EFFECTS OF FLOODING ON ETHANOL AND ETHYLENE PRODUCTION BY PEAR ROOTSTOCKS

Effects of waterlogging on ethanol and ethylene production by flood-to lerant pear rootstocks, Pyrus calleryana Decne, strains No. 6 and No. 8 and intolerant rootstocks, P. be tulaefolia Bunge and P. pyrifolia N akai were studied. Ethanol content and alcohol dehydrogenase (ADH) act ivity in the roots were measured under flooded condition. Ethanol cont ent increased in the roots with no significant differ ence among the r ootstocks, whereas ADH activity in P. calleryana, No. 6 and No. 8 was three times higher than that in P. betulaefolia and P. pyrifolia three days after the treatment. Roots of P. calleryana,No. 6 and No. 8 seem ed to secrete ethanol into the incubation medium, whereas P. betulaefo lia and P. pyrifolia did not. CO2 evolution from the fine roots was me asured in 10 to 10,000 ppm of ethanol solution. There was a little dif ference among the rootstocks in respiratory tolerance to ethanol. Inte rnal ethylene concentrations and 1-aminocyclopropane-1-carboxylic acid (ACC) content in the roots and leaves were measured during the floodi ng treatment. The rootstocks had similar patterns of ethylene and ACC fluctuations; they increased for 3 days after the treatments started t hen decreased gradually. Increase in ethylene concentration and ACC co ntent in the leaves was observed after the treatment for 5 days; it oc curred first in P. pyrifolia then detected in P. betulaefolia and two strains of P. calleryana in that order.