Microcalorimetric investigation on effects of La(III) on metabolic activity of mitochondria isolated from hybrid rice.

Rare earth elements (REEs) have beneficial influence on plant growth and are widely used in agriculture practice, but little is known about the behavior of the REEs in mitochondria of plant cell. Thermogenic metabolic curves were determined by the ampoule method at 303 K using a TAM air isothermal microcalorimeter in mitochondria isolated from hybrid rice Liangyoupeijiu (Oryza sativa L.), and the effect of La(III) on its mitochondrial metabolism was investigated. From the obtained heat flux curves, the crucial parameters including as activity recovery rate constant (k) and maximum heat power (P(max)) were determined. Application of La(3+) in concentrations ranging from 0 to 120 microg/ml significantly increased k and P(max) values with the high point reaching 346 and 222% of the control, respectively. Concentrations from 140-150 microg/ml had the opposite effect. These results were consistent with previous reports on the effects of REEs on plant growth. It was concluded that the La-induced change of mitochondrial metabolic activity is a possible mechanism by which La(III) ions influences hybrid rice growth.