RESPONSES OF CALLUS FROM ZYGOTAL AND MICROSPORAL TOBACCO (NICOTIANA TABACUM L.) TO VARIOUS COMBINATIONS OF INDOLE ACETIC ACID AND KINETIN

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SummaryCalluses from zygotal and microsporal plants of Nicotiana tabacum L.cv. Maryland Mammoth exhibited similar growth and morphogenetic responses to culture on twelve media consisting of a basal medium and all combinations of IAA (0, 1 × 10−5 M, 2 × 10 −5 M) and kinetin (0, 10−7 M, 10−6 M, 10−5 M). Five types of callus morphology are described, ranging from a loose soft‐textured type to a compact more or less radially symmetrical type and to a nodular type which was associated with regeneration of shoots. Anatomically the cell types ranged from thin‐walled isodiametric cells to elongated cells and to parenchyma of various shapes showing organized development. Particularly interesting was the induction of numerous individual tracheid‐like cells of diverse shapes making up about 60% of the cell population in calluses grown on 10−5 M kinetin medium with cither 1 or 2 × 10−5 M IAA. This contrasted with the complete absence of tracheary elements in calluses reared on kinetin‐free 10−5 M IAA medium, and the development of xylem on auxin‐free 10−5 M kinetin medium. The need for the introduction of the words microsporal and zygotal in connection with plants derived from anther, microspore and pollen grain culture is discussed.