The Effect of Light Pollution of FloraA study by: Spencer Kisler and Lawson WakemanWhat?

Answers.com defines light pollution as “Excess or obtrusive light created by humans.” Due to the fact that cities are being built closer and closer forests and plant life every day, plants are being increasingly affected by the lights of these cities and towns that surround them. Among the many effects, light pollution disrupts ecosystems, causes adverse health effects, obscures the stars for city dwellers, interferes with astronomical observatories, and wastes energy.”  This light pollution aside from being bothersome to humans and wild life may have a positive or negative effect on flora and plant life, the negative effect being the stunting of the plants ability to process excessive light and still be healthy, the positive being stimulating the plant to keep possessives going later into the evening. We thought that the light would hurt the plants because if you think about what happens when you leave a plant out in the sun too long; it wilts. This is because the suns rays dry up the water in the plant. The artificial light obviously doesn’t have this same effect or if it does it’s not as extreme Light pollution in New York City

How?First we obtained the necessary materials then we set up timers as follows:      Box 1: 12 hours of the full spectrum growth bulb, 12 hours of no light at all (control).      Box 2: 12 hours of the full spectrum growth bulb, 4 hours of fluorescent light (to simulate light pollution)      Box 3: 12 hours of the full spectrum growth bulb, 8 hours of fluorescent light (to simulate light pollution)      Box 4: 12 hours of the full spectrum growth bulb, 12 hours of fluorescent light (to simulate light pollution) We then put 1 cup of potting soil in each pot. Next we used a dowel to make a hole 1 inch deep and 1/4 inch in diameter. Then we proceeded to sow popcorn seeds (we choose pop corn seeds because they germinate quickly in, about 1 week) into the inch deep holes (one per hole). After that we had to cover seeds with fresh dirt and compressed lightly. Then we assembled the boxes so that one side is duct taped close (both inside and outside) and the other is still open and facing up and attached the light fixtures. Next we made an opening that could be opened and closed so we could monitor and water the plants. After that we setup the timers to control the lights and cut small holes in the boxes to allow air in and out. Finally we started data collection and observations.

Lawson assembling a light fixture

Results In our first try the first and second boxes produced nearly the same results and the third and fourth boxes had very few seeds germinate. We found these results to be inconclusive so we tried the experiment again and more closely monitored the plants and we got almost the opposite results. The graph to the left shows the results of our second and more accurate trial. It actually proved the opposite of what we were expecting. That is that the light pollution positively affected the plants rather than hurting the plants.

Average Height of Plants Per Day

0

5

10

15

20

25

0 2 4 6 8 10 12 14 16

Day

Heig

ht in

Inch

es box 1

box 2

Box 3

Box 4

Spencer planting the popcorn

DAY box 1 box 2 Box 3 Box 4day 1 0.333333 0.875 0.25 0.125day2 1.164063 1.125 0.9375 0.652778day 3 1.729167 1.345 1.607143 1.372024day 4 2.205714 2.154167 2.810714 2.657738day 5 3.218286 2.39881 3.521429 3.678571day 6 4.332857 3.285714 4.533854 5.767857day 7 5.192857 4.552083 5.747396 7.104167day 8 6.062143 5.447917 7.195313 9.458333day 9 6.992857 6.182292 8.463542 11.45536day 10 7.742857 6.945313 9.6875 12.76786day 11 8.207143 7.677083 11.33333 13.38988day 12 8.653571 9.210938 12.15179 15.10417day 13 9.55 10.5651 13.08594 16.6756day 14 10.18429 11.55208 14.8125 17.94048day 15 10.77857 12.63802 16.15104 19.98214

The chart above tells the average growth of each plant in each box (inches)

Now What? Since we had almost opposite results both times we could run the test a few more times to get a better idea of what we might have been doing wrong and we could then average the growth of all boxes.

Could this affect you? Since our results showed that light pollution had no affect and even helped the plants grow it most likely couldn’t, but since our results weren't as conclusive as we would have liked it could have some effect unseen by us. But if it turned out that the light did actually affect plants it could affect farms and other areas where you get your food.

Box four on day 15

Revised: Feb. 13, 2008