
TY  - JOUR
A1  - McDonald, Evan P. 
A1  - Erickson, John E. 
A1  - Kruger, Eric L. 
T1  - <emph type="2">Research note</emph>: Can decreased transpiration limit plant nitrogen acquisition in elevated CO<emph type="8">2</emph>?
JF  - Functional Plant Biology
JO  - Functional Plant Biol.
Y1  - 2002
VL  - 29
IS  - 9
SP  - 1115
EP  - 1120
KW  - 
UR  - https://doi.org/10.1071/FP02007 
N2  - N acquisition often lags behind accelerated C gain in plants exposed to CO2-enriched atmospheres. To help resolve the causes of this lag, we considered its possible link with stomatal closure, a common first-order response to elevated CO2 that can decrease transpiration. Specifically, we tested the hypothesis that declines in transpiration, and hence mass flow of soil solution, can decrease delivery of mobile N to the root and thereby limit plant N acquisition. We altered transpiration by manipulating relative humidity (RH) and atmospheric [CO2]. During a 7-d period, we grew potted cottonwood (Populus deltoides Bartr.) trees in humidified (76% RH) and non-humidified (43% RH) glasshouses ventilated with either CO2-enriched or non-enriched air (~1000 vs ~380 &#956;mol mol&#8211;1). We monitored effects of elevated humidity and/or CO2 on stomatal conductance, whole-plant transpiration, plant biomass gain, and N accumulation. To facilitate the latter, NO3&#8211; enriched in 15N (5 atom%) was added to all pots at the outset of the experiment. Transpiration and 15N accumulation decreased when either CO2 or humidity were elevated. The disparity between N accumulation and accelerated C gain in elevated CO2 led to a 19% decrease in shoot N concentration relative to ambient CO2. Across all treatments, 15N gain was positively correlated with root mass (P<0.0001), and a significant portion of the remaining variation (44%) was positively related to transpiration per unit root mass. At a given humidity, transpiration per unit leaf area was positively related to stomatal conductance. Thus, declines in plant N concentration and/or content under CO2 enrichment may be attributable in part to associated decreases in stomatal conductance and transpiration. 
ER  -

