INDEPENDENCE OF TISSUES DERIVED FROM APICAL LAYERS IN ONTOGENY OF THE TOBACCO LEAF AND OVARY

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Abstract
Six different homoplastidic periclinal chimeras of tobacco carrying the plastogene DP1 were selected after somatic segregation in heteroplastidic seedlings. Direct observation of the plane of division in epidermal cells of young leaves, and the number and size of sub‐epidermal green spots on leaves with the Green‐White‐White (G‐W‐W) pattern of variegation, indicated that the ratio of periclinal to anticlinal divisions in L‐I during development of the lamina was 1:3100. The number of green and white seedlings obtained from the different chimeral branches indicated a similar frequency of periclinal divisions in development of the ovary. The arrangement of green and white tissue in mature leaves of the various chimeral types indicated the extent of participation by the three apical layers in the initiation of the buttress, development of the axis, and formation of the lamina. During development of the lamina there must be three independent initial‐groups present. L‐I and L‐II initials remain marginal, but early in the growth of the lamina the leading edge of tissue derived from L‐III becomes separated from the submarginal (L‐II) initials by the products of frequent periclinal divisions of the L‐II initials.