Solubilization of aluminum phosphate by specific Penicillium spp.

The solubilization of hardly soluble aluminum phosphate （AlPO4） by specific Penicillium spp. isolated from wheat rhizospheric soils was investigated in Pikovskaya agar and liquid medium, respectively. Most of the Penicillium isolates except P. sirnplicissimum AP 11 and P. variabile AP 15 developed clear transparent zone around the colony margin in plate assays. Results of broth assays show that the Penicillium isolates can efficiently solubilize aluminum phosphate in Pikovskaya liquid medium, and vary in their capabilities to release soluble phosphate from aluminum phosphate. All the isolates exhibit different abilities to lower the pH and increase the titratable acidity in the broth compared to the control. HPLC analysis shows that most of the isolates except the species of P. aurantiogriseum can excrete different concentrations of organic acids, including gluconic acid, citric acid, oxalic acid, malic acid and tartaric acids, in the broth. The release of soluble phosphate by the isolate P. oxalicum AP2, which is the best solubilizer of aluminum phosphate among the isolates, is accompanied by a significant drop of pH and an obvious rise of titratable acidity during 7 d of aluminum phosphate-solubilizing experiments. The effects of temperature, initial pH, concentration of aluminum phosphate and shaking speed on aluminum phosphate solubilization by P. oxalicum AP2 were also investigated, and the maximum contents of soluble phosphate released are recorded at temperature 30 ℃, initial pH 6, aluminum phosphate concentration 20 g/L, and shaking speed 160 r/min.

Effects of temperature,algae biomass and ambient nutrient on the absorption of dissolved nitrogen and phosphate by Rhodophyte Gracilaria asiatica

Gracilaria asiatica, being highly efficient in nutrient absorption, is cultivated in sea cucumber ponds to remove nutrients such as nitrogen and phosphate. It was cultured in a laboratory simulating field conditions, and its nutrient absorption was measured to evaluate effects of environmental conditions. Ammonia nitrogen （AN）, nitrate nitrogen （NN）, total inorganic nitrogen （TIN）, and soluble reactive phosphorus （SRP） uptake rate and removal efficiency were determined in a 4~2 factorial design experiment in water temperatures （T） at 15~C and 25~C, algae biomass （AB） at 0.5 g/L and 1.0 g/L, total inorganic nitrogen （TIN） at 30 ~tmol/L and 60 ~tmol/L, and soluble reactive phosphorus （SRP） at 3 and 6 ~tmol/L. AB and ambient TIN or SRP levels significantly affected uptake rate and removal efficiency of AN, NN, TIN, and SRP （P〈0.001）. G. asiatica in AB of 0.5 g/L showed higher uptake rate and lower removal efficiency relative to that with AB of 1.0 g/L. Nitrogen and phosphorus uptake rate rose with increasing ambient nutrient concentrations; nutrient removal efficiency decreased at higher environmental nutrient concentrations. The algae preferred to absorb AN to NN. Uptake rates of AN, NN, and SRP were significantly affected by temperature （P〈0.001）; uptake rate was higher for the 25~C group than for the 15~C group at the initial experiment stage. Only the removal efficiency of AN and SRP showed a significant difference between the two temperature groups （P〈0.01）. The four factors had significant interactive effects on absorption of N and P, implying that G. asiatica has great bioremedial potential in sea cucumber culture ponds.

Study on the Application of Phoslock in Purifying Eutrophic Water in Dianchi Lake

As a modified product,Phoslock can purify soluble phosphate(SP) in water to control water eutrophication effectively.The results showed that Phoslock had better removal effect for SP in the water of Dianchi Lake and could control water eutrophication effectively.Phoslock not only reduced SP concentration in water but also kept it at a lower level for a long time.Eutrophic water of Dianchi Lake treated by Phoslock had higher transparency,and the concentration of SP and total phosphorus(TP) was lower,with stronger anti-pollution ability to domestic sewage and agricultural non-point pollution.Therefore,Phoslock was a new dephosphorization reagent used in sewage and was safe to natural waters and aquatic organisms.

Transformation of Sucrose to Starch and Protein in Rice Leaves and Grains under Two Establishment Methods

Six rice varieties, PR120, PR116, Feng Ai Zan, PR115, PAU201 and Punjab Mehak 1 were raised under aerobic and transplanting conditions to assess the effects of planting conditions on sucrose metabolising enzymes in relation to the transformation of free sugars to starch and protein in flag leaves and grains. Activities of sucrose synthase, sucrose phosphate synthase and acid invertase increased till flowering stage in leaves and mid-milky stage（14 d after flowering） in grains and thereafter declined in concomitant with the contents of reducing sugar. Under aerobic conditions, the activities of acid invertase and sucrose synthase（cleavage） significantly decreased in conjunction with the decrease in non-reducing sugars and starch content in all the varieties. Disruption of starch biosynthesis under the influence of aerobic conditions in both leaves and grains and the higher build up of sugars possibly resulted in their favoured utilization in nitrogen metabolism. Feng Ai Zan, PR115 and PR120 maintained higher levels of sucrose synthase enzymes in grains and leaves and contents of metabolites（amino acid, protein and non-reducing sugar） under aerobic conditions, while PR116, Punjab Mehak 1 and PAU201 performed better under transplanting conditions, thus showing their adaptation to environmental stress. Yield gap between aerobic and transplanting rice is attributed primarily to the difference in sink activity and strength. Overall, it appear that up-regulation of sucrose synthase（synthesis） and sucrose phosphate synthase under aerobic conditions might be responsible in enhancing growth and productivity of rice varieties.

Mechanism and inhibition of trisodium phosphate particle caking： Effect of particle shape and solubility

We investigated the influence of particle shape and solubility on the caking behavior of trisodium phosphate by considering the adhesion free energy and crystal bridge theory. Caking of trisodium phosphate during the drying process under static conditions is a two-step process： adhesion followed by crystal bridge formation between particles. The adhesion free energy plays an important role in adhesion. Trisodium phosphate particles cannot adhere to each other and cake when the adhesion free energy is greater than a critical value, which varies with particle shape. Compared with granular particles, cylindrical particles have larger contact area between particles, which results in more crystal bridges forming and a higher caking ratio. Thus, the critical value is about 100 mJ/m^2 for cylindrical particles, but 60 mJ/m^2 for granular particles at 25 ℃. Concerning the solubility, when particles are similar shapes and soluble in the rinsing liquid, the caking ratio has a linear relationship with adhesion free energy. However, if the particles are insoluble in the rinsing liquid, caking can be completely prevented regardless of adhesion free energy because no crystal bridges form during the growth process. Hence, caking of trisodium phosphate particles could be inhibited by screening rinsing liquids, and optimizing the particle shape and size distribution.

Halophile plant growth-promoting rhizobacteria induce salt tolerance traits in wheat seedlings(Triticum aestivum L.)

Salinity is one of the most important growth-limiting factors for most crops in arid and semi-arid regions;however,the use of plant growth-promoting rhizobacteria isolated from saline soils could reduce the effects of saline stress in crops.This study aimed to evaluate the efficiency of plant growth-promoting rhizobacteria(PGPRs),isolated from the rhizosphere of halophile plants,for the growth,Na^+/K^+balance,ethylene emission,and gene expression of wheat seedlings{Triticum aestivum L.)grown under saline conditions(100 mmol L^-1 NaCl)for 14 d.A total of 118 isolates obtained from saline soils of the deserts of Iran were tested for their capacity as PGPRs.Out of the 118 isolates,17 could solubilize phosphate(Ca3(P〇4)2),5 could produce siderophores,and 16 could synthesize indole-3-acetic acid.Additionally,PGPRs were also evaluated for aminocyclopropane-l-carboxylate deaminase activity.A pot experiment was conducted to evaluate the ability of 28 PGPR isolates to promote growth,regulate Na^+/K^+balance,and decrease ethylene emissions in plants.The most efficient PGPRs were Arthrobacter aurescens.Bacillus atrophaeus,Enterobacter ashuriae,and Pseudomonas fluorescens.Gene expression analysis revealed the up-regulation of H^+-PPase,HKT1,NHX7,CAT,and APX expression in roots of Enterobacter-inocuVdied salt-stressed plants.Salt-tolerant rhizobacteria exhibiting plant growth-promoting traits can facilitate the growth of wheat plants under saline conditions.Our results indicate that the isolation of these bacteria may be useful for formulating new inoculants to improve wheat cropping systems in saline soils.

Heavy metal phytoextraction by Sedum alfredii is affected by continual clipping and phosphorus fertilization amendment

Improving the efficacy of phytoextraction is critical for its successful application in metal contaminated soils. Mineral nutrition affects plant growth and metal absorption and subsequently the accumulation of heavy metal through hyper-accumulator plants. This study assessed the effects of di-hydrogen phosphates （KH2PO4, Ca（H2PO4）2, NaH2PO4 and NH4H2PO4） application at three levels （22, 88 and 352 mg P/kg soil） on Sedum alfredii growth and metal uptake by three consecutive harvests on aged and Zn/Cd combined contaminated paddy soil. The addition of phosphates （P） significantly increased the amount of Zn taken up by S. alfredii due to increased shoot Zn concentration and dry matter yield （DMY） （P 〈 0.05）. The highest phytoextraction of Zn and Cd was observed in KH2PO4 and NH4H2PO4 treatment at 352 mg P/kg soil. The amount of Zn removed by phytoextraction increased in the order of 1st clipping 〈 2nd clipping 〈 3rd clipping, and for Cd extraction the order was 2nd clipping 〈 1st clipping 〈 3rd clipping. These results indicate that the application of P fertilizers coupled with multiple cuttings can enhance the removal of Zn and Cd from contaminated soils by S. alfredii, thus shortening the time needed for accomplishing remediation goals.

Simulation on phosphorus release characteristics of Poyang Lake sediments under variable water levels and velocities

Since the construction of the Three Gorges Dam, the Poyang Lake hydrological characteristics obviously changed. During the impoundment period of the Three Gorges Reservoir, the hydrodynamic factors of Poyang Lake varied. Water level dropped, the velocity decreased and water exchange time lengthened, which changed the release of phosphorous from sediments. In order to investigate how the hydrodynamic factors influence the release of phosphorous from sediments, we used a two-way annular flume device to simulate the release characteristics of phosphorous from sediments under variable water levels and velocities. We found that both water level rising and velocity increasing could enhance the distur- bance intensity to sediments, which caused the increase of suspended solids （SS） concentration, total phosphorus （TP） concentration in the overlying water, and the ability that phosphorus released to overlying water from sediments enhanced as well： when overlying water velocity maintained 0.3 m/s, SS concentration increased to 4035.85 mg/L at the water level 25 cm which was about 25 times compared to the minimum value and TP concentration in the overlying water also reached the maximum value at the water level 25 cm which was 1.2 times that of the value at 10 cm; when water level maintained 15 cm, SS concentration increased to 4363.35 mg/L at the velocity of 0.5 m/s which was about 28 times compared to the value of 0 m/s, and TP concentration in the overlying water increased from 0.11 mg/L to 0.44 mg/L. When the water level maintained 15 cm, the phosphorous release rate reached the maximum value of 4,86 mg/（md） at 0.4 m/s. The concentration of total dissolved phosphorous （TDP） and soluble reactive phosphate （SRP） both in overlying water and sediment-water interface were negatively correlated with pH. Using the parabolic equation, the optimum water level at a velocity of 0.3 m/s was calculated to be 0.57 cm, and the optimum velocity at water level of 15 cm was found to be 0.2 m/s.