Autoradiography of ³²P in Maize Roots

Abstract

THE concentration of ions in the vascular system of a plant root may be very much higher than that in a surrounding nutrient solution. The phosphorus concentration in the transpiration stream of shaded barley seedlings has been estimated to be about 5 × 10⁻⁴ molar whereas that of the nutrient solution around their roots was 3 × 10⁻⁶ molar¹. Neither the mechanism of concentration nor its location is known. It is obvious, however, that an accurate knowledge of the distribution of ions within the root is essential to an understanding of the mechanisms of accumulation and translocation. Autoradiography of frozen tissue sections has been successful in the location of low molecular weight substances in cells and tissues^2,3. This communication describes the use of this technique to locate phosphorus-32 in transverse sections of maize roots.