Effects of ethylenediurea (EDU) on ozone-induced acceleration of foliar senescence in potato (Solanum tuberosum L)

Experiments were conducted to examine the effects of the anti-ozonant ethylenediurea (EDU) and chronic ozone (O-3) exposure on leaf physiology and senescence in an O-3-sensitive potato cultivar (Solanum tuberosum L. cv. Norland). A dose-response experiment showed that an EDU concentration of 15 mg l(-1) soil (given as a soil drench) provided complete protection from accelerated foliar senescence induced by exposure to 0.1 mu l l(-1) O-3 for 5 h day(-1) for 11 days. EDU doses of 45 and 75 mg active ingredient l(-1) soil also gave protection but were associated with symptoms of toxicity and delayed senescence. In further experiments, plants were given 0 or 15 mg EDU l(-1) soil and exposed to clean air or 0.1 mu l l(-1) O-3 for 5 h day(-1) for 14 days. Chronic O-3 exposure in the absence of EDU resulted in accelerated foliar senescence, characterized by early declines in net photosynthesis and Rubisco quantity in O-3-treated plants relative to controls. EDU in the presence of O-3 gave complete protection against symptoms of accelerated senescence. Senescence was not delayed in plants that received EDU in the absence of O-3, and no symptoms of EDU toxicity were evident. The results suggest that EDU-induced tolerance to O-3 was not based on 'anti-senescent' properties of this anti-ozonant. Copyright (C) 1996 Elsevier Science Ltd