peramine.
This cost can be seen when plants that use chemical defenses are compared to those plants that do not, in situations when herbivores are excluded. Several species of insects sequester and deploy plant chemicals for their own defense. [34] Caterpillar and adult monarch butterflies store cardiac glycosides from milkweed, making these organisms ...
Hence, a plant which produces variable levels of defensive chemicals is better defended than one that always produces the mean level of toxin. [5] Second, synthesizing a continually high level of defensive chemicals renders a cost to the plant. This is particularly the case where the presence of herbivorous insects is not always predictable. [7]
Some plants have physical defenses such as thorns, spines and prickles, but by far the most common type of protection is chemical. [ 1 ] Over millennia, through the process of natural selection , plants have evolved the means to produce a vast and complicated array of chemical compounds to deter herbivores.
Plants are able to determine what types of herbivore species are present, and will react differently given the herbivore's traits. If certain defense mechanisms are not effective, plants may turn to attracting natural enemies of herbivore populations. For example, wild tobacco plants use nicotine, a neurotoxin, to defend against herbivores ...
A large number of defensins were initially isolated from seeds, where they are linked to the defense of germinating seeds against fungal pathogens, [11] but recent advances in bioinformatics and molecular biology techniques have revealed that these peptides are present in other parts of the plant, including flowers and roots.