1,721,114 research outputs found
CATALYTIC HYDROLYSIS OF DICLOFOP-METHYL ON CA-MONTMORILLONITES, NA-MONTMORILLONITES AND K-MONTMORILLONITES
No full textFibrillar structure of Ca-polygalacturonate as a model for a soil-root interface. Part I. A hypothesis on the arrangement of the polymeric chains inside the fibrils 129,211-217
No full textFIBRILLAR STRUCTURE OF CA POLYGALACTURONATE AS MODEL FOR A SOIL-ROOTINTERFACE .1. A HYPOTHESIS ON THE ARRANGEMENT OF THE POLYMERIC CHAINS INSIDE THE FIBRILS
No full textThe movement of nutrients from soil towards the absorbing cells of the plant roots appears to be controlled by a mucilaginous interface composed prevalently of polysaccharides and characterized by a fibrillar structure. A network of Ca-polygalacturonate arranged in fibrils similar to those of plant roots has been obtained. In this paper such a formation is documented and discussed in structural terms
DIMEPIPERATE ADSORPTION AND HYDROLYSIS ON AL3+-MONTMORILLONITE, FE3+-MONTMORILLONITE, CA2+-MONTMORILLONITE, AND NA+-MONTMORILLONITE
No full textThe adsorption of the herbicide dimepiperate S-(alpha,alpha-dimethylbenzyl)-1-piperidinecarbothioate on homoionic Fe3+-, Al3+-, Ca2+-, and Na+-montmorillonite was studied in aqueous medium. The adsorption is described well by the Freundlich equation. The adsorption capacity decreases in the order Fe3+ > Al3+ > Ca2+ > Na+ clay. The dimepiperate adsorption from chloroform solution was also investigated by analytical, spectroscopic, and X-ray powder diffraction techniques. IR results suggest that the adsorption involves the interaction of the thioester carbonyl group of dimepiperate possibly with the surrounding water of metal ions. On Al3+ and Fe3+ clays, this interaction leads to hydrolysis of the thioester bond and formation of the thiol and carbamic acid derivatives that yield alpha-methylstyrene and piperidine, respectively
ADSORPTION OF TRICLOPYR ON SOIL AND SOME OF ITS COMPONENTS
No full textThe adsorption of triclopyr [[(3,5,6-trichloro-2-pyridynyl)oxy] acetic acid] by homoionic clays, soil organic matter (H- and Ca-saturated), and seven soils was studied. The extent of adsorption on clays decreased in the order of decreasing acidity of the saturating cations. The H-organic matter was more active in triclopyr adsorption than Ca-organic matter and Ca-clay, whereas studies on mixtures of clay and organic matter indicated that the interaction between these two soil components reduced the surfaces available for triclopyr adsorption. Adsorption isotherms conformed to the Freundlich equation. It was found that in soil the Freundlich adsorption constant decreased linearly with organic matter (r = 0.930) and adsorption decreased with increasing pH. Multiple-regression analysis indicated that k(f) values were better correlated if cation-exchange capacity and pH (r = 0.989) were simultaneously taken into account
Effetti della fertilizzazione fogliare sul clementine. Ricerche condotte su piante in condizioni di "stress" a livello di assorbimento radicale
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Montmorillonite surface-catalyzed hydrolysis of fenoxaprop-ethyl
No full textThe degradation of the herbicide fenoxaprop-ethyl [ethyl 2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoate] on homoionic Fe3+, Al3+, Ca2+, and Na+ montmorillonite in aqueous medium was studied. The results show that the hydrolysis of the pesticide may involve two different mechanisms, both depending on the nature of the exchangeable cations. The herbicide hydrolyzes to 6-chlorobenzoxazolinone and ethyl 2-(4-hydroxyphenoxy)propanoate on Fe3+ and Al3+ clays, whereas the fenoxaprop acid [2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoic acid] is the main hydrolysis product on Ca2+ and Na+ clays with minor amounts of 6-chlorobenzoxazolinone and 2-(4-hydroxyphenoxy)propanoic acid. The protonation of the benzoxazole ring nitrogen of the herbicide can be responsible for the cleavage of the ether bridge of fenoxaprop-ethyl in the Fe3+ and Al3+ systems. Instead, the hydrolysis of the ester bond appears to be favored by the coordination of the carbonyl oxygen of fenoxaprop-ethyl with the hydrated exchangeable metal ions in the Ca2+ and Na+ systems
Determination of free L- and D-alanine in hydrolysed protein fertilisers by capillary electrophoresis
No full textThe objective of this study was to determine the degree of racemisation of hydrolysed protein fertilisers (HPFs) using an inexpensive and easy to handle analytical method for qualitative control of the products. Using a polyacrylamide coated capillary and a run buffer containing 0.1 M Tris-borate+2.5 mM EDTA-Na2+0.1% sodium dodecylsulfate+10 mM β-cyclodextrin a quantitative separation of D- and L-alanine (Ala) was made from an not treated HPF sample derivatised with dansyl chlorine by capillary electrophoresis. The D-Ala:[D-Ala+L-Ala] ratio, called degree of racemisation (RD), was calculated. The analysis of ten commercial HPFs has shown that more than 60% of HPFs have an RD ≥40%, while only one product has shown an RD <5%. These results showed that most of the HPFs on the market are obtained with strong hydrolytic processes and high contents of D-amino acids are probably less effective as plant nutrients or even potentially dangerous to plants. © 2002 Elsevier Science B.V. All rights reserved
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