IMMUNOFLUORESCENCE MICROSCOPIC OBSERVATION OF CORTICAL MICROTUBULE ARRANGEMENT AS AFFECTED BY GIBBERELLIN IN D5 MUTANT OF ZEA-MAYS L

The relationship between the dwarf habit of growth and cortical microtubule (MT) orientation as affected by gibberellin was examined using a gibberellin responding dwarf mutant of Zea mays L. (d5). The 4 mm portion of the mesocotyl below the coleoptilar node of dark-grown seedlings was divided into four 1 mm segments. MTs were observed by means of immunofluorescence microscopy on the tangential surface of the epidermal cells (EP-t), the radial surfaces of epidermal (EP-r) and cortex cells (C-r) in both normal and d5 seedlings. MT arrangement in EP-t was transverse, oblique and/or longitudinal. In lower regions, cells with transversely oriented MTs decreased, while those with obliquely/longitudinally oriented MTs increased. The frequency of the occurrence of transversely oriented MTs was much higher in normal than in d5. In EP-r almost all the cells of the four regions had transversely oriented MTs. In d5 seedlings only a few percent of cells had obliquely oriented MTs. In C-r all the cells of the four regions of normal seedlings had transversely oriented MTs, while in d5, 20% of the uppermost region cells showed oblique/longitudinal orientation and more in lower regions. By GA3 (100-mu-M) treatment for 24 h, the growth of d5 mesocotyls was stimulated, and the orientation of MTs in EP-t, EP-r and C-r of any regions became transverse.