The effect of light on the permeability of lecithin.

Abstract

Plant protoplasm changes its permeability in the light (Lepeschkin, 1 Tröndle, 2 Blackman 3 ). These changes in permeability account for changes in turgor, and inasmuch as turgor-changes precede or accompany the photo-growth reactions in plants, the latter reactions might ultimately be traced to changes in permeability.

After Hansteen-Cranner's 4 careful ultra-microscopic observations, once more our attention is called to the importance of the lipoid component of plant protoplasm. The universal distribution of these lipoids justified our choice of lecithin as a material for permeability studies.

Membranes of lecithin-collodion were prepared in the following way. An ether solution containing 5 percent lecithin and 5 percent collodion, was carefully poured on glass plates, yielding membranes from 10 to 20 μ thick. The manipulations were carried on in the dark.

The dry membranes were mounted in the following way (Fig. 1). Rims were blown on pyrex glass tubes. After grinding the rims and covering them with soft paraffin the membranes, were pressed between two pyrex cells, one of which contained a pair of platinum electrodes. The electrode compartment was filled with twice distilled water, the other (compartment with .02 M KCl. Both compartments were sealed with cover slides by means of paraffin. The apparatus was mounted in a vertical position (electrode compartment below) in an asbestos box.