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During the total solar eclipse, the Sun’s corona, only visible during the total eclipse, is shown as a crown of white flares from the surface. Photo: NASA

The total eclipse that blocked the sun’s direct light for more than two minutes in a narrow swath across the United States was anticipated to have temporary but noticeable effects on the flora and fauna of the continental United States, where such a phenomenon hadn’t been seen in nearly a century.

An agricultural school in the South that was in the path of the eclipse catalogued some of those effects on dynamic plants that normally close and open their leaves depending on light and temperature – and found a variety of effects.

The scientists from the University of Missouri in Columbia took a group of four species, interrupting the circadian rhythms of some, in order to gauge the effect of the sudden reversal of day, they presented in the October annual meeting of the American Society of Agronomy, Crop Science Society of America, and the Soil Science Society of America.

“We were wondering if plants had a circadian rhythm – meaning that they have sensed when sunup and sundown are and have developed an internal clock, separate from sensing changes in light,” said Timothy Reinbott, the leader of the group, from UMC Farms. “So when we have a totality of the eclipse in the middle of the day, would they even react?”

The four plants were: mimosas, which close their leaves at night and at a touch; purple clover, which close their leaves and flowers at night; soybeans, which fold up leaves during the day and open them at night when stressed by drought; and corn, which uncurls at night but curls during the day to reduce stress when under water-lacking conditions.

The two mimosas were presented with different conditions: one was exposed to 72-hour cycles of light and darkness, while the other lived in a normal daily cycle of day and night. The control group of one did indeed close up its leaves during the approximately two minutes of total eclipse. But the experimental plant did not respond to the phenomenon – potentially because that 72-hour plant had grown responsive to different nuances of the light spectrum to prompt their response.

The purple clover (oxalis) opened its leaves like it was night, but did not fold its flowers. The researchers said this showed it only responded to the cooler temperature change of the eclipse, according to Reinbott.

The soybeans unfolded their leaves exactly as they would at dusk, indicating they responded to the light change alone – and did not have a circadian rhythm, they concluded.

The corn, on the other hand, showed no visible changes during the Aug. 21 eclipse.

The Missouri botanists were not the only ones to gauge changes in plant and animal life. Other teams over the centuries have documented strange phenomena in response to the unusual decrease in light and temperature. But total eclipses are rare enough, and short enough, to make long-term research difficult.

However, the Missouri team said it is planning to look closer at plants’ photosynthesis and water use during the next total eclipse in North America – this time in just seven years, in 2024.

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