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Nitrate Uptake Effectiveness of Four Plant Species¹

ABSTRACT

Little information is available on the characteristics of plant roots that determine their effectiveness in nitrate uptake. The effectiveness of nitrate uptake of corn (Zea mays L.), soybeans (Glycine max L.), sorghum (Sorghum bicolor L.), and bromegrass (Bromus inermus L.) intact roots were investigated in nutrient solution culture. The maximum uptake rate per centimeter of root for corn occurred at 10 mM, for sorghum at 2.4 mM, and for bromegrass at 0.8 mM. Increasing the nitrate level above 1.0 mM did not increase the growth rate during the first 3 weeks for any of these species.

The minimum level to which the plant roots reduced the nitrate concentration was 1.7, 2.7, 2.4, and 1.4 µM for forage sorghum, grain sorghum, soybeans, and bromegrass, respectively. Three cultivars of corn were compared. Two reduced the nitrate level to 2 µM and the third to 4 µM.

The results of this research indicate that the roots of the species investigated absorbed nitrate of maximum rates from relatively low nitrate concentrations provided the concentration was maintained. Also, the degree of reduction in nitrate level where nitrate in solution was not maintained indicated that these plant roots had the absorptive capacity to reduce solution nitrate to concentrations of 4 µM or less.

Key Words: corn • soybeans • sorghum • bromegrass • nitrate uptake rate

¹ Contribution from the Department of Agronomy. Purdue Univ. Agr. Exp. Sta., West Lafayette, Indiana 47907. Journal Paper No. 5068. Research support from the Office of Water Resources Research, USDI is gratefully acknowledged.

² Former Postdoctoral Associate, Purdue Univ., now Assistant Professor, Michigan State Univ. and Professor of Agronomy, Purdue Univ., respectively.

Received for publication April 6, 1973.