AUTORADIOGRAPHY AS AN AID IN DETERMINING THE GROSS ABSORPTION AND UTILIZATION OF FOLIAR APPLIED NUTRIENTS

Abstract

Autoradiography offers a means of obtaining visual records of the gross absorption, translocation, and selective mobilization of foliar applied nutrients. A method of simultaneously preparing a large number of autoradiograms is described. Following treatment with radio-phosphorus (P32) or radio-potassium (K42),intact plants are mounted and rapidly dried under pressure on 8 x 10-in. sheets of botanical pressing paper. The dried specimens are then covered with a protective sheet of thin pliofilm and placed in contact with 8 x 10 in. Kodak No-Screen X-ray film in a layered stack in a light-proof wood exposure box. Individual units are separated by 1/4-in.-thick steel plates which provide shielding as well as pressure for uniform film contact. Autoradiograms of bean, command tomato plants demonstrate that leaves are efficient organs for absorption of P32. Subsequent distr. in the bean plant of the foliar applied radionuclide is comparable to that taken up by roots. The relatively greater nutrient absorption efficiency of the younger expanding leaves is suggested.