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High-resolution quantification of root dynamics in split-nutrient rhizoslides reveals rapid and strong proliferation of maize roots in response to local high nitrogen.

in 't Zandt D, Le Marié C, Kirchgessner N, Visser EJ, Hund A - J. Exp. Bot. (2015)

Bottom Line: This may be a desirable trait in breeding programmes, since it decreases NO3(-) leaching and N2O emission.By contrast, laterals on the side without N did not show any detectable elongation beyond the first day after their emergence.We conclude that split-nutrient rhizoslides have great potential to improve our knowledge about nitrogen responsiveness and selection for contrasting genotypes.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Plant Ecology, Radboud University Nijmegen, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands Crop Science, Swiss Federal Institute of Technology Zurich, Universitätsstrasse 2, 8092 Zurich, Switzerland.

No MeSH data available.


Root dynamics of crown axis and first order crown lateral roots in split-root rhizoslides subjected to either no nitrogen (N) or high (17mM) N after 15 d of growing without N. Crown axile root elongation determined by (A) tracking crown root tips with charge coupled device (CCD) cameras from -1 days after solution change (DASC) until 1 DASC, and (B) tracings of all the crown root tips over the whole experimental period. (C) Lateral root density on the crown root axis, and (D) elongation rates of these lateral roots. The dashed, red line indicates the time point of solution change, and the light grey squares night time. Values are means ±SE (n=2−13), asterisks indicate significant differences between the no N and high N roots (paired t-test with Bonferroni correction, P<0.05).
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Figure 5: Root dynamics of crown axis and first order crown lateral roots in split-root rhizoslides subjected to either no nitrogen (N) or high (17mM) N after 15 d of growing without N. Crown axile root elongation determined by (A) tracking crown root tips with charge coupled device (CCD) cameras from -1 days after solution change (DASC) until 1 DASC, and (B) tracings of all the crown root tips over the whole experimental period. (C) Lateral root density on the crown root axis, and (D) elongation rates of these lateral roots. The dashed, red line indicates the time point of solution change, and the light grey squares night time. Values are means ±SE (n=2−13), asterisks indicate significant differences between the no N and high N roots (paired t-test with Bonferroni correction, P<0.05).

Mentions: Individual crown root tip elongation was monitored in high time-resolution from one day before until one day after the onset of local high N supply (i.e. solution change), to investigate if selective root placement was an immediate response to increased N. We only analysed those six plants for which at least one root on the high N side and one root on the side without N could be tracked. Crown axile root elongation rates before solution change were on average ~3cm d-1 (Fig. 5A), with some diurnal variation (lowest rates in the afternoon, at 2.0cm d-1, and fastest rates in the late morning, at 4.0cm d-1). Crown axile roots that received high N showed a relative decrease of elongation rates in the first half hour after solution change, but recovered thereafter. Overall, crown axile roots that received high N did not show a clear change in elongation rate within the first day compared to roots of the same plant that did not receive N (Fig. 5A). Apparently, if crown axile roots respond to an increase in local N, this needs a longer initiation period than 1 d. Therefore, root elongation was monitored at longer time intervals during the following 15 d. In contrast to the first day, crown axile root elongation rates over the remainder of the experimental period showed a striking response to locally applied N (Fig. 5B, Table 2). The slightly slowing elongation rates just before solution change continued for roots kept without N until the breakpoint at ~6.4 DASC, after which root elongation rates more or less stabilized at a rate of 1.2cm d-1. Crown axile root elongation rates of roots supplied with high N, however, showed a dramatic increase in growth rates, levelling off to a maximum asymptote of on average 5.3cm d-1. To estimate the rapidness of this response, we calculated the time at which the roots reached 95% of their asymptotic value. This 95% of the maximum elongation rate was reached at approximately 4 DASC and for the majority of roots stayed at this maximum until the end of the experiment at 15 DASC (Fig. 5B, Table 2, Supplementary Fig. S2).


High-resolution quantification of root dynamics in split-nutrient rhizoslides reveals rapid and strong proliferation of maize roots in response to local high nitrogen.

in 't Zandt D, Le Marié C, Kirchgessner N, Visser EJ, Hund A - J. Exp. Bot. (2015)

Root dynamics of crown axis and first order crown lateral roots in split-root rhizoslides subjected to either no nitrogen (N) or high (17mM) N after 15 d of growing without N. Crown axile root elongation determined by (A) tracking crown root tips with charge coupled device (CCD) cameras from -1 days after solution change (DASC) until 1 DASC, and (B) tracings of all the crown root tips over the whole experimental period. (C) Lateral root density on the crown root axis, and (D) elongation rates of these lateral roots. The dashed, red line indicates the time point of solution change, and the light grey squares night time. Values are means ±SE (n=2−13), asterisks indicate significant differences between the no N and high N roots (paired t-test with Bonferroni correction, P<0.05).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2
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Figure 5: Root dynamics of crown axis and first order crown lateral roots in split-root rhizoslides subjected to either no nitrogen (N) or high (17mM) N after 15 d of growing without N. Crown axile root elongation determined by (A) tracking crown root tips with charge coupled device (CCD) cameras from -1 days after solution change (DASC) until 1 DASC, and (B) tracings of all the crown root tips over the whole experimental period. (C) Lateral root density on the crown root axis, and (D) elongation rates of these lateral roots. The dashed, red line indicates the time point of solution change, and the light grey squares night time. Values are means ±SE (n=2−13), asterisks indicate significant differences between the no N and high N roots (paired t-test with Bonferroni correction, P<0.05).
Mentions: Individual crown root tip elongation was monitored in high time-resolution from one day before until one day after the onset of local high N supply (i.e. solution change), to investigate if selective root placement was an immediate response to increased N. We only analysed those six plants for which at least one root on the high N side and one root on the side without N could be tracked. Crown axile root elongation rates before solution change were on average ~3cm d-1 (Fig. 5A), with some diurnal variation (lowest rates in the afternoon, at 2.0cm d-1, and fastest rates in the late morning, at 4.0cm d-1). Crown axile roots that received high N showed a relative decrease of elongation rates in the first half hour after solution change, but recovered thereafter. Overall, crown axile roots that received high N did not show a clear change in elongation rate within the first day compared to roots of the same plant that did not receive N (Fig. 5A). Apparently, if crown axile roots respond to an increase in local N, this needs a longer initiation period than 1 d. Therefore, root elongation was monitored at longer time intervals during the following 15 d. In contrast to the first day, crown axile root elongation rates over the remainder of the experimental period showed a striking response to locally applied N (Fig. 5B, Table 2). The slightly slowing elongation rates just before solution change continued for roots kept without N until the breakpoint at ~6.4 DASC, after which root elongation rates more or less stabilized at a rate of 1.2cm d-1. Crown axile root elongation rates of roots supplied with high N, however, showed a dramatic increase in growth rates, levelling off to a maximum asymptote of on average 5.3cm d-1. To estimate the rapidness of this response, we calculated the time at which the roots reached 95% of their asymptotic value. This 95% of the maximum elongation rate was reached at approximately 4 DASC and for the majority of roots stayed at this maximum until the end of the experiment at 15 DASC (Fig. 5B, Table 2, Supplementary Fig. S2).

Bottom Line: This may be a desirable trait in breeding programmes, since it decreases NO3(-) leaching and N2O emission.By contrast, laterals on the side without N did not show any detectable elongation beyond the first day after their emergence.We conclude that split-nutrient rhizoslides have great potential to improve our knowledge about nitrogen responsiveness and selection for contrasting genotypes.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Plant Ecology, Radboud University Nijmegen, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands Crop Science, Swiss Federal Institute of Technology Zurich, Universitätsstrasse 2, 8092 Zurich, Switzerland.

No MeSH data available.