Agronomy Journal Journal of Natural Resources and Life Sciences Education
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Published online 1 September 1969
Published in Agron J 61:805-808 (1969)
© 1969 American Society of Agronomy
677 S. Segoe Rd., Madison, WI 53711 USA
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Effect of Phosphorus and Potassium on Alfalfa Root Anatomy1

M. G. Schnappinger, Jr., V. A. Bandel and C. B. Kresge2

The effects of P and K on alfalfa (Medicago saliva L.) root anatomy were determined. A sand culture method was used to grow the plants. Phosphorus (P) levels in the nutrient solutions were 0, 3.4, 6.9, 13.8, 27.7, and 55.4 ppm at the beginning of the experiment. Potassium (K) was supplied at the rates of 0, 4.3, 8.6, 17.3, 34.6, 51.9, 69.3, and 173.2 ppm. No effort was made to maintain the nutrient solutions at their initial levels.

Plants were harvested three times at approximately 28-day intervals when the plants were in the full-bloom stage. The roots were preserved in a 70% Formalin-acetoalcohol fixative. Permanent microscope slides were prepared from which various characteristics of alfalfa root anatomy could be studied.

Root diameter was Increased by the addition of either P or K to the nutrient solution. Xylem vessel diameter was decreased by the removal of either P or K. But, removal of P from the nutrient solution had a greater effect on xylem vessel diameter than did K. Xylem vessel differentiation as well as the percent of the root area occupied by xylem vessels was increased more by P than by K.

Key Words: Xylem vessel differentiation

1 Contribution No. 4152 and Scientific Article No. A1503 of the Maryland Agricultural Experiment Station, Department of Agronomy. Part of a thesis submitted by the senior author in partial fulfillment of the requirements for the M.S. degree. Presented before the Northeast Branch of the American Society of Agronomy, July 16, 1968 at Orono, Maine.

2 Graduate Assistant in Soils (now Graduate Research Assistant, Virginia Polytechnic Institute); Assistant Professor Soils, University of Maryland, College Park 20740; and Eastern Agronomist, American Potash Institute (formerly Associate Professor of Soils, University of Maryland). The authors gratefully acknowledge the American Potash Institute, Inc., for the financial assistance given toward the investigation.

Received for publication March 10, 1969.




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Copyright © 1969 by the American Society of Agronomy.