Experimental researches on vegetable assimilation and respira­tion. XIV. —Assimilation by submerged plants dilute solutions of bicarbonates and of acids: an improved bubble-counting technique

Abstract

The procedure of counting the bubbles given off from the cut stem of a submerged water plant, to obtain a measure of the magnitude of the plant’s assimilation, was introduced by Dutrochet in 1837 and matured by Sachs in 1864. It has been of great use in demonstrations and class work, and has also been seriously employed in a number of researches. From time to time it has been subjected to a good deal of criticism, as giving a faulty measure of the true rate of photosynthesis. It is, however, a striking fact that nothing has been done to improve the technique of the procedure since the method was originally introduced. The first part of the present paper describes a simple device which removes at once two of the very serious defects of the method, and renders it much more suitable for research work. The second part applies this method to an elucidation of the extraordinary effect of dilute mineral acids upon bubble rate brought forward by Treboux. In the third part the relation of bubbling in bicarbonates to bubbling in carbonic acid is investigated, and it is shown that Angelstein’s statement that water plants can actively split bicarbonates in solution is erroneous.