Gibberellin Control of Microtubule Arrangement in the Mesocotyl Epidermal Cells of the d_5 Mutant of Zea mays L.

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The mesocotyl length of dark-grown maize seedlings is much shorter in the dwarf (d_5) than in the normal. The elongating zone of d_5 mesocotyl is restricted to 1 mm below the coleoptilar node, while that of the normal extends to almost 4 mm. When the 4 mm portion below the node was marked at 1 mm intervals and designated as A, B, C and D from the top, gibberellin (GA_3) particularly stimulated elongation of the A-B region of d_5 and also C to some extent. Electronmicroscopic observation of microtubules in the epidermal cells of these regions of d_5 showed that microtubules were longitudinally and/or randomly oriented in all other regions except the region immediately below the node. Following 100 μM GA_3 treatment for 21 h, the microtubule arrangement became transverse to the cell axis in A and B. Even in C a significant number of transversely oriented microtubules were observed. On the other hand, in normal seedlings micro-tubules were oriented transversely to the cell axis in all four regions regardless of GA_3 treatment. Results indicate that the dwarf habit of d_5 seedlings can be ascribed to their possession of a small population of elongating cells, the microtubules of which are predominantly oriented transversely to the cell axis as a result of insufficient supply of endogenous gibberellin.
日本植物生理学会の論文