Morphological and kinetic parameters of the absorption of nitrogen forms for selection of Eucalyptus clones

Eucalyptus clones are selected according to productivity,wood quality,rooting capacity,and resistance to drought,frost and diseases.However,kinetic and morphological parameters that determine the absorption efficiency of nutrients such as nitrate(NO_(3)^(-)) and ammonium(NH_(4)^(+))are often not considered in breeding programs.The objective of this study was to evaluate the morphological,physiological and kinetic parameters of nitrogen uptake by clones of Eucalyptus saligna(32,864) and Eucalyptus grandis(GPC23).Morphological parameters in shoot and root systems,biomass and N concentrations in different organs,photosynthetic pigment concentrations,parameters of chlorophyll a fluorescence and photosynthetic rates were evaluated.Kinetic parameters,maximum absorption velocity(V_(max)),Michaelis-Menten constant(K_(m)),minimum concentration(C_(min)) and influx(I) were calculated for NO_(3)^(-)and NH_(4)^(+) in the two clones.E.granais clone was more efficient in the uptake of NO_(3)^(-)and NH_(4)^(+),and showed lower K_(m) and C_(min)values,allowing for the absorption of nitrogen at low concentrations due to the high affinity of the absorption sites of clone roots to NO_(3)^(-)and NH_(4)^(+).Higher root lengths,area and volume helped the E.grandis clone in absorption efficiency and consequently,resulted in higher root and shoot biomass.The E.saligna clone had higher K_(m) and Cmin for NO_(3)^(-)and NH_(4)^(+),indicating adaptation to environments with higher N availability.The results of NO_(3)^(-)and NH_(4)^(+) kinetic parameters indicate that they can be used in Eucalyptus clone selection and breeding programs as they can predict the ability of clones to absorb NO_(3)^(-)and NH_(4)^(+) at different concentrations.

Evaluation of arsenic pollution in field-contaminated soil at the soil’s actual pH

The pollution and ecological risks posed by arsenic(As)entering the soil are the major environmental challenges faced by human beings.Soil phosphatase can serve as a useful indicator for assessing As contamination under specific soil pH conditions.However,the study of phosphatase kinetics in long-term field As-contaminated soil remains unclear,presenting a significant obstacle to the monitoring and evaluation of As pollution and toxicity.The purpose of this study was to determine phosphatase activity and explore enzyme kinetics in soils subjected to long-term field As contamination.Results revealed that the soil phosphatase activity varied among the tested soil samples,depending on the concentrations of As.The relationship between total As,As fractions and phosphatase activity was found to be significant through negative exponential function fitting.Kinetic parameters,including maximum reaction velocity(Vmax),Michaelis constant(Km)and catalytic efficiency(V_(max)/K_(m)),ranged from 3.14×10^(−2)–53.88×10^(−2) mmol/(L·hr),0.61–7.92 mmol/L,and 0.46×10^(−2)–11.20×10^(−2) hr^(−1),respectively.Vmax and Vmax/Km of phosphatase decreased with increasing As pollution,while Km was less affected.Interestingly,Vmax/Km showed a significant negative correlationwith all As fractions and total As.The ecological doses(ED10)for the complete inhibition and partial inhibition models ranged from0.22–70.33 mg/kg and 0.001–55.27 mg/kg,respectively,indicating that V_(max)/K_(m) can be used as an index for assessing As pollution in field-contaminated soil.This study demonstrated that the phosphatase kinetics parameters in the soil’s pH system were better indicators than the optimal pH for evaluating the field ecotoxicity of As.

Valorization of banana peel intoα-amylase using one factor at a time(OFAT)assisted artificial neural network(ANN)and its partial purification,characterization,and kinetics study

In this present studyα-amylase producing bacteria were isolated from the soil near North Bengal University canteen on an amylase agar medium.Primary screening of the isolates was done by iodine test,based on the clear zone around the bacterial colonies in the media plates.Seven bacterial isolates were selected and quantitatively screened for amylase production.Among them,strain sps2 showing the highest amylase activity(215±2 IU/ml)was selected for further studies.Isolated strain sps2 was identified both morphologically and biochemically and further confirmed by 16s rRNA sequencing as Streptomyces pratensis sps2(Gene bank accession No.OP 236721).Optimization ofα-amylase produced by the isolate was conducted under submerged fermentation of low-cost carbon source banana peel,using a one factor at a time(OFAT)approach.Maximum amylase activity of 821.33±0.57 IU/ml was recorded after 2 days of fermentation.The artificial neural network(ANN)model was employed using the OFAT data to generate a predictive model for amylase production and the R-value of 0.94496 and the RMSE of 64.82 suggesting that the neural network has the precise capability to generate an optimization environment.Ammonium sulfate precipitation and dialysis techniques were used to partially purify theα-amylase and then characterized.The enzyme was found to have a molecular mass of 28 kDa(SDS-PAGE and zymogram)with a K_(m)and V_(max)of 2 mg/ml and 1000μmol/min,respectively.The enzyme was found to be thermostable in the temperature range of 4-90℃ and more stable at alkaline pH with optimum pH of 7.