Plant-Animal Warfare

These are just a few examples among many, and further examples are given in the references quoted at the end of this chapter. They are intended to illustrate the remarkable range of chemical structures among the toxic compounds produced by plants, which give evidence of the intensity of plant-animal warfare during the course of evolution. In some cases, they provide examples of how natural compounds have served—and continue to serve—as models for the development of new pesticides. 

Kaplowitz, N. Hepatotoxicity of herbal remedies insights into the intricacies of plant-animal warfare and cell death. Gastroenterology 1997 113 1408-1412... 

As explained in Chapter 1, the toxicity of natural xenobiotics has exerted a selection pressure upon living organisms since very early in evolutionary history. There is abundant evidence of compounds produced by plants and animals that are toxic to species other than their own and which are nsed as chemical warfare agents (Chapter 1). Also, as we have seen, wild animals can develop resistance mechanisms to the toxic componnds prodnced by plants. In Anstralia, for example, some marsupials have developed resistance to natnrally occnrring toxins produced by the plants upon which they feed (see Chapter 1, Section 1.2.2). 

Agosta, W. (1996). Bombardier Beetles andFeverTrees A Close-up Look at Chemical Warfare and Signals in Animals and Plants. Reading, MA Addison Wesley. 

Gonzalez FJ, Nebert DW. Evolution of the P450 gene superfamily animal-plant warfare , molecular drive, and human genetic differences in dmg oxidation. Trends Genet 1990 6 182-186. 

The Protos warfare on their Lept neighbors depended heavily on chemicals, but ants are by no means unique in making extensive use of chemicals for communication and warfare. From one-celled organisms to complex plants and animals, many living creatures do the same. As species develop over evolutionary time, it is relatively easy for them to adapt their cellular machinery to producing chemicals for communication, warfare, and other purposes. These chemicals facilitate the way of life of organisms spread all across the biological spectrum. 

Herbicides, used to kill or damage a plant, are the most rapidly growing segment of pesticides. Prior to the 1930s, herbicides were non-specific and often very toxic to humans as well as other animals. In the 1930s, in parallel with the development of new insecticides, researchers discovered several chemicals that selectively killed plants. These chemicals are now widely used to increase food production and have been used in warfare. Herbicides come in a variety of chemical structures and mechanisms of action, so they will be discussed in only general terms. Interested readers are referred to the many web sites and extensive literature on herbicides (see below and the presentation). 

Physiological Action.—Sulphur dioxide exerts a decidedly toxic effect on plants 3 and animals,4 and has been used in poison ga,s warfare (see p. 106) even as little as 0-04 per cent, by volume in the atmosphere will cause symptoms of poisoning in human beings after a few hours in larger quantities, either gaseous or dissolved, the effect may be fatal. The gas acts as a direct blood poison and also affects the blood circulation.5 The sulphites are not poisonous.6... 

The use of chemicals to dispatch enemies is not the sole prerogative of humans. Animals and plants have also adopted what is known as chemical warfare. Both animals and plants, as well as bacteria and fungi, can produce and contain some of the deadliest chemicals for the purpose of discouraging a predator or killing a potential meal. We come across such poisons in our everyday hves in the form of ant bites and wasp, bee, and nettle stings. In some countries the indigenous plants and animals may be especially hazardous, as we shall discover in Chapter 6. 

---