Abstract
Potentiometric changes. — Various types of electrodes, to be described later, were used in the work to be reported. In general, however, electrodes of thin tinfoil were used and were attached to the leaves or stems of plants by means of acid-free kaolin ground in a mortar with a little water and glycerine after the method of Sen. 1 In investigating potentiometric changes in leaves, both before and after irradiation, one electrode was fastened near the base of the leaf and the other one was placed at or near the tip of the leaf. Leads were then carried to a Leeds and Northrup potentiometer, using a high sensitivity galvanometer.
Various spectral filters, such as Corning Glass Company filters of special make (G 554 FF, G 24, G 34 R, G 584, G 586 A, G 586 AW, G 392, G 984 B, G 985 B, G 986 A) and transmitting only infrared, red, blue and ultraviolet rays, and so forth, respectively, were employed.
Infra-red (heat) energy, as such, could be removed from the sources of illumination (such as the quartz-mercury arc) by water cells of sufficient depth and possessing quartz bottoms. The visible and infra-red portions could be removed by water cells and solutions of certain substances or by special mediums transmitting selected portions of the ultraviolet light only.
The sources of energy used were infra-red lamps and arcs rich in ultraviolet irradiation. A large number of determinations on the energy received by the leaf under irradiation (from various sources and with various filters) was made as well as determinations of the relative energy of various lines of the spectrum of the quartz-mercury arc when operated at various voltages. Such measurements must be obtained if any attempt is to be made to correlate biologic reactions and reception of energy. So far as we know, this is the first attempt to correlate quantity and quality of incident energy with electrical and other changes in plants.
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