Differential effects of N, P and K on photosynthesis and partitioning of N in Pinus pinaster needles

Abstract

-We investigated the response of one-year-old Pinus pinaster Ait. growing on a sandy, nutrient-poor soil to the factorial addition of N, P and K. We tested two hypotheses: (1) fertiliser application increases rates of light-saturated photosynthesis (A max ) and leaf-level wateruse efficiency (WUE, as indicated by carbon isotope composition), and (2) greater concentrations of N and Rubisco explain fertiliser-promoted increases in A max and WUE. Two years after fertiliser application, the height of P. pinaster was significantly greater in plots to which P was added (127 ± 7 cm; mean ± SE of three replicate plots) compared to those without added P (70 ± 10 cm), but was unaffected by addition of N or K. The fraction of N present as Rubisco varied between 4 and 18% and was unrelated to N concentrations, but positively related to P and K concentrations. A max and δ 13 C did not vary significantly among treatments and were unrelated to concentrations of Rubisco, N, P or K. We conclude that fertiliser application two years previously has little effect on current A max and δ 13 C of P. pinaster, and thus the previously reported effects of fertiliser on gas exchange are likely ephemeral. nitrogen / phosphorus / potassium / photosynthesis / rubiscoRésumé -Effets différentiels de N, P et K sur la photosynthèse et le fractionnement de N dans les aiguilles de Pinus pinaster. La réponse de plant de Pinus pinaster Ait., poussant sur un sol sableux et pauvre, a été étudiée en fonction de l'addition de N, P et K. Deux hypothèses ont été testées : (1) la fertilisation accroît le taux de saturation lumineuse de la photosynthèse (A max ) et le niveau d'efficience de l'eau (WUE, évalué par la composition isotropique du carbone), (2) une plus grande concentration de N et de rubisco explique que la fertilisation accroît A max et WUE. Deux années après l'application de la fertilisation, la hauteur de P. pinaster était significativement plus grande dans les placeaux où P avait été ajouté (127 ± 7 cm, moyenne ± SE de 3 répétitions), comparativement à ceux sans addition de P (70 ± 10 cm) mais n'était pas affectée par l'addition de N et K. La fraction de N présente sous la forme de rubisco variait entre 4 et 18 % et n'était pas expliquée par les concentrations en N, mais était positivement expliqué par les concentrations en P et K. A max et δ 13 ne variaient pas significativement avec le traitement et n'était pas reliés aux concentrations en rubisco, N, P ou K. On conclue que l'application d'un fertilisant deux ans auparavant a peu d'effet sur les valeurs actuelles de A max et δ 13 C de P. pinaster et alors les effets rapportés auparavant des fertilisants sur les échanges gazeux sont probablement éphémères. azote / phosphore / potassium / photosynthèse / rubisco Abbreviations: A max , maximum rate of light-saturated photosynthesis at ambient CO 2 ; CE, capillary electrophoresis; C i , intercellular CO 2 concentration; Chl, chlorophyll; g s , stomatal conductance; LAI, leaf area index; PPFD, photosynthetic photon flux density; Rubis...

Field effect of P fertilization on N2 fixation rate of Ulex europaeus

“…P fertilization, used in maritime pine forests due to its positive effect on pine growth [7,24], may increase these natural inputs in two different ways: (i) by increasing the abundance and biomass of N 2 -fixing shrubs [3]; and (ii) by increasing the N 2 fixation rate [1]. This second point has been mostly developed in laboratory studies that suggest a P effect on N 2 fixation rate.…”

“…Pines C130: Circumference at 130 cm height. Significant differences are as given by a t-test with a 5% error threshold, and confirm the P effect on pine growth [7,24] …”

Nursery fertilisation affects the frost-tolerance and plant quality of Eucalyptus globulus Labill. cuttings

“…For instance, Picea mariana needed at least 1.28% N in shoot tissues to ensure hardening, while, with 0.64% N, it did not harden and seedlings with 0.87% N showed a lesser degree of hardiness than those with 1.28% [3]. Besides, other factors such as K/N ratio [15] and P/N ratio [58] could be important in cold hardening and growth. If we examine the values of leaf N concentration in both ours and other related experiments [16], we can observe that plants with more than 1.25% N responded to the freezing test significantly better than those that had less than 1.0%.…”

“…These strategies contribute to increasing the resistance in later unfavourable situations such as water stress or frost. The plant nutritional state also contributes in part to this capacity [21] due to its effect on plant growth, root growth capacity, biomass partitioning, leaf area, photosynthesis and/or nutrient mobilization from old to current growth after outplanting [13,42,58]. This depends, however, on species, nutrient concentrations and contents [8,57,58].…”

“…The plant nutritional state also contributes in part to this capacity [21] due to its effect on plant growth, root growth capacity, biomass partitioning, leaf area, photosynthesis and/or nutrient mobilization from old to current growth after outplanting [13,42,58]. This depends, however, on species, nutrient concentrations and contents [8,57,58]. Nevertheless, it still remains uncertain how fertilisation in nurseries influences plant quality and post-transplantation responses to low temperatures for most species [3], including E. globulus [16].…”