THE INFLUENCE OF SOIL OXYGEN DEFICIENCY ON ALCOHOL-DEHYDROGENASE ACTIVITY, ROOT POROSITY, ETHYLENE PRODUCTION AND PHOTOSYNTHESIS IN SPARTINA-PATENS

Laboratory experiments evaluated root-shoot responses of Spartina patens (Ait) Muhl. to changes in soil redox potential (Eh). Three levels of soil redox potential, + 460, + 230 and - 110 mV were imposed in microcosms where plants were grown. Leaf chlorophyll content, gas exchange, root aerenchyma formation, alcohol dehydrogenase (ADH) activity in the roots and ethylene production of leaf and roots in response to the redox treatments were measured. Root responses to hypoxia included a significantly increased porosity and greater ADH activity in hypoxic roots as compared to roots of control (aerated) plants. Ethylene production wa's significantly greater in leaves and roots of plants under hypoxic treatment as compared to control plants. Leaf chlorophyll content was not affected by the treatments; however, stomatal conductance and net carbon assimilation were reduced significantly in response to hypoxia, by 46 and 18%, respectively. Results show a close relationship between root hypoxia, increase in ADH activity, ethylene production and aerenchyma tissue development in S. patens. The enhanced ADH activity and ethylene production found in plants subjected to hypoxia support the postulate that these metabolites have adaptive significance for plants under hypoxic conditions.