.5, 5.0, and 7.5 m m N, respectively ( Fig. 5 ). Fig. 5. Root nitrogen content (RN), root carbon content (RC), root carbon to nitrogen ratio (R-C:N), and root nitrogen use efficiency (RNUE) as affected by 0-, 0.5-, 1.0-, 2.5-, 5.0-, and 7.5-m m
) the sum of leaf, stem, and bulb parts. Fig. 3. Biomass ratios in relation to the sum of leaf, stem, and bulb parts (LSB) and bulb characteristics of garlic plants grown in response to ambient and elevated carbon dioxide and nitrogen (N) treatments: low
1 Permanent address: Department of Horticulture, Henan Agricultural University, Zhengzhou 450001, P.R. China. 2 To whom reprint requests should be addressed: fax: 607-255-4355; e-mail: LC89@Cornell.edu This work was supported in part by USDA
The ability of mycorrhizal and nonmycorrhizal `Elliott' highbush blueberry (Vaccinium corymbosum L.) plants to acquire soil N under different preplant organic soil amendment regimes (forest litter, rotted sawdust, or no amendment) was investigated in a field experiment using 15N labeled (NH4)2SO4. Plants inoculated with an ericoid mycorrhizal isolate, Oidiodendron maius Dalpé (UAMH 9263), had lower leaf 15N enrichment and higher leaf N contents than noninoculated plants but similar leaf N concentrations, indicating mycorrhizal plants absorbed more nonlabeled soil N than nonmycorrhizal plants. Mycorrhizal plants produced more plant dry weight (DW) and larger canopy volumes. The effect of preplant organic amendments on the growth of highbush blueberry plants was clearly demonstrated. Plants grown in soil amended with forest litter produced higher DW than those in either the rotted sawdust amendment or no amendment. Plants grown in soils amended preplant with sawdust, the current commercial recommendation, were the smallest. Differences in the carbon to nitrogen ratio were likely responsible for growth differences among plants treated with different soil amendments.
temperatures, as noted in 2013, the plant shift from carbon gain to carbon loss is mainly due to a decrease in canopy Pn as temperatures increased above 24 °C. The ratio of R total to canopy Pn indicated high capacity for carbon gain (values of 1.2 to 1
One-year-old grapevines (Vitis labrusca L. `Concord') were supplied twice weekly for 5 weeks with 0, 5, 10, 15, or 20 mm nitrogen (N) in a modified Hoagland's solution to generate a wide range of leaf N status. Both light-saturated CO2 assimilation at ambient CO2 and at saturating CO2 increased curvilinearly as leaf N increased. Although stomatal conductance showed a similar response to leaf N as CO2 assimilation, calculated intercellular CO2 concentrations decreased. On a leaf area basis, activities of key enzymes in the Calvin cycle, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), NADP-glyceraldehyde-3-phosphate dehydrogenase (GAPDH), phosphoribulokinase (PRK), and key enzymes in sucrose and starch synthesis, fructose-1,6-bisphosphatase (FBPase), sucrose phosphate synthase (SPS), and ADP-glucose pyrophosphorylase (AGPase), increased linearly with increasing leaf N content. When expressed on a leaf N basis, activities of the Calvin cycle enzymes increased with increasing leaf N, whereas activities of FBPase, SPS, and AGPase did not show significant change. As leaf N increased, concentrations of glucose-6-phosphate (G6P), fructose-6-phosphate (F6P), and 3-phosphoglycerate (PGA) increased curvilinearly. The ratio of G6P/F6P remained unchanged over the leaf N range except for a significant drop at the lowest leaf N. Concentrations of glucose, fructose, and sucrose at dusk increased linearly with increasing leaf N, and there was no difference between predawn and dusk measurements. As leaf N increased, starch concentration increased linearly at dusk, but decreased linearly at predawn. The calculated carbon export from starch degradation during the night increased with increasing leaf N. These results showed that 1) grapes leaves accumulated less soluble carbohydrates under N-limitation; 2) the elevated starch level in low N leaves at predawn was the result of the reduced carbon export from starch degradation during the night; and 3) the reduced capacity of CO2 assimilation in low N leaves was caused by the coordinated decreases in the activities of key enzymes involved in CO2 assimilation as a result of direct N limitation, not by the indirect feedback repression of CO2 assimilation via sugar accumulation.
is associated with greater Pn than R or a Pn/R ratio greater than 1.0 when carbon assimilation rate exceeds carbon consumption rate. H and D caused severe decline in Pn, but enhanced R, leading to reduction in Pn/R ratio below 1.0 or carbon deficit
species such as cotton ( Gossypium hirsutum ) and bean ( Phaseolus vulgaris ), however, leaves developed under LNT may acclimate to such conditions, resulting in carbon exchange rates as high as in plants growing under higher temperatures ( Singh et al
, and use but ends with the impact of that product at the end of its useful life through recycling or disposal. Most published LCAs have focused on carbon footprint, but the tool can be used to assess other environmental impacts such as water footprint
area and dry weight from each leaf sample allowed calculation of specific leaf weight (i.e., leaf dry weight per unit area), area-based leaf N content, and photosynthetic nitrogen use efficiency [PNUE (the ratio of P n rate and area-based leaf N