Modulation of Solanum tuberosum L. Morphogenesis and Antioxidative Status in a Stem Explant Culture by Limitation of Gas Exchange: Putative Effects of Ethylene

The main objective of the present study was to test the hypothesis that increased concentrations of ethylene under conditions of limited gas exchange during in vitro cultivation of potato (Solanum tuberosum L.) stem explants may lead to increased capaciry of antioxidative defense. By varying the tightness of closure and application of inhibitors of ethylene biosynthesis it was possible to accumulate various concentrations of ethylene in the internal atmosphere of culture flasks, which depended on excision-stress induced ethylene biosynthesis. In tightly closed cultures inhibition of linear growth, promotion of radial expansion and development of an apical hook occurred. Treatment with inhibitors of ethylene action and ethylene biosynthesis prevented the inhibition of shoot growth. The results suggest that the accumulation of endogenously produced ethylene in culture flasks due to limitation of gas exchange and following wounding stress may cause changes in potato shoot morphogenesis. Ascorbate peroxidase activiry was induced in. newly developing shoots by both limited gas exchange and ethephon treatment. Limitation of gas exchange led to increased activities of other enzymes of the antioxidative system as well. A permanent effect of precultivation in high ethylene concentration on ethylene production and anti oxidative status of potato microplants during subsequent cultivation was found. The data suggest that cultivation of potato stem tissues at increased concentrations of ethylene may lead to improved endogenous oxidative stress tolerance.