Salt-Activated Respiration in Excised Roots of the Garden Pea

Abstract

1. An apparatus is described which was employed in measuring the O2 uptake and the CO2 output of excised pea roots immersed in a dilute salt solution. Oxygen uptake from the solution was measured polarographically with the dropping mercury electrode. Carbon dioxide given off by the roots was swept out of the solution with a CO2-free gas stream, absorbed by a NaOH solution, and determined by measuring the conductance of the latter. 2. When a solution of KCl was substituted for distilled water as the external medium, the uptake of O2 by excised roots increased rapidly during the first 30 minutes, usually passing through an optimum, and approached a steady rate. A subsequent increase in the concentration of KCl in the medium was followed, within 13 minutes, by a second increase in O2 uptake and the attainment of a higher steady rate. 3. In solutions of KCl, the steady-phase QO2 was positively correlated with the salt concentration until an optimum was reached at about 1.0 x 10-2 M. Below 1.0 x 10-3 M, the QO...