The citrus leaf cuticle in relation to measurement of leaf water potential using thermocouple psychrometers*

Abstract. Cuticular resistance to water vapour diffusion is an important aspect of thermocouple psychrometry and may introduce significant error in the measurement of leaf water potential (Ψ). The effect of the citrus (Citrus mitis Blanco) leaf cuticle on water vapour movement was studied using the times required for vapour pressure equilibration during thermocouple psychrometric measurement of Ψ. Cuticular abrasion with various carborundum powders was used to reduce the diffusive resistance of both the adaxial and abaxial leaf surfaces, and the extent of the disruption to the leaf was investigated with light and electron microscopy. Cuticular abrasion resulted in reduced equilibration times due to decreased cuticular resistance and greater water vapour movement between the leaf and the psychrometer chamber. Equilibration times were reduced from over 5 h in the unabraded control leaves to 1 h with cuticle abrasion. This was associated with the decrease in diffusive resistance with cuticular abrasion from over 55 s cm^?1 to less than 8 s cm^?1 for both the adaxial and abaxial leaf surfaces. Scanning electron micrographs of the abraded leaf tissue revealed considerable disruption of the stomatal ledge and of the guard cells, surface smoothing and displacement of waxes into the stomatal aperture, and damage to veins. Observations with the transmission electron microscope revealed frequent disruption of epidermal cell walls, and damage to both the cytoplasmic and vacuolar membranes.     

Microsatellites identify depredated waterfowl remains from glaucous gull stomachs

Prey remains can provide valuable sources of information regarding causes of predation and the species composition of a predator's diet. Unfortunately, the highly degraded state of many prey samples from gastrointestinal tracts often precludes unambiguous identification. We describe a procedure by which PCR amplification of taxonomically informative microsatellite loci were used to identify species of waterfowl predated by glaucous gulls ( Larus hyperboreus ). We found that one microsatellite locus unambiguously distinguished between species of the subfamily Anserinae (whistling ducks, geese and swans) and those of the subfamily Anatidae (all other ducks). An additional locus distinguished the remains of all geese and swan species known to nest on the Yukon–Kuskokwim delta in western Alaska. The study focused on two waterfowl species which have experienced precipitous declines in population numbers: emperor geese ( Chen canagica ) and spectacled eiders ( Somateria fischeri ). No evidence of predation on spectacled eiders was observed. Twenty-six percent of all glaucous gull stomachs examined contained the remains of juvenile emperor geese.     

Partitioning of Nitrogen Derived from N2 Fixation and Reserves in Nodulated Medicago sativa L. During Regrowth

Nodul{macron}ted alfalfa plants were grown hydroponically. Inorder to quantify N₂ fixation and remobilization of N reservesduring regrowth the plants were pulse-chase-labelled with ¹⁵N.Starch and ethanol-soluble sugar contents were analysed to examinechanges associated with those of N compounds. Shoot removalcaused a severe decline in N₂ fixation and starch reserves within6 d after cutting. The tap root was the major storage site formetabolizable carbohydrate compounds used for regrowth; initiallyits starch content decreased and after 14 d started to recoverreaching 50% of the initial value on day 24. Recovery of N₂fixation followed the same pattern as shoot regrowth. Afteran initial decline during the first 10 d following shoot removal,the N₂ fixation, leaf area and shoot dry weight increased sorapidly that their levels on day 24 exceeded initial values.Distribution of ¹⁵N within the plant clearly showed that a significantamount of endogenous nitrogen in the roots was used by regrowingshoots. The greatest use of N reserves (about 80% of N incrementin the regrowing shoot) occurred during the first 10 d and thencompensated for the low N₂ fixation. The distribution of N derivedeither from fixation or from reserves of source organs (taproots and lateral roots) clearly showed that shoots are thestronger sink for nitrogen during regrowth. In non-defoliatedplants, the tap roots and stems were weak sinks for N from reserves.By contrast, relative distribution within the plant of N assimilatedin nodules was unaffected by defoliation treatment. Key words: Medicago sativa L., N₂ fixation, N remobilization, N₂ partitioning, regrowth     

External Features of the First Instar Larva of Damaster (Coptolabrus) jankowskii jankowskii (Coleoptera; Carabidae)

ABSTRACT Larval features of the carabid beetle, Damaster (Coptolabrus) jankowskii jankowskii (Oberthür) were investigated for the first time. For accomplishing the purpose, the adult beetles were collected by pitfall traps in the deciduous forest of Mt. Palgongsan, southern Korea. They have been reared under the laboratory condition of 16L: 8D at 20°C. The first instar larvae were obtained by isolating eggs after oviposition and were kept at the same condition. In the present study, external morphology of the first instar larva of this subspecies are described and its important character states and comparisons with the kin species are also discussed.     

Characterization of High Density Lipophorin (HDLP) Receptor from the Fat Body of Galleria mellonella by Ligand Blot Analysis

ABSTRACT To identify and characterize the HDLP (high density lipophorin) receptor from Galleria mellonella (LPR_Gm), we used techniques of ligand blotting. This method was, to our knowledge, firstly used to characterize the lipophorin receptor (LPR) in insect. LPR_gm had the approximate molecular weight of 100 kDa under non-reducing conditions and bound the HDLP very rapidly and specifically. The receptor had an absolute requirement of Ca²⁺ but exceeding concentration of Ca²⁺ has shown some inhibitory effect, and this result was supported by the effect of EDTA, here used for Ca²⁺ chelating reagent. LPR_Gm has the high binding affinity to HDLP and its binding with HDLP was rapid and specific. Suramin (polysulfated polycyclic hydrocarbon) effectively inhibited the LPR_Gm and HDLP binding. LPR_Gm showed the stage specific binding activity especially in day 1-3 last instar larval, prepupal, and adult stages.     

AROMA PROPERTIES AND THRESHOLDS OF SOME BRANCHED-CHAIN AND OTHER MINOR VOLATILE FATTY ACIDS OCCURRING IN MILKFAT AND MEAT LIPIDS1

Aroma properties of twenty-three branched-chain, odd-numbered, or unsaturated fatty acids which had each been dispersed in acidic aqueous media (pH 2.0) were evaluated. Aroma threshold values were determined using approximately 95 judges for assessing the presence of aromas over dilutions of each fatty acid. Qualitative aroma threshold values for individual fatty acids ranged from 0.006 to 82.4 ppm in the acidic solutions, and 4-ethyloctanoic acid exhibited the lowest threshold of the group tested. Qualitative aroma assessments of dilutions of each fatty acid showed a wide range of unique aroma properties. Fatty acids exhibiting branching at the 4-position had goaty/muttony/sheepy aroma notes as did other fatty acids containing 8-carbon chain structures. Cheese-like aromas were associated with the shorter branched-chain fatty acids.     

Records of palaeo‐seawater condition from oxygen‐isotope profiles of early Pleistocene fossil molluscs from the Seoguipo Formation (Korea)

Kim, J.K., Khim, B.‐K., Woo, K.S., & Yoon, S.H. 2009: Records of palaeo‐seawater condition from oxygen‐isotope profiles of early Pleistocene fossil molluscs from the Seoguipo Formation (Korea). Lethaia, Vol. 43, pp. 170–181. High‐resolution δ¹⁸O profiles of early Pleistocene fossil molluscs (Mizuhopecten tokyoensis hokurikuensis) from the shallow‐marine sedimentary Seoguipo Formation (Korea) were found to exhibit distinct annual cycles identified by their unique seasonality (δ¹⁸O amplitude). A direct comparison of fossil δ¹⁸O profiles with that of living shells (Amusium japonicum japonicumi) indicated that the palaeoseawater conditions differed from present‐day seawater. Specifically, the positive δ¹⁸O shift in the isotope profile of the fossil specimens relative to that of the living mollusc shell reflected that palaeotemperature was lower than that today. However, a comparison of the coldest palaeotemperatures (determined from the heaviest δ¹⁸O values of fossil shells), with the present‐day winter temperatures indicates that temperature variation alone cannot account for the entire positive δ¹⁸O offset. These findings indicate that variation in the seawater δ¹⁸O_w values plays a dominant role in the biogenic carbonate precipitation of fossils. Thus, the fossil shells obtained from stratigraphic units suggest different palaeoenvironmental conditions, including lower temperatures and ¹⁸O‐enriched glacial seawater, when compared with the present‐day conditions. The Seoguipo Formation records at least five cycles of relative sea‐level fluctuations, with changes in fossil δ¹⁸O amplitudes separated by sequence boundaries likely to reflect variations of unique palaeoseawater condition, although the oxygen‐isotope profile of fossil molluscs appears to provide a snap‐shot of the palaeoclimatic signature. □Early Pleistocene, mollusc fossils, oxygen isotope, palaeoenvironment, seawater temperature.