PHYSIOLOGICAL AND BIOCHEMICAL STUDIES IN PLANT METABOLISM: III. THE EFFECTS OF STARVATION AND MECHANICAL STIMULATION ON THE RESPIRATORY METABOLISM OF THE FIRST LEAF OF THE WHEAT PLANT

Abstract

The oxygen uptake and carbon dioxide output records of detached starving first leaves of wheat have been investigated. Small changes in the oxygen tension or carbon dioxide tension of the surrounding air do not make any difference in the records. The data obtained with the Barcroft method agree with those obtained by the Pettenkofer method. The form of the starvation air line is described. It is generally similar in the four quarters of the leaf but the senescent hump of the basal quarter is much flatter and its peak much lower than in the other three quarters. The total senescent hump carbon dioxide is shown to be proportional to the protein nitrogen in each of the four quarters. The effect on the air lines of rubbing and quartering the leaves is described. There is a great temporary increase in carbon dioxide output as a result of rubbing. This quickly subsides and the respiration rate after the rubbing settles down to a value slightly in excess of that prior to the rubbing. Rubbing and quartering have no effect on the R.Q. of the starving leaves.