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1.An O-methyltransferase catalyzing the transfer of the S-methyl group of S-adenosyl-L-methionine to the 4'-hydrozyl group of isoflavones has been detected in seedlings of Cicer arietinum L. and in cell suspension cultures of this plant.2.After transfer of the cell cultures to fresh medium the activity of the methyltransferase rose after a lag period of about 2 and reached a maximum after about 20 h and then declined. Illumination of the cell cultures had no effect on the enzyme activity. 3.The enzyme has been purified 360-fold by (NH4)2SO4 fractionation, chromatography on DEAE-cellulose and hydroxyapatite and Sephadex G-200 gel filtration. 4.The S-adenosylmethionine : isoflavone 4'-0-methyltransferase was isolated as a soluble enzyme with a pH optimum of 9 in glcine-NaOH buffer. It requires - SH-protecting agents for activity. The elution volume from a Sephadex G-200 column to be about 110000 estimated the molecular weight of the enzyme. 5.The enzyme is specific for the methylation of 4'-hydrozyisoflavones. Intermediates in the biosynthetic pathway to isoflavones, e.g. p-hydroxycinnamic acid and 5,7,4'-trighdroxyflavone, were not methylated. The Km values for daidzein (7,4'-dihydroxyisoflavone) and S-adenosylmethionine were determined to be 80μM and 0.16mM, respectively. Because of the high specificity of the methyltransferase for isoflavones it can be concluded that methylation is the last step in the biosynthesis of 4'-methoxyisoflavones. 6.The enzyme was inhibited by S-adenosylhomocysteine. The Ki values for S-adenosylhomocysteine versus daidzein and S-adenosylmethionine were determined to be 0.3 mM and 30μM, respectively. From the inhibition kinetics it can be concluded that the reaction follows an Ordered BiBi mechanism with S-adenosylmethionine and S-adenosylhomocysteine as leading reaction partners. [ABSTRACT FROM AUTHOR]

Plants of a pure line variety, G 24, of Cicer arietinum L. were grown in sand culture. After an initial dose of a complete nutrient solution, a nitrogen free nutrient solution was supplied to the sand at intervals and a standard rhizobial culture was added twice. The plants were treated with two concentrations of gibberellic acid (20 mg/l and 100 mg/l) through the rooting medium. At suitable intervals two pots from each treatment were sampled. Observations were made regarding the earliest initiation of nodulation, the number, weight and colour of nodules and the nitrogen content of different plant organs under various treatments. GA3 treatments enhanced nodule initiation. While 20 mg/l somewhat enhanced nodule number, weight and nitrogen content, 100 mg/l caused detrimental effects in the long run. Pod formation was delayed with GA3, the effect being much more pronounced with the higher concentration used. Pod and seed weights under 20 mg/l somewhat enhanced nodule number, weight and nitrogen content, 100 mg/l caused detrimental effects in the long run. Pod formation was delayed with GA3, the effect being much more pronounced with the higher concentration used. Pod and seed weights under 20 mg/l GA3 were almost comparable to the control, but 100 mg/l proved very deleterious. [ABSTRACT FROM AUTHOR]