
%0 Journal Article
%A Esashi, Y 
%A Watanabe, K 
%A Ohhara, Y 
%A Katoh, H 
%T Dormancy and Impotency of Cocklebur Seeds. V. Growth and Ethylene Production of Axial Segments in Response to Oxygen
%J Functional Plant Biology
%D 1976/10/01
%V 3
%N 5
%P 701-710
%K 
%R https://doi.org/10.1071/PP9760701
%U https://www.publish.csiro.au/paper/PP9760701 
%X Growth responses to exogenous CO2 or ethylene and the production of CO2 or ethylene in embryonic axes excised from dormant or non-dormant seeds of cocklebur (Xanthium pensylvanicum Wallr.) were examined in relation to oxygen tension. There were two ethylene-producing systems in the axes, one anaerobic and one aerobic. The former was active in dormant seeds and the latter was active in non-dormant seeds. The axes from non-dormant but impotent small seeds, incapable of germinating under ordinary conditions, showed higher activities for both systems. However, there was no qualitative difference in the oxygen response as to CO2 output between the dormant and non-dormant axes, but CO2 output under aerobic conditions was greater with non-dormant seeds.    Regardless of dormancy status, growth stimulation of axes by CO2 occurred when it was applied during the beginning of incubation and in atmospheres with oxygen concentrations insufficient to permit normal axial growth. Nevertheless, the stimulation of ethylene production by CO2 was parallel with the increase of oxygen tension, suggesting that the CO2-stimulated ethylene production could not be the result of CO2-stimulated axial growth.    The growth response was most sensitive to ethylene after the CO2-sensitive period and before an oxygen-requiring period. Similarly to the action of CO2, the most striking effect of ethylene on the growth of non-dormant axes was obtained in oxygen-deficient atmospheres. However, the synergistic interaction between CO*2 and ethylene occurred only in aerobic conditions. Unlike the non-dormant axes, the dormant ones, whose aerobic ethylene productivity was very small, responded to ethylene with increased growth in proportion to increasing oxygen tension. 
