Nitrate assimilation in leaf blades of wheat of different age

A field experiment on wheat ( Triticum aestivum L.) ev. Shera grown at 120 kg N ha −1 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 NO 3 − content and NO 3 − 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 (μg/ml) and total amount (kg ha −1 ). The upper leaf blades were examined for their capacity to assimilate NO 3 − . Highly significant correlation between NR (nitrate reductase) activity and NO 3 − content in the leaf blades. NR activity and soil NO 3 − , and between soil NO 3 − and leaf blade NO 3 − was observed. Findings on low soil NO 3 − status during the reproductive phase and the capacity of the upper leaf blades to assimilate additional amounts of NO 3 − , point to the need for developing a programme of soil fertilizer application whereby all the leaf blades can utilize the NO 3 − optimally and thus result in greater N harvest.