Respiration of soybean plants in relation to their physiological conditions. III. The characteristics of respiration in leaves and roots under attached and detached conditions.

Time course challges of respiration rate in a leaf and roots were examined in attached and detached conditions to obtain information of the internal factors determining the time course change of respiration in different organs. In the attached condition, an expanding leaf showed a rapid increase of respiration around midnight (Midnight rise of respiration, MRR), while, an expanded leaf showed a steady state of respiration around midnight, followed by a rapid decrease, resulting in a vague MRR. The attached roots showed a clear MRR. In the detached condition the changes in leaf respiration rate were almost the same as in attached condition; whereas in roots, MRR completely disappeared. The results suggested that the respiration of a leaf is not affcted by other organs, whereas that of roots was strongly dependent on the existence of a shoot. The results also suggested that the internal factors causing MRR existed in a leaf, especially in an expanding leaf.