Soybean plants were grown for 90 days and spinach plants for 64 days in a mixture of sterilized greenhouse soil and sand containing 10 ppm pentachlorophenol. All plant parts and soil samples were extracted and separated into nonpolar and polar fractions. Major nonpolar and polar metabolites were identified by gas-liquid chromatography and mass spectrometry. Nonpolar fractions from both soybean and spinach plants were found to contain pentachlorophenol and its metabolites, 2,3,4,6-tetrachlorophenol, methoxytetrachlorophenol, 2,3,4,6-tetrachloroanisole, and pentachloroanisole. Cleavage of polar metabolites from the soybean plants by acid hydrolysis yielded organic solvent-extractable products. These products were identified as pentachlorophenol, 2,3,4,6-tetrachlorophenol, and methoxytetrachlorophenol. Cleavage of polar materials from spinach plants yielded only pentachlorophenol. The polar metabolites from the soybean plants were also subjected to enzymatic cleavage by beta-glucosidase. The conjugates consisted mostly of O-glucosides of the same metabolites released by acid hydrolysis. Failure of hydrolysis by aryl sulfatase indicated that very little or no sulfates were present. The metabolites found in the plants were not detected in soil samples obtained from pots immediately after the plants were harvested.

Biotransformation↗

PubMed1982

Cadmium-binding components in soybean plants.

Soybean (Glycine max L.) plants exposed to (109)Cd readily absorb the element. Differential centrifugation of leaf, stem, and root homogenates followed by radioassay showed that Cd was associated primarily with the 105,000g supernatant. Separation of this fraction by gel chromatography and subsequent analysis by radioassays revealed that (109)Cd was bound to macromolecules of >50,000, 13,800, and 2,280 molecular weights. The >50,000 and 2,280 molecular weight fractions probably are nonspecific binding of Cd to normal cell components. The 13,800 molecular weight (109)Cd-bound component was found to be inducible by cadmium. It had a high ultraviolet absorbance at 254 nm and a low absorbance at 280 nm at pH 8.6.

Journal Article↗

PubMed1980

Organic Acids and Ionic Balance in Xylem Exudate of Wheat during Nitrate or Sulfate Absorption.

Experiments were designed to study the importance of organic acids as counterions for K(+) translocation in the xylem during excess cation uptake. A comparison was made of xylem exudate from wheat seedlings treated 72 hours with either 1.0 millimolar KNO(3) or 0.5 millimolar K(2)SO(4), both in the presence of 0.2 millimolar CaSO(4). Exudation from KNO(3) plants had twice the volume and twice the K(+) and Ca(2+) fluxes or rate of delivery to shoots, as K(2)SO(4) plants. Malate flux was 25% higher in K(2)SO(4) than in KNO(3) exudate. Malate was the principal anion accompanying K(+) or Ca(2+) in K(2)SO(4) treatment, while in the KNO(3) treatment, NO(3) (-) was the principal anion. The contribution of SO(4) (2-) was negligible in both treatments. In a second experiment, exudate was collected every 4 hours during the daytime throughout a 72-hour treatment with KNO(3). Malate was the only anion present in exudate at first, just after the CaSO(4) pretreatment had ended. Malate concentration decreased and NO(3) (-) concentration increased with time and these concentrations were negatively correlated. By 62 hours, NO(3) (-) represented 80% of exudate anions. K(+) and NO(3) (-) concentrations in exudate were strongly correlated with K(+) and NO(3) (-) uptake, respectively. The first 36 hours of absorption from KNO(3) solution resembled the continuous absorption of K(2)SO(4), in that malate was the principal counterion for translocation of K(+).

Journal Article↗

PubMed1978

Cation pretreatment effects on nitrate uptake, xylem exudate, and malate levels in wheat seedlings.

Week-old wheat seedlings absorbed at least 40% NO(3) (-) from NaNO(3) when preloaded with K(+) than when preloaded with Na(+) or Ca(2+). Cultures of Triticum vulgare L. cv. Arthur were grown for 5 days on 0.2 mm CaSO(4), pretreated for 48 hours with either 1 mm CaSO(4), K(2)SO(4), or Na(2)SO(4), and then transferred to 1 mm NaNO(3). All solutions contained 0.2 mm CaSO(4). Shoots of K(+)-preloaded plants accumulated three times more NO(3) (-) than shoots of the other two treatments. Initially, the K(+)-preloaded plants contained 10-fold more malate than either Na(+)- or Ca(2+)-preloaded seedlings. During the 48-hour treatment with NaNO(3), malate in both roots and shoots of the K(+)-preloaded seedlings decreased. Seedlings preloaded with K(+) reduced 25% more NO(3) (-) than those preloaded with either Na(+) or Ca(2+). These experiments indicate that K(+) enhanced NO(3) (-) uptake and reduction even though the absorption of K(+) and NO(3) (-) were separated in time. Xylem exudate of K(+)-pretreated plants contained roughly equivalent concentrations of K(+) and NO(3) (-), but exudate from Na(+) and Ca(2+)-pretreated plants contained two to four times more NO(3) (-) than K(+). Therefore K(+) is not an obligatory counterion for NO(3) (-) transport in xylem.

Journal Article↗

PubMed1978

Role of potassium and malate in nitrate uptake and translocation by wheat seedlings.

Wheat seedlings (Triticum vulgare) treated with 1 mm KNO(3) or NaNO(3), in the presence of 0.2 mm CaSO(4), were compared during a 48-hour period with respect to nitrate uptake, translocation, accumulation and reduction; cation uptake and accumulation; and malate accumulation. Seedlings treated with KNO(3) absorbed and accumulated more nitrate, had higher nitrate reductase levels in leaves but less in roots, accumulated 17 times more malate in leaves, and accumulated more of the accompanying cation than seedlings treated with NaNO(3). Within seedlings of each treatment, changes in nitrate reductase activity and malate accumulation were parallel in leaves and in roots. Despite the great difference in malate accumulation, leaves of the KNO(3)-treated seedlings had only slightly greater levels of phosphoenolpyruvate carboxylase than leaves of NaNO(3)-treated seedlings. NADP-malic enzyme levels increased only slightly in leaves and roots of both KNO(3)- and NaNO(3)-treated seedlings. The effects of K(+) and Na(+) on all of these parameters can best be explained by their effects on nitrate translocation, which in turn affects the other parameters. In a separate experiment, we confirmed that phosphoenolpyruvate carboxylase activity increased about 2-fold during 36 hours of KNO(3) treatment, and increased only slightly in the KCl control.

Journal Article↗

PubMed1970

Dipyridyl-induced Cell Elongation and Inhibition of Cell Wall Hydroxyproline Biosynthesis.

Incubation of soybean hypocotyl sections with 0.1 millimolar 2,2'-dipyridyl in the absence of auxin results in increases in growth rate and in cell wall extensibility lasting for about 3 hours. This is accompanied by greatly decreased biosynthesis of hydroxyproline, which ultimately appears in the wall, and in slightly reduced oxygen uptake, both of which continue for at least 9 hours. Continuous synthesis of hydroxyproline which appears in the cell wall is thus not necessary for short term growth. The decrease in growth and cell wall extensibility that occurs between the 3rd and 9th hours of dipyridyl inhibition cannot be attributed to cross-linking of newly synthesized hydroxyproline, since its synthesis is still inhibited.

Journal Article↗

PubMed1967

RNA and protein biosynthesis and the regulation of cell elongation by auxin.

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Carbon Isotopes↗

PubMed1967

The role of the external assessor in the diploma course for teachers of physiotherapy.

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Female↗

PubMed1966

Amino Acid and protein metabolism in bermuda grass during water stress.

The ability of Arizona Common and Coastal Bermuda grass [Cynodon dactylon (L.) Pers.] to synthesize amino acids and proteins during water stress was investigated. Amino acids were continually synthesized during the water stress treatments, but protein synthesis was inhibited and protein levels decreased.Water stress induced a 10- to 100-fold accumulation of free proline in shoots and a 2- to 6-fold accumulation of free asparagine, both of which are characteristic responses of water-stressed plants. Valine levels increased, and glutamic acid and alanine levels decreased.(14)C labeling experiments showed that free proline turns over more slowly than any other free amino acid during water stress. This proline is readily synthesized and accumulated from glutamic acid. It is suggested that during water stress free proline functions as a storage compound.No significant differences were found in the amino acid and protein metabolism of the 2 varieties of Bermuda grass.

Journal Article↗