Experimental modification of the reaction pattern ofLemna leaf cells to polarized light

1. In the mesophyll cells ofLemna trisulca three different reaction patterns to polarized light were found. In the directed one (I) the chloroplasts displaced in the high light intensity rearrangements avoid the side walls situated parallel or nearly parallel to the E-vector of light. In the undirected reaction pattern (II) the position of chloroplasts on the side walls is not influenced by the plane of polarization. An intermediate reaction pattern (I–II) was also found. The occurence of the mentioned types among differentLemna strains and in a leaf topography were described. 2. The reaction pattern I is quite stable and its modification is very difficult. Only in alkaline phosphate buffers a tendency to an intermediate type was seen. Reaction pattern II can be changed into directed or intermediate ones by very high light intensity as well as by a number of chemical factors inducing shrinkage of the plasma membranes. 3. The behaviour of chloroplasts shows that in the directed pattern the molecules of the photoreceptor active in the displacements of chloroplasts are oriented, their vector of absorption being parallel to the cell surface. In an undirected reaction pattern they are randomly situated. The possible reasons of such a phenomenon have been discussed. Undulations of the outer plasma membrane in the type II of reaction have been considered as most probable.