Home About us Contact
|
Home About us Contact | ||
|
|
||
P Nutrition (p + nutrition)
Selected AbstractsUptake of residual phosphate and freshly applied diammonium phosphate by Lolium perenne and Trifolium repens,JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 5 2003Anne Gallet Abstract Residual fertilizer phosphorus (residual P) may significantly contribute to crop P nutrition. To test this hypothesis, a pot experiment was conducted with ryegrass (Lolium perenne) and clover (Trifolium repens) grown separately on three different soils which either had not received P fertilizer for at least nine years (0F) or had received P fertilizer equivalent to crop P off-take (F). Soils in the pot experiment were given either none (0F, F) or a single rate of 15 mg P (kg soil),1 as diammonium phosphate (0F+DAP, F+DAP). In the treatments 0F+DAP and F+DAP DAP had been labeled with 33PO4 while in the treatments 0F and F the pool of available soil P had been labeled with carrier-free 33PO4. This allowed estimating the quantities of P in plant dry matter that derived from native soil P, residual fertilizer P or fresh fertilizer P. Fourteen to 62,% of the P in the above ground biomass of white clover or perennial ryegrass were derived from residual P whereas 7 to 28,% were derived from freshly applied DAP. The proportion of P derived from residual P was correlated to the total amount of P fertilizer added to the soils, while the proportion of P derived from DAP was correlated to the concentration of P in the soil solution of the 0F and F soils. Aufnahme von Phosphat aus Rückständen von früherer Düngung und aus frisch ausgebrachtem Diammoniumphosphat durch Lolium perenneund Trifolium repens In Düngerrückständen enthaltener Phosphor (P) kann möglicherweise signifikant zur P-Ernährung von Kulturpflanzen beitragen. Um diese Hypothese zu prüfen, wurde im Topfversuch die P-Aufnahme durch Lolium perenne und Trifolium repens untersucht. Als Substrat dienten drei Böden, die entweder seit mindestens 1989 keine P-Gabe mehr erhalten hatten (0F) oder die jährlich P-Gaben im Umfang der P-Entzüge durch die vorgängigen Kulturen erhalten hatten und deshalb P-Rückstände enthielten (F). Es ergaben sich folgende Verfahren: 0F: ohne P aus Düngerrückständen und frischer Düngung; 0F+DAP: mit P aus frischer Düngung (Diammoniumphosphat, 15 mg P (kg Boden),1); F: mit P aus Düngerrückständen; F+DAP: mit P aus Düngerrückständen und frischer Düngung. In den Verfahren 0F + DAP und F + DAP war DAP mit 33PO4 markiert. In den Verfahren 0F und F war der verfügbare P des Bodens mit carrier-freiem 33PO4 markiert. Dies ermöglichte die Erfassung der Aufnahme von P durch die Pflanzen differenziert nach Herkunft aus Boden, Düngerrückständen und frischem Dünger. Von Düngerrückständen stammten 14,62,%, von frischem Dünger 7,28,% des in den Sprossen der Pflanzen gefundenen P. Der von Düngerrückständen stammende Anteil P in den Pflanzensprossen war korreliert mit dem gesamten Gehalt an P das dem Boden als Dünger zugeführt worden war. Der von frischem DAP stammende Anteil war korreliert mit der P-Konzentration in der Bodenlösung. [source] Nitrogen and phosphorus availability limit N2 fixation in beanNEW PHYTOLOGIST, Issue 2 2000E. O. LEIDI Availability of nitrogen (N) and phosphorus (P) might significantly affect N2 fixation in legumes. The interaction of N and P was studied in common bean (Phaseolus vulgaris), considering their effects on nodulation and N2 fixation, nitrate reductase activity, and the composition of N compounds in xylem sap. The effect of N on the uptake of P by plants was estimated by analysing rhizospheric pH and P concentration in xylem sap and in plant shoots. Inoculated bean plants were grown in pots containing perlite/vermiculite in two experiments with different amounts of P and N. In a third experiment, bean plants were grown on two soil types or on river sand supplied with different concentrations of N. At harvest, shoot growth, number of nodules and mass, and nitrogenase activity were determined. Xylem sap was collected for the determination of ureides, amino acids, nitrate and phosphate concentration. At low nitrate concentration (1 mM), increasing amounts of P promoted both nodule formation and N2 fixation, measured as ureide content in the xylem sap. However, at high nitrate concentration (10 mM), nodulation and N2 fixation did not improve with increased P supply. Glutamine and aspartate were the main organic N compounds transported in the xylem sap of plants grown in low nitrate, whereas asparagine was the dominant N compound in xylem sap from plants grown in high nitrate. Nitrate reductase activity in roots was higher than in shoots of plants grown with low P and high N. In both soils and in the sand experiment, increased application of N decreased nodule mass and number, nitrogenase activity and xylem ureides but increased the concentration of asparagine in xylem sap. Increasing P nutrition improved symbiotic N2 fixation in bean only at low N concentrations. It did not alleviate the inhibitory effect of high nitrate concentration on N2 fixation. A decrease in plant P uptake was observed, as indicated by a lower concentration of P in the xylem sap and shoots, correlating with the amount of N supplied. Simultaneously with the specific inhibition of N2 fixation, high nitrate concentrations might decrease P availability, thus inhibiting even further the symbiotic association because of the high P requirement for nodulation and N2 fixation. [source] Interactions between the effects of atmospheric CO2 content and P nutrition on photosynthesis in white lupin (Lupinus albus L.)PLANT CELL & ENVIRONMENT, Issue 5 2006CATHERINE D. CAMPBELL ABSTRACT Phosphorus (P) is a major factor limiting the response of carbon acquisition of plants and ecosystems to increasing atmospheric CO2 content. An important consideration, however, is the effect of P deficiency at the low atmospheric CO2 content common in recent geological history, because plants adapted to these conditions may also be limited in their ability to respond to further increases in CO2 content. To ascertain the effects of low P on various components of photosynthesis, white lupin (Lupinus albus L.) was grown hydroponically at 200, 400 and 750 µmol mol,1 CO2, under sufficient and deficient P supply (250 and 0.69 µm P, respectively). Increasing growth CO2 content increased photosynthesis only under sufficient growth P. Ribulose 1,5-biphosphate carboxylase/oxygenase (Rubisco) content and activation state were not reduced to the same degree as the net CO2 assimilation rate (A), and the in vivo rate of electron transport was sufficient to support photosynthesis in all cases. The rate of triose phosphate use did not appear limiting either, because all the treatments continued to respond positively to a drop in oxygen levels. We conclude that, at ambient and elevated CO2 content, photosynthesis in low-P plants appears limited by the rate of ribulose biphosphate (RuBP) regeneration, probably through inhibition of the Calvin cycle. This failure of P-deficient plants to respond to rising CO2 content above 200 µmol mol,1 indicates that P status already imposes a widespread restriction in plant responses to increases in CO2 content from the pre-industrial level to current values. [source] Physiological changes in soybean (Glycine max) Wuyin9 in response to N and P nutritionANNALS OF APPLIED BIOLOGY, Issue 3 2002YINBO GAN Summary Phosphorus deficiency is a very common problem in the acid soil of central China. Previous research has shown that starter N and N topdressing at the flowering stage (Rl) increased soybean (Glycine max) yield and N2 fixation (Gan et al, 1997, 2000). However, there is little information available concerning soybean response to P-fertiliser in soybean production in central China (Gan, 1999). A field experiment was conducted to investigate the response to P (0 kg P ha,1, 22 kg P ha,1, 44 kg P ha,1 before sowing) and N fertiliser application (N1: 0 kg N ha,1, N2: 25 kg N ha,1 before sowing, N3: N2 + 50 kg N ha,1 at the V2 stage and N4: N2 + 50 kg N ha,1 at the R1 stage) on growth, yield and N2 fixation of soybean. Both N and P fertiliser increased growth and seed yield of soybean (P < 0.01). Application of basal P fertiliser at 22 kg P ha,1 or 44 kg P ha,1 increased total N accumulation by 11% and 10% (P < 0.01) and seed yield by 12% and 13% (P < 0.01), respectively, compared to the zero P treatment. Although application of starter N at 25 kg N ha,1 had no positive effect on seed yield at any P level (P > 0.05), an application of a topdressing of 50 kg N ha,1 at the V2 or R1 stage increased total N accumulation by 11% and 14% (P < 0.01) and seed yield by 16% and 21% (P < 0.01), respectively, compared to the zero N treatment. Soybean plants were grown on sterilised Perlite in the greenhouse experiment to study the physiological response to different concentrations of phosphate (P1: 0 mM; P2: 0.05 mM; P3: 0.5 mM; P4:1.0 mN) and nitrate (N1: 0 mM with inoculation, N2: 20 mM with inoculation). The result confirmed that N and P nutrients both had positive effects on growth, nodulation and yield (P < 0.01). The relative importance of growth parameters that contributed to the larger biomass with N and P fertilisation was in decreasing order: (i) total leaf area, (ii) individual leaf area, (iii) shoot/root ratio, (iv) leaf area ratio and (v) specific leaf area. The yield increase at N and P supply was mainly associated with more seeds and a larger pod number per plant, which confirmed the result from the field experiment. [source] Identification of mutants in phosphorus metabolismANNALS OF APPLIED BIOLOGY, Issue 1 2001JULIE C LLOYD Summary Phosphorus availability is often limiting for plant growth. However, little is known of the pathways and mechanisms that regulate phosphorus (P) uptake and distribution in plants. We have developed a screen based on the induction of secreted root acid phosphatase activity by low-P stress to identify mutants of Arabidopsis thaliana with defects in P metabolism. Acid phosphatase activity was detected visually in the roots of A. thaliana seedlings grown in vitro on low-P medium, using the chromogenic substrate, 5-bromo-4-chloro-3-indolyl-phosphate (BCIP). In low-P stress conditions the roots of wild-type plants stained blue, as the induced root acid phosphatase cleaved BCIP to release the coloured product. Potential mutants were identified as having white, or pale blue, roots under these conditions. Out of approximately 79 000 T-DNA mutagenised seedlings screened, two mutants with reduced acid phosphatase staining were further characterised. Both exhibited reduced growth and differences in their P contents when compared to wild-type A. thaliana. The mutant with the most severe phenotype, pho3, accumulated high levels of anthocyanins and starch in a distinctive visual pattern within the leaves. The phenotypes of these mutants are distinct from two previously identified phosphorus mutants (phol and pho2) and from an acid phosphatase deficient mutant (pupl) of A. thaliana. This suggested that the screening method was robust and might lead to the identification of further mutants with the potential for increasing our understanding of P nutrition. [source] | ||||||||||