Effect of dimethyl sulfoxide (DMSO) on zinc availability (L-value), growth and metabolic activities of rice plants

Summary Effects of soil application (0.01, 0.1 and 1%) and foliar sprays (0.001, 0.01 and 0.1%) of dimethyl sulfoxide (DMSO) and soil application of Zn (10 and 20 ppm) on growth, yield, photosynthetic pigments and some enzymatic activities of rice (Oryza sativa L. variety Jaya) were investigated in a Zn-deficient soil under pot culture trials. Control plants showed typical Zn deficiency symptoms, very low dry matter and chlorophyll contents and significantly lower activities of carbonic anhydrase and tryptophan synthetase. Application of 10 or 20 ppm Zn to the soil markedly improved plant growth, chlorophyll content, enzymatic activities, Zn availability (L-value), and grain yield. Application of 1% DMSO to the soil proved to be severly phytotoxic for plant growth and dry matter accumulation. Application of lower doses of DMSO to the soil (0.01 and 0.1%) or as foliar sprays (0.001 and 0.01%), however, slightly increased dry weights of all plant parts at 45 days after transplanting. Grain yield was significantly increased by all DMSO treatments, except 1% soil application which completely suppressed the grain formation.Enzymatic activities and chlorophyll and carotenoid accumulation showed concentration-dependent stimulation or inhibition by DMSO treatments. Carbonic anhydrase activity was significantly increased by most of the DMSO treatments whereas tryptophan synthetase activity was stimulated only by the lowest dose of soil (0.01%) and foliar (0.001%) applications. Chlorophyll content was stimulated by lower doses of foliar application of DMSO (0.001 and 0.01%) but the other DMSO treatments brought about a concentration-dependent decrease in chlorophyll accumulation. Carotenoid accumulation was inversely related to that of chlorophylls. Chlorophyll: carotenoid ratio was increased by all DMSO and Zn treatments except 1% soil application of DMSO. Zn availability (L-value) of the soil was increased by all DMSO treatments. Zn content of leaf blades was positively correlated with chlorophyll content (r=0.579), tryptophan synthetase (r=0.700) and carbonic anhydrase (r=0.537) activities but negatively correlated with that of carotenoid content (r=–0.896). The possible mechanisms of DMSO on plants are discussed in relation to its possible agricultural utility.Publication No. 811 under Journal Series of the Experiment Station, G.B. Pant of Agriculture & Technology, Pantnagar (Nainital), India.