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The identity, composition, and concentration of the total, free, esterified, and glycosidic sterol fractions were determined during germination of tobacco seeds. The total, free, and esterified sterols increased, with stigmasterol and campesterol accounting for most of the increase. Steryl glycosides decreased during germination, and stigmasteryl and sitosteryl glycosides showed the largest decrease. During germination, sitosterol was the major sterol in all fractions but stigmasterol and campesterol showed the greatest changes. The fatty acid composition of the steryl esters and acylated steryl glycosides most closely resembled the di-and triglycerides.Four sterol forms have been isolated from higher plants; namely free sterol, steryl ester, steryl glycoside, and acylated steryl glycoside (2,5,11). The physiological function of these various sterol forms have never been established. It has been postulated that the free sterols are an integral part of plant cell membranes (8,15), in a manner similar to cholesterol in mammalian membranes; and that these sterols may influence cell permeability (10, 11). From in vitro enzyme studies with soybean seeds Hou et al. (12) have suggested that the steryl glycosides may serve in the storage of sterols. Least defined is the role of the steryl esters; however, analogous with the cholesteryl ester in animals, it might be possible that the steryl esters are involved in the transport of sterols.A number of higher plants at various physiological stages have been analyzed for sterols in the hope of explaining the physiological functions of the different sterol forms (2,5,12,13,15,16) (16). They examined the free and esterified sterol changes in 4-to 14-day-old corn seedlings. On a per seedling basis they found an increase in the free sterol content with seedling development; however, they did not isolate the steryl glycosides. Our study was undertaken to characterize the free, esterified, and glycosidic sterols during seed germination. MATERIALS AND METHODSGermination of Seeds. Tobacco seeds (Nicotiana tabacum L. var. Burley 21) were germinated on Whatman No. 3 filter paper in covered transparent plastic trays. Both ends of the filter paper were submerged in distilled water to insure constant moisture. Seeds were germinated at 27 C, relative humidity of 90 to 100% and a 14-hr day produced with coolwhite fluorescent lamps. By visual inspection seeds germinated uniformly, with radicle protrusion occurring between 2 and 2.5 days.Chlorophyll Determination. Tobacco seedlings were homogenized with an Omni-Mixer in 80% (v/v) acetone and approximately 4 g of fine glass beads (0.05-0.45 mm). The acetone extract was centrifuged at 20,000g for 10 min. The supernatant was made to 100 ml with 80% acetone and the absorbancies were measured at 663, 645, and 480 nm with the Hitachi Perkin-Elmer 139 spectrophotometer. The chlorophyll concentration was determined from the nomogram of Kirk (17). Changes in carotenoid content were estimated by correcting the absorbancy at 480 nm for contribu...

The following sterols were identified in barley shoots: stigmasterol, 8-sitosterol, campesterol, and cholesterol. The total sterol content of green and etiolated tissue was 2.84 and 3.20 milligrams per gram dry weight, respectively. The free sterols accounted for most of the difference in total sterol content. The sterol ester, sterol glycoside, and acylated sterol glycoside contents of green and etiolated barley shoots were essentially the same. Etiolated tissue had twice as much total 8-sitosterol as stigmasterol, while green tissue had equal amounts of these two sterols. The campesterol and cholesterol content was the same in green and etiolated tissue. This same sterol composition pattern held true for the free, glycosidic, and acylated glycosidic sterols; however, the sterol ester fraction had a completely different composition pattern. The esterified stigmasterol content was quite low in green and etiolated tissue, and campesterol was the second largest esterfied sterol component in etiolated tissue. Etiolated barley seedlings exposed to light had a shift in the ratio of free stigmasterol to 6-sitosterol in favor of stigmasterol; however, no correlation was observed between chlorophyll synthesis and shift in sterol composition. Goodwin and Mercer (8) The barley shoots were homogenized in twice the amount of acetone (w/v) and extracted in a Soxhlet apparatus for 24 hr. A measured aliquot of acetone extract (about 5 g dry weight equivalent) was taken to dryness under vacuum and applied in n-hexane to a silica gel column for serial elution (7,22). A 1.5-cm diameter column was packed with 30 g of silica gel (70-325 mesh) as a slurry in n-hexane. Serial elution was carried out as follows: 150 ml of n-hexane followed by 150 ml of 10% benzene in n-hexane (discard); 700 ml of 40% benzene in nhexane (sterol esters); 150 ml of 100% benzene followed by 800 ml of chloroform (free sterols); 700 ml of 2% methanol in chloroform (acylated sterol glycosides); and 600 ml of 5% methanol in chloroform (sterol glycosides). The four sterolcontaining fractions were taken to dryness under vacuum. Added to the sterol ester fraction were 30 ml of 5% KOH in 95% methanol, and the fraction was refluxed for 30 min to hydrolyze the ester linkage. The free sterol fraction was dissolved in 30 ml of 95% methanol and heated for a few minutes. Added to the acylated sterol glycoside and sterol glycoside fraction were 30 ml of 95% methanol containing 0.15 ml H2SO4, and the fraction was refluxed for 12 hr to hydrolyze the glycosides.Analysis for total sterols was carried out by a modified method of Stedman and Rusaniwskyj (24). A measured aliquot (about 5 g dry weight equivalent) of acetone extract was taken to dryness and 25 ml of 95% ethanol containing 0.13 ml H2SO4 were added to the sample, refluxed for 12 hr, and cooled; then 15 ml of 10% KOH in 95% ethanol were added and the fraction was refluxed for 30 min. This sample gave total sterols since all glycosides and esters had been hydrolyzed.The sterols were extracted from all the ...

Hair, muscle, and liver mercury concentrations were determined in river otter (Lutra canadensis) carcasses collected from the lower coastal plain and piedmont of Georgia. Mean muscle and hair mercury concentrations were greater (P < 0.001) in otters from the lower coastal plain (4.42 and 24.25 mg/kg wet wt, respectively) compared to otters from the piedmont (1.48 and 15.24 mg/kg, respectively). Liver tissue from lower coastal plain otters averaged 7.53 mg/kg mercury. Mean fetus brain and muscle mercury concentrations were 1.03 and 1.58 mg/kg wet wt, respectively, and fetal muscle mercury concentrations were correlated (r = 0.92) with maternal muscle mercury concentrations. Comparison of mercury concentrations found in Georgia otters to those associated with adverse effects in otter and mink (Mustela vison), indicate sublethal contamination with concentrations in some individuals approaching that observed in experimentally dosed individuals that developed clinical signs of mercurialism. Mercury concentrations in fish from the lower coastal plain approached or exceeded concentrations demonstrated to be toxic to experimentally dosed otters.

Clopyralid, picloram, triclopyr, metsulfuron, and tebuthiuron were applied to control kudzu on four loblolly pine forest regeneration sites during July 1997. Spot treatments were applied to recovering kudzu in June 1998 and June 1999. Soil leachate was monitored for these five herbicides from July 1997 to December 2000. All herbicides were detected in shallow (51–58 cm deep) and deep lysimeters (84–109 cm deep). Clopyralid was not persistent and limited leaching occurred, with residue levels of 0.4 to 2.8 μg L−1in 12 of 102 deep lysimeter samples. Picloram was mobile and persisted at 0.6 to 2.5 μg L−1in shallow and deep lysimeters for at least 10 mo after the initial application. Triclopyr residues were not persistent in shallow lysimeters and remained &lt; 6 μg L−1during the study. Metsulfuron persisted at &lt; 0.1 μg L−1for 182 to 353 d in shallow lysimeters and at &lt; 0.07 μg L−1for 182 to 300 d in the deep lysimeters in various plots. Tebuthiuron peaks in the deep lysimeters ranged from 69 to 734 μg L−134 to 77 d after the first spot treatment. In the soil that was essentially a fill area, tebuthiuron residues remained &gt; 400 μg L−1(402–1,660 μg L−1) in the shallow lysimeter samples and &gt; 180 μg L−1(181–734 μg L−1) in the deep lysimeters throughout a 354-d period that followed the first spot application. When used as part of a forest regeneration program, the relative potentials of the herbicides to move into shallow groundwater were: tebuthiuron &gt; picloram &gt; metsulfuron &gt; clopyralid &gt; triclopyr.