Nitrate assimilation in leaf blades of wheat of different age

Abstract

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 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 (µg/ml) and total amount (kg ha^-1). The upper leaf blades were examined for their capacity to assimilate NO₃^-. Highly significant correlation between NR (nitrate reductase) activity and NO₃^- 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.