High nitrogen and elevated [CO2] effects on the growth, defense and photosynthetic performance of two eucalypt species

Atmospheric nitrogen deposition and [CO2] are increasing and represent environmental problems. Planting fast-growing species is prospering to moderate these environmental impacts by fixing CO2. Therefore, we examined the responses of growth, photosynthesis, and defense chemical in leaves of Eucalyptus urophylla (U) and the hybrid of E. deglupta × E. camadulensis (H) to different CO2 and nitrogen levels. High nitrogen load significantly increased plant growth, leaf N, net photosynthetic rate (Agrowth), and photosynthetic water use efficiency (WUE). High CO2 significantly increased Agrowth, photosynthetic nitrogen use efficiency (PNUE) and WUE. Secondary metabolite (SM, i.e. total phenolics and condensed tannin) was specifically altered; as SM of U increased by high N load but not by elevated [CO2], and vice versa for SM of H.

► Photosynthesis, leaf traits, and growth of eucalypts were improved by high soil N.
► Growth was not profoundly affected by elevated [CO2].
► SM of U increased by high N load but not by elevated [CO2], vice versa for SM of H.
► SM was specifically altered, thus responses to environmental change varied widely.