Hans Gfeller

Incorporation of atmospheric 15NO2-nitrogen into free amino acids by Norway spruce Picea abies (L.) Karst.

During spring and autumn 1991, potted 6-yearold spruce trees (Picea abies (L.) Karst.) were fumigated with 60 nl·1−115NO2 for 4 days under controlled conditions in constant light. Current and previous flush needles, the bark and the fine roots were analysed for total 15N content and incorporation of 15N into the α-amino nitrogen of free amino acids. In addition, in vitro nitrate reductase activity and stomatal conductance of the needles were measured. Nitrate reductase activity was significantly higher in the needles of fumigated trees compared to control trees exposed to filtered air. With an average of 9.1% 15N, free glutamate was the pool with the most label. Taking into account the time-course of the labelling of this pool, this figure can be taken as an estimate of the minimum contribution of NO2 to the N nutrition of the needles. 15N-labelled amino acids were also detected in the bark and the roots, indicating export from the needles.

Sequestration ofVeratrum alkaloids by specialistRhadinoceraea nodicornis konow (Hymenoptera, Tenthredinidae) and its ecoethological implications

The larvae of the specialist sawflyRhadinoceraea nodicornis Konow (Hymenoptera, Tenthredinidae) store in their hemolymph ceveratrum alkaloids originating from the host plantVeratrum album L. (Liliales, Melanthiaceae). The major alkaloid found in the hemolymph is 3-acetyl-zygadenine. Qualitative and quantitative data showed that the plant alkaloid 3-angeloylzygadenine is most probably metabolized in the larval gut to zygadenine and then acetylated. A still unidentified alkaloid with a molecular weight of 591 Da was detected in plant leaves as well as in the gut, hemolymph, and excrement of larvae. Protoveratrine A and B, on the other hand, seem to be degraded by the larvae. These findings indicate that the pathway of ceveratrum alkaloids inR. nodicornis larvae is fourfold: direct sequestration, metabolism followed by sequestration, excretion of intact alkaloids, and degradation. In contrast, no ceveratrum alkaloids were detected in the hemolymph and excrement of larvae of the generalist sawflyAglaostigma sp. fed withV. album leaves. Bioassays with the antMyrmica rubra L. proved that the hemolymph ofR. nodicornis larvae is highly deterrent and toxic. In bioassays evaluating defensive efficiency against predators (ants, spiders, and bushcrickets), no larvae were eaten. Ceveratrum alkaloids were also detected in the hibernating prepupae ofR. nodicornis. In feeding bioassays, the shrewCrocidura russula Hermann rarely fed upon prepupae, suggesting that this stage is also protected from predation to some degree. In field surveys, the only parasitoids recorded were two ichneumonid species that are believed to be specialized onR. nodicornis. Bioassays and field observations enable us to suppose thatR. nodicornis and its enemies produce a food web of ion connectance.

1(3),2-Diacylglyceryl-3(1)-O-2′-(hydroxymethyl)(N,N,N,-trimethyl)-β-alanine (DGTA): A novel betaine lipid from Ochoromonas danica (Chrysophyceae)

Abstract The structure of lipid B, another betaine lipid from Ochromonas danica (Crysophyceae) has been elucidated by NMR, MS and IR data from the intact lipid and from derivatives obtained by chemical degradation. The structure of 1(3),2-diacylglyceryl-3(1)- O -2′- (hydroxymethyl)( N , N , N -trimethyl)-β-alanine (DGTA) has been assigned to the intact lipid which is a structural isomer of the already known homoserine lipid or 1(3),2-diacylglyceryl-3(1)- O -4′-( N , N , N -trimethyl)-homoserine (DGTS). 1(3),2- Diacylglyceryl-3(1)- O -2′-(hydroxymethyl)-propenoic acid was obtained from DGTA by deamination in chloroform with traces of formic acid. 1(3),2-diacylglycerol-3(1)- O -2′-(hydroxymethyl)-propanoic acid methyl ester was formed by treatment of DGTA with diazomethane in the presence of formic acid and by subsequent hydrogenation. From this compound, the corresponding diacetyl derivative was obtained by trans -esterification and acetylation. The diacetate was identical with synthetic 1(3),2-diacetylglyceryl-3(1)- O - 2′-(hydroxymethyl)-propanoic acid methyl ester, the preparation of which, starting from isopropylideneglycerol and 2-(bromomethyl)-acrylic acid methyl ester, is described. DGTA accounts for approximately 5% of the total lipids of O. danica . The major fatty acids of DGTA are 22:5 (42%), 18:0 (15%), 20:4 (13%); 20:2 (6%), 18:1 (5%), 20:3 (4%) 18:2 (4%), 22:4 (3%) and 16:0 (2%). From DGTA, trimethylamine is produced by a spontaneous deamination.

The Secretion of the Ventral Glands in Hoplocampa Sawfly Larvae

The defensive secretion of the ventral glands of both species, Hoplocampa testudinea and H. flava is mainly composed of acetogenins. Major compounds are (E)-2-octenal, (E,Z)- and (E,E)-2,4-decadienal and (E,Z,Z)-2,4,7-decatrienal that was identified for the first time in an insect. Benzaldehyde is abundant in H. flava. A comparison of Hoplocampa with taxonomically related genera suggests that, for those acetogenins present as major compounds in the secretion, the chain length decreased during evolution of nematine sawflies. Only the last larval instar of Hoplocampa species produces large amounts of secretions. For H. testudinea, the last instar as compared with previous ones was more efficiently protected against ants in a bioassay, and possessed allometrically larger glands. Hoplocampa larvae live concealed within the fruit that they infest until dropping off the plant for pupation in the soil. The relative importance during the ontogeny of the mechanical protection offered by the fruit and the chemical defence provided by the ventral glands is discussed, also with respect to field observations on the interactions between ants and sawfly larvae. Our hypothesis is that nematine sawfly larvae with a concealed life style will show a relative reduction in glandular size and defensive significance of the glandular secretion.

Phosphatidyl-O-[N-(2-Hydroxyethyl)Glycine] (PHEG), a New Glycerophospholipid from Brown Algae (Phaeophyceae)

Summary The phosphoglyceride phosphatidyl- O -[ N (2-hydroxyethyl)glycine] (PHEG) has been isolated from Fucus serratus L. (Fucales, Phaeophyceae) and its structure determined by IR, NMR, MS and chemical data of the intact lipid (formerly called PX), its lyso compound and the deacylated lipid. The fatty acid composition was about 82 mol% 20: 4, 9% 20: 5 and 6% 20: 0 acids in both the sn -1 and the sn -2 positions of the glycerol part. PHEG was present in 30 different species representing the 16 orders of brown algae in amounts of 8–25 mol% of total phospholipids, and is suggested to be a compulsory lipid constituent of brown algae.

Gas chromatographic-mass spectrometric identification of betaine lipids in Chroomonas salina

Abstract The betaine lipids diacylglycerylhydroxymethyltrimethyl-β-alanine (DGTA) and diacylglyceryltrimethylhomoserine (DGTS) can be identified by derivatization of their polar groups. Demethylation, deacylation and silylation of DGTS yields demethyl-deacyl-DGTS-TMSi; dihydro-deamino-deacyl-DGTA-TMSi is produced by deamination, hydrogenation, deacylation and silylation of DGTA. The characterization of the derivatives by GC-MS was used as a diagnostic method for the identification of DGTA in Chroomonas salina, where this lipid accounts for 20% of the total polar lipids. Major fatty acids of DGTA (%) are 22:6n−3 (22), 20:5n−3 (14), 18:1n−7 (12), 18:4n−3 (11), 16:0 (8), and 14:0 (8), indicating that this lipid contains a broad variety of different molecular species in this alga.

Uptake and Distribution of NO2 in Norway Spruce (Picea Abies [L.] Karst.)

Potted spruce trees (Picea abies [L.] Karst.) were fumigated with NO2 or 15NO2 under controlled conditions in constant light. Current and previous flush needles, the bark and the fine roots were analysed for total 15N content and incorporation of 15N into the α-amino nitrogen of free amino acids. In addition, in vitro nitrate reductase activity and stomatal conductance of the needles were measured. In fumigated trees, nitrate reductase activity increased after a lag period of about four hours to levels which were five times higher than in controls exposed to filtered air. After a fumigation period of 24 hours nitrate reductase activity was linearly dependant on the NO2 concentration used for fumigation both in previous and current flush. With an average of 9.1% 15N, free glutamate was the pool with the most label. Taking into account the time-course of the labelling of this pool, this figure can be taken as an estimate of the minimum contribution of NO2 to the N nutrition of the needles. 15N labelled amino acids were also detected in the bark and the roots, indicating export from the needles. There were linear correlations between the stomatal conductance and the 15N uptake and between the 15N uptake and nitrate reductase activity.