Some aspects of nitrogen metabolism, during grain development, of the upper three leaf blades on the mainshoot of wheat (Triticum aestivum L.) cv. Pusa Lerma, grown under three soil nitrogen levels (0, 30 and 120 kg ha‐1), were investigated. It was observed that these leaf blades were active in NO‐3 assimilation. Of the leaf blades, the flag lead blade had significantly higher nitrate reductase activity, higher amount of free amino acid and soluble protein content, whereas the content of NO‐3 was significantly lower than in the other two leaf blades. Application of soil nitrogen significantly enhanced the nitrate reductase activity (N30 over N0 and N120 over N30), free amino acid (N30 over N0 and N120 over N30), soluble protein (N120 over N0) and NO‐3 content (N30 and N120 over N0) in all three leaf blades. During the 35‐day period, viz. from 7 days prior to anthesis to 28 days after anthesis, the three leaf blades together reduced 280, 608 and 1397 NO‐3μmol under N0, N30 and N120, respectively.

Upper three leaf blades on the mainshoot of wheat cultivar, cv. Pusa Lerma, grown under three soil nitrogen levels (0, 30 and 120 kg ha‐1), were examined for changes in total reduced nitrogen and protease activity at pH 4.0 and 7.0. No net loss of reduced nitrogen takes place prior to and around anthesis. The protease activity is low during this period. At later stages there is rise in the loss of nitrogen which is paralleled by enhancement in protease activity. From amongst the leaf blades, nitrogen concentration is significantly high in the flag and penultimate as compared to the values in the third leaf blade. There were significant differences in protease activity (pH 4.0) amongst the leaf blades. At pH 7.0, however, the differences between the flag and penultimate leaf blades were not significant. Highest enzyme activity was in the flag followed by penultimate and then third leaf blade. Soil N application significantly enhanced the nitrogen content of all the leaf blades. At pH 4.0, the protease activity (g fr. wt.‐1) increased significantly due to soil N application (N30 over N0). There was, however, decline in the enzyme activity at pH 7.0, though the differences at different soil N levels were not significant. Analysis in terms of μmol N (reduced form) accumulated in the grains (ear)‐1 revealed that two‐thirds of N is translocated by 28‐day stage and the rest between 28‐day and final harvest. The three leaf blades together contributed 22.7, 32.6 and 48.5% of the grain N (ear)‐1 at N0, N30 and N120‐ respectively. Most of the nitrogen applied to the soil is reduced by these leaf blades.

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A field experiment on wheat (Triticum aestivum L.) cv. Shera grown at 120 kg N ha"' was conducted. Half of the dose of fertilizer N was applied at the pre-sowing stage and the other half when the seedlings were one month old. The leaf blades were examined for their NO3~ content and NO3^ assimilatory activity at various stages of growth and development. Soil nitrate level at 50 cm depth was determined throughout the wheat growing season in terms of cencentration ((ig/ml) and total amount (kg ha~'). The upper leaf blades were examined for their capacity to assimilate NO3". Highly significant correlation between NR (nitrate reductase) activity and NO^"^ content in the leaf blades. NR activity and soil NO3", and between soil NO3^ and leaf blade NO3~ was observed. Findings on low soil NO3~ status during the reproductive phase and the capacity of the upper leaf blades to assimilate additional amounts of NO3*, point to the need for developing a programme of soil fertilizer application whereby all the leaf blades can utilize the NO3" optimally and thus result in greater N harvest.