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Deposition of ammonium and nitrate in the roots of maize seedlings supplied with different nitrogen salts.

Bloom AJ, Randall L, Taylor AR, Silk WK - J. Exp. Bot. (2012)

Bottom Line: In contrast, net root NO(3)(-) influx under NH(4)NO(3) was less than the local deposition rate in the growth zone, indicating that additional NO(3)(-) was imported or metabolically produced.The profile of NO(3)(-) deposition rate in the growth zone, however, was similar for the plants receiving Ca(NO(3))(2) or NH(4)NO(3).These results suggest that NO(3)(-) may serve a major role as an osmoticant for supporting root elongation in the basal part of the growth zone and maintaining root function in the young mature tissues.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Sciences, University of California, Davis, CA 95616, USA. ajbloom@ucdavis.edu

ABSTRACT
This study measured total osmolarity and concentrations of NH(4)(+), NO(3)(-), K(+), soluble carbohydrates, and organic acids in maize seminal roots as a function of distance from the apex, and NH(4)(+) and NO(3)(-) in xylem sap for plants receiving NH(4)(+) or NO(3)(-) as a sole N-source, NH(4)(+) plus NO(3)(-), or no nitrogen at all. The disparity between net deposition rates and net exogenous influx of NH(4)(+) indicated that growing cells imported NH(4)(+) from more mature tissue, whereas more mature root tissues assimilated or translocated a portion of the NH(4)(+) absorbed. Net root NO(3)(-) influx under Ca(NO(3))(2) nutrition was adequate to account for pools found in the growth zone and provided twice as much as was deposited locally throughout the non-growing tissue. In contrast, net root NO(3)(-) influx under NH(4)NO(3) was less than the local deposition rate in the growth zone, indicating that additional NO(3)(-) was imported or metabolically produced. The profile of NO(3)(-) deposition rate in the growth zone, however, was similar for the plants receiving Ca(NO(3))(2) or NH(4)NO(3). These results suggest that NO(3)(-) may serve a major role as an osmoticant for supporting root elongation in the basal part of the growth zone and maintaining root function in the young mature tissues.

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Influx [based on Taylor and Bloom (1998)] and deposition of (A) NH4+ and (B) NO3– at various distances from the apex of a maize seminal root for plants receiving nutrient solutions that contained either 100 mmol m−3 NH4NO3 (n = 6) or 50 mmol m−3 Ca(NO3)2 (n = 9).
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fig6: Influx [based on Taylor and Bloom (1998)] and deposition of (A) NH4+ and (B) NO3– at various distances from the apex of a maize seminal root for plants receiving nutrient solutions that contained either 100 mmol m−3 NH4NO3 (n = 6) or 50 mmol m−3 Ca(NO3)2 (n = 9).

Mentions: Deposition of NH4+ tended to exceed influx of exogenous NH4+, but the reverse was true in the more basal regions (Fig. 6A). A similar trend was observed for NO3– in the treatment receiving NH4NO3, but NO3– deposition tended to be slower than exogenous NO3– influx along the entire root apex in the treatment receiving Ca(NO3)2 (Fig. 6B).


Deposition of ammonium and nitrate in the roots of maize seedlings supplied with different nitrogen salts.

Bloom AJ, Randall L, Taylor AR, Silk WK - J. Exp. Bot. (2012)

Influx [based on Taylor and Bloom (1998)] and deposition of (A) NH4+ and (B) NO3– at various distances from the apex of a maize seminal root for plants receiving nutrient solutions that contained either 100 mmol m−3 NH4NO3 (n = 6) or 50 mmol m−3 Ca(NO3)2 (n = 9).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3295394&req=5

fig6: Influx [based on Taylor and Bloom (1998)] and deposition of (A) NH4+ and (B) NO3– at various distances from the apex of a maize seminal root for plants receiving nutrient solutions that contained either 100 mmol m−3 NH4NO3 (n = 6) or 50 mmol m−3 Ca(NO3)2 (n = 9).
Mentions: Deposition of NH4+ tended to exceed influx of exogenous NH4+, but the reverse was true in the more basal regions (Fig. 6A). A similar trend was observed for NO3– in the treatment receiving NH4NO3, but NO3– deposition tended to be slower than exogenous NO3– influx along the entire root apex in the treatment receiving Ca(NO3)2 (Fig. 6B).

Bottom Line: In contrast, net root NO(3)(-) influx under NH(4)NO(3) was less than the local deposition rate in the growth zone, indicating that additional NO(3)(-) was imported or metabolically produced.The profile of NO(3)(-) deposition rate in the growth zone, however, was similar for the plants receiving Ca(NO(3))(2) or NH(4)NO(3).These results suggest that NO(3)(-) may serve a major role as an osmoticant for supporting root elongation in the basal part of the growth zone and maintaining root function in the young mature tissues.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Sciences, University of California, Davis, CA 95616, USA. ajbloom@ucdavis.edu

ABSTRACT
This study measured total osmolarity and concentrations of NH(4)(+), NO(3)(-), K(+), soluble carbohydrates, and organic acids in maize seminal roots as a function of distance from the apex, and NH(4)(+) and NO(3)(-) in xylem sap for plants receiving NH(4)(+) or NO(3)(-) as a sole N-source, NH(4)(+) plus NO(3)(-), or no nitrogen at all. The disparity between net deposition rates and net exogenous influx of NH(4)(+) indicated that growing cells imported NH(4)(+) from more mature tissue, whereas more mature root tissues assimilated or translocated a portion of the NH(4)(+) absorbed. Net root NO(3)(-) influx under Ca(NO(3))(2) nutrition was adequate to account for pools found in the growth zone and provided twice as much as was deposited locally throughout the non-growing tissue. In contrast, net root NO(3)(-) influx under NH(4)NO(3) was less than the local deposition rate in the growth zone, indicating that additional NO(3)(-) was imported or metabolically produced. The profile of NO(3)(-) deposition rate in the growth zone, however, was similar for the plants receiving Ca(NO(3))(2) or NH(4)NO(3). These results suggest that NO(3)(-) may serve a major role as an osmoticant for supporting root elongation in the basal part of the growth zone and maintaining root function in the young mature tissues.

Show MeSH