KINETICS OF MAIZE LEAF ELONGATION .3. SILVER THIOSULFATE INCREASES THE YIELD THRESHOLD OF SALT-STRESSED PLANTS, BUT ETHYLENE IS NOT INVOLVED

The involvement of ethylene in the short-term responses of maize (Zea mays L.) leaf elongation to salinity was investigated. Leaf elongation rates (LER) were monitored with linear variable differential transformers. Salinity (80 mm NaCl) rapidly inhibited LER. Pretreatment with 4 mm silver thiosulfate (STS), an inhibitor of ethylene action, decreased LER of salt-stressed plants, but not that of controls. Investigation of the growth parameters affected by the interaction of STS and salinity indicated that the yield threshold was increased and the cell wall extensibility was decreased. All other growth parameters controlling cell elongation were unaffected. Further investigation indicated that ethylene production may not be involved in this reponse because treatments with 10 mum aminoethoxyvinylglycine, an ethylene biosynthesis inhibitor, did not affect the growth of salt-stressed plants, and no increase in ethylene production was detected in salt-stressed plants compared with controls. No changes in sensitivity to ethylene were evident because LER of both control and salt-stressed plants were inhibited to the same extent with exposure to 1.2 ppm ethylene. The above evidence indicated that ethylene was not involved in the short-term LER responses of salt-stressed maize.