The seeds shown to the right all come from trees that take advantage of the wind to help in seed dispersal. But maple seeds (top) and tree-of-heaven seeds (bottom) behave very differently as they fall through the air.

To account for the seeds' rates of descent and their different behaviors while falling, students need to investigate both the large-scale factors that affect their rate of falling through the air (e.g. wing-loading, the ratio of seed mass to seed surface area) and the small-scale factors that can strongly influence seed behavior (e.g. the twisted shape of the tree-of-heaven seeds).

A Kodak high-speed camera and imaging system is used to photograph falling seeds at 1000 frames per second, about 33 times faster than normal video speed. The resulting video, played back 33 times more slowly than normal video, reveals the details of motions that are too fast for the un-aided eye to see.

Click on the image to view high-speed images of these seeds falling...

Click on the image to view high-speed images of these seeds falling...

-- an image is made (either with a film camera or with a video camera) and then digitized using software called NIH Image. For efficiency, the images of several seeds are made at one time (I)

-- a single digitized image is selected (II) and its edges are found (III)

-- the outline is filled with black (IV)

-- NIH Image then calculates the area filled with black pixels (V)

-- Now that the seed's surface area is known, one can measure its weight and then calculate wing loading.

V