Effects of Flooding on Ethanol and Ethylene Production by Pear Rootstocks

Abstract

Effects of waterlogging on ethanol and ethylene production by flood-tolerant pear rootstocks, Pyrus calleryana Decne, strains No. 6 and No. 8 and intolerant rootstocks, P. be-tulaefolia Bunge and P. pyrifolia Nakai were studied.
Ethanol content and alcohol dehydrogenase (ADH) activity in the roots were measured under flooded condition. Ethanol content increased in the roots with no significant difference among the rootstocks, 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 seemed to secrete ethanol into the incuba-tion medium, whereas P. betulaefolia and P. pyrifolia did not.
CO₂ evolution from the fine roots was measured in 10 to 10, 000 ppm of ethanol solution. There was a little difference among the rootstocks in respiratory tolerance to ethanol.
Internal ethylene concentrations and 1-aminocyclopropane-1-carboxylic acid (ACC) content in the roots and leaves were measured during the flooding treatment. The rootstocks had similar patterns of ethylene and ACC fluctuations; they increased for 3 days after the treatments started then decreased gradually. Increase in ethylene concentration and ACC content in the leaves was observed after the treatment for 5 days ; it occurred first in P. pyrifolia then detected in P. betulaefolia and two strains of P. calleryana in that order.