Fire-"The Component of Several Ecosystems"

e., allelopathic compounds); and (3) reduced rates of round off from both herbivores and pathogens (2:22).

Fire has a issuing of different effectuate on seeds (3:203-206). Various factors may be capable of touch germination. Such "cues" may include, for example, heat, in thorough nutrients, and the destruction of allelopathic compounds (2:1-22). In addition, chemical substance compounds associated with blackened or charred wood and scum bag may excessively cause germination.

In the scouring environment, researchers have shown that germination give the gate be induced by both heat jerking and chemicals leached from charred wood. The temporary cover that results from these influences includes "specialized ' give the gate annuals' and specialized ' cease perennials (7:1608-1621).'" Fire annuals ar usually only present in the first postfire year, whereas fire perennials reach their maximum population size in the tierce or fourth year by and by a fire.

umteen fire annuals such as Emmenanthe penduliflora and Phacelia species, among others, have refractory seeds with considerable longevity: Went (1969) reported that the seeds of a few fire annuals failed to germinate for 20 years (7:1608-1621). The heavily sclerified seed coats and compact cuticle of these species act as a physical prohibition to water and gases. Furthermore, it is widely believed that these seed coats can only be compromised by exposure to ext

1.Baldwin, I. T.; Morse, L. Up in smoke II. Germination of Nicotiana attenuata in reaction to smoke-derived cues and nutrients in burned and unburned soils. diary of Chemical Ecology. 20:2373-2391; 1994.

7.Keeley, S. C.; Keeley, J. E.; Hutchinson, S. M.; Johnson, A. W. Postfire taking over of the herbaceous flora in Southern California chaparral. Ecology. 62:1608-1621; 1981.

3.Brown, N. A. C. Seed germination in the fynbos fire ephemeral, Syncarpha vestita (L.)B.Nord is promoted by smoke, aqueous extracts of smoke and charred wood derived from burning the ericoid-leaved shrub, Passerina vulgaris Thoday. International Journal of Wildland Fire. 3:203-206; 1993.

5.Keeley, J. E.; Keeley, S. C.

Role of fire in the germination of chaparral herbs and suffrutescents. Madro?o. 34:240-249; 1987.

Similarly, Baldwin et al. (1994) found that wood smoke stimulates seed germination in the native tobacco specify, Nicotiana attenuata. In fact, the seeds of this southwesterly North American summer annual germinate after exposures of less than a minute to both cooled wood smoke and polar extracts of wood smoke. Moreover, it does not appear to matter what species of nominate is used to produce the smoke; even the combustion of comminuted cellulose is capable of inducing germination (1:2373-2391).

Various experiments have served to finish off the nature of the stimulating agent in charred wood. A number of chemical substances are known to be capable of break of serve seed dormancy. These include both simple compounds such as potassium nitrate, and more complicated molecules such as the plant hormone, gibberellin (9:90-99). The active ingredient in charred wood has been found to be water soluble and capable of passing through a 0.2 micrometer nitrocellulose filter. In addition, the fact that neither completely ashed wood nor Hoagland's solution has the same stimulatory effect suggests that the agent is an organic compound. Researchers have also observed tha
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