David M. Orcutt

Biochemical composition of three algal species proposed as food for captive freshwater mussels

To identify potential diets for rearing captive freshwater mussels, the protein, carbohydrate (CHO), and lipid contents of two green algae, Neochloris oleoabundans, Bracteacoccus grandis, and one diatom, Phaeodactylum tricornutum, were compared at different growth stages. The fatty acid and sterol composition were also identified. Protein was greatest (55–70%) for all species at late log growth stage (LL), and declined in late stationary (LS) growth. CHO was greatest at LS stage for all species (33.9–56.4% dry wt). No significant change in lipid levels occurred with growth stage, but tended to increase in N. oleoabundans. Mean lipid content differed significantly in the order: N. oleoabundans > P. tricornutum > B. grandis. Total fatty acids (TFA) were higher at LS stage compared to other stages in the two green algae, and stationary stage in the diatom. Mean unsaturated fatty acids (UFA) as %TFA was significantly higher in N. oleoabundans than the other species. The green algae contained high percentages of C-18 polyunsaturated fatty acids (PUFAs), while the diatom was abundant in C-16 saturated and mono-unsaturated fatty acids and C-20 PUFA fatty acids. Growth stage had no effect on sterol concentration of any species. B. grandis showed significantly higher sterol levels than the other species except P. tricornutum at S stage. B. grandis was characterized by predominantly Δ5, C-29 sterols, while N. oleoabundans synthesized Δ5,7, Δ5,7,22 , and Δ7, C-28 sterols. P. tricornutum produced primarily a Δ5,22, C-28 sterol, and a small amount of a Δ7,22, C-28 sterol.

Evaluation of the mechanism of action of the bleaching herbicide SC-0051 by HPLC analysis

Abstract The accumulation of leaf pigments in soybean [ Glycine max (L.) Merr. cv. Essex] plants treated with the bleaching herbicides norflurazon (20 ppm, w w ) and SC-0051 (2.5 ppm, w w ) was investigated by means of high-performance liquid chromatography analysis. SC-0051 is a new experimental herbicide whose chemistry has not been released. Both SC-0051 and norflurazon reduced the relative concentrations of xanthophylls, chlorophylls, and colored carotenoids and induced the accumulation of the colorless carotene, phytoene, in the leaves of treated soybeans. These results confirm that the mechanism of the bleaching action of the herbicide SC-0051 is similar to that of norflurazon and includes the inhibition of the desaturation reactions of carotenoid biosynthesis. In addition to their phytoene-accumulating activity, both SC-0051 and norflurazon induced the accumulation of an additional pigment which was not present in leaf extracts obtained from untreated soybeans. Although the exact identity of this pigment is unknown, it appears to be a derivative of phytoene.

LIPIDS IN BLUE‐GREEN ALGAL MATS (MODERN STROMATOLITES) FROM ANTARCTIC OASIS LAKES1

Lipids comprising the stenols, stanols, polar lipid fatty acids, alkanes and alkenes of blue‐green algal‐(diatomaceous)‐microbial mats and cores (modern cold water stromatolites) collected from three Antarctic lakes were identified and compared with those of other algae. The major stenols were: (cholesta‐5, 22‐dien‐3β‐ol, cholest‐5‐en‐3β‐ol, 24‐methylcholesta‐5, 22‐dien‐3β‐ol, 24‐methyl‐cholest‐5‐en‐3β‐ol, 24‐ethylcholesta‐5, 22‐dien‐3β‐ol, and 24‐ethylcholest‐5‐en‐3β‐ol). The presence of C28 Δ3, 22 stenols, as well as other C28 stenols, was suggestive of diatom input. C29 stenols may have originated from blue‐grern algae. However, the high concentrations of stenols present and the lack of Δ7 stenols was atypical for known stenol components of several blue‐green algal species previously reported. The occurrence of these stenols and other lipid markers strongls implicate diatoms as well as blue‐green algae as important biogenetic sources of lipids and has established the potential for studies of lipid diagenesis in these unique cold, freshwater stromatolites.

Influence of drought on the concentration and distribution of 2,4-diaminobutyric acid and other free amino acids in tissues of flatpea (Lathyrus sylvestris L.)

2,4-Diaminobutyric acid (A2bu) may be responsible for the apparent toxicity of flatpea (Lathyrus sylvestris L.) forage to some livestock. To obtain information relative to environmental regulation of A2bu, 3-month old flatpea plants, cv. “Lathco”, were subjected to water-deficit stress for 1, 2, and 4 weeks. A2bu, the most abundant free amino acid in roots, stems, and leaves, increased nearly 100% in roots of stressed plants. Increases in the concentrations of asparagine (Asn), proline (Pro), and arginine (Arg) occurred in roots; Asn, Pro, and 4-aminobutyric acid (Abu) in stems; and Pro and homoserine (Hse) in leaves also occurred in response to drought stress. Proline was a minor constituent of the free amino acid pool, even under water-deficit stress. The distribution of A2bu and Pro in the stressed plants (roots > stems > leaves) was the reverse of that in plants supplied with adequate water (roots < stems < leaves). As concentrations of Asn and Abu decreased from roots to leaves in control tissues, concentrations of Hse and A2bu increased in roughly the same proportions. This observation suggests that Abu and Asn may be precursors of A2bu and Hse, respectively. The increase in A2bu levels in aerial parts of drought-stressed flatpea plants is probably not sufficient to lower the feed value of the forage.

Effects of temperature on triazine-resistant weed biotypes

Abstract Studies were initiated to determine the effects of different temperature regimes on triazine-resistant and -susceptible biotypes of common lambsquarters ( Chenopodium album L.) and smooth pigweed ( Amaranthus hybridus L.) from different geographical locations. Shoot height, weight, chlorophyll a and b content and fatty acid content of common lambsquarters and smooth pigweed were determined at 18/14, 26/22 or 36/26°C. Common lambsquaters biotypes from Virginia, Maryland and Switzerland were examined. These data indicate common lambsquarters biotypes had a differential growth response to temperature, but no relationship between triazine resistance or susceptibility was noted in response to temperature with the parameters used in these studies. Differences in growth were detected between triazine-resistant and -susceptible smooth pigweed biotypes which indicated that the susceptible biotypes were vigorous at lower temperatures than triazine-resistant biotypes. Chlorophyll analyses indicated that all triazine-resistant biotypes of common lambsquarters and smooth pigweed had lower chlorophyll a / b ratios than triazine-susceptible biotypes at all temperature regimes. An increase in saturated fatty acids was found in both triazine-resistant and -susceptible biotypes of common lambsquarters at higher temperatures. At higher temperatures, the triazine-susceptible biotype of smooth pigweed contained a higher unsaturated fatty acid ratio.

Pyridazinone (BASF 13-338) alleviation of ethanol-induced stress effects on the growth and lipid composition of Chlorella vulgaris

Abstract Ethanol at 0.33% completely inhibited growth of Chlorella vulgaris after about 30 hr, causing increases in cellular concentrations of triglycerides, free sterols, and phosphatidylcholine. The ratio of linoleate to linolenate decreased in the triglyceride and free fatty acid fractions, while the double bond index increased as a result of ethanol treatment. Combined treatments of ethanol and [4-chloro-5-(dimethylamino)-2-phenyl-3(2H) pyridazinone (BASF 13-338) resulted in partial alleviation of growth inhibition and a reversal of the ethanol-induced lipid effects. In addition, BASF 13-338 caused a qualitative change in the sterol composition of the alga, resulting in the accumulation of sterol precursors. In as much as BASF 13-338 reportedly inhibits the synthesis of linolenate from linoleate and now affects sterol synthesis in C. vulgaris, it is possible that the alleviation of ethanol-induced stress could be via alteration of unsaturated fatty acid and/or sterol synthesis.

Nonprotein amino acid composition of flatpea (Lathyrus sylvestris L.) as affected by ethephon seed treatments and seedling fertilization

Use of flatpea (Lathyrus sylvestris L.) as a forage is limited because of nonuniform seed germination and the potentially toxic effects of 2,4-diaminobutyric acid (A2bu), a nonprotein amino acid found in seeds and vegetative tissues. The effects of ethephon (2-chloroethyl phosphonic acid) on seed germination, amino acid leachates of seeds, and amino acid composition (particularly A2bu) of seedlings were investigated. Germination of flatpea seeds, imbibed for 16 h in 0, 100, 200, 400, 800, and 1600 mg/L ethephon, did not differ, but amino acid leachates tended to increase up to 200 mg/L ethephon and then decline at higher concentrations. The major amino acid constituents in leachates were A2bu, 4-aminobutyric acid (Abu), and homoserine (Hse). Dry matter accumulation of seedlings grown from ethephon-treated seeds was reduced for second cuttings grown from ethephon-treated seeds and high nitrogen grown plants. During regrowth, free amino acid accumulation was most pronounced in leaves of plants supplied with high nitrogen. The most abundant free amino acids in flatpea tissues were the same as those in seed leachates, but concentration and relative abundance varied with nitrogen level, plant part, and ethephon treatment. Results suggest that ethephon seed treatments can have persistent effects on the growth and amino acid composition of flatpea seedlings grown under different nitrogen regimes.