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  • 1990-1994  (3)
  • 1
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Although the taxonomy of deep-sea protobranch bivalves is becoming better known, relatively little information is available on their reproductive biology and whether or not populations show reproductive periodicities. We have examined the reproductive biology of three common sympatric species as part of a long-term time-series of samples taken from 2900 m in the Rockall Trough from 1973 to 1983. Malletia cuneata Jeffreys, 1876 produces a maximum of 30 oocytes at any one time and these grow to a maximum size of 240 μm. Maximum fecundity of Ledella pustulosa (Jeffreys, 1876) and Yoldiella jeffreysi (Hidalgo, 1877) is 174 and 360, respectively, and both species produce an egg of ∼ 120 μm in diameter. These data indicate lecithotrophic early development in L. pustulosa and Y. jeffreysi, but direct development in M. cuneata; however, evidence from the prodissoconch length of M. cuneata suggests lecithotrophic development. L. pustulosa and Y. jeffreysi also differ from M. cuneata in having a distinct reproductive cycle with spawnout in the winter months. Both the continuously breeding M. cuneata and the seasonally breeding L. pustulosa ingest diatoms, coccoliths and foraminiferans, but whereas the diet of M. cuneata appears to be constant throughout the year there is an apparent reduction in the feeding activity of L. pustulosa concomitant with the deposition of phytodetritus on the deep-sea bed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 17 (1994), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Two direct but independent approaches were developed to identify the average δ18O value of the water fraction in the chloroplasts of transpiring leaves. In the first approach, we used the δ18O value of CO2 in isotopic equilibrium with leaf water to reconstruct the δ18O value of water in the chloroplasts. This method was based on the idea that the enzyme carbonic anhydrase facilitates isotopic equilibrium between CO2 and H2O predominantly in the chloroplasts, at a rate that is several orders of magnitude faster than the non-catalysed exchange in other leaf water fractions. In the second approach, we measured the δ18O value of O2 from photosynthetic water oxidation in the chloroplasts of intact leaves. Since O2 is produced from chloroplast water irreversibly and without discrimination, the δ18O value of the O2 should be identical to that of chloroplast water. In intact, transpiring leaves of sunflower (Helianthus annuus cv. giant mammoth) under the experimental conditions used, the average δ18O value of chloroplasts water was displaced by 3—10 % (depending on relative humidity and atmospheric composition) below the value predicted by the conventional Craig & Gordon model. Furthermore, this δ18O value was always lower than the δ18O value that was measured for bulk leaf water. Our results have implications for a variety of environmental studies since it is the δ18O value of water in the chloroplasts that is the relevant quantity in considering terrestrial plants influence on the δ18O values of atmospheric CO2 and O2, as well as in influencing the δ18O of plant organic matter.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 233 (1992), S. 350-356 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Literature referring to the conflicting results of investigations into the possible existence and composition of the lamina splendens is reviewed. Two hundred micrometer thick histological sections from 80 human cadaveric lower lumbar zygapophyseal joint articular cartilages were examined by ordinary light and darkfield microscopy. The findings illustrate what appears to be an acellular surface lamina on the opposing cartilaginous surfaces. No speculation is made regarding the possible physiological significance of the lamina based on this anatomical study. © 1992 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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