کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
4426768 | 1309135 | 2008 | 8 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Usnic acid controls the acidity tolerance of lichens Usnic acid controls the acidity tolerance of lichens](/preview/png/4426768.png)
The hypotheses were tested that, firstly, lichens producing the dibenzofuran usnic acid colonize substrates characterized by specific pH ranges, secondly, this preferred pH is in a range where soluble usnic acid and its corresponding anion occur in similar concentrations, and thirdly, usnic acid makes lichens vulnerable to acidity. Lichens with usnic acid prefer an ambient pH range between 3.5 and 5.5 with an optimum between 4.0 and 4.5. This optimum is close to the pKa1 value of usnic acid of 4.4. Below this optimum pH, dissolved SO2 reduces the chlorophyll fluorescence yield more in lichens with than without their natural content of usnic acid. This suggests that usnic acid influences the acidity tolerance of lichens. The putative mechanism of the limited acidity tolerance of usnic acid-containing lichens is the acidification of the cytosol by molecules of protonated usnic acid shuttling protons through the plasma membrane at an apoplastic pH < pKa1.
Journal: Environmental Pollution - Volume 156, Issue 1, November 2008, Pages 115–122