Bio 270 - 2008 Direct Effects of Simulated Acid Rain (SAR) Experiment: Photos

Green house set up in 2008. Overview: This experiment examined the direct foliar effects of acute, short-term exposure to SAR on seedlings of three domesticated plant species: sunflower, radish, and clover. Simulated acid rain of pH 3.5 and pH 2 (tapwater acidified with a 2:1 molar ratio of sulfuric:nitric acids) was sprayed onto the above-soil foliage of 11 day old seedlings once daily to completely wet the foliage and moisten the soil surface for a total of 19 daily applications. The controls were similarly treated with plain tap water (pH 6.8 at initiation of treatment phase). The seedlings were watered to soil saturation once daily with tapwater either several hours before or after treatment application.There were 14 replicates (pots of seedlings) per species per treatment group in 2008. The plants were measured for stem and leaf lengths, dry biomass per plant, total chlorophyll content (sunflower only in 2008), the proportion of plants that exhibited any damage (dead cells, lesions, spotting, etc.), and the percent leaf area exhibiting damage. Leaf wettability was examined by placing drops (20-30 ul) on the leaves and observing retention and drop shape. Leaf samples were also prepared and viewed using a scanning electron microscope to document microscale effects (view poster of SEM images). Seedling Establishment (11 day) Day 8 of SAR Applications CONTROLS pH 3.5 pH 2.0 Day 17 of SAR Applications CONTROLS pH 3.5 pH 2.0 SAR applications were (will be) stopped on Feb 9th, 2008. Following are detail shots of the typical physical effects of the acid treatment on the pH 2 plants. These photos are from various years, but typify direct effects we see routinely in this experiment.   pH 2 sunflower with true leaf petiole growing from cotyledon position on stem.   Abnormal leaf development in sunflowers. These were seen in pH 3.5 and control.   Same as above.   Sunflower pH 2 stem lesions day 19.   Scanning electron micrograph of acid burn on a sunflower leaf treated with pH 2 simulated acid rain.   2008 Bates College Modified on 2-6-08 GA