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Carbon dioxide level and form of soil nitrogen regulate assimilation of atmospheric ammonia in young trees.

Silva LC, Salamanca-Jimenez A, Doane TA, Horwath WR - Sci Rep (2015)

Bottom Line: Using Coffea arabica as a model tree species, we observed an additive effect on growth, by which aboveground productivity was highest under elevated CO2 and ammonium fertilization, while nitrate fertilization favored greater belowground biomass allocation regardless of CO2 concentration.Surprisingly, trees with the largest aboveground biomass assimilated significantly less NH3 than the smaller trees.Nitrogen form is therefore an intrinsic component of physiological responses to atmospheric change, including assimilation of gaseous nitrogen as influenced by plant growth history.

View Article: PubMed Central - PubMed

Affiliation: Department of Land Air and Water Resources. University of California, Davis, CA-95616.

ABSTRACT
The influence of carbon dioxide (CO2) and soil fertility on the physiological performance of plants has been extensively studied, but their combined effect is notoriously difficult to predict. Using Coffea arabica as a model tree species, we observed an additive effect on growth, by which aboveground productivity was highest under elevated CO2 and ammonium fertilization, while nitrate fertilization favored greater belowground biomass allocation regardless of CO2 concentration. A pulse of labelled gases ((13)CO2 and (15)NH3) was administered to these trees as a means to determine the legacy effect of CO2 level and soil nitrogen form on foliar gas uptake and translocation. Surprisingly, trees with the largest aboveground biomass assimilated significantly less NH3 than the smaller trees. This was partly explained by declines in stomatal conductance in plants grown under elevated CO2. However, unlike the (13)CO2 pulse, assimilation and transport of the (15)NH3 pulse to shoots and roots varied as a function of interactions between stomatal conductance and direct plant response to the form of soil nitrogen, observed as differences in tissue nitrogen content and biomass allocation. Nitrogen form is therefore an intrinsic component of physiological responses to atmospheric change, including assimilation of gaseous nitrogen as influenced by plant growth history.

No MeSH data available.


Related in: MedlinePlus

Least square regressions describing initial plant growth (phase I), showing the effects of ambient and elevated CO2 on foliar area and dry biomass accumulation in shoots, roots and root to shoot ratio, in plants receiving nitrate (NO3−) or ammonium (NH4+) as the sole nitrogen source.Shaded areas represent 95% confidence intervals of the average slope (solid lines). Significance levels correspond to the effect of treatments (fixed effects) as determined by repeated measure analysis of variance where time (day) is a random effect. Root to shoot ratios were not measured at time zero.
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f1: Least square regressions describing initial plant growth (phase I), showing the effects of ambient and elevated CO2 on foliar area and dry biomass accumulation in shoots, roots and root to shoot ratio, in plants receiving nitrate (NO3−) or ammonium (NH4+) as the sole nitrogen source.Shaded areas represent 95% confidence intervals of the average slope (solid lines). Significance levels correspond to the effect of treatments (fixed effects) as determined by repeated measure analysis of variance where time (day) is a random effect. Root to shoot ratios were not measured at time zero.

Mentions: The first phase of the experiment was designed to test the combined effect of CO2 level and form of soil nitrogen on initial tree development under four different treatments: Ambient CO2 and NH4+ (A-NH4+); Ambient CO2 and NO3− (A-NO3−); Elevated CO2 and NH4+ (E-NH4+); Elevated CO2 and NO3− (E-NO3−). During five months, tree growth showed a significant additive effect of CO2 enrichment and form of soil nitrogen. Shoot growth was consistently higher under CO2 enrichment, with plants receiving NH4+ showing greater leaf area and total aboveground biomass than those receiving NO3− (Fig. 1). Tree productivity is generally expected to increase under elevated CO212 and here the positive effect of CO2 enrichment on the initial phase of tree development was enhanced by NH4+ fertilization. Despite this effect, no overall significant differences were observed for total plant biomass among all treatments; however, large contrasts in morphology occurred in response to soil nitrogen form, with twice as much biomass allocated to roots relative to shoots in NO3− treatments as compared to NH4+ treatments. Leaf area was also strongly affected by soil nitrogen form and, as a result, plants grown under A-NO3− and E-NH4+ treatments represented the low and high ends of the aboveground productivity spectrum, respectively (Fig. 1). The fact that these differences in structure and biomass allocation were largely independent of CO2 level but dependent on the form of soil nitrogen may be partially responsible for the observed effect of growth history on gaseous nitrogen uptake (discussed below).


Carbon dioxide level and form of soil nitrogen regulate assimilation of atmospheric ammonia in young trees.

Silva LC, Salamanca-Jimenez A, Doane TA, Horwath WR - Sci Rep (2015)

Least square regressions describing initial plant growth (phase I), showing the effects of ambient and elevated CO2 on foliar area and dry biomass accumulation in shoots, roots and root to shoot ratio, in plants receiving nitrate (NO3−) or ammonium (NH4+) as the sole nitrogen source.Shaded areas represent 95% confidence intervals of the average slope (solid lines). Significance levels correspond to the effect of treatments (fixed effects) as determined by repeated measure analysis of variance where time (day) is a random effect. Root to shoot ratios were not measured at time zero.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4543970&req=5

f1: Least square regressions describing initial plant growth (phase I), showing the effects of ambient and elevated CO2 on foliar area and dry biomass accumulation in shoots, roots and root to shoot ratio, in plants receiving nitrate (NO3−) or ammonium (NH4+) as the sole nitrogen source.Shaded areas represent 95% confidence intervals of the average slope (solid lines). Significance levels correspond to the effect of treatments (fixed effects) as determined by repeated measure analysis of variance where time (day) is a random effect. Root to shoot ratios were not measured at time zero.
Mentions: The first phase of the experiment was designed to test the combined effect of CO2 level and form of soil nitrogen on initial tree development under four different treatments: Ambient CO2 and NH4+ (A-NH4+); Ambient CO2 and NO3− (A-NO3−); Elevated CO2 and NH4+ (E-NH4+); Elevated CO2 and NO3− (E-NO3−). During five months, tree growth showed a significant additive effect of CO2 enrichment and form of soil nitrogen. Shoot growth was consistently higher under CO2 enrichment, with plants receiving NH4+ showing greater leaf area and total aboveground biomass than those receiving NO3− (Fig. 1). Tree productivity is generally expected to increase under elevated CO212 and here the positive effect of CO2 enrichment on the initial phase of tree development was enhanced by NH4+ fertilization. Despite this effect, no overall significant differences were observed for total plant biomass among all treatments; however, large contrasts in morphology occurred in response to soil nitrogen form, with twice as much biomass allocated to roots relative to shoots in NO3− treatments as compared to NH4+ treatments. Leaf area was also strongly affected by soil nitrogen form and, as a result, plants grown under A-NO3− and E-NH4+ treatments represented the low and high ends of the aboveground productivity spectrum, respectively (Fig. 1). The fact that these differences in structure and biomass allocation were largely independent of CO2 level but dependent on the form of soil nitrogen may be partially responsible for the observed effect of growth history on gaseous nitrogen uptake (discussed below).

Bottom Line: Using Coffea arabica as a model tree species, we observed an additive effect on growth, by which aboveground productivity was highest under elevated CO2 and ammonium fertilization, while nitrate fertilization favored greater belowground biomass allocation regardless of CO2 concentration.Surprisingly, trees with the largest aboveground biomass assimilated significantly less NH3 than the smaller trees.Nitrogen form is therefore an intrinsic component of physiological responses to atmospheric change, including assimilation of gaseous nitrogen as influenced by plant growth history.

View Article: PubMed Central - PubMed

Affiliation: Department of Land Air and Water Resources. University of California, Davis, CA-95616.

ABSTRACT
The influence of carbon dioxide (CO2) and soil fertility on the physiological performance of plants has been extensively studied, but their combined effect is notoriously difficult to predict. Using Coffea arabica as a model tree species, we observed an additive effect on growth, by which aboveground productivity was highest under elevated CO2 and ammonium fertilization, while nitrate fertilization favored greater belowground biomass allocation regardless of CO2 concentration. A pulse of labelled gases ((13)CO2 and (15)NH3) was administered to these trees as a means to determine the legacy effect of CO2 level and soil nitrogen form on foliar gas uptake and translocation. Surprisingly, trees with the largest aboveground biomass assimilated significantly less NH3 than the smaller trees. This was partly explained by declines in stomatal conductance in plants grown under elevated CO2. However, unlike the (13)CO2 pulse, assimilation and transport of the (15)NH3 pulse to shoots and roots varied as a function of interactions between stomatal conductance and direct plant response to the form of soil nitrogen, observed as differences in tissue nitrogen content and biomass allocation. Nitrogen form is therefore an intrinsic component of physiological responses to atmospheric change, including assimilation of gaseous nitrogen as influenced by plant growth history.

No MeSH data available.


Related in: MedlinePlus