tropisms, theory of

Proposed by Jacques Loeb (1859-1924), a physiologist and physician who was associated with the Rockefeller Institute in New York. The concept that all the activities of animals and humans are determined by tropisms, just as plant movements are determined by tropisms.

Loeb believed that matters of the mind and inner life will ultimately be explained by physio-chemical mechanisms that remain elusive today.

Source:
G Blandino, Theories on the Nature of Life (New York, 1969)

tropism (from Greek τρόπος, tropos, “a turning”) is a biological phenomenon, indicating growth or turning movement of a biological organism, usually a plant, in response to an environmental stimulus. In tropisms, this response is dependent on the direction of the stimulus (as opposed to nastic movements which are non-directional responses). Viruses and other pathogens also affect what is called “host tropism”, “tissue tropism”, or “cell tropism”; in which case tropism refers to the way in which different viruses/pathogens have evolved to preferentially target specific host species, specific tissue, or specific cell types within those species. Tropisms are usually named for the stimulus involved (for example, a phototropism is a reaction to sunlight) and may be either positive (towards the stimulus) or negative (away from the stimulus).

Tropisms occur in three sequential steps. First, there is a sensation to a stimulus, which is usually beneficial to the plant. Next, signal transduction occurs. And finally, the directional growth response occurs.

Tropisms are typically associated with plants (although not necessarily restricted to them).[a] Where an organism is capable of directed physical movement (motility), movement or activity in response to a specific stimulus is more likely to be regarded by behaviorists as a taxis (directional response) or a kinesis (non-directional response).

In English, the word tropism is used to indicate an action done without cognitive thought: However, “tropism” in this sense has a proper, although non-scientific, meaning as an innate tendency, natural inclination, or propensity to act in a certain manner towards a certain stimulus.

In botany, the Cholodny–Went model, proposed in 1927, is an early model describing tropism in emerging shoots of monocotyledons, including the tendencies for the stalk to grow towards light (phototropism) and the roots to grow downward (gravitropism). In both cases the directional growth is considered to be due to asymmetrical distribution of auxin, a plant growth hormone.[1]

3 thoughts on “tropisms, theory of

  1. Marceline Oyellette says:

    I like the valuable information you provide on your articles. I will bookmark your blog and check once more here frequently. I am quite sure I’ll be informed plenty of new stuff proper here! Good luck for the next!

  2. Carmela says:

    This is really interesting, You are a very skilled blogger.
    I’ve joined your feed and look forward to seeking more of your fantastic post.

    Also, I have shared your web site in my social networks!

  3. Eugenio says:

    Nice post. I learn something new and challenging on blogs I stumbleupon every day.
    It’s always exciting to read through articles
    from other authors and practice a little something from other
    websites.

Leave a Reply

Your email address will not be published. Required fields are marked *