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Abstract
Diurnal patterns of nitrate, potassium, and phosphate uptake by seedlings of five corn genotypes were compared. Whereas phosphate uptake showed little daily variation (<30% difference between minimal and maximal rates), both nitrate and potassium uptake varied more than two‐fold during a 24 h cycle. The data indicate that the uptake of phosphate is subject to metabolic controls separate from those affecting potassium and nitrate.
The daily patterns of nitrate and potassium uptake differed between two single‐cross hybrids, but were not directly related to the patterns exhibited by their parental inbred lines. Maximal differences in nitrate and potassium uptake among genotypes were observed between 4 and 8 h after the start of the light period, and reflected genotypic differences in total nitrate and potassium uptake over the 24 h cycle. These results provide a basis for establishing an appropriate time interval for the screening of maize genotypes for nitrate uptake. A single‐plant evaluation conducted during the middle of the light period clearly revealed differences in nitrate uptake by the two hybrids with each exhibiting a wide range among individual plants.