FOLIAR ABSORPTION OF (NH)-N-15 BY WHEAT AND RICE VARIETIES

Plant tops are considered as both sink and source of various N gases a nd other air pollutants which therefore, may influence the gaseous N c ontent of the environment. Five varieties each of wheat (Triticum aest ivum L. and T. durum L.) viz., Pak-81, LU-26, Sarsabz, Durum and M-143 and rice (Oryza sativa L.) viz., Bas-370, Bas-385, DM-25, Kashmir Bas mati and IR-6, were compared for NH3 absorption and its correlation wi th leaf area and N content of the plants. Eight week old plants grown in plastic pots were exposed to (NH3)-N-15 for 24 h in an air-tight ca nopy able to provide a limited supply of CO2. Labelled NH3 was generat ed by reacting N-15-labelled ammonium sulphate with NaOH in the canopy . Total N and N-15 content of the dried and powdered plant material wa s then determined. Upto 44% in rice and 50% in wheat of the (NH3)-N-15 generated in the canopy was assimilated by the plants. Varietal diffe rences in foliar absorption of NH3 were observed. No correlation was o btained between leaf area and the amount of (NH3)-N-15 absorbed by dif ferent varieties indicating that NH3 absorption was not solely depende nt on leaf area and/or photosynthetic activity of the plants.