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During investigations of their metabolism fragments of plant tissue are most commonly incubated in watery solutions in order to replace the conditions within the intact organ approximately. -- This paper reports experiments performed to investigate the influence of a hypotonic medium on several parameters of importance in cell metabolism (protein synthesis, enzymatic activity, concentrations of metabolic intermediates, respiration, and cell division). -- It could be shown that protein synthesis is severely inhibited in hypotonically exposed potato tuber discs. As a consequence the activities of two dehydrogenases of the pentose phosphate shunt (glucose-6-phosphate- and 6-phosphogluconate-dehydrogenase) are very low as compared with tissue in air. Since the activated pentose shunt evidently contributes to the respiratory reaction after derepression of the tissue, lowered activities of these dehydrogenases must consequently result in lower respiratory activity. This is actually realized in washed tissue, Likewise the mitotic activity is inhibited to a considerable extent. -- The destruction of permeability barriers within the cell as a consequence of slicing causes leakage of a variety of metabolites such as glucose, glucose-6-phosphate, fructose-6-phosphate and pyruvate. Thus leaching of metabolic active substances is certainly one of the causal factors in the complex reaction of tissue slices exposed to a hypotonic medium, although such important parameters as changes gas conditions and the various effects of altered hydration of cell cytoplasm must be considered. [ABSTRACT FROM AUTHOR]

This paper focuses on resistance test against parasitic fungi in forest trees in Sweden. Forest resistance research is carried out at the Department of Forest Botany and Pathology at the Royal College of Forestry in Stockholm in close contact with Forest Genetics research and is performed as a resistance test of plants from seed orchards and tested progenies. Biochemical research concerning the resistance mechanism and an electronmicroscopic investigation is carried out. At present the tests only cover Picea abies and above all Pinus silvestris. The parasitic fungi tested at present are Lophodermium pinastri, Phacidium infestans, Scieroderris lagerbergii, Melampsora pinitorqua and Periderinium pini.

The paper describes the mode of infection and subsequent deterioration of spruce root wood by Forties annosus using light and electronmicroscopic observations. In the secondary xylem the overall penetration of cell walls is effected by means of microhyphae which produce boreholes. The degradation of cell walls is initiated in the S2 layer by diffusion of enzymes along the cellulose fibrils with subsequent hydrolysis of the amorphic incrusting substances.

Thiolase was purified 600–700 fold from a crude extract of pig heart by use of differential adsorption on Al(OH)3 gel, ammonium sulfate fractionation and ion exchange chromatography on DEAE­Sephadex and phosphorylated cellulose. The enzyme preparation is homogenous by the following criteria: sedimentation analysis and electrophoresis on polyacrylamide gel and on cellulose acetate membranes. The isoelectric poit of the protein was found to be approximately pH 7.2–7.3. The enzyme crystallized from ammonium sulfate solutions as thin plates of irregular shape. Crystalline thiolase stored for 18 months at –10° did not show any loss of activity. The thiolytic activity and the acyl transferase activity of the enzyme could be demonstrated separately. The thiolytic activity was demontrated by the specific incorporation of 14C from [1 ­14C]­acetyl­CoA into the carboxyl position of unlabelled acetoacetyl­CoA on incubation wtih the enzyme. The acyl transferase activity eas studied using either [1­14C]­CoA and patethein as substrates or 14C­labelled CoA and acyl­CoA derivatives of varius chain length. A remarkable specificity was found for the transfer of the acetyl group. Thiolase activity and acyl transferase activity of the enzyme were diminished with the same kinetics during heat treatment or incubation with N ­ethylmaleeimide, ρ­cholomercuribenzoate or iodoacetamide. this indicates that both activities belong to the same protein. Inhibition of thiolase and acyltranferase activities by iodoacetamide (5 x 10­5 could be prevented by preicubation of the enzyme with acetoacetyl­CoA or acetyl­CoA. The acyl transfer is the rate determining step when the thiolase reaction operates in the direction of chain cleavage. Incubation of thiolase with acetyl­Coa results in binding of acetyl groups to the protein. The uptake of acetyl groups is dependent upon the specific activity of the enzyme and corresponds to 3 acetyl residues per molecule of protein (molecular weight 170,000) for the highest enzymatic activity obtained. both incorporation of acetyl groups into the enzyme and thiolase activity are inhibited to the same extent by iodoacetamide. the incorportion of radioactivity into the enztme during incubation with iodo­[1­14C]­acetamide can be divided into two different reactions: a fast incorporation with accompanying loss of enzymatic and a much slower process which continues after complete inactivation. From the initial rate of incorporation, it was calculaetd that incorporation of 3.1 carbamoylmethyl residues per molecule of protein would completely inhibit the enzyme withthe highest obtained activity. this ration cmpares well with the results obtained by acetyl binding studies and indicates a minimum of 3 active sites per molecule of enzyme. Enzyme labelled with iodo­[1­14C]acetamide was hydrolyzed with 6 N HCl. Approximately 95% of the radioactivity in the hydrolysate was found to coincide with S­carboxymethyl­L­cystine on electrophoresis and paper chromatography. Repeated crystallization with authentic carboxymethyl­cystine did not result in a decrease of specific radioactivity. [ABSTRACT FROM AUTHOR]