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

Abstract

-We evaluated gas exchange, chlorophyll index (CI) using SPAD-502 chlorophyll meter, and leaf nutritional responses in one-year-old northern red oak (Quercus rubra L.) container seedlings transplanted into control (unfertilized) or fertilized (0.86 g N plant −1 ) sand culture and grown in a greenhouse for 90 days. We labeled current nitrogen (N) uptake with ( 15 NH 4 ) 2 SO 4 and directly quantified proportional contributions of N derived from fertilizer (NF) compared with retranslocation or N derived from plant (NP) in leaf growth of red oak seedlings. NF met a greater N demand in leaf growth of fertilized plants while unfertilized seedlings relied entirely on NP for their leaf growth. Fertilization increased leaf dry mass by 67% and new stem dry mass by 253% 90 days after transplanting compared to control seedlings. Specific leaf area (SLA) was not significantly altered but CI increased 90 days after transplanting. Higher leaf N concentration and content in fertilized compared with control seedlings was linked to greater chlorophyll concentrations in the former plants. The higher coefficient of determination (r 2 = 0.72) noted between leaf N concentrations and CI suggests that the SPAD meter could be a useful tool for assessing leaf N status in northern red oak seedlings. Fertilized seedlings exhibited higher net assimilation, stomatal conductance, and transpiration rates compared with controls. Increased seedling growth in response to fertilization was related to maintenance of higher gas exchange and greater nutrient uptake, which could improve outplanting success. fertilization / gas exchange / northern red oak / nitrogen / photosynthesis / retranslocation / SPAD meter Résumé -Croissance, échanges gazeux et réponses nutritionnelles de jeunes semis de Quercus rubra soumis à une fertilisation par ( 15 NH 4 ) 2 SO 4 . Nous avons estimé les échanges gazeux foliaires, un index de teneurs en chlorophylles (IC) avec un chlorophylle-mètre SPAD-502 et les teneurs en nutriments dans les feuilles de jeunes plants de chêne rouge d'Amérique (Quercus rubra L.) âgés d'un an. Les plants ont été transplantés dans du substrat sableux non fertilisé (témoins) ou fertilisé avec 0.86 g N par plante, et cultivés pendant 90 jours sous serre. L'azote apporté par la fertilisation était marqué avec ( 15 NH 4 ) 2 SO 4 et nous avons directement quantifié les contributions à la croissance foliaire de N apporté par la fertilisation (NF) par rapport à celle de N remobilisé depuis les pools de réserve de la plante (NP). NF constituait la fraction la plus importante d'azote foliaire de plants fertilisés, alors que l'azote foliaire des plants non fertilisés était exclusivement constitué de NP. La fertilisation s'est traduite par une augmentation, par rapport aux plantes témoins, de 67 % de la biomasse foliaire et de 253 % de la biomasse de tiges nouvellement formées 90 jours après la transplantation. La surface spécifique des feuilles n'était pas affectée par la fertilisation alors que CI avait significativement augmenté. Des teneur...

Estimation of leaf nitrogen concentrations in Quercus robur L. using the CCM-200 portable chlorophyll meter for different patterns of vegetative growth and acorn production

“…According to these results, 38-87 % of the total variation of LNC of first-and second-flush leaves was explained using CCI as an independent variable (Table 2). This finding is consistent with the results of earlier research conducted on forest trees (Chang and Robison 2003;Van den Berg and Perkins 2004;Percival et al 2008;Salifu et al 2008;Ghasemi et al 2011).…”

Drought susceptibility and recovery of transplanted Quercus rubra seedlings in relation to root system morphology

“…This response may correspond to that of cork oak (Quercus suber L.) seedlings, in which increased specific leaf area associated with shading under water limiting conditions resulted in equivalent biomass production despite reductions in instantaneous photosynthetic rates (Puértolas et al, 2008). In addition, N and carbohydrate reserves are essential for new growth development before significant root uptake and photosynthesis (Salifu et al, 2008;Sloan and Jacobs, 2008). Therefore, higher internal nutrient reserves or stored carbohydrates may have contributed to growth in large plants.…”

Nitrogen retranslocation, allocation, and utilization in bare root Larix olgensis seedlings

“…Studies have focused on nutrient retranslocation in juvenile evergreen conifer seedlings (Nambiar andFife 1987, 1991;van den Driessche 1984;Imo and Timmer 2001;Timmer 2001, 2003), hardwood seedlings (Salifu et al 2008(Salifu et al , 2009, and mature tree stands (Helmisaari 1992;Mead and Preston 1994;Chapin and Kedrowski 1983). The main conclusions from these reports include: (1) the leaf is the main source and sink of retranslocated nutrients in evergreen conifers (Nambiar andFife 1987, 1991).…”

“…Nitrogen (N) availability is one of the important factors influencing growth of tree seedlings Timmer 2001, 2003;Salifu et al 2008Salifu et al , 2009Bown et al 2010). Storage of N is important for young trees because buds break in the spring is sub-optimal when N uptake by the roots before photosynthesis can provide carbon skeletons for amino acid synthesis (Millard and Neilsen 1989).…”