Initial studies to quantify direct carbon monoxide photoproduction from several plant species are reported. In addition to measuring CO emissions from live plant leaves, emission rates from dead leaf matter were also determined. Senescent leaf matter photoproduced CO at rates that ranged from 1.3 to 5.4 times higher per unit area than living leaves, and dead leaves photoproduced CO about an order of magnitude more rapidly than living leaves. It may therefore be necessary to incorporate CO photoproduction from dead plant matter into predictions of global CO emissions from plants. Methods are presented for direct measurement of CO photoproduction from live, intact leaves, from excised leaves, and from fallen leaves. Although these techniques were initially used for laboratory studies, they are directly applicable to field studies. Results of mechanistic studies indicate that oxygen affects CO photoproduction but that carbon dioxide exhibits no direct influence. Formation of CO was shown to be the result of direct photochemical transformation on or in the plant matter. Furthermore, for live plant leaves, CO photoproduction was observed to occur internal to the leaf. ¿ American Geophysical Union 1995