ISSN:
1399-3054
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
Relationships among growth, N accumulation and assimilation were investigated in Chrysanthemum morifolium Ramat cv. Fiesta in experiments testing the effects of varying levels of NO–33supply and of increasing NH+4 added to a constant level of NO–33 Flowing solution culture systems were used to provide NO−3at concentrations of 0.03 to 5.0 mol m–3 and NH+4 levels from 0.05 to 0.3 mmol m–3 added to 0.1 mol m–3NO−3. Rates of growth, N absorption, accumulation, distribution and utilization were estimated by regression analysis of data obtained from sequential plant harvests, and rates of NO−3 and NH−4 net uptake were estimated from solution depletion.A sustained ambient NO−3 concentration of 0.03 mol m–3 was evidently adequate to support growth, since relative growth rates were not affected by increasing NO−3 supply from 0.03 to 1.0 mol m–3, nor from 0.25 to 5.0 mol m–3, in separate experiments. Shoot growth rates were stimulated by NH4 added to NO−3 one experiment, but not when the experiment was repeated under ambient conditions less favorable to growth.Relative accumulation rates for total N increased with increasing NO−3 and with NH+4added to NO−3 A constant proportion of NO−3 taken up was reduced when NO−3 alone was supplied. Both the proportion of total N taken up as NO−3 and the proportion of NO−3 reduced decreased with increasing NH+3 added to NO−3 NH+4 uptake apparently must exceed a threshold of about 30% of the total uptake to inhibit NO−3 uptake.Utilization of N in chrysanthemum was apparently limited by redistribution since relative accumulation rates for total N were equal to or greater than relative growth rates, in contrast to results reported for several other species. Results of this study and other information support the postulate that NH+4 added to NO−3might stimulate growth by increasing transport of reduced N from roots to shoots, thus increasing the supply of reduced N available to support growth of shoot meristems.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1399-3054.1983.tb00907.x
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