THE GROWTH AND DIFFERENTIATION OF CULTURED BARLEY EMBRYOS

Norstog , Knut . (Wittenberg U., Springfield, Ohio.) The growth and differentiation of cultured barley embryos. Amer. Jour. Bot. 48(10): 876–884. Illus. 1961.—Cultures of excised embryos of barley, Hordeum vulgare L., were made on a number of different media. Growth on White's medium was promoted by adding coconut milk. In the absence of coconut milk, amino acids did not promote growth and differentiation. Embryos as small as 60 μ were successfully grown in vitro. Smaller embryos had the capacity to initiate root and shoot primordia but did not possess the ability to form such embryonic organs as the scutellum and epiblast. Proembryos developed shoots and roots only after a period of irregular growth in which unorganized masses of cells were formed. Multiple centers of shoot initiation were observed in such embryos. The results of the study suggest that, in barley at least, embryonic form may result from an interaction between the embryo and nutritional, spatial and other factors within the ovule.     

Age of European silver eels during a period of declining abundance in Norway

The European eel (Anguilla anguilla) is critically endangered throughout its range. Knowledge about age distribution of future spawners (silver eels) is essential to monitor the status and contribute to the recovery of this species. Determination of age in anguillid eels is challenging, especially in eels from the northern part of the distribution area where growth is slow and age at maturation can be up to 30 years or more. Eels from the river Imsa in Norway have been monitored since 1975, and this reference time series has been used to assess the stock at the European level. Population dynamics in this catchment were analyzed during the late 1980s by estimating ages on whole cleared otoliths. However, techniques for revealing annual increments on otoliths have evolved over the years sometimes yielding significant differences in age estimates. In this study, the historical otolith data were reanalyzed using a grinding and polishing method rather than reading the whole otolith. The new age estimates were considerably higher than the previous ones, sometimes by up to 29 years. Since the 1980s, mean age of silver eels only slightly increased (from 19 to 21 years in the 2010s). This was mainly due to the disappearance of younger silver eels (<15 years) in the 2010s. The new age estimates agreed with the steep decline in recruitment which occurred in the late 1980s in the Imsa catchment. Mean growth (30 mm/year, min–max: 16–64 mm/year) has not changed since the 1980s, although density in the catchment has decreased. Revealing and reading age of slow‐growing eels remain a challenge but adding a measure of otolith reading uncertainty may improve age data collection and contribute to recovery measures for this species.     

Product profiles in enzymic and non-enzymic oxidations of the lignin model compound erythro-1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)-1,3-propanediol

The erythro form of the lignin model compound 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)-1,3-propanediol (1) was oxidized with laccase/ABTS, lead(IV) tetraacetate (LTA), lignin peroxidase/H₂O₂, cerium(IV) ammonium nitrate (CAN) and Fenton's reagent. The product profiles obtained with the different oxidants were compared after separation, identification and quantification of the products using HPLC, UV-diode array detector and electrospray ionization mass spectrometry in positive ionization mode. The oxidants generated different product profiles that reflected their different properties. Oxidation with laccase/ABTS resulted almost exclusively in formation of 1-(3,4-dimethoxyphenyl)-3-hydroxy-2-(2-methoxyphenoxy)-1-propanone (2). Oxidation with LTA resulted in more 3,4-dimethoxybenzaldehyde (3) than ketone 2. Lignin peroxidase and CAN gave similar product profiles and aldehyde 3 was the predominant product (only small amounts of ketone 2 were formed). Oxidation with Fenton's reagent resulted in the formation of more aldehyde 3 than ketone 2 but the yields were very low. CAN served as an excellent model for the lignin peroxidase-catalyzed oxidation, while the laccase-mediator system, LTA and Fenton's reagent provided distinctly different product profiles. Erythro-1-(3,4-dimethoxyphenyl)-1,2,3-propanetriol was present among the products obtained on oxidation with LTA, lignin peroxidase, CAN and Fenton's reagent. The differences in redox potential between the oxidants afford an explanation of the diverse product patterns but other factors may also be of importance. The reactions leading to cleavage of the β-ether bond with formation of 1-(3,4-dimethoxyphenyl)-1,2,3-propanetriol (veratrylglycerol) were found to proceed without affecting the configuration at the β-carbon atom.     

Molecular characterization of the cai operon necessary for carnitine metabolism in Escherichia coii

The sequence encompassing the cai genes of Escherichia coli, which encode the carnitine pathway, has been determined. Apart from the already identified caiB gene coding for the carnitine dehydratase, five additional open reading frames were identified. They belong to the caiTABCDE operon, which was shown to be located at the first minute on the chromosome and transcribed during anaerobic growth in the presence of carnitine. The activity of carnitine dehydratase was dependent on the CRP regulatory protein and strongly enhanced in the absence of a functional H-NS protein, in relation to the consensus sequences detected in the promoter region of the cai operon. In vivo expression studies led to the synthesis of five polypeptides in addition to CaiB, with predicted molecular masses of 56 613 Da (CaiT), 42 564 Da (CaiA), 59311 Da (CaiC), 32 329 Da (CaiD) and 21 930 Da (CaiE). Amino acid sequence similarity or enzymatic analysis supported the function assigned to each protein. CaiT was suggested to be the transport system for carnitine or betaines, CaiA an oxidoreduction enzyme, and CaiC a crotonobetaine/carnitine CoA ligase. CaiD bears strong homology with enoyl hydratases/isomerases. Overproduction of CaiE was shown to stimulate the carnitine racemase activity of the CaiD protein and to markedly increase the basal level of carnitine dehydratase activity. It is inferred that CaiE is an enzyme involved in the synthesis or the activation of the still unknown cofactor required for carnitine dehydratase and carnitine racemase activities. Taken together, these data suggest that the carnitine pathway in E. coli resembles that found in a strain situated between Agrobacterium and Rhizobium.     

Nitrogen cycling and storage in <Emphasis Type="Italic">Gagea spathacea</Emphasis> (Liliaceae): ecological insights for protecting a rare woodland species

Strategies to globally protect biological diversity are often hampered by an insufficient ecological knowledge about target species. This also applies to Gagea spathacea (Liliaceae), a ‘vulnerable’ woodland spring geophyte with a distribution largely restricted to the lowlands of Central Europe. We studied whether the species’ linkage to highly fertile forest soils is related to its high nitrogen (N) demands during its short developmental cycle. We hypothesized that the species exhibits a highly efficient N (re)cycling strategy, characterized by efficient resorption of N from the leaves and reallocation to bulbs at the end of the growing season. To test this assumption, we conducted a ¹⁵N tracer experiment and quantified ¹⁵N flows between soil, leaves, bulbs, and roots. Our findings support our hypothesis that G. spathacea is exceptionally efficient in recycling N, shown by the resorption of 68% of leaf N and its reallocation to bulbs at the end of the growing season. After 6 weeks of growth the plant showed a distinct shift in its N metabolism: The C:N ratio of leaves strongly increased and those of bulbs decreased, leaf ¹⁵N enrichment and recovery started to decrease, while total plant ¹⁵N recovery remained constant, indicating no further N uptake from the soil. Leaf N reallocation to bulbs was accompanied by a twofold increase of the bulbs’ biomass. Because of the stenoecious behaviour of G. spathacea, a careful protection and sustainable management of G. spathacea forest habitats is necessary, particularly in its Central European core area.     

Midribs of cycad pinnae

Comparisons of midribs of three cycad genera,Chigua, Cycas, andStangeria, the only three genera characterized by midribs in the pinnae, show that those ofChigua andStangeria are very similar to each other and quite unlike those ofCycas. Midribs ofCycas include a single, median vein, and the pinnae of these species lack lateral veins. Pinnae midribs ofChigua andStangeria include several (2–5 and 2–8, respectively) longitudinal parallel veins, and dichotomizing lateral veins arising from the midrib. Pinnae of other cycads, includingZamia, with whichChigua appears to be most closely allied, exhibit evenly spaced, longitudinally parallel, dichotomizing veins, a character considered to be primitive. All veins in cycad leaves have a single mesarch protoxylem pole. The midrib condition inChigua andStangeria represents an advanced state in comparison to that in the leaf of the Marattiales, for example, where there is a single veined midrib but with numerous mesarch protoxylem poles. It would appear that the midrib has been derived independently at least three times within the cycads, once in each major group.