CHANGED RESPONSE OF EXCISED TOMATO ROOTS TO PYRIDOXIN DEFICIENCY FOLLOWING PROLONGED STERILE CULTURE

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Abstract
A clone of excised tomato roots, selected originally for its marked requirement for vitamin B6, has been maintained in continuous culture in pyridoxin-containing medium since 1956. Growth in pyridoxin-free medium is now considerably greater than when the clone was originally isolated. A subclone of this clone was isolated in 1957 and maintained in medium in which pyridoxin was replaced with ethanolamine. This subclone does not show the change in response to pyridoxin deficiency. Because of this and other evidence it is concluded that the change occurs because of a change in the clone and is not an artefact due to faulty technique.The result is discussed in relation to (a) other reported changes in tissue cultures including the phenomenon of "adaptation" (accoutumance) to indole acetic acid, (b) the cellular control of metabolism.