Plant defense against herbivory which differ from one another in both functional groups, and in basic carbon skeletons. Monoterpenoids, continuing 2 isoprene units, are volatile essential oils such as citronella, limonene, menthol, camphor, and pinene. Diterpenoids, 4 isoprene units, are widely distributed in latex and resins, and can be quite toxic. Diterpenes are responsible for making "Rhododendron" leaves poisonous. Plant steroids and sterols are also produced from terpenoid precursors, including vitamin D, glycosides (such as digitalis) and saponins (which lyse red blood cells of herbivores). Phenolics, sometimes called "phenols", consist of an aromatic 6-carbon ring bonded to a hydroxy group. Some phenols have antiseptic
Nothing comes from nothing Nothing comes from nothing Nothing comes from nothing () is a philosophical expression of a thesis first argued by Parmenides. It is associated with ancient Greek cosmology, such as is presented not just in the works of Homer and Hesiod, but also in virtually every internal system—there is no break in-between a world that did not exist and one that did, since it could not be created in the first place. The idea that "nothing comes from nothing", as articulated by Parmenides, first appears in his "Physics": The above, in a translation based on the John Burnet translation, appears as