Source:  Janice VanCleave, 200 Gooey, Slippery, Slimy, Weird and Fun Experiments #45, p.26.

Potted plant

1.  Coat the top of a minimum of three leaves (depending on the plant's amount of leaves)
2.  Coat the same number of leaves on the underside of the leaves with a heavy layer of Vaseline
3.  Mark the same number of leaves (with string or something that doesn't damage the leaves) as the control leaves.
4.  Observe the leaves daily for one week or until a change occurs
5.  Determine if there is any difference in the three sets of leaves

The leaves that had Vaseline coat on the underside died.  The other leaves remained unchanged.

Openings on the underside of plant leaves called stomata that allow gases to move into and out of the leaves.  The Vaseline plugged the openings and the leaf was not able to receive necessary carbon dioxide gas and eliminate excess oxygen.

Kelley Bassett, 2000.