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O2 release into the sediment, or why PS and heat cables are bunk.

Discussion in 'General Plant Topics' started by Tom Barr, Mar 31, 2010.

  1. Tom Barr

    Tom Barr Founder
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    http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T4F-48XMK9W-9P&_user=4421&_coverDate=12%2F31%2F1991&_fmt=abstract&_orig=search&_cdi=4973&view=c&_acct=C000059598&_version=1&_urlVersion=0&_userid=4421&md5=bfa05381d91e435aaf8cc710e35c3cb2&ref=full

    I read the whole paper, nothing new for me, but one issue did stand out.
    When placed in the dark, pondweed stopped putting out O2 after only 2 minutes.
    This plays some role in respiration, growth and also bacteria and root health.

    What, I'm not sure, but with organic rich sediments, reducing ones, not plain sands etc, this will have an even larger impact.

    Regards,
    Tom Barr
     
  2. Tom Barr

    Tom Barr Founder
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    "Oxygen release appears to be directly linked to photosynthetic 02 production,
    occurring only when plants are illuminated (Carpenter et al., 1983; Smith
    et al., 1984; Sorrell and Dromgoole, 1987 ). Root-rhizome 02 release has been
    measured for several different species, using hydroponic incubations in splitcompartment
    chambers. Low to moderate 02 release rates, 1-23% of total 02
    produced, have been reported for a variety of macrophytes, including: Potamogeton
    spp. (Sand-Jensen et al., 1982; Kemp and Murray, 1986), Egeria
    densa Planch. (Sorrell and Dromgoole, 1987 ), Ruppia maritima L. and Zostera
    marina (Iizumi et al., 1980; Sand-Jensen et al., 1982; Thursby, 1984).
    In isoetid species, which possess specialized morphological adaptations such
    as thick leaf cuticles, short distances between leaves and roots, and large lacunal
    volumes, relatively high 02 release rates, between 28 and 100% of total
    photosynthetic 02 production, have been measured (Sand-Jensen et al.,
    1982 ). In addition to these differences among species and habitats, stem length
    is an important factor regulating 02 release from macrophyte roots. Oxygen
    release was inversely related to stem length in emergent (Yamasaki, 1984)
    and submersed macrophytes (Kemp and Murray, 1986)."

    Regards,
    Tom Barr
     
  3. jonny_ftm

    jonny_ftm Guru Class Expert

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    Thank you for the great article. I read abstract and will try to grab full version tomorrow if my office has a subscription.

    But, I didn't well get the quoted part: what will be the influence of organic sediment, like castings for example? Favor or decrease O2 in substrate?
     
  4. nipat

    nipat Guru Class Expert

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    Tom, then isn't this support the use of heat cable?
    Because plants root only pump O2 when there is light.
    But then, again, there is no heat cable in nature (or is there?).

    Just curious.
     
  5. Tom Barr

    Tom Barr Founder
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    More OM: Decreases O2.

    So adding roots, they add O2, so the OM is oxidized around the roots. This is a natural biological action from hydrophytes growing in flooded soils.
    If you have too much O2, then the soil is wasted and oxidized/consumed by bacteria.

    You want to keep the reduced sediments for long term nutrient supply, but have the roots have enough O2.
    Roots do this fine on their own.

    If you add too much OM, then roots cannot keep up, this is about +10% OM or more.
    Peat is harder to decompose, so adding this is less of an issue.

    Regards,
    Tom Barr
     
  6. Tom Barr

    Tom Barr Founder
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    O2 is toxic and causes photorespiration. Plants need a little bit for respiration at night. This is stored in the lacunae. During the day, they produce excess amounts and give O2 off.
    This prevents anaerobic spots in soil. While they stop after 2 min, they have been adding and pumping O2 all day lomng, so it takes a few hours to drain this in the rhizosphere to the point where it is detrimental.

    Internally, the plant still has plenty of O2 for the night.
    The bacteria will slow down and depelet the O2 at night, and simply stop MET, but the plants should be fine.
    Then the lights come back on, and the cycle starts again.

    In some cases, CO2 comes into the roots at night and some CO2 recycling also occurs, but this takes O2 first.......and then they get the respired CO2.
    So diffusion from the water column 24/7 and from the roots during the day.

    This seems optimal within 10% or less OM.

    Regards,
    Tom Barr
     
  7. jonny_ftm

    jonny_ftm Guru Class Expert

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    So the receipt with earthworm castings mixed with sand at the 1:1 ratio you suggested could be bad? Hopefully, till now, I didn't notice any anaerobic melting in the soil of my DSM tank
     
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