Endogenous light-on rhythm in respiration of a long-day duckweed, Lemna gibba G3 II. On basic and rhythmic components of the rhythm |
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Authors: | MlYATA HlSAO |
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Affiliation: | Biological Institute, Faculty of Science, Nagoya University Nagoya 464, Japan |
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Abstract: | Effects of respiratory substrates (glucose, malate, citrateand pyruvate) and inhibitors (fluoride, iodoacetate, azide andDNP) on the O2-uptake rhythm in a long-day duckweed,Lemna gibbaG3 in continuous light period were examined. Rates of O2-uptake at the starting point (6 hr after the beginningof a continuous light period) and at the time of the first peakof the rhythm (18 hr after the beginning of a continuous lightperiod) were equally increased by exogenous substrates. Sensitivityof respiration to fluoride or iodoacetate was almost the sameat the 6th and 18th hr. The O2-uptake (at the 6th, 18th, 30thand 42nd hr) was increased by DNP by the same amount. Azideat lower concentrations than 5X104 M did not affect O2-uptakeat the 6th hr, but inhibited uptake at the 18th hr. In the presenceof 5 X 104 M of azide the rates of O2-uptake at the 18th,30th or 42nd hr were down to the rate at the 6th hr, which wasinsensitive to azide. These results suggest that the O2-uptakerhythm consists of two components, i.e. the basic respirationwhich is promoted by exogenous substrate, sensitive to DNP andinsensitive to azide; and rhythmic respiration, which is sensitiveto azide, but is not influenced by exogenous substrate and DNP. (Received February 19, 1971; ) |
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