Nitrogen Nutrition, Growth and Gas Exchange in Eucalyptus globulus Labill. Seedling

Abstract

Potted Eucalyptus globulus Labill. seedlings were grown in sand with added inorganic nutrients. Three treatments were applied: (1) inorganic nitrogen was added regulary (N2), (2) in a small initial quantity only (N1) and (3) after a period of N deficiency (N3); other nutrients were supplied regularly. Biomass increment, foliar nutrient concentrations and gas exchange of leaves were measured. Carbon assimilation, N uptake, growth, and leaf production and expansion were all greater at higher N. Partitioning of dry matter to roots and tops of seedlings was unaffected by treatment. Carbon assimilation and diffusive conductance were linearly related at saturating light and were positively associated with foliar N concentrations; intercellular CO2 partial pressures were constant at c. 246 μbar. The relationship between carbon assimilation and foliar N concentration was better when calculated per leaf weight than per leaf area. Dark respiration was positively associated with foliar N concentration. Following refertilisation of N-deficient seedlings, foliar N and carbon assimilation increased rapidly; about 20 days later N uptake declined and seedling biomass started to increase. Instantaneous transpiration efficiency [c. 5 mmol (CO2) mol-1 (H2O)] was not significantly affected by foliar N concentration or treatment. Instantaneous nitrogen use efficiency of leaves: (rate of carbon assimilation)/(leaf N content) was greater at higher N. In contrast to the literature, there was no simple relationship between nitrogen use efficiency of whole seedlings (biomass gain)/(nitrogen concentration) and seedling N. Instantaneous transpiration and nitrogen use efficiencies were generally high compared with values published for many woody plants. A simple model predicted that, with no environmental constraints, exposed mature leaves with high N (1.5 mmol g-1) assimilate 5.4 times more carbon than similar leaves with low N (0.5 mmol g-1). Night respiration of foliage is a greater proportion of daily carbon balance for leaves with low N. When environmental factors constrain carbon assimilation foliage with high N is most affected.

Fertilization with phosphorus increases soil nitrogen absorption in young plants of Eucalyptus grandis

“…In general P-fertilization ameliorated leaf nutrient status and presumably photosynthetic capacity (Kirschbaum and Tompkins, 1990;Kirschbaum et al, 1992;Sheriff and Nambiar, 1991). Our results show that P-fertilization improved leaf nutrient status more than N-fertilization, which can explain the higher effect on growth of P-fertilization.…”

Physiological regulation of productivity and water use in Eucalyptus: a review

“…The effects of atmospheric and soil water stress on photosynthesis are primarily caused by changes in g s in response to D and c, respectively (Leuning, 1990). Positive associations between A max and leaf nitrogen concentration in E. globulus (Sheriff and Nambiar, 1991;Pereira et al, 1994) and E. grandis (Leuning et al, 1991a), and leaf phosphorus concentration in E. grandis (Kirschbaum and Tompkins, 1990) have been found for Eucalyptus species. In an investigation using E. globulus seedlings, Sheriff and Nambiar (1991) observed a linear relationship between A max and leaf nitrogen concentration when A max was <12.2 mmol m À2 s À1 .…”

“…Roberts and Rosier (1993) adopted a single-layer model because of the lack of changes in values of g s , temperature and vapour pressure deficit with depth in the canopies. Transpiration was very sensitive to the value of L and largely Table 6 Values of maximum stomatal conductance (g smax ) maximum photosynthesis rates (A max ) maximum rates of carboxylation activity (V cmax ) and rates of electron transport at saturating irradiance (J max ) for selected Eucalyptus species This Table is compiled from data published by Grassi et al (2002), Kirschbaum and Farquhar (1984), Kirschbaum and Tompkins (1990), Kuppers et al (1987), Dye and Olbrich (1993), Roberts and Rosier (1993), Sheriff and Nambiar (1991), Sheriff (1992), Wullschleger (1993), Eamus et al (1995), David et al (1997), Eamus and Cole (1997), Myers et al (1997), Kallarackal and Somen (1997), Mielke et al (1999), White et al (1999White et al ( , 2000, James and Bell (2000), Clearwater and Meinzer (2001), Close and Beadle (2003). insensitive to changes in available energy, temperature and g b .…”

Photosynthetic capacity of Eucalyptus globulus is higher when grown in mixture with Acacia mearnsii

“…However, they also found that A. melanoxylon had a negative influence on E. pauciflora foliar N, Rubisco and pigment concentrations, and concluded that the facilitative influence is clearly species specific, with A. melanoxylon characteristic of a later successional stage. Experiments in fertiliser trials have also shown positive relationships between N a and A max , V cmax or J max (Leuning et al 1991;Sheriff and Nambiar 1991;Pereira et al 1992;Turnbull et al 2007) although others have found no relationships suggesting that N a was in excess of photosynthetic requirements and that A max was limited by other factors (Warren et al 2000;Close et al 2004). The improved foliar nutrition of A. mearnsii in mixtures may be a result of a reduction in competition for those nutrients by E. globulus compared to other A. mearnsii.…”

“…Turnbull et al (2007) also found that the application of N, P and K fertiliser increased g s of E. globulus trees in monocultures, perhaps by ameliorating K limitations on stomatal functioning. However, while a positive and linear correlation was found between g s and N a in an N fertiliser experiment with E. globulus (Sheriff and Nambiar 1991), N fertiliser did not influence g s of E. grandis, where the effect of fertiliser on A max was biochemical (higher V cmax and J max ) (Grassi et al 2002).…”