Excessive supply of fertilizer N can lead to inefficient use of supplied N and consequently affect plant quality. Reduction of supplied fertilizer N can possibly increase plant N usage efficiency and improve quality. Chrysanthemummorifolium Ramat. cv. `Yellow Favor' was grown single stem in 10 cm pots on an ebb and flow benching system. All plants received 18.5 mM NO3- N, until the mid point of this ten wk crop, at which time the following NO3- concentrations (mM) were employed: 18.5, 15.5, 12.5, 9.5, clear water and clear water alternating with 18.5 mM NO3-. Plants were harvested at two wk intervals, cut in half and separated into leaves, stems plus petioles and inflorescence (when developed). Plant tissue from the lower half of the plant was analyzed for total and NO3- N, with reduced N being estimated as the difference between these two values. All growth parameters measured did not significantly differ, although termination of N fertilization (clear water) and reduction of NO3- level to 9.5 mM significantly reduced NO3- levels in the lower leaf and stem plus petioles, with a concomitant increase in reduced N in these tissues, over the 6-10 wk period. Total amounts of N accumulated in plant tissues analyzed did not differ significantly at flowering.
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