The leaves of some plants protect from webworm caterpillars and other pests because as they are chewed, they release a chemical combination of acids and alcohols that attracts pest-eating yellow jackets.
Summary: The yellow jacket hunting for a meal needs a chemical signal. A plant injured by a chewing insect such as a webworm will give off a chemical that would draw in yellow jackets.
"The heat that the webworm produces in its chewing isn't sufficient to identify it, as that's only produced at a low level and mixes with the general heat coming up from the leaves anyway. And similarly for any bubbles of gas from the surface wax of the leaf: a leaf is always releasing microbubbles of wax on its own, so the webworm's contribution is not going to mark it out…How could the bush make a signal, using only plant-available materials, that could float and pass on a coherent message to the circling wasp?…It's in two steps. If a plant leaf is damaged, one of the acids that's released changes from its usual heavy form into a lighter kind which evaporates more easily…What the wasp will respond to is a mixture of that smell with something else. In the leaf of our lawn-edge bush, there's another chemical mixed in…But suppose it could be made in a way that it would transform into a lighter, evaporating form only when it was crushed by something like the fastidious webworm caterpillar?…When the pressure of a biting insect is applied to the second chemical, alcohols much like our ordinary drinking alcohols split loose…alchohols easily evaporate to carry an odor outward." (Bodanis 1992:58) Learn more about this functional adaptation.
Bodanis, D. 1992. The Secret Garden: Dawn to Dusk in the Astonishing Hidden World of the Garden. Simon & Schuster. 187 p.
"The transport system that drives sap ascent from soil to leaves is extraordinary and controversial. More than a century ago, H. H. Dixon (1896) proposed that a pulling force was generated at the evaporative surface of leaves and that this force was transmitted downward through water columns under tension to lift water much like a rope under tension can lift a weight. The cohesion–tension theory (C–T theory), as it is known, supposes both adhesion of water to conduit walls and cohesion of water molecules to each other." (Tyree 2003: 923) Learn more about this functional adaptation.
Tyree, Melvin T. 2003. Plant hydraulics: The ascent of water. Nature. 423(6943): 923-923.
"Figure 5: Part of a stem of a robust grass, in cross section. Here mechanical strength of the stem is provided by the vascular bundles set in a matrix of thinner-walled cells, rather like rod reinforcements. Each vascular bundle has an outer sheath of fibres, forming a strong tube in which the two wide vessels can conduct water, and the strand of thin-walled, narrow cells (phloem) can transport sugar solutions with little risk of damage. Just to the inner side of the outer ring of smaller vessels the several layers of narrow cells eventually become thick-walled and provide additional strength in the form of a cylinder to the whole stem." (Cutler 2005:101) Learn more about this functional adaptation.
Cutler, DF. 2005. Design in plants. In: Collins, MW; Atherton, MA; Bryant, JA, editors. Nature and Design. Southampton, Boston: WIT Press. p 95-124
Based on studies in: South Africa (Estuarine) USA: New York, Long Island (Marine) USA: Texas (Lake or pond) USA: California (Marine) Malawi (River) Africa, Crocodile Creek, Lake Nyasa (Lake or pond) USA: California, Coachella Valley (Desert or dune) Puerto Rico, El Verde (Rainforest) New Zealand: Otago, Dempster's Stream, Taieri River, 3 O'Clock catchment (River) New Zealand: Otago, Healy Stream, Taieri River, Kye Burn catchment (River) New Zealand: Otago, Sutton Stream, Taieri River, Sutton catchment (River)
This list may not be complete but is based on published studies.
J. H. Day, The biology of Knysna estuary, South Africa. In: Estuaries, G. H. Lauff, Ed. (American Association for the Advancement of Science Publication 83, Washington, DC, 1967), pp. 397-407, from p. 406.
G. M. Woodwell, Toxic substances and ecological cycles, Sci. Am. 216(3):24-31, from pp. 26-27 (March 1967).
G. Fryer, The trophic interrelationships and ecology of some littoral communities of Lake Nyasa, Proc. London Zool. Soc. 132:153-229, from p. 219 (1959).
G. Fryer, 1957. The trophic interrelationships and ecology of some littoral communities of Lake Nyasa with special reference to the fishes, and a discussion of the evolution of a group of rock-frequenting Cichlidae. Proc. Zool. Soc. London 132:153-281, f
Townsend, CR, Thompson, RM, McIntosh, AR, Kilroy, C, Edwards, ED, Scarsbrook, MR. 1998. Disturbance, resource supply and food-web architecture in streams. Ecology Letters 1:200-209.
Thompson, RM and Townsend, CR. 1999. The effect of seasonal variation on the community structure and food-web attributes of two streams: implications for food-web science. Oikos 87: 75-88.
B. C. Patten and 40 co-authors, Total ecosystem model for a cove in Lake Texoma. In: Systems Analysis and Simulation in Ecology, B. C. Patten, Ed. (Academic Press, New York, 1975), 3:205-421, from pp. 236, 258, 268.
R. F. Johnston, Predation by short-eared owls on a Salicornia salt marsh, Wilson Bull. 68(2):91-102, from p. 99 (1956).
Polis GA (1991) Complex desert food webs: an empirical critique of food web theory. Am Nat 138:123155
Waide RB, Reagan WB (eds) (1996) The food web of a tropical rainforest. University of Chicago Press, Chicago
"Virtually all true mire vascular plants are perennial. This is a most effective way to ensure a large biomass, both below and above ground. In a nutrient-poor environment, a relatively large root biomass is required to obtain enough resources, and this cannot easily be built up within one season. Also, the large above-ground biomass which may be necessary for light capture in wooded mires can be built only by perennials." (Rydin and Jeglum 2006:50) Learn more about this functional adaptation.
Rydin, H.; Jeglum, J. K. 2006. The Biology of Peatlands. Oxford University Press. 343 p.
"There has been relatively little attempt to produce an artificial analogue to wood because wood is cheap, lightweight, tough, moldable, and easily shaped. However, when a hole is drilled in timber, it weakens the structure. The tree, however, drills no holes, even though it must disrupt the trunk's wood where a new branch pushes through. The fibers deform around a knothole, remaining continuous. George Jeronimidis of the Univ. of Reading Center for Biometrics is proposing to study how this can be used in fibrous composite materials." (Courtesy of the Biomimicry Guild) Learn more about this functional adaptation.