Root and Nodule Respiration in Relation to Acetylene Reduction in Intact Nodulated Peas 1

AUTOR(ES)

Mahon, John D.

RESUMO

Inoculated pea plants (Pisum sativum L.) were grown with N-free nutrients in a controlled environment room and rates of respiratory CO2 evolution and C2H2 reduction by the intact nodulated roots were determined. Experiments followed changes related to diurnal cycles, light and dark treatments, partial defoliation, aging of plants and NH4NO3 addition. In all experiments, changes in C2H2 reduction were associated with parallel changes in the respiration rate, although in all but the defoliation experiment there was a basal level of respiration which was independent of the rate of C2H2 reduction. In conditions which affected growth or plant size as well as C2H2 reduction, respiration changed by an average of 0.42 mg CO2 (μmol C2H2 reduced)−1. However, some treatments decreased C2H2 reduction without greatly changing the growth and in these conditions respiration was decreased by an average of 0.27 mg CO2 (μmol C2H2 reduced)−1. While this value may also include some respiration associated with other processes, it is proposed that it more closely estimates respiration directly associated with energy utilization for acetylene reduction; whereas the higher value includes respiration related to maintenance and growth processes as well.

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