抄録
The nitrate reducing power of plant roots, i. e. nitrate respiration, has been studied in reference to oxygen transport from the top down to the roots. The results obtained are summarized as follows: (1) Attached roots of lowland plants, which are equipped with the highly developed ventilating system, are by far weak in their power of nitrate reduction, as compared with those of upland plants, whose system is feebly developed. (2) Detached roots of any species reduce nitrate very strongly. (3) These results indicate that the plant roots are, without exception, able to reduce nitrate for the purpose of liberation of free energy, as the oxygen content in a culture medium becomes too low for the roots to perform aerobic respiration, in case internal supply of oxygen is suspended. (4) Nitrate reduction may be catalyzed by nitrate reducing enzyme system, whose activity in the foots is not varied so widely with plant species. Occasional exudation of this system from a wounded part of the roots into a medium may expedite nitrate reduction in vitro, consequently giving rise to a feigned increase in the nitrate reduction by the roots.
