The nutritional value of distillers dried grains with solubles (DDGS) has not been assessed in swine. The nutritional value of corn and wheat DDGS, and possibilities to improve the nutritional value of wheat DDGS were for swine were investigated in two studies. <p>In study 1, two experiments were conducted to determine digestibility and digestible contents of energy, amino acids (AA) and P in corn and wheat DDGS and wheat grain, together with N and P excretion and growth performance in grower-finisher pigs. In experiment 1, 12 barrows (64.6 ± 6.4 kg) were fitted with ileal T-cannulae and had restricted access (2.6 x maintenance) to a wheat control diet or one of three diets with 40% corn, wheat+corn (4:1) or wheat DDGS. For energy, apparent total tract digestibility was highest for wheat (85%; P < 0.05) and did not differ among DDGS (77 to 79%; P > 0.10). Total tract digestible energy (DE) was highest for corn DDGS (4292 kcal kg-1 DM; P < 0.05) and tended to differ among wheat+corn and wheat DDGS and wheat (4038, 4019, and 3807, respectively; P = 0.06). For lysine, apparent ileal digestibility (AID) was highest for wheat (71%; P < 0.05) and did not differ among DDGS (59 to 63%; P > 0.10). The apparent ileal digestible lysine content was highest for corn DDGS (0.51% DM; P < 0.05), intermediate for wheat+corn and wheat DDGS (0.45 and 0.42), and lowest for wheat (0.37%). For P, total tract digestibility was lowest for wheat (15%; P < 0.05) and did not differ among DDGS samples (53 to 56%; P > 0.10). Total N excretion was highest for wheat+corn and wheat DDGS (55 and 58 g d-1; P < 0.05), intermediate for corn DDGS (44) and lowest for wheat (36). Total P excretion did not differ among DDGS (11 g d-1) and was lowest for wheat (8; P < 0.05). In experiment 2, 100 pigs (52.0 ± 3.3 kg) were fed a wheat-pea control diet or one of three 25%-DDGS (corn, wheat+corn or wheat) diets (3.375 Mcal DE kg-1; 2.50 g AID lysine Mcal-1 DE) for 5 wk. Overall, average daily feed intake (ADFI) and daily gain (ADG) were higher for wheat than DDGS (P < 0.05) but feed efficiency did not differ (P > 0.10). In summary, the nutritional value of wheat DDGS for swine is higher than wheat and lower than corn DDGS and feeding DDGS reduced growth performance, partly via a reduced ADFI, indicating that anti-nutritional factors in DDGS require further investigation.<p>In study 2, the effect of xylanase supplementation of wheat DDGS on nutrient digestibility and nutrient excretion was evaluated in grower-finisher pigs. Wheat-based diets with or without 40% wheat DDGS were tested with or without supplementary xylanase (4,000 U kg-1 feed) as a 2 x 2 factorial arrangement in a repeated Latin square design using eight barrows (29.4 ± 2.0 kg) fitted with ileal T-cannulae. Following a 6-day acclimation, faeces and urine were collected for 3 d, and ileal digesta for 2 d. The apparent ileal energy digestibility and DE content were not affected either by ingredient or xylanase (P > 0.05). The total tract energy digestibility and DE content were affected by ingredient (P > 0.05), but not by xylanase (P > 0.05). The total-tract energy digestibility was higher for wheat, but DE content was higher for wheat DDGS. The AID of arginine, isoleucine, leucine, phenylalanine, threonine, tryptophan and total AA were higher (P < 0.05), and of cysteine, histidine and lysine were similar (P > 0.05), and SID of phenylalanine was higher (P < 0.05), and of the other AA was similar (P > 0.10) for wheat DDGS compared to wheat. Supplementary xylanase improved AID and SID of most of the indispensable AA in wheat (P < 0.05), but not in wheat DDGS (P > 0.05). The apparent and standardized ileal AA contents were affected by ingredients (P < 0.05), but not by xylanase (P > 0.05). Digestible AA contents were higher for wheat DDGS than for wheat. The digestibility and digestible content of P were affected by ingredient and xylanse (P < 0.05). The P digestibility and digestible P contents were higher for wheat DDGS compared to wheat. Neither ingredient nor supplementary xylanase affected DM intake (P > 0.05). The DM excretion on daily basis and as a percentage of intake were affected by ingredient (P < 0.05), but not by xylanase (P > 0.05). Ingredients affected all N and P variables (P < 0.05), except percentage retained for both nutrients (P > 0.05). None of N variables (P > 0.05), but P intake and, retention on daily basis and as a percentage of intake were affected by xylanase (P < 0.05). The DM excretion and N and P intake, excretion and daily retention were higher for wheat DDGS compared to wheat. Lack of beneficial response to supplementary xylanase might be due to inappropriate enzyme level or insufficient substrate level of wheat DDGS. In addition, unidentified factors associated with fermentation and drying processes might constrain the nutritional value of wheat DDGS. Further studies are required to determine the proper xylanase inclusion level and/or to identify the factors associated with reduced nutrient digestibility of wheat DDGS.

The nutritional value of distillers dried grains with solubles (DDGS) has not been assessed in swine. The nutritional value of corn and wheat DDGS, and possibilities to improve the nutritional value of wheat DDGS were for swine were investigated in two studies. <p>In study 1, two experiments were conducted to determine digestibility and digestible contents of energy, amino acids (AA) and P in corn and wheat DDGS and wheat grain, together with N and P excretion and growth performance in grower-finisher pigs. In experiment 1, 12 barrows (64.6 ± 6.4 kg) were fitted with ileal T-cannulae and had restricted access (2.6 x maintenance) to a wheat control diet or one of three diets with 40% corn, wheat+corn (4:1) or wheat DDGS. For energy, apparent total tract digestibility was highest for wheat (85%; P < 0.05) and did not differ among DDGS (77 to 79%; P > 0.10). Total tract digestible energy (DE) was highest for corn DDGS (4292 kcal kg-1 DM; P < 0.05) and tended to differ among wheat+corn and wheat DDGS and wheat (4038, 4019, and 3807, respectively; P = 0.06). For lysine, apparent ileal digestibility (AID) was highest for wheat (71%; P < 0.05) and did not differ among DDGS (59 to 63%; P > 0.10). The apparent ileal digestible lysine content was highest for corn DDGS (0.51% DM; P < 0.05), intermediate for wheat+corn and wheat DDGS (0.45 and 0.42), and lowest for wheat (0.37%). For P, total tract digestibility was lowest for wheat (15%; P < 0.05) and did not differ among DDGS samples (53 to 56%; P > 0.10). Total N excretion was highest for wheat+corn and wheat DDGS (55 and 58 g d-1; P < 0.05), intermediate for corn DDGS (44) and lowest for wheat (36). Total P excretion did not differ among DDGS (11 g d-1) and was lowest for wheat (8; P < 0.05). In experiment 2, 100 pigs (52.0 ± 3.3 kg) were fed a wheat-pea control diet or one of three 25%-DDGS (corn, wheat+corn or wheat) diets (3.375 Mcal DE kg-1; 2.50 g AID lysine Mcal-1 DE) for 5 wk. Overall, average daily feed intake (ADFI) and daily gain (ADG) were higher for wheat than DDGS (P < 0.05) but feed efficiency did not differ (P > 0.10). In summary, the nutritional value of wheat DDGS for swine is higher than wheat and lower than corn DDGS and feeding DDGS reduced growth performance, partly via a reduced ADFI, indicating that anti-nutritional factors in DDGS require further investigation.<p>In study 2, the effect of xylanase supplementation of wheat DDGS on nutrient digestibility and nutrient excretion was evaluated in grower-finisher pigs. Wheat-based diets with or without 40% wheat DDGS were tested with or without supplementary xylanase (4,000 U kg-1 feed) as a 2 x 2 factorial arrangement in a repeated Latin square design using eight barrows (29.4 ± 2.0 kg) fitted with ileal T-cannulae. Following a 6-day acclimation, faeces and urine were collected for 3 d, and ileal digesta for 2 d. The apparent ileal energy digestibility and DE content were not affected either by ingredient or xylanase (P > 0.05). The total tract energy digestibility and DE content were affected by ingredient (P > 0.05), but not by xylanase (P > 0.05). The total-tract energy digestibility was higher for wheat, but DE content was higher for wheat DDGS. The AID of arginine, isoleucine, leucine, phenylalanine, threonine, tryptophan and total AA were higher (P < 0.05), and of cysteine, histidine and lysine were similar (P > 0.05), and SID of phenylalanine was higher (P < 0.05), and of the other AA was similar (P > 0.10) for wheat DDGS compared to wheat. Supplementary xylanase improved AID and SID of most of the indispensable AA in wheat (P < 0.05), but not in wheat DDGS (P > 0.05). The apparent and standardized ileal AA contents were affected by ingredients (P < 0.05), but not by xylanase (P > 0.05). Digestible AA contents were higher for wheat DDGS than for wheat. The digestibility and digestible content of P were affected by ingredient and xylanse (P < 0.05). The P digestibility and digestible P contents were higher for wheat DDGS compared to wheat. Neither ingredient nor supplementary xylanase affected DM intake (P > 0.05). The DM excretion on daily basis and as a percentage of intake were affected by ingredient (P < 0.05), but not by xylanase (P > 0.05). Ingredients affected all N and P variables (P < 0.05), except percentage retained for both nutrients (P > 0.05). None of N variables (P > 0.05), but P intake and, retention on daily basis and as a percentage of intake were affected by xylanase (P < 0.05). The DM excretion and N and P intake, excretion and daily retention were higher for wheat DDGS compared to wheat. Lack of beneficial response to supplementary xylanase might be due to inappropriate enzyme level or insufficient substrate level of wheat DDGS. In addition, unidentified factors associated with fermentation and drying processes might constrain the nutritional value of wheat DDGS. Further studies are required to determine the proper xylanase inclusion level and/or to identify the factors associated with reduced nutrient digestibility of wheat DDGS.

The objective of this research was to isolate and characterize soybean genes involved in phytic acid metabolism for use in genetic engineering strategies to improve phosphorus utilization. A soybean phytase from germinated cotyledons was purified 28,000-fold to apparent homogeneity and was determined to be a glycosylated homodimer with 70 kD subunits. Soybean phytase preferred phytate as substrate (Km = 60 mM) and was capable of removing of all six phosphate groups from phytate. The pH and temperature optima for soybean phytase activity were 4.5 and 58*C, respectively. The N-terminus and four internal peptides from the purified soybean phytase were sequenced by Edman degradation. The amino acid sequence data were used to design degenerate oligonucleotide primers for PCR amplification of the soybean phytase coding sequence. A protein 547 amino acids in length was predicted from the 1641 bp coding sequence. The phytase protein showed significant similarity to plant purple acid phosphatases (PAPs) and contained the conserved metallo-phosphomonoesterase active site motif. The soybean phytase coding sequence was placed under the control of a constitutive 35S CaMV promoter in a soybean biolistic transformation vector and was introduced into "Williams 82" suspension culture cells by particle bombardment. Stably transformed cell suspension lines were recovered. DNA blot analysis demonstrated that the recombinant soybean phytase coding sequence had integrated into the genomes of two cell lines. Expression of the transgene was confirmed by RNA blot analysis. Phytase activity was three to four fold higher in these two lines compared to control non-transformed cultures. A soybean L-myo-insoitol-1-phosphate synthase (MIPS) cDNA was isolated from total RNA from developing seeds. The protein encoded by the soybean MIPS cDNA showed 87-91% homology to MIPS protein sequences from other plant species. RNA blot analysis of staged developing soybean seeds revealed that MIPS is transcribed early in the cotyledonary stage of development. Compared to other soybean tissues, MIPS expression levels were highest in developing seeds. DNA blot analysis demonstrated that multiple copies of the MIPS gene are present within the soybean genome. / Ph. D.

No description available.

In environments characterized by low pH and/or high nitrate, the biomineralization of U(VI)-phosphate minerals represents a uniquely suited bioremediation method involving microbially-mediated hydrolysis of organophosphates coupled to a chemical precipitation of sparingly soluble U(VI)-phosphate minerals. In this study, the ability of natural microbial phytases to hydrolyze phytate, a naturally-occurring and abundant organophosphate, and precipitate uranium-phosphate minerals was investigated through a combination of sediment microcosms, soil slurries, and pure culture studies. In this study, biomineralization of U(VI)-phosphate minerals promoted by addition of glycerol-2-phosphate was shown to outcompete bioreduction in anaerobically-maintained sediment microcosms containing contaminated soils. Addition of phytate to aerobic soils slurries containing ORFRC soils also resulted in significant production of inorganic phosphate, and two microorganisms that efficiently hydrolyze phytate were isolated from these experiments. Overall, the results of this study demonstrate phytate hydrolysis by subsurface microorganisms coupled to precipitation of U(VI)-phosphate minerals for the first time, suggesting that phytate may represent an ideal organophosphate to promote this process.

Phytate is the major storage form of phosphorus in crop seeds, but is not well digested by humans and non-ruminant animals. In addition, phytate chelates several essential micronutrients which are also excreted contributing to phosphorus pollution in the environment. This research was aimed at the biochemical and molecular characterization of two low phytate pea mutant lines, 1-150-81 and 1-2347-144 developed at the Crop Development Centre, University of Saskatchewan in collaboration with Dr. Victor Raboy, USDA, Idaho. Low phytic acid (lpa) crops are low in phytic acid and high in inorganic phosphorus (Pi). In Study I, two lpa pea genotypes, 1-150-81, 1-2347-144, and their progenitor CDC Bronco were evaluated in field trials for two years. The lpa genotypes did not significantly differ from CDC Bronco in all agronomic traits assessed except for lower seed weight and grain yield. The concentration of IP6 at 14 DAF was not significantly different among CDC Bronco, 1-150-81 and 1-2347-144. However, the concentrations of IP6 among CDC Bronco, 1-150-81 and 1-2347-144 started to differ significantly from 21 DAF onwards. The lpa genotypes 1-150-81 and 1-2347-144 showed 65% and 60% reduction in IP6, respectively, when compared to their progenitor CDC Bronco at 49 DAF. The Pi concentrations between the lpa genotypes were similar and significantly higher than CDC Bronco from 21 DAF to 49 DAF. At 49 DAF, 1-150-81 and 1-2347-144 were 72 and 84% higher in Pi, respectively, than CDC Bronco. The total P concentration was similar in lpa genotypes and CDC Bronco throughout the seed development. This study elucidated the rate and accumulation of phosphorus compounds in lpa genotypes. In Study II, aiming at understanding the genetic basis of the lpa mutation in pea lines 1-150-81 and 1-2347-144, a 1530 bp open reading frame of myo-inositol phosphate synthase gene (MIPS) was amplified from CDC Bronco and the lpa genotypes. Sequencing results showed no difference in coding sequence in MIPS between CDC Bronco and lpa genotypes. Transcript levels of both MIPS and myo-inositol tetrakisphosphate1-kinase (ITPK1) were relatively lower at 49 DAF than at 14 DAF for CDC Bronco and lpa lines. There was no difference in expression level of both MIPS and ITPK1 between CDC Bronco and the lpa genotypes at 49 DAF. The data demonstrated that mutation in MIPS was not responsible for lpa trait in pea. Study III was aimed at developing a single nucleotide polymorphism (SNP) based genetic linkage map and mapping genomic regions associated with phytic acid-phosphorus (PA-P) concentration using PR-15 recombinant inbred lines (RILs) derived from a cross between a low phytate (lpa) pea genotype, 1-2347-144 and normal phytate pea cultivar CDC Meadow. A total of 163 RILs were genotyped using 1536 SNP markers in an Illumina GoldenGate array. Three hundred and sixty seven polymorphic SNP markers, ordered into 7 linkage groups (LGs), generated a linkage map with a total length of 437.2 cM. The phytic acid locus was mapped on to LG5. A quantitative trait locus (QTL) for iron bioavailability was mapped on to the same location in LG5 as phytic acid concentration. Potential benefits arising out of this research include improved bioavailability of phosphorus, iron and zinc in foods and feeds, less phosphorus excretion and environmental pollution and a saving in feed costs.

The antioxidant activity of carnosine and phytic acid was investigated using several model systems. Carnosine and phytic acid alone inhibited metal ion-catalyzed deoxyribose degradation. Carnosine strongly inhibited metal ion-catalyzed lipid peroxidation in liposomes and in ground beef homogenates. Phytic acid facilitated oxidation of Fe (II) to Fe (III), and it inhibited hemeprotein + H202-catalyzed lipid peroxidation in linoleic acid micelles. Antioxidant and color stabilizing effects of carnosine and phytate were investigated in a beef model system. Both compounds increased the rate of pH decline in pre-rigor beef muscle and stabilized fresh meat color by inhibiting metmyoglobin formation and lipid peroxidation in raw samples during storage at 4°C. Both compounds inhibited heme degradation and lipid peroxidation in cooked beef during storage at 4°C. Iron released from heme was strongly related to lipid peroxidation in cooked beef. Ascorbic acid inhibited metmyoglobin formation on the surface of ground beef patties but not in the bulk of the product. In contrast, camosine inhibited metmyoglobin formation and brown color development throughout the product. Carnosine increased cook yield and salt-soluble protein, but ascorbic acid had no effect on cook yield and decreased salt-soluble protein. Carnosine was more effective on inhibition of lipid peroxidation than was ascorbic acid. Phytate greatly enhanced water-holding capacity of raw and cooked meat in a dilute beef model system. Effects of 0.5% sodium phytate, sodium pyrophosphate, and sodium tripolyphosphate, along with 1% NaCl, on physicochemical properties of restructured raw and cooked beef were compared. In raw beef, the treatments with sodium phytate, sodium pyrophosphate, and sodium tripolyphosphate increased meat pH and salt-soluble protein level, and inhibited metmyoglobin formation and lipid peroxidation, compared to the control. In cooked beef, the treatments with sodium phytate, sodium pyrophosphate, and sodium tripolyphosphate increased bind strength, cooked yield, moisture level, and meat pH, and inhibited lipid peroxidation. The treatments with sodium pyrophosphate and sodium tripolyphosphate increased inorganic orthophosphate level in both raw and cooked beef, compared to sodium phytate and the control. These results indicate that carnosine and phytate can be used as meat preservatives for extending shelf-life and enhancing water-holding capacity of meat and meat products.

The development of soybean [Glycine max (L.) Merr.] cultivars with modified phosphorus (P) composition has nutritional and environmental benefits, but poor seed germination and emergence presents challenges for commercial production. Different genetic mutations in two sources of germplasm, CX1834 and V99-5089, decrease the phytate and increase the inorganic phosphorus (Pi) content of seed. In V99-5089, a mutation in the D-myo-inositol 3-phosphate synthase 1 gene (MIPS1) also results in elevated sucrose content with a concomitant decrease in raffinose and stachyose content, further improving the nutritional value of soybean meal. Prior to the release of V99-5089-derived germplasm, germplasm with the MIPS1 mutation was characterized and compared to CX1834-derived germplasm to determine the effects of this mutation on agronomic and seed composition traits in multiple environments. The correlations between P and sugar seed composition traits were favorable for improving the nutritional composition of soybean. Lack of genotype à environment interaction for sugar traits allows for selection in one growing environment. Despite the significant genotype à environment interaction for phytate and Pi, lines with the MIPS1 gene could readily be distinguished from normal phytate lines, even in unfavorable environments. Phenotypic selection for seed Pi content was more effective than marker assisted selection with the Satt453 marker. The CX1834-derived lines were lower for phytate and higher for Pi content compared to the V99-5089-derived lines. The use of subtropical winter nursery environments for population development resulted in significant reductions in emergence of low phytate genotypes, skewing segregation ratios and prohibiting the analysis of agronomic traits. Emergence was significantly affected by genotype, environment, and the genotype à environment interaction in three emergence tests of advanced low phytate lines. Emergence of modified lines was reduced but some were in a range that would not prohibit commercialization of P modified cultivars. Yields of the best emerging lines were not significantly different from the control cultivars. The results of this study indicate that the development of commercial cultivars with the V99-5089-derived MIPS1 mutation is possible but breeders and producers must focus attention on emergence during population development and seed production to emphasize selection of lines with high emergence potential. / Ph. D.

Phytate is the major storage form of phosphorus in seeds of soybeans. Because phytate chelates mineral cations including calcium, iron, and zinc, these mixed salts are often excreted by non-ruminant animals such as humans, swine, poultry, and fish. While this causes iron and zinc deficiencies, phytate is also considered a water pollutant due to the excess phosphorus excreted in animal waste. These negative environmental and nutritional effects, create a need for low phytate soybeans. While several low phytate soybean lines have been developed, a major drawback is the reduced seedling emergence of these lines resulting in low yields. Therefore, understanding the genetic and molecular bases of the low emergence trait in relation to seed phytate content in major crops such as soybean is of great economic importance. This PhD project worked towards the long term goal of developing low phytate soybean cultivars with good seedling emergence and high-yield. This dissertation focused on metabolomic differences between low and normal phytate lines and how these could relate to the low emergence phenotype. The genetic materials used here include four near isogenic lines that differ in mutations in two multi drug resistance-associated proteins (MRPs). Only the line with both mutations was low phytate. The phytate levels, field- and lab-based emergence rates were determined for these lines, their parents and a control line through replicated field experiments for three consecutive years. The emergence rates of the low phytate lines were not always reduced. This showed that the environment the seeds were produced in is highly important, especially when breeding and commercially growing low phytate lines. A protocol was developed for successful metabolomic discrimination of these closely related soybean lines. The polar and non-polar metabolite profiles were determined using ultra performance liquid chromatography mass spectrometry and metabolomic differences between the low and normal phytate lines were identified. The low phytate double mutant did not contain C22 glucose terminated Group A soyasaponins and almost exclusively contained C22 xylose terminated Group A soyasaponins (A4, A5 and A6). Compared to the normal phytate lines, the low phytate soybean line showed a higher concentration of storage lipids (triacylglycerols and diacylglycerols) and certain phospholipids. / Ph. D.

Le phosphore (P) est un élément indispensable pour la croissance des plantes. De nombreux travaux montrent des réponses très précoces à une limitation de la disponibilité en P. Pendant la germination et la croissance juvénile, la demande en P des plantules peut être satisfaite par la remobilisation des réserves en P des graines et le prélèvement racinaire. Les objectifs de la thèse sont d’étudier la contribution respective de la remobilisation des réserves en P des graines et du prélèvement racinaire de P à l’alimentation en P des plantules de maïs, et les interactions entre ces deux processus. Différentes expériences ont été conduites pour i) étudier les cinétiques de la remobilisation des réserves en P des graines, ii) identifier précisément le début du prélèvement de P exogène par les racines, iii) quantifier la contribution relative de ces flux à l’alimentation en P de la plantule, iv) comprendre les interactions entre ces flux. Des graines riches et des graines pauvres en P on été cultivées à différents niveaux de disponibilités P exogènes pendant quatre semaines. Le traçage isotopique du P exogène (32P) a été utilisé pour quantifier le flux de prélèvement et calculer le flux de remobilisation du P des graines. Initialement, 86% du P sous forme phytate et 13% du C de la graine est localisé dans le scutellum indépendamment du niveau de richesse en P de la graine. 4 jours après le semis, 98% des phytates des graines sont hydrolysés. La cinétique d’hydrolyse des phytates est indépendante de la richesse en P des graines et de la disponibilité en P dans le milieu. Le P issu de l’hydrolyse des phytates est stocké temporairement dans la graine avant d’être transporté vers les organes en croissance de la plantule. Le prélèvement de P exogène commence dès l’émergence de la radicule (4ième jour) et dépend de la disponibilité en P dans le milieu. L’initiation du prélèvement et son intensité ne dépend pas du flux de remobilisation des réserves en P de la graine. Le P issu de la remobilisation et du prélèvement est distribué dans les mêmes proportions entre les parties ariennes et racinaires. Un bilan de P à l’échelle de la plantule entière et de la graine a permis de mettre en évidence un efflux de P depuis la graine vers l’extérieur pendant la phase d’hydrolyse des phytates. La modélisation des flux de P pendant la germination et la croissance précoce permet de rendre compte des observations sous l’hypothèse d’absence d’interaction entre les flux de remobilisation et de prélèvement de P bien que ces deux processus se chevauchent dans le temps. Nos résultats démontrent l’importance de la disponibilité locale en P dans le milieu pendant les stades précoces indépendamment du niveau de richesse en P des graines. / Phosphorus (P) is an essential element for plant growth. Many studies have shown a very early seedling response to the limitation on the availability of P. During germination and early growth, the seedling P demand may be satisfied by the remobilization of seed P reserves and exogenous P uptake by developing roots. The objective of the thesis was to study the relative contribution of remobilization of seed P reserves, the exogenous P uptake by seedling roots and the interaction between these two processes. Various experiments were conducted to i) study the kinetics of the remobilization of seed P reserves, ii) identify precisely the beginning of exogenous P uptake by seedling roots, iii) quantify the relative contribution P fluxes in developing seedlings and iv) the interaction between these two P fluxes. Seeds with low and high P reserves were cultivated at different levels of exogenous P availability for the growth period of four weeks. The exogenous P was labelled with radioactive P (32P) to identify and quantify the P flux in young seedlings coming from exogenous P uptake and seed P reserves remobilization. Initially, 86% of P in the form of phytate and 13% C of seed reserves is localised in scutellum regardless of P initial seed P reserves. Four days after germination, 98% of seed phytate reserves are hydrolyzed. The kinetics of seed phytate hydrolysis was independent of seed P reserves and exogenous P availability. The hydrolyzed forms of phytate were temporarily stored in the seed before being translocated towards newly growing seedling compartments. The exogenous P uptake started soon after the radicle emergence (4th day) and depend mainly on the availability of exogenous P in the growth medium. The beginning of exogenous P uptake and its intensity was not influenced by the seed P reserves remobilization. The proportion of distribution of remobilized seed P reserves and the exogenous P uptake was similar among seedling shoot and roots. The whole seed and seedling P budget showed the significant P losses from germinating seeds by P efflux with the beginning of phytate hydrolysis in seeds. We proposed a model for the seed P remobilization and exogenous P uptake during germination and early growth. Assuming no interaction between seed P reserves remobilization and exogenous P uptake, the simulations were found to be in close agreement with experimental data. Our results showed the importance of exogenous P availability in growth medium during early growth stages regardless of seed P reserves.