Impact of industrial-age climate change on the relationship between water uptake and tissue nitrogen in eucalypt seedlings.

Sherwin, Gyro L.; George, Laurel; Kannangara, Kamali; Tissue, David T.; Ghannoum, Oula

This study explored reductions in tissue nitrogen concentration ([N]) at elevated CO [sub 2] concentrations ([CO [sub 2]]), and changes in plant water and N uptake. Eucalyptus saligna Sm. seedlings were grown under three [CO [sub 2]] levels (preindustrial (280 μL L-1), current (400 μL L-1) or projected (640 μL L-1)) and two air temperatures (current, (current + 4°C)). Gravimetric water use, leaf gas exchange and tissue dry mass and %N were determined. Solid-state 15N-NMR spectroscopy was used for determining the partitioning of N chemical groups in the dry matter fractions. Water use efficiency (WUE) improved with increasing [CO [sub 2]] at ambient temperature, but strong leaf area and weak reductions in transpiration rates led to greater water use at elevated [CO [sub 2]]. High temperature increased plant water use, such that WUE was not significantly stimulated by increasing [CO [sub 2]] at high temperature. Total N uptake increased with increasing [CO [sub 2]] but not temperature, less than the increase recorded for plant biomass. Tissue [N] decreased with rising [CO [sub 2]] and at high temperature, but N use efficiency increased with rising [CO [sub 2]]. Total N uptake was positively correlated with total water use and root biomass under all treatments. Growth [CO [sub 2]] and temperature did not affect the partitioning of 15N among the N chemical groups. The reductions of tissue [N] with [CO [sub 2]] and temperature were generic, not specific to particular N compounds. The results suggest that reductions in tissue [N] are caused by changes in root N uptake by mass flow due to altered transpiration rates at elevated [CO [sub 2]] and temperature. Seedlings of Eucalyptus saligna Sm. were grown under three CO [sub 2] concentrations (280, 400 or 640 μL L-1) and two air temperatures (current or current + 4°C). Total plant N uptake scaled with total water use and root biomass across all treatments, suggesting that reductions in tissue N concentration may be attributed to changes in root N uptake by mass flow due to altered transpiration rates.

EUCALYPTUS; TREE seedlings; CLIMATE change; MYRTACEAE; PLANT physiology

Functional Plant Biology, 2013, Vol 40, Issue 2, p5

1445-4408

Academic Journal

10.1071/FP12130