Influence of the Photodynamic Effect on the Tissue Water Exchange in Some Monocotyledonous and Dicotyledonous Plants

The influence of some early precursors of chlorophyll biosynthesis such as δ-aminolevulinic acid (ALA) and glutamic acid (GA), together with the modulator of chlorophyll synthesis – 2,2 ́-dipyridyl (DP) on dynamic of the tissue water exchange was studied as a consequence of photodynamic action. The accumulation of porphyrines, caused by the combination of chlorophyll precursor and DP, has a photodestructive effect on dicotylednous plants. One of the most probable mechanism of this action is the destruction of the cell membranes, which causes increased water transfer trough the membrane and this might be the reason of a total change in water exchange in the tissues in some green dicotyledonous plants. The plants respond to the water deficit, caused by the destruction of the cell membranes, by lowering their osmotic potential and an increase of the amount of the inflow water from the hypotonic solutions, and the decrease of the amount of the outflow water in hypertonic concentrations. The results from water tissue exchange show that this effect is very little in monocotyledonous plants. The dicotyledonous plants are more sensitive to such treatment showing mostly an increased water loss from the treated leaves.