Analysis of Physiological Properties of Plant Dwarfism

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1. The relationship between the dwarf habit of growth and cortical microtubule (MT) orientation in mesocotyl cells as affected was examined using a gibberellin (GA) responding dwarf mutant of maize (d5). Mts were observed by immunofluorescence microscopy. MT arrangement in the tangential surface of epidermal cells (EP-t) was oblique and /or longitudinal. The frequency of occurrence of transversely oriented MTs is much less in d5 than normal. In the radial surface of epidermal cells (EP-r), almost all the cells had transversely oriented MTs. In d5 seedlings only a few percent of cells had obliquely oriented MTs. In the radial surface of cortex cells (c-r), all the cells of normal mesocotyls had transversely oriented MTs, while in d5, MTs in considerably a large number of cells showed oblique/longitudinal orientation By GA treatment for 24 h, the growth of d5 mesocotyls was stimulated, and the orientation of MTs in EP-t, EP-r and C-r became transverse.2. The endogenous IAA level in d5 seedlings was lower than that in normal seedlings at the early period of growth, but at later stages the level declined and no significant difference was detected between d5 and normal. GA had no effect on the level in d5 seedlings.3. The content of the hemicellulose B (HB) fraction of d5 seedlings was higher than that of normal seedings during the growth period, and GA treatment resulted in a decrease of HB. The HB of d5 showed a higher molecular-weight distribution than that of normal. GA treatment caused a shift in the distribution to the lower molecular weight range.