|MadSci Network: Botany|
Plastids are organelles rather than cells. Technically, a leucoplast is not the same as an amyloplast. There are many different types of plastids. The two main categories are based on color. Chromoplasts are colored. Leucoplasts are colorless. Chromoplasts that contain chlorophyll are usually green and are termed chloroplasts. Leucoplasts can be amyloplasts, elaioplasts (oil storage plastids), proteinoplasts or proteoplasts (protein storage plastids), proplastids (precusors to plastids) or etioplasts (proplastid arrested in development due to lack of light). What stimulated your question seems to be that some authorities defined leucoplast incorrectly. The American Heritage Dictionary of the English Language defined leucoplast as "A colorless plastid in the cytoplasm of plant cells around which starch collects." That is incorrect in two ways. A leucoplast will not necessarily contain starch, and the starch always forms inside a plastid, not around it. There are hundreds of plant misconceptions in the literature. There are several other reasons there are duplicate names for the same thing including, 1. Terms become obsolete but remain in use. For example, geotropism and gravitropism describe the same response but geotropism is considered obsolete and inaccurate because the response is to gravity not the earth (geo). However, geotropism persists in the literature. 2. There are sometimes common versions of scientific terms, for example amyloplasts are often called starch grains. 3. Some scientists coin new terms when existing terms are sufficient. For example the term skototropism was termed to describe the negative phototropism of certain vine stems. That may also be the case with the synonymns proteinoplasts or proteoplasts. There are also sometimes multiple definitions for the same term. For example, at least one scientist defines a leucoplast as a distinct kind of plastid rather than simply as colorless plastids (see last reference). I agree with you that duplicate terms for the same thing are frustrating but I'm not sure it is avoidable. One solution might be to create an international scientific dictionary with one definition for each term and one term for each concept. We have an International Code of Botanical Nomenclature and an International System of Units so it might be possible. However, dictionary publishers might be against it. References Incorrect definition of Leucoplastid Correct definition of Leucoplast Avoid Misconceptions When Teaching about Plants Amyloplasts Carde, J.P. 1984. Leucoplasts: a distinct kind of organelles lacking typical 70S ribosomes and free thylakoids. Eur J Cell Biol. 34(1):18-26.
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