ASSESSMENT OF OZONE EFFECTS ON BEECH (FAGUS-SYLVATICA) BY INJECTION OF A PROTECTANT CHEMICAL

Ethylenediurea (N-[2-(2-oxo-1-imidazolidinyl)ethyl]-N'-phenylurea; EDU), is known to protect a wide range of plants against ozone-induced injury. Stem injection of EDU may eventually allow ozone effects on large trees to be assessed in the field. This paper describes an experiment to investigate whether EDU injections can provide protection against ozone episodes over a complete growing season. Young beech (Fagus sylvatica) were exposed during 1989 in semi-open-top chambers to three 2-week episodes of 80 nl l-1 ozone for 8 h day-1 or to background concentrations. Immediately before each episode some plants were injected with either EDU solution or water, while others were not injected. The injection technique allowed treatments to be made with little difficulty, and comparison of uninjected and water-injected plants showed only minor effects on ps exchange and growth. There were significant effects of ozone and ozone x EDU interactions on ps exchange, but it was not possible to identify a clear protective effect of EDU. Some growth parameters were reduced by ozone exposure both during 1989 (leaf weight) and at harvest in 1990 (root weight, pre-1989 shoot weight, total biomass), but these parameters showed no effect of EDU treatment. Basal diameter growth between October 1989, and June 1990, showed a significant ozone x EDU interaction: high ozone reduced growth of water-injected trees but increased growth of EDU-injected trees. Overall, protection by injection of EDU against the effects of a season of realistic ozone exposure has not yet been demonstrated.