INCIDENCE OF LETTUCE TIPBURN AS RELATED TO HYDROPONIC SYSTEM AND CULTIVAR

The incidence of tipburn was studied by growing late winter and spring lettuce cultivars in two consecutive experiments, in hydroponics, either with Deep Flow Technique (DFT) or on solid growth substrates, in Messinia, NW, Greece. Both experiments showed that the fresh marketable yield of lettuce in DFT was approximately twice as great compared to that of plants grown on solid substrates. Tipburn injury was not observed in the late winter experiment whereas it was severe in the spring one. In particular, lettuce grown with DFT in the spring presented significantly greater level of injury whereas when grown on perlite the least. Their shoot calcium concentration was significantly lowest whereas when grown on perlite the highest. Between the two spring cultivars included, ‘Merlin’, which presented the greatest injury, also had significantly higher shoot fresh weight, lower root/shoot ratio, higher tissue water content, and lower nitrogen, potassium, calcium, and magnesium concentrations compared to ‘Gramsi’.     

A DFT study on formaldehyde reduction in dielectric barrier discharges

Density functional theory (DFT)is used to study the thermodynamics of formaldehyde removal under dielectric barrier discharges (DBD)non-thermal plasma (NTP)conditions at atmospheric pressure and ambient temperature. A calculation model is defined. The calculated reaction relative energies in this work confirm that the DBD plasma is effective for formaldehyde reduction at ambient conditions and at 1 atm. Present calculations indicate that the reactions of HCHO with primary free radicals such as OH·,O·,and H· are all thermodynamically favored. Moreover,theoretical results show that the main routes of O radical generation from O2 are direct dissociation and dissociative attachment-releasing electron, and the main pathways of H· and OH· from H2O are dissociation and attachment. The only thermodynamic obstacle to HO2· formation is 2H2O→H2O2+H2. The reactions of HO2· with other radicals are all thermodynamically favored. Comparative results between the previous investigation and the present work demonstrate that theoretical calculation with DFT can be an efficient and reliable supplement for experimental research.     

锰对厚皮甜瓜生长发育和产量品质的影响

在深液流水培技术条件下研究不同锰素营养水平对厚皮甜瓜生长发育、产量和品质的影响。结果表明,当营养液中Mn2+浓度在0～1.0mg·L-1范围内时,厚皮甜瓜的生长发育速度和净光合速率随Mn2+浓度的提高而提高,产量和品质也相应提高;Mn2+浓度高于2.0mg·L-1时,厚皮甜瓜的生长发育速度、净光合速率及产量、品质明显下降;Mn2+浓度高于8.0mg·L-1时,厚皮甜瓜不能正常开花结果。厚皮甜瓜深液流水培营养液配方中Mn2+浓度以0.5～2.0mg·L-1为宜。     

基于银川地区水质的空心菜营养液配方筛选研究

应用四元二次通用旋转组合设计,采用DFT无土栽培,在二代节能日光温室内研究了营养液配方中的NO3--N、P、K、Ca的摩尔浓度对空心菜生长的影响,得到了二者之间的回归方程,并进行了方差分析。结果表明:四个元素对空心菜产量的影响大小顺序是:氮>钾>磷>钙;通过对方程的解析,得到空心菜氮与钾的交互效应在较低水平时有一定的正相关关系,在较高水平时存在着一定的负相关关系;通过计算机模拟寻优,空心菜达到单株最高产量108.81 g时,NO3-N、P、K、Ca 4个因子营养液的最优配方为:9、0.5、4.5和4.0 mmol/L。     

CH3·与CO反应机理的理论研究

采用密度泛函B3LYP/6-311G**和QC ISD(T)/6-311G**方法计算研究了CH3.与CO反应机理,全参数优化了反应势能面上各驻点的几何构型,用内禀反应坐标(IRC)计算和频率分析方法,对过渡态进行了验证。研究结果表明:CO对CH3.自由基有稳定化作用。该反应的研究将为烃类的燃烧和大气环境的保护提供理论依据。