Inducible defense

Head Kairomone components from head of robber bee Lestrimelitta limao that induce defensive behavior Citral 85 86, 6-methylhept-5-en-2-one 106 [156]... 

Keywords Marine chemical defense Activated defense Induced defense Plankton Chemical ecology... 

Condensation of coumaric acid with malonic acid yields the basic chalcone and stilbane skeletons (see Fig. 3.6). Stilbenes are found in most vascular plants, where they exhibit fungicidal and to a lesser extent antibiotic properties. They function as both constitutive and inducible defense substances. Some stilbenes inhibit fungal spore germination and hyphal growth, whereas others are toxic to insects and parasitic nematodes (round-worms). They also possess antifeeding and nematicide properties in mammals. For example, resveratrol (a stilbene in red wine) suppresses tumor formation in mammals. 

UV-C technology is widely used as an alternative to chemical sterilization and microorganism reduction in food products (Lamikanra 2002 Fan and others 2008). Ultraviolet light also induces biological stress in plants and defense mechanisms in plant tissues with the consequent production of phytochemical compounds (Lee and Kader 2000). Phytoalexin accumulation could be accompanied by other inducible defenses such as cell-wall modifications, defense enzymes, and antioxidant activity, which have been reported with health benefits (Gonzalez-Aguilar and others 2007). It is well documented that UV-C irradiation has an effect in secondary metabolism. 

Owing to the costs of defenses, natural selection will optimize defenses. There are various aspects in this optimization, including defense allocation with respect to temporal variation in grazing pressure and within-plant defense allocation with respect to grazing risk and the value of different plant parts (reviewed in Stamp 2003). Here we will focus on both the induced defenses and within-plant allocation of defenses, because these aspects have been widely studied in macroalgae. 

Amsler CD (2001) Induced defenses in macroalgae the herbivore makes a difference. J Phycol 37 353-356... 

Rothausler E, Macaya EC, Molis M, Wahl M, Thiel M (2005) Laboratory experiments examining inducible defense show variable responses of temperate brown and red macroalgae. Revista Chilena de Historia Natural 78 603-614... 

Graeve M, Dauby P, Scailteur Y (2001) Combined lipid, fatty acid and digestive tract content analyses a penetrating approach to estimate feeding modes of Antarctic amphipods. Polar Biol 24 853-862 Harvell CD (1990) The ecology and evolution of inducible defenses. Q Rev Biol 65 323-340 Hay ME (1996) Marine chemical ecology what s known and what s next J Exp Mar Biol Ecol 200 103-134... 

To date, no clear evidence of inducible defenses among freshwater macroalgae has been reported, in contrast to their marine algal counterparts. For example, certain species of marine brown algae increase phlorotannin production in response to damage by mesograzers (Amsler and Fairhead 2006 see Chaps. 3 and 7). Whether Chara and Cladophora, two species of freshwater chlorophytes with putative allelopathic activity, increase allelochemical concentration in response to competitors remains to be seen (see Sect. 5.7.3). 

Hansson, LA, Gustafsson S, Rengefors K, Bomark L (2007) Cyanobacterial chemical warfare affects zooplankton community composition. Freshwater Biol 52 1290-1301 Harvell CD (1986) The ecology and evolution of inducible defenses in a marine bryozoan cues, costs, and consequences. Am Nat 128 810-823... 

Two recent meta-analysis studies (Toth and Pavia 2007, and Chap. 3) have aided in clarifying patterns of induced defenses in macroalgae. These studies determined factors that do not play a role in inducing herbivore response (i.e., type of elicitor, artificial vs. natural food), highlighted factors that are important (i.e., size of the herbivore used and the timescale of the experiment), and illustrated distinct differences between algal groups in their ability to induce responses as observed through herbivore reactions (Toth and Pavia 2007, Chaps. 3 and 7). 

Specificity of molecular bioactivity and differentially induced defenses are only two examples of factors that can confound the interpretation of patterns at the macroscale. As our knowledge of marine systems continues to expand, the relative abundance of secondary metabolites in different geographic locations may be better understood. However, the literature supports the idea that local pressures and habitat, genetic composition, mode of response and metabolism of the algae play a significant role in shaping distribution patterns of secondary metabolites (e.g. Wright... 

Peckol P, Krane JM, Yates JL (1996) Interactive effects of inducible defense and resource availability on phlorotannins in the North Atlantic brown algaFucus vesiculosus. Mar Ecol Prog Ser 138 209-217... 

Table 7.1 Published studies explicitly testing hypotheses derived from the Induced Defense Model, a corollary model to the Optimal Defense Model, concerning variation in the concentration of secondary metabolites or resistance to herbivores in different macroalgal species... 

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