abscission by auxin. Plant Physiol 39:963-9, 1964. The authors found that auxin stimulated ethylene production, and that it was the gas which promoted abscission after the ability of auxin to delay aging was lost. This paper provided experimental proof for the principle that ethylene could act as a second messenger in some of the effects of auxin on plant growth and development. [The SCI ® Indicates that this paper was cited 139 times in the period 1964-1977.