H215O translocation in rice was enhanced by 10 μm 5-aminolevulinic acid as monitored by positron emitting tracer imaging system (PETIS)

5-Aminolevulinic acid (ALA) acts to increase chlorophyll biosynthesis, photosynthesis, cold stress tolerance, and salt tolerance at low concentrations. We studied the effects of ALA on (H2O)-O-15 translocation from the roots to the shoots of rice plants (Oryza sativa L. cv. Nipponbare) in real time by a positron-emitting tracer imaging system (PETIS). When the plant was treated with 10mum ALA, the velocity of the (H2O)-O-15 translocation from 2 to 12 min after absorption increased to 126, 137, 140% that of the control at 1.5, 2.5, and 3.5 h after ALA treatment, respectively. However, ALA did not affect the (H2O)-O-15 translocation within 0.5 h of treatment. When the plant was treated with 0.1 mm ABA at 4 It after 10 pm ALA treatment, the velocity of the (H2O)-O-15 translocation decreased at 0.5 h after ABA treatment. Those observations suggested ALA might be absorbed and transported to the guard cells within 1.5 h and functioned to expand the stomatal aperture.