Does soil nitrogen influence growth, water transport and survival of snow gum ( Eucalyptus pauciflora Sieber ex Sprengel.) under CO₂ enrichment?

ATWELL, BRIAN J.; HENERY, MARTIN L.; BALL, MARILYN C.

Eucalyptus pauciflora Sieber ex Sprengel. (snow gum) was grown under ambient (370 µL L−1) and elevated (700 µL L−1) atmospheric [CO2] in open-top chambers (OTCs) in the field and temperature-controlled glasshouses. Nitrogen applications to the soil ranged from 0.1 to 2.75 g N per plant. Trees in the field at high N levels grew rapidly during summer, particularly in CO2-enriched atmosphere, but suffered high mortality during summer heatwaves. Generally, wider and more numerous secondary xylem vessels at the root–shoot junction in CO2-enriched trees conferred fourfold higher below-ground hydraulic conductance. Enhanced hydraulic capacity was typical of plants at elevated [CO2] (in which root and shoot growth was accelerated), but did not result from high N supply. However, because high rates of N application consistently made trees prone to dehydration during heatwaves, glasshouse studies were required to identify the effect of N nutrition on root development and hydraulics. While the effects of elevated [CO2] were again predominantly on hydraulic conductivity, N nutrition acted specifically by constraining deep root penetration into soil. Specifically, 15–40% shallower root systems supported marginally larger shoot canopies. Independent changes to hydraulics and root penetration have implications for survival of fertilized trees under elevated atmospheric [CO2], particularly during water stress.

PLANT physiology; EUCALYPTUS; EUCALYPTUS citriodora; MYRTACEAE; WATER distribution; VASCULAR system of plants; PLANT cells & tissues

Plant, Cell & Environment, 2009, Vol 32, Issue 5, p553

0140-7791

Academic Journal

10.1111/j.1365-3040.2009.01949.x