by Emily M.

[Emily was one of just three students from her school whose project was selected to go on to the regional science fair, where she won Honorable Mention, winter 2001. Following is a short version of her science project report.]

HYPOTHESIS: This experiment tests the hypothesis that white elm mushrooms would grow bigger and faster under natural light and the fruiting bodies would exhibit fluorescence.

2 mushroom kits
15 watt black light (41 cm tube)
4 trays/ plates
spray bottle

1) The two matched mushroom growing kits were unwrapped and cut in half, leaving four "blocks" of equal size. Measurements were approximately 10.5cm in width, 16.25cm in length and 11.5cm in depth. Each block was rewrapped in plastic wrap.

2) After letting the cuts heal for two days, a slit of approximately 2.5cm was made through the plastic wrap on one side of two of the blocks. This is where the fruiting bodies, if any, should appear. These blocks were labeled ''A." The other two blocks, labeled "B", were allowed to rest two more days before cutting a slit in them.

3) Each block was then placed on a separate plate. One plate was placed in a tray of water to provide a source of moisture. The water was approximately 4mm deep, just below the surface of the plate. This tray was labeled "black light." The same process was repeated for another tray labeled "natural light." Water in both trays was refilled, as needed.

4) The tray labeled "black light" was then placed in a closed closet with a 15 watt black light (41 cm tube). The tray labeled "natural light" was placed outside the closet in indirect sunlight. Initially, the blocks were placed on their sides with the slit side close to the water.

5) Both trays were exposed to their light source for about the same time the sun was in the sky. The average amount of daylight during this period of time was approximately 10 hours and 14 minutes per day.

6) The mushrooms remained in darkness during the night. To better mimic the temperatures of fall, the season this kind of mushroom is most active, the temperature at night was kept cooler. During the day, room temperature averaged 69 degrees Fahrenheit (22.2 degrees Celsius), and at night, the temperature in the room was closer to 59 degrees Fahrenheit (16.2 degrees Celsius).

7) Once the fruiting bodies appeared and grew to approximately 2.5cm, the block was rotated so that the mushrooms would be growing upward. At this point, the mushrooms were given a spray mist of water in the morning and evening, following the directions of the mushroom growing kit.

8) When the mushrooms reached their upright position, daily measurements of the most prominent mushroom height (top of cap to bottom of stem) and width (from one end of cap to the other) were recorded, along with any other observations, at approximately the same time every evening.

9) Mushrooms were harvested and final observations made when the mushroom caps stopped growing. Spore prints were taken of mushrooms from block B by placing a harvested mushroom cap on a piece of black paper and placing this under an bowl for several hours to collect the microscopic spores. The spore prints were placed under the black light to see if they exhibited fluorescence.

The role that light plays in the growth of mushrooms has not been fully explored. This experiment was designed to test the hypothesis that mushrooms would grow bigger and faster in indirect, natural light than under a black light. Since the type of mushroom used in this project was the white elm, and many white objects fluoresce under a black light, the hypothesis also stated that the mushrooms would fluoresce. Two starter blocks, Block A and Block B, were cut in half. Half of Block A and half of Block B were put in indirect, natural light. The other halves were placed under a black light. The blocks were treated the same way in all other respects (humidity, temperature, amount of time in darkness, etc.) The quality of indirect light, height and width of the biggest mushroom on each block, along with other observations were recorded daily. When the mushrooms stopped growing, they were harvested and final observations were made of size, color, taste, texture, rate of growth, and fluorescence.

Results from the experiment showed that the hypothesis was not correct. The mushrooms all grew to approximately the same height, and any differences in width or speed was not necessarily a direct result of the different light sources. The mushrooms grown under the black light were similar to the ones grown in natural light in most respects. In addition, none of the mushrooms exhibited fluorescence.

The mushrooms in the black light started to grow first on both blocks. Black light block A grew at a slower pace than natural light block A. Although the mushrooms under natural light started to grow later, they shot up quickly (especially block A) and caught up to the black light mushrooms height . All blocks reached similar heights. The mushrooms that grew under the black light block A were the only ones that grew on the 2.5cm slit. On all other blocks, the mushrooms forced their growth along seam lines of the plastic wrap, giving themselves more growing room than the 2.5cm slit. Fewer mushrooms could grow along the slit, but since there were fewer fruiting bodies, they had more space to grow in width.

All of the blocks started off with a larger quantity of mushrooms, but slowly the number declined. When some of the mushrooms got bigger, they blocked out the light to their smaller neighbors. The smaller ones that didnšt get as much light eventually shriveled up. The mushrooms on block A exhibited a 62-67% decrease and the mushrooms on block B exhibited a 40-46% decrease in quantity with the black light showing the slightly smaller decrease on both blocks. The relationship between the quantity of mushrooms and width can be seen in the scatterplot [not shown].

When harvested, each cluster had about the same taste, texture, and color. The taste of the cap was intense and slightly nutty. The stem was tasteless and rubbery. The texture of the mushroom caps was smooth and got harder with time. The color of all the caps was a tan/ brown, while the stalks remained white. There was no real difference in taste, color, and texture of all four blocks harvested.

The caps of the mushrooms appeared white at first and took on a more brown tone with time while the stalks kept their white color throughout the growth process. However, the fruiting bodies did not fluoresce at any point in time. The spores from the mushrooms were a more pure white, but did not fluoresce when put under the black light.

The hypothesis that white elm mushrooms would grow bigger and faster under natural light and the fruiting bodies would exhibit fluorescence did not prove to be correct. The mushrooms under natural light did not grow either bigger or faster. The mushrooms grew to approximately the same height and the difference in width or rate of growth was not necessarily due to the difference in light source. Neither the fruiting bodies nor the spores of the white elm mushroom exhibited fluorescence.

Because of the amount of time needed to grow these mushrooms, this experiment could only be repeated twice. However, this experiment does not seem worthy to continue because the results did not indicate that mushrooms could grow bigger or faster under natural light. However, the ability of white elm mushrooms to be grown under a black light has been proven. Perhaps another experiment that varies the amount of time mushrooms are exposed to a black light or one that uses different sizes of black light bulbs could be done to see if the strength of the ultraviolet light affects the growth of mushrooms would be more worthwhile.