THE ROLE OF ETHYLENE IN THE DEVELOPMENT OF CONSTANT-LIGHT INJURY OF POTATO AND TOMATO

The role of ethylene in the development of constant-light injury of po tato (Solanum tuberosum L.) and tomato (Lycopersicon esculentum Mill.) was investigated, In one study, silver thiosulfate (STS) was applied to the foliage of four potato cultivars growing under constant light. Leaf area and shoot dry mass of 'Kennebec' and 'Superior', cultivars n ormally injured by constant light, were greater(P < 0.05) than those o f control plants given foliar applications of distilled mater, Examina tion of STS-treated 'Kennebec' leaflets revealed significantly less in jury (necrotic spotting and reduced starch content) than the water-tre ated controls. 'Norland' and 'Denali', cultivars tolerant of constant light, exhibited no differences in growth between treatments, In a sec ond study, injury (necrotic spotting and reduced starch content) was i nduced in leaflets of 'Denali' when exposed to spray applications of 0 .5 mmol.L-1 ethephon or air containing 0.5 to 0.8 mu L.L-1 ethylene, I n a third study, three genotypes of 'Ailsa Craig' tomato were grown un der constant light, Leaves of the normal 'Ailsa Craig' exhibited epina sty, reduced chlorophyll concentration, and reduced starch content. Le aves of a mutant 'Ailsa Craig', containing the Never ripe mutation, di d not exhibit epinasty but exhibited the same amount of reduced chloro phyll concentration and starch content as normal plants, Leaves of a t ransgenic 'Ailsa Craig', containing an antisense gene of 1-aminocyclop ropane 1-carboxylate (ACC) oxidase, were epinastic, but chlorophyll co ncentration and starch content were greater than in leaves of normal a nd mutant plants. These results suggest that transgenic plants were mo re tolerant of constant light than the other genotypes, Evidence from these studies indicates that ethylene, combined with constant light, h as an important role in the development of constant-light injury.