Relationship Between Soil Boron Adsorption Kinetics and Rape Plant Boron Response

The boron adsorption kinetic experiment in soil by means of a flow displacement technique showed that the kinetic data could be described with some mathematic equations. The average values of the correlation coefficient for zero-order, first-order, parabolic diffusion, Elovich, power function and exponential equations were 0.957, 0.982, 0.981, 0.984, 0.981 and 0.902, respectively. The correlation between adsorbed boron or its other expression form and time were the highest for first-order, parabolic diffusion, Elovich, and power function equations, the second for the zeroorder equation, and the lowest for the exponential equation. The parabolic diffusion equation fitted well the experimental results, with the least standard error among the six kinetic equations, showing that the movement of boron from soil solution to soil colloid surface may be controlled by boron diffusion speed. The boron content of rape seedling obtained from soil cultivation was correlated with the rate constants of the kinetic equations. The constants of first-order, parabolic diffusion,and exponential equations were significantly correlated with the boron content of the crop of NPK treatment at a 95% probability level, with correlation coefficients being 0.686, 0.691 and 0.641, respectively. In the case of zero-order equation, it was significant at 99% probability level (r =0.736). These results showed that the absorption kinetic constants of soil boron were closely related with the rape plant response to boron.

Response of plant physiological parameters to soil water availability during prolonged drought is affected by soil texture

Soil water deficit is increasingly threatening the sustainable vegetation restoration and ecological construction on the Loess Plateau of China due to the climate warming and human activities.To determine the response thresholds of Amygdalus pedunculata(AP)and Salix psammophila(SP)to soil water availability under different textural soils,we measured the changes in net photosynthetic rate(Pn),stomatal conductance(Gs),intercellular CO2 concentration(Ci),leaf water potential(ψw),water use efficiency(WUE)and daily transpiration rate(Td)of the two plant species during soil water content(SWC)decreased from 100%field capacity(FC)to 20%FC in the sandy and loamy soils on the Loess Plateau in the growing season from June to August in 2018.Results showed that Pn,Gs,WUE and Td of AP and SP remained relatively constant at the beginning of soil water deficit but decreased rapidly as plant available soil water content(PASWC)fell below the threshold values in both the sandy and loamy soils.The PASWC thresholds corresponding to Pn,Gs and Ci of AP in the loamy soil(0.61,0.62 and 0.70,respectively)were lower than those in the sandy soil(0.70,0.63 and 0.75,respectively),whereas the PASWC thresholds corresponding to Pn,Gs and Ci of SP in the loamy soil(0.63,0.68 and 0.78,respectively)were higher than those in the sandy soil(0.58,0.62 and 0.66,respectively).In addition,the PASWC thresholds in relation to Td and WUE of AP(0.60 and 0.58,respectively)and SP(0.62 and 0.60,respectively)in the loamy soil were higher than the corresponding PASWC thresholds of AP(0.58 and 0.52,respectively)and SP(0.55 and 0.56,respectively)in the sandy soil.Furthermore,the PASWC thresholds for the instantaneous gas exchange parameters(e.g.,Pn and Gs)at the transient scale were higher than the thresholds for the parameters(e.g.,Td)at the daily scale.Our study demonstrates that different plant species and/or different physiological parameters exhibit different thresholds of PASWC and that the thresholds are affected by soil texture.The result can provide guidance for the rational allocation and sustainable management of reforestation species under different soil conditions in the loess regions.

Analysis of Steady-state Characters of Aquatic Environment and Dynamic Changes in the Biomass of Submerged Plants in Dongqian Lake

To study the eutrophic status of Dongqian Lake,the contents of total nitrogen（ TN）,total phosphorus（ TP） and chlorophyll（ Chla） and the biomass of submerged plants in Dongqian Lake were monitored from April to September 2014,and their correlations were discussed. The results showed that there were regular changes in the TN,TP,and Chla content,and the biomass of submerged plants in Dongqian Lake,that is,the water quality of the lake was inferior in the early growth period of submerged plants and phytoplankton. The correlation analysis showed that the biomass of submerged plants correlated with TP and TN content negatively. In a word,the increase in the biomass of submerged plants was a key factor leading to the shift of water quality in Dongqian Lake in the later period,indicating that submerged plants played an important role in the steady-state shift of aquatic environment in Dongqian Lake.

Characteristics of phosphorus chemistry and its geographical distribution in the Haihe River valley,North China

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The Influence of Nitrogen Fertilizer Application on Yields and Nitrogen Use Efficiencies of <i>Solanum macrocarpon</i>and <i>Solanum scabrum</i>in Southwest Nigeria

Solanum macrocarpon and Solanum scabrum are good sources of vitamin, minerals, protein, anti-oxidants and fiber in southwest Nigeria. The study examined the effects of nitrogen fertilizer application on yields and nitrogen use efficiencies of Solanum macrocarpon and Solanum scabrum in Iwaro-Oka, Ondo State in southwest Nigeria in 2014 and 2015. The experiment was a 4 × 4 factorial arranged into a randomized complete block design with four rates of urea-N drilled at 0, 40, 80 and 160 kg/ha and replicated four times. Each plot was 3 m × 2 m with space of 1 m between plots. Vegetable seeds were planted by drilling. Fresh shoot and dry matter yields were determined. Nitrogen content and uptake were determined, and nitrogen use efficiency estimated. The result showed that average dry matter weight for S. macrocarpon was 228 kg/ha and S. scabrum was 6116 kg/ha. Average nitrogen uptake was 5.90 kg/h and 158.60 kg/ha for S. macrocarpon and S. scabrum, respectively. Nitrogen use efficiencies were 6.48 kg/ha, 0.15 kg/ha and 0.1 kg/ha for S. macrocarpon and 87.33 kg/ha, 26.14 kg/ha and 24.35 kg/ha for S. scabrum at 40, 80 and 160 kg N/ha, respectively. Negative values were obtained for N-recovery for S. macrocarpon while S. scabrum gave 5.85%, 2.10% and 1.44% at 40, 80 and 160 kg N/ha, respectively. The study concluded that S. scabrum had higher nitrogen use efficiency in the soil than S. macrocarpon and that highest NUE and N recovery were obtained at 40 kg N/ha.

Abiotic and Biotic Stresses and Changes in the Lignin Content and Composition in Plants

Lignin is a polymer of phenylpropanoid compounds formed through a complex biosynthesis route, represented by a metabolic grid for which most of the genes involved have been sequenced in several plants, mainly in the model-plants Arabidopsis thaliana and Populus. Plants are exposed to different stresses, which may change lignin content and composition. In many cases, particularly for plant-microbe interactions, this has been suggested as defence responses of plants to the stress. Thus, understanding how a stressor modulates expression of the genes related with lignin biosynthesis may allow us to develop study-models to increase our knowledge on the metabolic control of lignin deposition in the cell wall. This review focuses on recent literature reporting on the main types of abiotic and biotic stresses that alter the biosynthesis of lignin in plants.

Water Yield of Xitiaoxi River Basin Based on InVEST Modeling

Water yield calculation and mapping are of great importance to water resource planning and management and hydropower station construction. A water yield model based on InVEST was employed to estimate water runoff in the Xitiaoxi River basin. The data included land use and land cover, average annual precipitation and potential evapotranspiration, soil depth, and plant available water content. In order to test model accuracy the natural runoff of Xitiaoxi River was estimated based on linear regression relation of rainfall-runoff in a ‘reference period’. After repeated validation, when the Z value was 6.5 the water yield was 8.30 E＋8 m3 and this was a smaller difference with natural runoff. From the distribution of water yield, south and southwestern areas of the watershed had higher water yield volumes per hectare.