Photosynthetic Response of Yellow-Poplar Seedlings to the Antioxidant Chemical Ethylenediurea

Abstract

An antioxidant chemical, ethylenediurea (EDU), was applied by soil drench or by stem injection to 2-yr-old containerized seedlings of yellow-poplar (Liriodendron tulipifera) growing in the greenhouse. Net photosynthesis (Pn) was measured before EDU treatment and again 2, 4, and 7 days after treatment. The same seedlings were then fumigated with 0, 0.35 or 0.95 ppm ozone (O3) for 3 hr and Pn remeasured after 2 days. No significant change in Pn was observed for those seedlings treated with EDU (either soil drench or stem injection) when compared to the controls. Following Og fumigation, the decline in Pn for EDU-treated seedlings was appreciably less than that for seedlings without EDU. Stomatal conductance measurements taken on foliage from EDUtreated and untreated plants, both before and after 03 fumigation, suggest that EDU may affect Pn indirectly through its influence on stomatal opening.