No abstract

Phosphorus deficiency in citrus leaves resulted in reduced glutamic‐oxaloacetic transaminase (GOT) activity and low pyridoxal‐phosphate (PLP) content. GOT activity was estimated in crude enzyme extracts by spectrophotometry PLP content was detected colorimetrically in water‐alcoholic extracts. K and Cu deficiencies increased; ‐N, ‐S and ‐Zn decreased and ‐Mg, ‐Fe and ‐Mn did not affect GOT activity in citrus leaves. Experiments were conducted to restore enzyme activity either by direct addition of PLP to the reaction mixture or by infiltration of PLP or KH2PO4 to detached, intact leaves. The infiltration was carried out in vacuo and the leaves were incubated on wet paper for 26 h, after which enzyme activity was estimated. Transamination activity of ‐P leaves more restored by PLP than by KH2PO4 treatments. In zinc‐deficient leaves the enzyme activity was not restored by infiltration of KH2PO4.

The uptake ad metabolism of a-15-14Clketoglutarate by phospborusdeficient and full nutrient (control) iemo (Citus lmn) leaves were studied over various thme intervals. After 45 minutes In P-deficient leaves, the bulk of Incorporated 14C appeared In organk acids and much less In amino acids, while In the control leaves, the 14C contests of organic and amino acids were equal. In P-efcient leaves, after loger Incubation times the 14C content of organic acids and anino acids Increased, whRe that of CO and residue fractions remaied iow. In full nutrient leaves the "C content of amino acids and organic acids decreased after ionger iocubaton time and Increased in the insolube residue and CO2. In full utient leaves the organic and amino acid metaboUsm were ciosely related and accompanied by protein synthesis and CO2 release, whie in P-deficient leaves an accelerating accumulation of arginine and citric acid was iHnked together With hibitio of protein syntheis and CO liberation.Accumulation of arginine is a well recognized metabolic disturbance induced by phosphorus deficiency in various plants (6,10,11,21). In P-deficient lemon seedlings we found an inverse relationship between their growth and arginine accumulation: as the rate of growth declined the concentration of arginine rose, while the other amino acids and protein remained low in comparison with seedlings grown in full nutrient solution (1). This deviation from the normal pattern of amino acid synthesis may be attributed to a decrease in activity of transaminases, enzymes which require pyridoxal phosphate as a coenzyme (2). In a study of the correlation among phosphate ratio, GOT2 activity, and PLP content, we found that the reduced activity of enzyme could be restored by infiltration of pyridoxal phosphate or mineral phosphate into the P-deficient leaves (2). On the other hand, determinations oforganic acids disclosed extensive accumulation ofcitrate in P-deficient lemon leaves (unpublished data).In the present study we followed the incorporation of a-ketoglutarate into various cell metabolities in P-deficient and normal citrus leaves. In each jar, a small vial containing 1.5 ml of methanol-ethanolamine (4:1, v/v), was placed to trap the "CO2.At the end of the incubation period the radioactivity of CO2 was counted in 10 ml of toluene fluor. During the incubation period, the jars were shaken gently in a water bath at 35 C. The incubation periods were 45, 90, and 180 min. Each combination of treatments (mineral nutrition and incubation period) was tested in three replicates.At the end of the incubation period the buffer solution was filtered through Miracloth. The discs were rinsed with deionized H20, blotted on filter paper, and boiled in 15 ml of 100%o ethanol for 10 min.Extraction. The discs were homogenized for 2 min in a VirTis blender set at speed 60, and centrifuged at 10,000g. The pellet was reextracted four times by shaking for 10 min with 10-ml portions of 80% (v/v) ethanol and then centrifuged (22).The insoluble residue was dried over silica ge...

Soil samples with and without a past history of dimethyl-2,3,5,6-tetrachloroterephthalate (DCPA) treatment were obtained from New York. A third sample was obtained from a field in Colorado where DCPA had been ineffective as a herbicide. The populations of bacteria and actinomycetes in these soils were determined and the actinomycetes were more prevalent in the samples with previous DCPA treatment than in untreated samples. Subsequent treatment resulted in an increase in actinomycete population and little change in bacterial population. In pure culture and in soils, the addition of DCPA had no adverse effect upon microbial growth, and several microorganisms appeared to utilize the herbicide as a carbon source. Two degradation products were methyl-2,3,5,6-tetrachloroterephthalate and 2,3,5,6-tetrachloroterethalic acid.