SELENOMETHIONINE UPTAKE BY WHEAT SEEDLINGS

Selenium acquisition by crops is of interest because it is an essential element for higher animals and because excessive levels are toxic to humans and livestock. This research was conducted to test whether uptake by plants of an important organic Se compound, selenomethionine, occurred through a metabolically active process. Selenomethionine absorption in 30-d-old wheat (Triticum aestivum L.) seedlings was measured by using a depletion method with two initial nutrient solution concentrations (0.5 and 1.0-mu-M) selenomethionine. Observed uptake rates were functions of solution concentration and were not affected by initial concentration. Uptake kinetics appeared to conform to the Michaelis-Menten function but the initial concentrations were too low to estimate either K(m) or V(max) (maximum uptake rate when carrier or permease is saturated). Selenomethionine uptake was inhibited by a metabolic inhibitor, 2,4-dinitrophenol, and by anaerobic conditions. Absorption resumed when aerobic conditions were restored to the anaerobic treatment. Experimental evidence shows that wheat seedlings can acquire the biologically important organic Se compound, selenomethionine. This acquistion is under metabolic control which further suggests that organic forms of Se must be considered as sources of plant available Se.