Organic phosphorus compounds as a phosphorus source for higher plants through the activity of phosphatases produced by plant roots and microorganisms

Summary The efficiency of phosphatases produced by clover, barley, oats and wheat was investigated in soils treated with sodium glycerophosphate, lecithin and phytin. Root exudates of aseptically grown clover were also examined for the breakdown of different organic P compounds in order to test the efficiency of plant-produced phosphatases. In general, the plants were able to use P from all the organic sources used in the study almost as efficiently as inorganic sources. Dry-matter yield, P uptake, acid and alkaline phosphatase activity and microbial population were increased in all the P treatments. Organic P enhanced alkaline phosphatase activity. Lecithin increased fungal, and phytin bacterial growth. There was no alkaline phosphatase activity in the asepticallly grown clover root exudates. Phosphatase released in aseptic culture after 4 weeks of clover growth was able to efficiently hydrolyse sodium glycerophosphate, lecithin and phytin. The amount of organic P hydrolysed in this and in the soil experiment surpassed plant uptake by a factor of 20. This suggests that the limiting factor on plant utilization of organic P is the availability of hydrolysable organic P sources.     

Effects of aerobic conditions in the rhizosphere of rice on the dynamics and availability of phosphorus in a flooded soil – A model experiment

The secretion of O₂ by rice roots results in aerobic conditions in the rhizoshere compared to the bulk flooded soil. The effect of this phenomenon on the adsorption/desorption behavior and on the availability of phosphorus (P) in a flooded soil was investigated in a model experiment. An experimental set‐up was developed that imitates both O₂ release and P uptake by the rice root. The results showed that O₂ secretion significantly reduced P adsorption/retention and increased P desorption/release in the “rhizosphere” soil, compared to the anaerobic bulk soil. The P uptake by an anion exchange resin from both unfertilized and P‐amended soil was significantly increased. The results confirm that the O₂ secretion is an important mechanism to enhance P availability and P uptake of rice under flooded conditions, where the “physico‐chemical” availability of P in the anaerobic bulk soil is strongly reduced. The decrease of P availability in the P‐amended flooded bulk soil was mainly associated with the almost complete transformation of the precedingly enriched Al‐P fraction into Fe‐bound P with extremely low desorption/release characteristics during the subsequent flooding.     

不同甘蓝型油菜品种磷素籽粒生产效率的配合力及遗传参数分析

以22个甘蓝型油菜品种(系)为亲本(17个母本,5个父本),按NCⅡ设计配成175=85个F1,在不施磷肥（CK）和施P2O5 150 kg/hm2（P150）两个处理条件下,对不同品系油菜磷素籽粒生产效率进行配合力和遗传参数分析。结果表明, 磷素籽粒生产效率（PUEs）杂交组合平均值在P150和CK处理中分别比亲本平均值高6.41%和7.64%。离中亲优势的正向组合数明显多于负向组合数,超亲优势的正向组合数（超高亲）明显多于负向组合数（超低亲）,表明PUEs存在杂种优势。PUEs的遗传参数在P150处理和CK处理中一般配合力方差相对较小,特殊配合力相对较大,PUEs遗传以非加性效应（显性效应及上位性效应）为主。在两个肥力水平下,品系9（ZS-3）的一般配合力较高,620（SY07湘05499）、 1320（NY-14湘05499）、 1421（湘05487YY-7）三个组合的特殊配合力较高。     

The ability of the DGT soil phosphorus test to predict pasture response in Australian pasture soils – a preliminary assessment

Diffusive gradients in thin‐films (DGT) technology provides an alternative assessment of available phosphorus (P) for a range of crops, suggesting a preliminary examination of the performance of the new DGT‐P test, compared to existing bicarbonate extractable Olsen and Colwell P tests, for pastures is justified. This study utilized historic data from the Australian National Reactive Phosphate Rock (NRPR) study (1992–1994) that included 25 experimental sites representing a wide range of soil types and climates used for pasture production. Stored (~19 yr) soil samples were analysed for DGT‐P, Olsen P and a single point P buffering index (PBI) and re‐analysed for Colwell P. Results showed the traditional bicarbonate extractable Colwell (r² = 0.45, P < 0.001) and Olsen P (r² = 0.27, P < 0.001) methods predicted relative pasture P response more accurately, compared to the novel DGT‐P test (r² = 0.09, P = 0.03) when all 3 yr of data were examined. We hypothesize that the harsher bicarbonate extraction used for the Olsen and Colwell methods more accurately reflects the ability of perennial pasture roots to access less labile forms of P, in contrast to the DGT‐P test, which does not change the soil pH or dilute the soil and appears unable to fully account for a plants ability to solubilize P. Further studies are needed to compare the capacity of DGT‐P to measure P availability in perennial pasture systems and to better understand the soil chemical differences between pasture and cropping systems.     

H2O2 Accumulation in Sunflower Leaves as a Consequence of Iron Deprivation

Abstract

The present work aimed at evaluating in sunflower leaves: the relationship between Fe‐deficiency and the possible accumulation of H₂O₂; the activity of some extracellular enzymatic and non‐enzymatic systems involved in H₂O₂ production and scavenging. Iron‐deficient leaves exhibited a significant H₂O₂ accumulation, monitored at extracellular level by electron microscopy analysis. Such an increase in H₂O₂ level could derive from the significant decrease in extracellular ascorbate peroxidase (APX) activity, accompanied by a lower APX protein content detected by immuno‐electrophoresis. Also, extracellular ascorbic acid content was significantly affected by Fe‐deficiency, implying a reduced capacity for H₂O₂ scavenging. The contribute of peroxidases (PODs) involved in lignification process in keeping H₂O₂ levels under the toxic threshold was dependent on their subcellular location: the activity of covalently‐bound (CB) isoforms being increased while that of ionically‐bound (IB) ones decreased. NAD(P)H oxidation activity, known to produce H₂O₂, was found to decrease in apoplastic fluid and IB fraction and to slightly increase in the CB fraction. In conclusion, H₂O₂ accumulation observed in Fe‐deficient sunflower leaves seems to be mostly due to a reduced scavenging capacity of ASA, APX, and PODs, although the possibility of increased H₂O₂ production cannot be excluded.     

Absorption of potassium,sodium, calcium,and phosphorus by two date palm cultivars and the effect of Gibberellin treatment

Experiments were conducted to avaluate the K, Na, Ca, and P uptake by seedlings of two date palm (phoenix dactylifera L.) cultivars, Khedhri and Sekkeri as well as the effect of gibberellin (GA₃) treatment, Khedhri cultivar showed a typical hyperbolic curve of absorption of K,N, end low concentration of Ca (up to 5mM) but at higher Ca concentration, there seems to be another phase of absorption. Sekkeri cultivar exhibited similar but lower absorption rate of K and Ca while Na seems to be extruded at lower substrate concentration. The rate of P uptake by Sekkeri was irregular. Applied GA₃ slightly stimulate Na uptake by Sekkeri cultivar but at 10^–4M GA₃ enhancement of both Ca and P accummulation in both cultivars was observed.     

Band-applied elemental sulfur to enhance the phytoavailability of phosphorus in alkaline calcareous soils

Summary Applications of elemental sulfur (S°) increase the phytoavailability of P in alkaline high-Ca soils through the production of H₂SO₄ which is induced by microbial oxidation of S. Concentrated S bands, allowing time release acidity, may aid in maintaining the phytoavailability of both residual and fertilizer P. Greenhouse and field studies were therefore conducted to determine the effectiveness of band-applied S° for increasing the phytoavailability of residual and fertilizer P for spring wheat (Triticum aestivum L.) and corn (Zea mays L.). We also used inoculation of S° with Thiobacillus thioparus to determine whether it is necessary or helpful in alkaline soils to initiate acidification. Treatments were inoculation, S°, S° + inoculation, triple superphosphate, triple superphosphate + S°, triple superphosphate + inoculation, and triple superphosphate + S° + inoculation applied to three alkaline soils: Typic Argiborolls, Borollic Calciorthids, and Ustollic Haplargids. P availability was determined by plant uptake of P, NaHCO₃-extractable P, dry-matter yield, grain yield and grain-protein production, and on available-P index (NaHCO₃-extractable P, post-harvest, + plant uptake of P). Application of S° with triple superphosphate gave a significantly higher available-P index than triple superphosphate alone on all three soils. Inoculation of S° with T. thioparus increased soil acidity; however, in some cases this treatment eliminated the beneficial effect of S°. Grain yields of wheat increased with S° applications at one of two field sites. These results suggest that applying S° with triple superphosphate may be an effective means of increasing soil P availability and the efficiency of superphosphate fertilizers on alkaline high-Ca soils.     

Examination of nanoparticulate phosphate rock as both a liming agent and phosphorus source to enhance the growth of spinach in acid soil

ABSTRACT

To examine the effect of nanoparticulate phosphate rock (NPR) as both a liming agent and phosphorus source in a tropical acid soil. The study examined five rates of NPR (0, 250, 500, 1000, or 2000 kg ha^?1), which supplies 30, 60, 120 or 240 kg P ha^?1, in a randomized complete pot experiment design with 3 replications. The pots of soil were incubated in a climate-controlled greenhouse for 21 days and then spinach was grown for 49 days. Soil parameters (pH, available P and exchangeable acidity), spinach parameters (leaf area, root hair surface area, root length and dry matter yield) and the effectiveness of NPR dissolution were estimated. The soil and plant parameters and the effective NPR dissolution all increased to the same degree at 1000 and 2000 kg NPR ha^?1. Therefore, the use of 1000 kg ha^?1 was most economically justified. Although, NPR has been appeared as an effective liming agent and phosphorus source in tropical acid soil. However, a regular application of NPR and further research for economic comparison between NPR and both of lime and superphosphate, as well as the original PR, will be needed.     

A review of phosphate oxygen isotope values in global bedrocks: Characterising a critical endmember to the soil phosphorus system

Understanding the phosphate oxygen isotope (δ¹⁸O‐PO₄) composition of bedrock phosphate sources is becoming ever more important, especially in areas of soil research which use this isotope signature as a proxy for biological cycling of phosphorus (P). For many of these studies, obtaining a sample of the source bedrock or applied mineral fertiliser for isotope analysis is impossible; meaning there is now a demand for a comprehensive characterisation of global bedrock δ¹⁸O‐PO₄ to support this work. Here we compile δ¹⁸O‐PO₄ data from a wide range of global bedrocks, including 56 new values produced as part of this study and a comprehensive overview of those within the previously existing literature. We present δ¹⁸O‐PO₄ data from the range of major phosphatic lithologies alongside as much metadata for the samples as could be gathered. Much of the data comes from bedrocks of marine sedimentary origin (< 1 Ma = > +22‰, > 540 Ma = ≈ +12‰), but we also present data from bedrocks associated with guano (range: +19.5 to +15‰) and igneous deposits (range: +12 to –0.8‰), both of which have distinct δ¹⁸O‐PO₄ signatures due to their formation mechanisms. We show that where repeat measurements of the same formation have been undertaken, regardless of method or exact sample location, there is an average within formation error of ± 1.25‰. This is important, as is constitutes a reasonable level of uncertainty for phosphorus cycling studies which need to estimate bedrock δ¹⁸O‐PO₄ composition based on the literature. In combination, this data set presents 284 δ¹⁸O‐PO₄ values from 56 countries; a comprehensive starting point for researchers interested in understanding bedrock end member δ¹⁸O‐PO₄.     

An assessment of the genetic diversity within a collection of<Emphasis Type="Italic">Saccharum spontaneum</Emphasis> L. with RAPD-PCR

A local collection of 33Saccharum spontaneum L. clones and two sugarcane cultivars (LCP 82-89 and LCP 85-384) were assessed for genetic variability using random amplified polymorphic DNA (RAPD)-PCR. A total of 157 polymorphic RAPD-PCR bands were scored with 17 primers. The number of RAPD-PCR products per primer ranged from four to 16. The data were analyzed with two multivariate analysis software programs, NTSYSpc and DNAMAN®. Although these two programs yielded similar results, a bootstrapped phylogenetic tree could only be generated with the DNAMAN® software. A substantial degree of genetic diversity was found within the localS. spontaneum collection. Pairwise genetic homology coefficients ranged from 65% (SES, 196/Tainan 2n = 96) to 88.5% (IND 81-80/IND 81-144). LCP 82-89 and LCP 85-384 shared a greater similarity (82%) than either was to any clone ofS. spontaneum (ranging from 60.5 to 75.2%). The 33S. spontaneum clones were assigned to eight groups independent of their geographic origin or morphology, while the two sugarcane cultivars were assigned to the ninth group. All but two pairs ofS. spontaneum clones could be distinguished by a single RAPD primer OPBB-02. The use of a second primer, either OPBE-04 or Primer 262, separated allS. spontaneum clones. One amplification product from the RAPD primer OPA-11, OPA-11-336, proved to be cultivar-specific and has been adopted for use in our breeding program. Information from this study would help conserve the genetic diversity ofS. spontaneum. Disclaimer: Product names and trademarks are mentioned to report on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA does not imply the approval of the product to the exclusion of others that may also be suitable. The experiments reported comply with the current laws of the USA.     

An evaluation of Colwell‐P as a measure of plant‐available phosphorus in soils of volcanic and non‐volcanic origins in the highlands of Papua New Guinea

Various soil test methods including Olsen, Colwell, Bray and Truog have been used to assess the levels of plant‐available P (PAP) in soils situated in the highlands of Papua New Guinea (PNG). Up until now, though, there has been no guarantee that these tests provide valid assessments of PAP in these somewhat atypical organic matter‐rich tropical soils. Furthermore, the critical soil‐P concentrations associated with the tests have been based on studies conducted elsewhere in sub‐tropical and temperate latitudes and as such may or may not be valid for soils or cropping situations in PNG. Soil (Colwell)‐P and leaf‐P data collected during a recent survey of sweet potato gardens in the highlands of PNG were therefore used to determine if useful relationships existed between these variables for different groups of soils, and if they do, to use these relationships to evaluate critical soil Colwell‐P concentrations corresponding to a known critical concentration of P in sweet potato index leaf tissue. Separate, highly significant linear relationships were obtained between leaf‐P and Colwell‐P for soils of volcanic and non‐volcanic origins. Based on these relationships, the critical Colwell‐P concentration for volcanic soils was found to be four times greater than that for non‐volcanic soils, presumably because much of the P extracted from the former soils with alkaline sodium bicarbonate had been chemically ‘fixed’ via sorption and precipitation reactions with sesquioxides and rendered unavailable to plants at ambient soil pH. These critical Colwell‐P concentrations if adopted as benchmark values for the soil groups in question should ensure that the results of future soil fertility surveys involving Colwell‐P assessments are correctly interpreted.     

Growth and iron nutrition of broccoli (Brassica oleracea L. var. italica Plenck), grown in a Typic Ustochrept, as influenced by vesicular-arbuscular mycorrhizal fungi in the presence of pyrite and farmyard manure

Greenhouse experiments were conducted using potted soil (Fe-deficient Typic Ustochrept) to study the influence of the vesicular-arbuscular mycorrhizal fungi (VAM), Glomus macrocarpum and G. fasciculatum, on the mobilisation of Fe in broccoli (Brassica oleracea L. var. italica Plenck) in the presence of pyrite and farmyard manure (FYM). Individual applications of either VAM or pyrite with NPK fertiliser significantly enhanced both the Fe²⁺ content in leaf tissue and total uptake of Fe and resulted in increased curd and straw yields of broccoli compared to those observed with NPK alone. Though the application of FYM decreased the Fe²⁺ content in leaf tissue relative to plants supplied NPK alone, this result was not statistically significant. The available Fe content in soil, after harvest of broccoli, was found to be lower in the presence of VAM than in the control. Received: 18 June 1997