Roles of Carbon Gain and Allocation in Growth at Different Nitrogen Nutrition in Eucalyptus camaldulensis and Eucalyptus globulus Seedlings

Abstract

Potted Eucalyptus camaldulensis and E. globulus seedlings were grown in sand with added mineral nutrients. Mineral nitrogen was added, either (I) only a small initial quantity (N1) or (2) regularly (Nz). Other nutrients were supplied regularly to both treatments. Biomass increment and nutrient concentrations of organs and gas exchange of leaves were measured.Growth, foliage area, and foliar N concentration changed little in Nl seedlings, all increased exponentially in N2 seedlings. Partitioning of dry matter and nitrogen was unaffected by ontogeny or treatment in E. globulus, but changed with time in E. camaldulensis. Within a treatment biomass increase was similar for both species, but foliar biomass and area, total foliar N, and response of carbon assimilation to foliar N were greater in E. globulus. Effects of these on carbon assimilation were partly offset by higher foliar N concentrations in E. camaldulensis. Comparative growth rates of the species were not related to leaf area.Carbon assimilation and diffusive conductance were linearly related with different relationships for the two treatments. Intercellular partial pressures of C 0 2 were constant at c . 300 and 220 pPa Pa-' in N1 and N2 treatments of both species. This indicates a controlling mechanism that maintained intercellular C 0 2 constant, but was affected by treatment.Instantaneous potential assimilatory transpiration efficiency [(rate of carbon assimilation)/(rate of transpiration)] and instantaneous potential assimilatory nitrogen use efficiency [(rate of carbon assimilation)/(N content)] of leaves (at saturating light) were similar in the two species and showed treatment effects apparently not caused by foliar N concentration. These efficiencies were generally high compared to values published for woody plants.A simple model illustrates the importance in predicting growth of accurately knowing: foliage mass, partitioning of biomass to foliage, and rates of carbon assimilation. Effects of small differences in carbon assimilation on biomass increment are shown to be potentially large because they can cause accumulation of large differences in foliar mass.

Growth, physiology, and nutrient retranslocation in nitrogen-15 fertilized Quercus rubra seedlings

“…While the lower A rates in control seedlings could be attributed to lack of chlorophyll synthesis and activity of photosynthetic enzymes [17,51], a reduction in g s in the presence of environmental stresses is often linked to decline in root water flow and root growth [1,2,10]. Although we did not measure root water flow in the present study, we observed decreased g s , E rates, and less root growth in control seedlings ( Figs.…”

“…Nitrogen deficiency often inhibits plant productivity [31,41] by reducing number of leaves, leaf area, and leaf N content [40], ultimately reducing maximum rates of photosynthesis [36]. Photosynthesis is reduced by N deficiency through its effects on chlorophyll synthesis and activity of photosynthetic enzymes [17,51]. Thus, a decrease in leaf N concentration could partly explain the observed chlorosis and lower CI (SPAD readings) in unfertilized plants (Fig.…”

Photosynthetic nitrogen-use efficiency of species that differ inherently in specific leaf area

“…The pH was set to 5.8 and regularly maintained. Walters & Field 1987;Harrington et al 1989, Mulkey et al 1991Reich et al 1991;Hollinger 1992, Lloyd et al 1992Sheri 1992;Thompson et al 1992;Gower et al 1993;DeLucia & Schlesinger 1995;Reich et al 1995aReich et al , 1997; broken lines: PNUE amb estimates from Konings et al 1989;Boot & Den Dubbelden 1990;Pons et al 1994;Atkin et al 1996 Two growth cabinets were used for the experiment, each cabinet divided by black shadecloth into a high light and a low light compartment. All plant species were grown once in each cabinet.…”

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

“…Values of maximum stomatal conductance (g smax ) are also high but appear to vary by at least a factor of two within a species, an observation that is probably linked to the marked response of g s to D referred to in the previous section. As Eucalyptus leaves combine a high capacity for carbon fixation, it is perhaps unsurprising that strong linear relationships are observed between photosynthesis (A) and stomatal conductance (g s ) (Wong et al, 1979) although the slopes of these relationships in Eucalyptus can be affected by species (E. camaldulensis versus E. globulus) and treatment (low versus high nitrogen in E. globulus) (Sheriff, 1992). At very high values of g s in E. nitens, there was no relationship between A and g s .…”

“…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 .…”