Water Quality and pH Effects on Umbilicaria mammulata (Ach.) Tuck.

Publisher Website
Google Scholar
Abstract
The influence of water quality and pH on net CO2 exchange over time in the lichen U. mammulata was investigated. The experiments were set up to allow repeated exposure of thalli, over a 2-3 mo. period, to solutions with a predetermined chemistry and pH. The solutions used included Hoagland''s nutrient solution, tap water, mediated snow, distilled water, and distilled water adjusted to achieve pH levels of 2-10. The lichens showed reductions in net photosynthesis when exposed to the first two of the above solutions, but rates of decline over time were basically the same for all other treatments. This suggests that pH and water quality have relatively little control over rates of gas exchange in this species. In contrast, there was a large reduction in net CO2 exchange over time for all treatments, suggesting that the frequency of watering and the nature of the environment on which the plants were growing had a greater effect than did any of the treatments the plants were growing had a greater effect than did any of the treatments the plants were exposed to. The duration and frequency of precipitation is of far greater consequence to this plant in the field than is the pH or water quality of the rain itself.