The Direct Effects of Simulated Acid Rain (SAR) - 2016 Experiment

Greenhouse set up in 2016


Overview: This greenhouse-based experiment examines the direct foliar effects of acute, short-term exposure to simulated acid rain (SAR) on seedlings of three domesticated plant species: sunflower, radish, and clover. The photo above show the typical arrangement of plants during the experiment. At least once during the treatment phase the treatment groups are shifted between tables and the pots randomized to some extent. Simulated acid rain of pH 3.5 and pH 2 (tapwater acidified with a 2:1 molar ratio of sulfuric:nitric acids) is sprayed onto the above-soil foliage of 10 day old seedlings once daily to completely wet the foliage and moisten the soil surface for a total of 19 daily applications. The controls are similarly treated with plain tap water (typically ~pH 6.8-7.4). The seedlings are watered to soil saturation once daily with tapwater either several hours before or after treatment application.There are 21 replicates (pots of seedlings) per species per treatment group in 2016. Upon completion of the treatment phase, the plants are measured for stem length and leaf area, dry biomass per plant, the proportion of plants that exhibit any damage (dead cells, lesions, spotting, etc.), and the percent leaf area exhibiting damage. Leaf wettability is examined by placing drops (20-30 ul) on the leaves and observing retention and drop shape (contact angle). Leaf samples are also prepared and viewed using a scanning electron microscope to document microscale effects on tissues, surface structures, and epicuticular wax (view poster of 2008 experiment SEM images).

Seedling Establishment 2016 (1/25/16 - Day 1 SAR application)



Day 8 of SAR Applications 2-2-2016

Click the individual images to see larger overview of plants in each treatment group.

 DAY 8 SAR 2-2-16 Sunflower side views


pH 3.5

pH 2

 Day 16 SAR applications - Feb 9, 2016.


Control overview  pH 3.5 overiew  pH 2 overview
Control wetted leaf  pH 3.5 wetted leaf  pH 2 wetted leaf


Control overview  pH 3.5 overview  pH 2 overview
Control wetted leaf  pH 3.5 wetted leaf  pH 2 wetted leaf


Control side view  pH 3.5 side view  pH 2 side view
Control wetted leaf  pH 3.5 wetted leaf  pH 2 wetted leaf
Control typical leaf appearance  pH 3.5 typical leaf appearance  pH 2 typical leaf appearance



Appearance at data collection (Feb 15-16, 2016)
Last SAR applications on Feb 13th, 2016. Total of 19 applications.

 Clover Control overview
 Clover pH 3.5 overview
 Clover pH 2 overview
 Clover Control whole view
 Clover pH 3.5 whole view
 Clover pH 2 whole view
 Clover pH 2 typical damage
 Radish Control overview
 Radish pH 3.5 overview
 Radish pH 2 overview
 Radish Control whole view
 Radish pH 3.5 whole view
 Radish pH 2 whole view
 Radish Control bolting plants
 Radish Control pH 3.5 plants
 >>>no bolting observed<<<
 Sunflower Control side view
 Sunflower pH 3.5 side view
 Sunflower pH 2 side view
Leaf fusion malformation - Control
 Typical effects at pH 2

Droplet formation images (from 2009 experiment)




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.

 SEM acid burn

Scanning electron micrograph of acid burn on a sunflower leaf treated with pH 2 simulated acid rain.


2015 Bates College
Modified on 2-23-2015 GA