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  • 1
    Electronic Resource
    Electronic Resource
    Crassulacean acid metabolism (CAM) in high elevation tropical cactus (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 12 (1989), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Several taxa of cacti are distributed in high elevation tropical alpine habitats between 4000–4700 m in central Peru. This region has a marked dry season with soil water potentials as low as – 25 MPa. The barrel type cactus Oroya peruviana and the low ceaspitose Tephrocactus floccosus (both the typical hairy form and a hairless form) all exhibited diurnal fluctuations of malic acid (10–100 μmol/g FW), indicative of CAM photosynthesis. δ3C carbon isotope ratios were – 13 to – 14 suggesting that for these CAM plants the bulk of the net carbon gain is through night-time carbon uptake. This occurs in spite of overnight temperatures below 0°C. CAM activity was observed on nights when air temperature dropped to – 8°C and subepidermal temperatures reached as low as –3°C. In central Peru, the typical form of T. floccosus has a dense covering of long silvery white hairs. Comparisons with an adjacent ‘hairless’ form showed that the hairy morph maintained a subepidermal temperature several degrees higher during the night. At a site where the ‘hairless’ morph was rare, the hairy T. floccosus had substantially higher overnight acid accumulation. At another site where the ‘hairless’ morph was abundant, the hairy T. floccosus had substantially lower acid accumulation relative to the ‘hairless’ form.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1989.tb01948.x
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  • 2
    Electronic Resource
    Electronic Resource
    Carbon: freshwater plants (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 15 (1992), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: δ13C values for freshwater aquatic plant matter varies from −11 to −50‰ and is not a clear indicator of photosynthetic pathway as in terrestrial plants. Several factors affect δ13C of aquatic plant matter. These include: (1) The δ13C signature of the source carbon has been observed to range from +1‰ for HCO3− derived from limestone to −30‰ for CO2 derived from respiration. (2) Some plants assimilate HCO3−, which is –7 to –11‰ less negative than CO2. (3) C3, C4, and CAM photosynthetic pathways are present in aquatic plants. (4) Diffusional resistances are orders of magnitude greater in the aquatic environment than in the aerial environment. The greater viscosity of water acts to reduce mixing of the carbon pool in the boundary layer with that of the bulk solution. In effect, many aquatic plants draw from a finite carbon pool, and as in terrestrial plants growing in a closed system, biochemical discrimination is reduced. In standing water, this factor results in most aquatic plants having a δ13C value similar to the source carbon. Using Farquhar's equation and other physiological data, it is possible to use δ13C values to evaluate various parameters affecting photosynthesis, such as limitations imposed by CO2 diffusion and carbon source.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1992.tb01653.x
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  • 3
    Electronic Resource
    Electronic Resource
    Stomatal mechanism as the basis of evolution of crassulacean acid metabolism (1985)
    [s.l.] : Nature Publishing Group
    Nature 314 (1985), S. 200-200 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] KEELEY ET AL. REPLY-We agree with Cockburn that, although the presence of CAM in astomatous Stylites does not support his theory on the stomatal origin of CAM, it does not necessarily falsify the theory either. We also agree with Thomas that Stylites most reasonably should be included with ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/314200c0
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  • 4
    Electronic Resource
    Electronic Resource
    Seed germination patterns of Salvia mellifera in fire-prone environments (1986)
    Springer
    Oecologia 71 (1986), S. 1-5 
    Details
    ISSN: 1432-1939
    Keywords: Chaparral ; Ecotypes, fire ; Germination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Salvia mellifera seeds from coastal sage, chaparal and desert scrub in southern California failed to germinate in the dark unless exposed to powdered charred wood. This pattern was observed for seeds given a one month stratification at 5 C and for ones not stratified and also for seeds incubated under continuous 23 C or a diurnal alternation of 13 C/23 C. Dark inhibition of germination was also overcome, but only in seeds from chaparral populations, if seeds were incubated on commerical potting soil under alternating 13 C/23 C. Seeds in the light germinated readily in all but one population from desert scrub vegetation. Germination of seeds from this population was markedly stimulated by dry heating of the seeds at either 70 C for 5 h or 115 C for 5 min. For all populations there were numerous significant interactions between incubation temperature, pre-chilling stratification, light, and heating/charred wood treatments. Timing of germination was remarkably consistent between populations; the vast majority of seeds germinated within the first week at 23 C (or 13 C/23 C) regardless of whether or not they had received a pre-chilling treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377311
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