Erica's Original Notes There is a strong interdependence of all living things on this earth, and the following are some examples how plants fit into this system:
Eucalyptus has a toxic substance in its leaves which prevents competition and protects against predators.
Desert plants use toxic compounds to hold other plants at bay, as in Artemesia californicaand Salvia leucophylla, which grow together, surrounded by a denuded 6-8 foot zone, in which only their seedlings will grow, the soil having absorbed the plants' terpenes.
Balsam fir has terpenes similar to the juvenile hormone of the larvae of a harmful tree-defoliating moth. This was discovered by accident; it was found that the larvae housed in containers lined by paper towels made from the Balsam fir did not mature.
Nature's insecticides are found in plants with strong alkaloids, which are particularly well protected against insect enemies. Examples are pyrethrum, nicotine in tobacco, quinine in cinchona, caffeine in coffee, strychnos in strychnine, cocaine in coca, marijuana in hemp, and morphine in the opium poppy.
More about insects: Some acacias have resident ants for defense; they feed on the nectar provided by their host; their main enemy is the leaf-cutting ant (who was a farmer long before man!). These ants maintain a pure culture of fungi in subterranean gardens thanks to their antibiotic saliva on bits of leaves they have collected; the fungi produce the usual mycelium (roots); and, instead of fruiting bodies, they produce bromatia (white globules) on which the ants feed. The young Queen Ant takes some of the fungus with her to start a new colony, much as the early pioneers took some 'starter' dough with them!
Chemicals and insects: The female flightless Polyphemus moth sits on the red oak which has chemicals that stimulate the formation of her 'perfume' to attract a male suitor; scientists have found a chemical to block this action. A fruit fly is lured by angelica oil. Monarch butterfly larvae feed on milkweed which contains glycosides, and birds have long since learned to avoid monarch butterflies. Viceroy butterflies have cleverly learned to mimic monarchs to avoid being eaten.
Carnivorous plants: (See also Leaves). These plants need to seek protein because they live in marshes which are nitrogen deficient. They have a system of reducing the flesh of victims to a digestible state after having successfully trapped them with visual and other devices. Darlingtonia drown their victims, and bladderworts have trap doors. Butterworts have a surface resembling fly paper to trap insects; the edges then curl to entrap them, the insect being kept in this temporary stomach for two to three days while it is being 'digested'. This plant was used to curdle milk. Sundews (Drosera) have sticky droplets on moving, entrapping hairs.