Effects of 6-Benzylaminopurine–Calcium Chloride–Salicylic Acid on Yellowing and Reactive Oxygen Metabolism of Broccoli

In this study,we investigated the effects of 6-benzylaminopurine(6-BA)–calcium chloride(CaCl_2)–salicylic acid(SA) treatment on the yellowing and reactive oxygen metabolism of harvested broccoli heads. We dipped fresh broccoli heads in a compound solution(0.6 mmol/L 6-BA + 40 mmol/L CaCl_2 + 3 mmol/L SA) for 5 min and then stored them at 23 °C for 4 days. The results showed that the 6-BA–CaCl_2 –SA postharvest treatment effectively retarded the increase in color values(e.g.,variations from black to white,from green to red,and from blue to yellow) and the decline in chlorophyll content of the broccoli heads. Compared with the control broccoli,the rate of superoxide anion radical(O_2^( ·-)) production and the hydrogen peroxide(H_2O_2) content were lowered by the treatment. We also found significant diff erences in the activities of superoxide dismutase(SOD),catalase(CAT) and peroxidase(POD) in the treated broccoli. Based on these results,we consider 6-BA–CaCl_2 –SA to inhibit the accumulation of reactive oxygen,delay the degradation of chlorophyll,and prolong the shelf life of broccoli heads at 23 °C.

Investigation of Nonlinear PI Multi-loop Control Strategy for Aircraft HVDC Generator System with Wound Rotor Synchronous Machine

In order to enhance the transient performance of aircraft high voltage DC(HVDC)generation system with wound rotor synchronous machine(WRSM)under a wide speed range,the nonlinear PI multi-loop control strategy is proposed in this paper.Traditional voltage control method is hard to achieve the dynamic performance requirements of the HVDC generation system under a wide speed range,so the nonlinear PI parameter adjustment,load current feedback and speed feedback are added to the voltage and excitation current double loop control.The transfer function of the HVDC generation system is derived,and the relationship between speed,load current and PI parameters is obtained.The PI parameters corresponding to the load at certain speed are used to shorten the adjusting time when the load suddenly changes.The dynamic responses in transient processes are analyzed by experiment.The results illustrate that the WRSM HVDC generator system with this method has better dynamic performance.

Late spring cold reduces grain number at various spike positions by regulating spike growth and assimilate distribution in winter wheat

Late spring cold(LSC) occurred in the reproductive period of wheat impairs spike and floret differentiation during the reproductive period,when young spikelets are very cold-sensitive.However,under LSC,the responses of wheat spikelets at various positions,leaves,and stems and the interactions between them at physiological levels remain unclear.In the present study,two-year treatments at terminal spikelet stage under two temperatures(2 C,-2 C) and durations(1,2,and 3 days) were imposed in an artificial climate chamber to compare the effects of LSC on grain number and yield in the wheat cultivars Yannong 19(YN19,cold-tolerant) and Xinmai 26(XM26,cold-sensitive).The night temperature regimes were designed to reproduce natural temperature variation.LSC delayed plant growth and inhibited spike and floret differentiation,leading to high yield losses in both cultivars.LSC reduced dry matter accumulation(DMA,g) in spikes,stems,and leaves,reducing the DMA ratios of the spike to leaf and spike to stem.Plant cell wall invertase(CWINV) activity increased in upper and basal spikelets in YN19,whereas CWINV increased in middle spikelets in XM26.Under LSC,soluble sugar and glucose were transported and distributed mainly in upper and basal spikelets for glume and rachis development,so that spike development was relatively complete in YN19,whereas the upper and basal spikelets were severely damaged and most of the glumes in middle spikelets were relatively completely developed in XM26,resulting in pollen abortion mainly in upper and basal spikelets.The development of glumes and rachides was influenced and grain number per spike was decreased after LSC,with kernels present mainly in middle spikelets.Overall,reduced total DMA and dry matter partitioning to spikes under LSC results in poor spikelet development,leading to high losses of grain yield.

Evaluation of Wheat Varietal Performance under Different Nitrogen Sources

Nitrogen fertilization plays a very important role for crop productivity. New developed wheat varieties need proper fertilization for improved crop productivity. The present study was carried out to quantify, the effects of nitrogen derived from urea and FYM on the four newly developed wheat varieties i.e. Siran-2009, Ata Habib, Janbaz-2009 and Pirsabak-2008 for yield improvement, quality and soil fertility status. The N treatments were control, 100% of the recommended nitrogen from urea as well as FYM, and 50% from each source. The experiment was carried out at New Developmental Farm, Khyber Pakhtunkhwa Agricultural University Peshawar Pakistan, during Rabi 2011-2012. Results of the data showed that Janbaz-2009 was more responsive to biological yield (11,011 kg·ha-1), grain yield (4339 kg·ha-1), and nitrogen use efficiency (14.8%), whereas Siran-2010 performed better for grain N contents (2.31%). Plots having both urea and FYM had improved biological yield (11,958 kg·ha-1), and grain yield (4901 kg·ha-1). Urea application had improved straw N contents (0.92%) in addition to Mix application of urea and FYM (0.93%). Mix application of both sources and sole FYM had higher grains N content (2.25%), whereas control plots in addition to mix application had improved nitrogen use efficiency (14.8%). Siran-2010 and Janbaz-2009 performed better in FYM and mix FYM and urea plots for most of the parameters. It was concluded from the experiment that Janbaz-2009 had improved yield and yield components, whereas Siran-2010 had improved the grain N content. Similarly, Mix application of FYM and urea had improved crop productivity, soil fertility and grains as well as straw N content. Thus wheat varieties Janbaz-2009 sown in mix FYM and urea is recommended for general cultivation in agro-climatic condition of Peshawar.

Study on positive-negative pressure seed metering device for wide-seedling-strip-seeding

In order to solve the problem of poor uniformity of wheat strip sowing,this paper designs a positive-negative pressure wheat wide-seedling-strip-seeding precision seed metering device,which adopts the roller structure with the principle of combined positive-negative pressure.Through theoretical analysis and relevant data,the structure of the seed metering device and the structure of the positive-negative pressure air chamber were designed.The internal flow field conditions were simulated by Fluent software under different structural parameters.The design of the seed holes was completed by analyzing the pressure cloud diagram and the flow velocity vector diagram,and the optimal combination of parameters was obtained and the influence law of negative pressure on the flow field was obtained.The effect of rotational speed on the flow field was studied by EDEM-Fluent coupling technique.In this paper,a three-factor and three-level response surface test was conducted on a JPS-12 test bench with Liangxin-99 wheat as the research object.The experiment was conducted with the rotational speed of seed metering device,the negative pressure of seed suction and the seeding height as factors,and the qualified index,the reseeding index and the miss-seeding index as evaluation indicators.Through the test,the optimal structure and working parameters of the seed metering device were determined as follows:the diameter of the seed hole was 2 mm,and the number of seed holes per row was 28,negative pressure was−3.5 kPa,rotational speed of seed metering device was 19 r/min,and seeding height was 180 mm.Validation test was carried out on the optimized seed metering device:the qualified index was 80.62%,the reseeding index was 9.22%,and the miss-seeding index was 10.16%,which reached the parameter indicator in JB/T 10293-2013 Technical conditions of single seed(precision)seeder and met the agronomic requirements for wheat wide-seedling-strip-seeding.

Parameter optimization and experiment of the negative pressure precision seed-metering device for wheat

In order to ensure the most reasonable distribution of wheat seeds in the field to improve seeding quality and uniformity,a set of negative pressure precision seed-metering device was designed,which shares a hollow shaft.Every seed-metering device can sow two rows of wheat.By the STAR-CCM+,the analysis of nephogram,vectogram and streamline graph showed that more ideal structural parameters of the seed-metering device are 0.5 mm width of the slit sucking seed(WSS),150-200 mm diameter of the seed-metering disc(DSD),2.0 mm axial depth of air chamber in the seed-metering disc(ADS),and arc-shaped cross-section shape of the ring groove sucking seed(CSGS).Single-factor test on the JPS-12 test-bed analyzed the influence of the CSGS,WSS,DSD,and ADS on the qualified index(Iq),multiple index(Imul),miss index(Imiss)and coefficient of variation of qualified seed spacing(CV).Through the orthogonal on the JPS-12 test-bed,it is found that the influence of vacuum negative pressure and seed-metering device shaft speed is significant on the Iq,Imiss and Imul.Based on these,the structural parameters of the seed-metering device were optimized.The DSD is 180 mm,the WSS is 0.7 mm,the ADS is 2.5 mm,and the CSGS is arc-shaped.The optimization seed-metering device was tested on the JPS-12 test-bed.The Iq is 86.66%,the Imiss is 5.09%,the Imul is 8.25%,and the CV is 24.50%.These testing results fully coincide with the standard JB/T 10293-2013 Specifications of single seed drill(precision drill).The seed-metering device meets fully the requirements for wheat precision seeding.

Electronic control seed-metering system for precision seeding maize based on fuzzy PID

Aiming at the problem of poor uniformity of maize sowing caused by ground wheel slip,an electronic control seed-metering system(ECSMS)for maize single seed precision sowing was designed and a mathematical model for motor control of the ECSMS was determined.The PID parameters were set by Z-N method and fuzzy control.The fuzzy PID control design and Simulink simulation were completed by MATLAB,which reduced response time of the system by 0.23 s and improved the control accuracy.Experiments on the JPS-12 test bench show that the qualification index(QI)of maize seed-metering device with the ECSMS increases by 4.47%,the multiples index(MI)decreases by 1.96%,the miss index(MIX)decreases by 2.81%,and the coefficient of variation(CV)of qualified seed spacing decreases by 5.06%,and the sowing uniformity has been greatly improved.Test results of the soil-tank test bench show that the system has good sowing uniformity and stability.And the QI is 96.74%,the MI is 2.15%,the MIX is 1.10%,and the CV of qualified seed spacing is 16.24%.Under different setting seed spacing and different sowing operation speed,the change range of seeding quality index was within 10%.The results of field sowing test show that the QI was 84.21%,the MI was 2.63%,the MIX was 7.89%,and the CV of qualified seed spacing was 22.15%,which meet the requirements of JB/T 10293-2013‘Specification for single seed planters(precision planters)’and the agronomic requirements for maize precision sowing.The system runs stably and reliably in practical operation and has good operation performance.

Overview and Development of Variable Frequency AC Generators for More Electric Aircraft Generation System

With the development of more electric aircraft(MEA),higher demands for electrical energy are put forward in generation systems.Compared to constant frequency AC(CFAC)generation systems,the constant speed drive(CSD)is eliminated and integrated starter/generator(SG)can be realized in variable frequency AC(VFAC)generation systems.In this paper,an overview of VFAC generators for safety-critical aircraft applications is presented,with a particular focus on the key features and requirements of candidate generators and the starting control strategies.Wound rotor synchronous machines(WRSMs)are typical generators used in VFAC generation systems so far.Meanwhile,hybrid excitation synchronous machines(HESMs)and cage-type induction machines are promising candidates for VFAC generation systems.The generation operation of WRSM is relatively mature,however,the SG technology of WRSM is still full of challenges.As one of the most important issues,the starting excitation methods of WRSM are summarized.An HESM-based VFAC SG system is proposed and developed in this paper.The experimental results show that the starting mode,transition mode and generating mode of the VFAC SG system are realized.The continuous progress of VFAC generation system makes great contributions to the realization of MEA.

Autotetraploidy induced in Nianmaohuangqin (Radix Scutellariae viscidulae) with colchicine in vitro

OBJECTIVE： To establish and optimize the propaga- tion of Nianmaohuangqin （Radix Scutellariae Viscid- ulae） and induce and characterize polyploidy of Nianmaohuangqin （Radix Scutellariae Viscidulae）. METHODS： Buds from germinating seed-derived explants were induced by tissue culture. With an or- thogonal test, different concentrations of 6-benzyl- aminopurine （BAP）, indole-3-acetic acid （IAA） and kinetin （KT） were used to determine the optimal concentrations for the propagation of Nianmaohuangqin （Radix Scutellariae Viscidulae）. The differ- ent concentrations of IAA and rooting powder （ABT） were used to induce rooting. A 0.3% w/v col- chicine solution was used to induce polyploidy and the induced buds was identified by root-tip chromosome determination and stomatal apparatus ob- servation. RESULTS： A large number of buds could be in- duced directly from epicotyl and hypocotyl ex- plants on Murashige and Skoog （MS） （Murashige and Skoog 1962） medium supplemented with 1.1-1.3 mg/L BAP and 0.2 mg/L IAA. Root induction and development could be observed within 20 days of inoculation on 1/2 MS medium supplemented with 0.2 mg/L IAA and 0.1 mg/L ABTo Furthermore, 27 lines of autotetraploid individuals were ob- tained with a plantlet chromosome number of 2n= 4x=36. CONCLUSION： Autotetraploid lines could be ob- tained through induction with colchicine in vitro, proving that this method might be used for plant selection and breeding.