This is why they are excellent environmental indicator. An indicator species is an organism whose presence or absence reflects the overall health of an environment. Lichens flourish where there is good air quality; however, they cannot survive where the air is polluted and toxins loom.
This is because they have no stomata, or pores, to shut to keep the toxins out; therefore, absorbing all of the pollutants in the air. Because they are such unique organisms, they accumulate different metal anions in the air than other organisms, like plants do, for example. Lichens attract toxic metal ions.An ion is a charged atom. If the ion has a positive charge, it is a action. An ion with a negative charge is an anion. During the ion exchange process, Hydrogen, an anion, is released and metal actions move in. This process occurs when lichens are exposed to polluted air.
When the lichens are dropped into any of the metal solutions, their cell wall releases the methyl blue ions, which are replaced by metal actions. Upon their detachment, the ions integrate into the solution, which in turn, colors it blue. The darker the solution, the more metal actions taken in by the lichen.Valence is a measure of how much an atom wants to combine with something else. If the valence of a metal ion affects lichen uptake, then the higher the action, the faster the uptake process.
Materials and Methods This experiment was performed October 23, 2014. Seventy Foliose lichens were punched into small disks using a hole puncher. The disks were soaked in methyl blue indicator solution for thirty minutes. When time expired, a kitchen strainer was used to remove the lichens from the solution. The lichens then had to be rinsed with distilled water to remove any excess methyl blue.
Ten millimeters of cadmium chloride was measured out and poured into a test tube, proceeded by measuring out ten millimeters of lithium chloride, manganese chloride, sodium chloride, and zinc chloride and pouring into separate test tubes. In the seventh test tube, ten millimeters of distilled water was added. Five lichen disks were then dropped into each of the seven test tubes. The tubes were shaken every five minutes for thirty minutes. The last time the tubes are shaken, they were arranged in order, from lightest to darkest and labeled accordingly.
ResultsThe table below clearly shows the relationship between lichen disk uptake and valence of the actions. The higher the valence of the action, the faster the lichen discharged the methyl blue and absorbed the metal solution. Valence Greatest Lead 4+ Cadmium 2+ Manganese Zinc Lithium Sodium 1+ Water Discussion In this experiment, lichens absorbed the actions with a higher valence faster, which supports the hypothesis.