Elicitation of volatile compounds in photomixotrophic cell culture of Petroselinum crispum

Photomixotrophic cells of Petroselinum crispum accumulated >500 mg chlorophyll per kg wet weight and grew well in a broad range of phytoeffector conditions. Autoclaved fungal cells were lethal for photoheterotrophic cells, but induced in photomixotrophic cells the formation of volatile n-alkanes, phthalides, coumarins, and elemicine. Most of the compounds elicited reached a concentration maximum between 20 and 30 h after addition of the mycelium, whereas the group of n-alkanes increased steadily during the 90 h monitored. Maximum concentrations were: 12 mg of graveolone, 1 mg of bergapten, 0.5 mg of sedanenolide, and 0.5 mg of n-tetradecane per 1 nutrient medium. A dose/effect relationship was found; 10 to 25 g of fungal wet weight per 1 culture medium resulted in maximum accumulation of volatiles. The formation of volatiles by photomixotrophic in vitro cells is discussed as an integral part of plant responses to ecological stress.     

The use of N-urethane-protected N-carboxyanhydrides (UNCAs) in amino acid and peptide synthesis

N-Urethane-protected N-carboxyanhydrides (UNCAs) are very reactives. They have been successfully used in peptide synthesis, in both solution and solid phase. We have demonstrated that UNCAs are interesting starting materials for the synthesis of various amino acid derivatives. Chemoselective reduction of UNCAs with sodium borohydride led the corresponding N-protected β amino alcohols. Reaction of UNCAs with Meldrum's acid, followed by cyclisation, yielded enantiomerially pure tetramic acid derivatives. Diastereoselective reduction of tetramic acid derivatives produced (4S,5S)-N-alkoxycarbonyl-4-hydroxy-5-alkylpyrrolidin-2-ones derived from amino acids, which after hydrolysis yielded statine and statine analogues. Tetramic acid derivatives could also be obtained by reaction of UNCAs with benzyl ethyl followed by hydrogenolytic deprotection and decarboxylation. UNCAs also reacted with phosphoranes to produce the ketophosphorane in excellent yields. Subsequent oxidation with oxone or with [bis(acetoxy)-iodol]-benzene produced vicinal tricarbonyl derivatives. These reactions usually proceeded smoothly and with high yields.     

Rhodium-catalyzed synthesis of 2(5H)-furanones from terminal alkynes and non-substituted alkynes under water-gas shift reaction conditions

Rhodium-catalyzed synthesis of 2(5H)-furanones from alkynes under water-gas shift reaction conditions was studied. By improving the reaction conditions for internal alkynes reported previously, the reaction could be extended to terminal alkynes. Terminal alkynes are selectively converted into 3- and 4-substituted 2(5H)-furanones (2 and 3). When acetylene itself is used, 2(5H)-furanone (2n) is obtained in a good yield. Examination of reaction solutions by IR spectroscopy and some other experimental findings suggest that the active species would be an alkyne-coordinated monomeric rhodium anion. A new reaction path is proposed.     

Leaf chemistry and food selection by common langurs (Presbytis entellus) in Rajaji National Park,Uttar Pradesh,India

Food selection in folivorous primates has been hypothesized to be correlated with leaf chemistry. To test this hypothesis, we conducted a 5-month study on Presbytis entellusin a moist deciduous forest in the Rajaji National Park,Uttar Pradesh, India. The study period covered two seasons, winter and spring. We used the percentage time spent feeding on each food item as an index of food selection, which we estimated from group scan data collected from one study group for 6 days each month. We estimated the selection ratio for each item as the ratio of time spent feeding to availability. We estimated food availability from vegetation sampling and phenological data in the home range of the study group. We estimated crude protein (CP), acid detergent fiber (ADF) and tannins in mature and young leaves of 12 major food species in the laboratory. Food selection is positively correlated with CP in winter and negatively correlated with ADF in both seasons. It also is correlated with CPJADF ratio, but to a lesser extent than the best predictor in winter and spring. Selection ratio is not correlated with CP and ADF in both seasons. It is probable that the inclusion of other factors, such as micronutrients,condensed tannins, and digestibility, might give a better prediction of food selection.     

Carbon dioxide consumption during soil development

Carbon is sequestered in soils by accumulation of recalcitrant organic matter and by bicarbonate weathering of silicate minerals. Carbon fixation by ecosystems helps drive weathering processes in soils and that in turn diverts carbon from annual photosynthesis-soil respiration cycling into the long-term geological carbon cycle. To quantify rates of carbon transfer during soil development in moist temperate grassland and desert scrubland ecosystems, we measured organic and inorganic residues derived from the interaction of soil biota and silicate mineral weathering for twenty-two soil profiles in arkosic sediments of differing ages. In moist temperate grasslands, net annual removal of carbon from the atmosphere by organic carbon accumulation and silicate weathering ranges from about 8.5 g m^–2 yr^–1 for young soils to 0.7 g M^–2 yr^–1 for old soils. In desert scrublands, net annual carbon removal is about 0.2 g m^–2 yr^–1 for young soils and 0.01 g m^–2 yr^–1 for old soils. In soils of both ecosystems, organic carbon accumulation exceeds CO₂ removal by weathering, however, as soils age, rates of CO₂ consumption by weathering accounts for greater amounts of carbon sequestration, increasing from 2% to 8% in the grassland soils and from 2% to 40% in the scrubland soils. In soils of desert scrublands, carbonate accumulation far outstrips organic carbon accumulation, but about 90% of this mass is derived from aerosolic sources that do not contribute to long-term sequestration of atmospheric carbon dioxide.     

Herbivory on calcicolous lichens: different food preferences and growth rates in two co-existing land snails

A total of 32 calcicolous lichen species, one alga and one bryophyte were recorded on a limestone wall in the grassland Great Alvar on the Baltic island of Öland, Sweden. Fourteen (41%) of these 34 species and free-living cyanobacteria showed herbivore damage, most probably due to grazing by the land snails Chondrina clienta and Balea perversa which inhabited the limestone wall. Three laboratory experiments were conducted to examine the food preferences of individuals of C. clienta and B. perversa collected at this site and to evaluate any association between their preference and the net food quality of the lichens to the snails. Chondrina clienta and B. perversa exhibited food preferences, which differed significantly between species. Within species, variation in food choice was similar among individuals. This indicates that snail populations may be composed of polyphagous individuals with similar food preferences. Different lichen species were of different net food quality to the snails as indicated by growth rate differences. In both snail species the most preferred lichen species of the choice experiment caused the largest weight increase in juveniles, viz. Caloplaca flavovirescens for C. clienta and Aspicilia calcarea for B. perversa. This suggest that the snail species studied differ in their abilities to deal with secondary compounds and physical characteristics of certain lichens or that they can utilize the energy and nutrients of these lichens to a different extent. It is suggested that differential food preferences might reduce the intensity of interspecific competition for resources (lichens) between C. clienta and B. perversa.     

Nutrient content and photosynthesis of young yellowing Norway spruce trees (Picea abies L. Karst.) following calcium and magnesium fertilisation

Severely yellowed ten-year-old spruce trees growing in the Vosges Mountains on an acidic soil were fertilised with Magnesium lime during the spring of 1990. The effects of this treatment were assessed 18 months later. A very significant improvement of the mineral status of the trees was detected, with increasing Mg contents in the needles, and as a consequence, reduced yellowing and improved chlorophyll content. Only slight differences with control trees were observed for height increase. Effects of this improved nutrition on photosynthesis were tested measuring net CO₂ assimilation rates and chlorophyll a fluorescence. Light-saturated net assimilation rates of current-year needles were high, reaching 5.3 mol m^–2 s^–1 on a total needle area basis. The improvement in chlorophyll and Mg content had no significant effect on net assimilation rates or on any parameter describing photochemical functions of both current-and previous-year needles. Despite the strong inter-individual variability in needle chlorophyll and Mg contents (ranging from 0.2 to 0.8 mg g^–1 fresh weight, and 0.05 to 0.5 mg g^-1 dry weight respectively), photochemical efficiency of PS II under limiting irradiance only decreased significantly on older needles displaying Mg contents below 0.1 mg g^–1. It is concluded from these results that spruce trees exhibit a high degree of plasticity with regard to Mg deficiency on acidic soils, and that improved Mg nutrition and increased chlorophyll content do not necessarily improve photosynthesis and height growth.Abbreviations A light-saturated net CO₂ assimilation rate (mol m^–2 s^–1) - g_w light-saturated needle conductance to water vapour (mmol m^–2 s^–1) - _wp and _wm pre-dawn and mid-day needle water potential (MPa) - osmotic potential of sap expressed from needles (MPa) - PFD photosynthetic photon flux density (mol m^–2 s^–1) - F_v/F_m photochemical efficiency of PS II after 20 min dark adaptation - F/F_m ^' photochemical efficiency of PS II reaction centres after 10 min at a PFD of 220 mol m^–2 s^–1     

Iron toxicity and other chemical soil constraints to rice in highland swamps of Burundi

Iron toxicity is suspected to be a major nutritional disorder in rice cropping systems established on flooded organic soils that contain reductible iron. A pot trial was carried out to assess Fe toxicity to rice in flooded Burundi highland swamp soils with a wide range of organic carbon contents. Soil and leaf analyses were performed and total grain weight was determined. Clear Fe toxicity was diagnosed, based on leaf Fe content at panicle differentiation. Leaf Fe contents higher than 250 g g^–1 dry matter induced lower Mg (and probably Mn) uptake, and a 50% total grain weight reduction. These features were associated with exchangeable Fe equivalent fractions higher than 86%. Besides, several non-Fe toxic soils exhibited an Mg-Mn imbalance.     

Plant growth and nutrient uptake characteristics of Fe-deficiency chlorosis susceptible and resistant subclovers

The objective of this study was to evaluate the growth and nutrient-uptake characteristics of Fe-deficiency resistant and susceptible subclover (Trifolium subterraneum L., T. yanninicum Katzn. and Morley, T. brachcalycinum Katzn. and Morley) cultivars on a calcareous soil. Ten subclover cultivars showing varying susceptibilities to Fe-deficiency chlorosis (Karridale, Nangeela, Geraldton, Mt. Barker, Woogenellup, Larisa, Trikkala, Rosedale, Koala and Clare) were grown on a low-Fe, calcareous soil (Petrocalcic Paleustoll) under moist (18% water content, 85% of water holding capacity) and water-saturated conditions using a Cone-tainer^® culture system. Chlorosis and its correlation with growth traits and mineral nutrition of the 10 cultivars were examined. The Fe-deficiency susceptibilities of the 10 cultivars decreased in the above order under the moist condition, but in slightly different order under the saturated condition. Shoot and root dry weights, total dry weight, and root-to-shoot ratio were each negatively correlated with chlorosis under both soil-moisture conditions, as was total shoot content of P, Ca, Fe, Mn and Zn. Shoot P and Fe concentrations were each positively correlated with chlorosis under the moist soil condition. Iron and Cu utilization efficiencies (biomass per unit weight of nutrient) in the shoot were each negatively correlated with chlorosis under the moist soil condition. These results suggest that there may be several characteristics of Fe-deficiency chlorosis resistance in subclovers, such as a more effective soil-Fe mobilizing mechanism(s), more balanced nutrition, lower required Fe concentration in the shoot, higher shoot-Fe utilization efficiency, and higher root/shoot ratio under Fe-deficiency stress conditions.     

Microbial transformation of ethylpyridines

Pyridine and its derivatives have been found as pollutants in the environment. Although alkylpyridines constitute the largest class of pyridines contaminating the environment, little information is available concerning the fate and transformation of these compounds. In this investigation ethylpyridines have been used as model compounds for investigating the biodegradability of alkylpyridines. A mixed culture of ethylpyridine-degrading microorganisms was obtained from a soil that had been exposed to a variety of pyridine derivatives for several decades. The enrichment culture was able to degrade 2-, 3-, and 4-ethylpyridine (100 mg/L) at 28° C and pH 7 within two weeks under aerobic conditions. The degradation rate was greatest for 2-ethylpyridine and least for 3-ethylpyridine. Transformation of ethylpyridines was dependent on substrate concentration, pH, and incubation temperature. Studies on the metabolic pathway of 4-ethylpyridine revealed two products; these chemicals were identified by MS and NMR analyses as 4-ethyl-2(1H)-pyridone and 4-ethyl-2-piperidone. 6-Ethyl-2(1H)-pyridone was determined to be a product of 2-ethylpyridine degradation. These results indicate that the transformation mechanism of ethylpyridines involves hydroxylation and reduction of the aromatic ring before ring cleavage.