Plankton as a Source of Food


IN reply to the latest communication under this heading1, I would like briefly to recall (a) the common agricultural practice of green manuring2 in which often the only obvious addition to the land is of ‘carbon’3 though the benefit to future crops is undeniable4, (b) the importance of freshwater algæ as soil surfacebinders5 even if the addition of potential humus is small, (c) the facts that many algæ are notoriously rich in vitamins6 and are now known to contain growth–substances7 in such amounts as might conceivably be absorbed from the soil by seeds8 and roots9 and have a formative and growth–promoting action upon various organs of vegetable plants10, (d) that the exact manurial and other treatment can further condition the vitamin content and growth and robustness of a crop for reasons not yet understood4, (e) the ubiquity and usual wastage of the human system as a source of combined nitrogen and phosphorus as well as of auxins10, and (ƒ) that Cyanophyceæ capable of fixing nitrogen can be grown in mineral solutions as well as on or near the surface of soil11, while the presence of other algæ increases nitrogen–fixation by bacteria5; on the other hand it is often wasteful and may be harmful to add nitrates and ammonium salts to soils that have to be watered12.

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  1. 1

    NATURE, 148, 314 (September 13, 1941).

  2. 2

    Imperial Bureau of Soil Science, Technical Communication No. 22.

  3. 3

    Russell, "Soil Conditions and Plant Growth", 7th ed., London (1937).

  4. 4

    Jenkins, "Organic Manures", Imperial Bureau of Soil Science, Technical Communication No. 33 (1935).

  5. 5

    Fritsch, "The Rô1e of the Terrestrial Alga in Nature", Essays in Geobotany â¦, 195, California (1936).

  6. 6

    Tilden, "The Algæ and their Life Relations", London (1935).

  7. 7

    van Overbeek, Bot. Gaz., 101, 940 (1940).

  8. 8

    Croxall and Ogilvie, J. Pomol. and Hort. Sci., 17, 362 (1940).

  9. 9

    Hitchcock and Zimmerman, Contrib. Boyce Thompson Inst., 7, 447 (1935); Pfahler, Jahrb. wiss. Bot., 86, 675 (1938).

  10. 10

    Went and Thimann, "Phytohormones", New York (1937); Meyer and Anderson, "Plant Physiology", London (1940).

  11. 11

    NATURE, 142, 878 (1938).

  12. 12

    Barker, "The Use of Fertilizers", London (1935).

  13. 13

    NATURE, 148, 143 (1941).

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POLUNIN, N. Plankton as a Source of Food. Nature 148, 375 (1941) doi:10.1038/148375b0

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