Search Results - (Author, Cooperation:A. J. Duncan)

2018-01-03

The American Society for Microbiology (ASM)

0099-2240

1098-5336

Biology

2011-04-23

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

1432-1939

Key words Carbon-nutrient balance ; Elevated CO2 ; Pinus sylvestris L. ; Tannins ; Terpenes

Springer Online Journal Archives 1860-2000

Biology

Abstract This study investigated changes in carbon-based plant secondary metabolite concentrations in the needles of Pinus sylvestris saplings, in response to long-term elevation of atmospheric CO2, at two rates of nutrient supply. Experimental trees were grown for 3 years in eight open-top chambers (OTCs), four of which were maintained at ambient (∼350 μmol mol−1) and four at elevated (700 μmol mol−1) CO2 concentrations, plus four open air control plots. Within each of these treatments, plants received either high (7.0 g N m−2 year−1 added) or low (no nutrients added) rates of nutrient supply for two years. Needles from lateral branches were analysed chemically for concentrations of condensed tannins and monoterpenes. Biochemical determinations of cellulase digestibility and protein precipitating capacity of their phenolic extracts were made because of their potential of importance in ecological interactions between pine and other organisms including herbivores and decomposers. Elevated CO2 concentration caused an increase (P〈0.05) in dry mass per needle, tree height and the concentration of the monoterpene α-pinene, but there were no direct effects of CO2 concentration on any of the other chemical measurements made. High nutrient availability increased cellulase digestibility of pine needles. There was a significant negative effect of the OTCs on protein precipitating capacity of the needle extracts in comparison to the open-air controls. Results suggest that predicted changes in atmospheric CO2 concentration will be insufficient to produce large changes in the concentration of condensed tannins and monoterpenes in Scots pine. Processes which are influenced by these compounds, such as decomposition and herbivore food selection, along with their effects on ecosystem functioning, are therefore unlikely to be directly affected through changes in these secondary metabolites.

Electronic Resource

1434-6079

03.65.Bz ; 07.60.−j ; 42.50.Dv

Springer Online Journal Archives 1860-2000

Physics

Abstract A technique of depolarization is used to investigate the coherence and spectral properties of the radiation emitted in the two-photon decay of metastable atomic deuterium. The results agree with the quantum mechanical predictions but may also be interpreted to show that a single photon of a two-photon pair can be considered to have a very short coherence length, a very short coherence time and a broad bandwidth, all limited, in practice, by the transmission properties of the detection system.

Electronic Resource

1573-1561

Conditioned flavor aversions ; condensed tannins ; intake ; oxalic acid ; plant secondary compounds ; sheep ; toxins

Springer Online Journal Archives 1860-2000

Biology

Chemistry and Pharmacology

Abstract The objectives of the experiment were to test whether sheep develop conditioned flavor aversions (CFAs) towards a food flavor associated with the administration of a plant secondary compound, and providing that such CFAs develop, to determine how long they persist. For experimental purposes, two natural secondary compounds were used—quebracho (mainly condensed tannins) and oxalic acid—at doses previously known to produce negative postingestive consequences in sheep. The experiment consisted of four conditioning periods (each eight days long) during which the novel flavored foods (flavored hay) were offered concurrently with oral administration by gavage of the secondary compounds. In the conditioning period four groups of sheep (N = 6 each) were arranged such that each group received different flavored feeds (orange and aniseed) for two-day sequential periods. One flavor was paired with one of the model secondary compounds. Between the two sets of two days and after the second two-day period there was a period of two “rest” days, to avoid residual physiological effects of secondary compound administration. The intakes of flavored hay were recorded during each conditioning day and the effects of the secondary compounds were quantified in rumen (for volatile fatty acids and ammonia concentrations) and blood samples (for plasma calcium levels). At the end of each conditioning period, the preference for the two flavors was measured by a two-choice short-term preference test (20 min each); the persistence of the CFAs was similarly measured at 0, 10, 30 and 60 days after the completion of the conditioning with two-choice longterm preference tests (3 hr each). Results of the experiment indicated that quebracho administration did not lead to development of CFAs at the level administered. This does not necessarily reflect the sheep's inability to develop CFAs towards tannins but may reflect possible trade-offs between the ingestion of nutrients and secondary compound concentration that might have been imposed on the sheep in this experiment. In other words, it might reflect the increased familiarization with the hay (i.e., increase in its intake and hence of nutrients), which overcame the negative effects of quebracho administration. However, oxalic acid caused CFA in sheep: hay intake tended to be reduced during the days that the secondary compound was administered, and importantly the secondary compound associated flavored hay was partially avoided during the two-choice preference tests. The latter avoidance was not affected by time (consistent across conditioning periods). This CFA persisted for up to 60 days after the completion of conditioning in the absence of intervening oxalic acid exposure. Thus, sheep were able to form CFAs towards a flavor associated with the administration of a naturally occurring organic plant secondary compound.

Electronic Resource