Gibberellin-Induced Changes in Growth Anisotropy Precede Gibberellin-Dependent Changes in Cortical Microtubule Orientation in Developing Epidermal Cells of Barley Leaves. Kinematic and Cytological Studies on a Gibberellin-Responsive Dwarf Mutant, M489

• Published in: Plant physiology (Bethesda) 2000-10, Vol.124 (2), p.813-822
• Main Authors: Carol L. Wenzel, Williamson, Richard E., Wasteneys, Geoffrey O.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Barley; Biological and medical sciences; Cell growth; Chemical agents; Development and Hormone Action; Economic plant physiology; Epidermal cells; Fundamental and applied biological sciences. Psychology; Gibberellins - metabolism; Gibberellins - pharmacology; Growth and development; Guard cells; Hordeum - drug effects; Hordeum - genetics; Hordeum - growth & development; Hordeum - metabolism; Ligules; Meristem - drug effects; Meristem - growth & development; Meristem - metabolism; Mesophyll cells; Microscopy, Confocal; Microtubules; Microtubules - drug effects; Morphogenesis, differentiation, rhizogenesis, tuberization. Senescence; Mother cells; Mutation; Plant cells; Plant Leaves - drug effects; Plant Leaves - growth & development; Plant Leaves - metabolism; Plant physiology and development; Plants; Vegetative apparatus, growth and morphogenesis. Senescence
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.124.2.813

We conducted kinematic and cytological studies on "between vein" epidermal cells of the gibberellin (GA)-deficient M489 dwarf mutant of barley (Hordeum vulgare L. Himalaya). GAs affect radial and axial components of cell expansion and cortical microtubule orientation. Adaxial cells in particular expand radially after leaving the elongation zone (EZ), probably as part of leaf unrolling. Exogenous gibberellic acid corrects the mutant's short, wide blades, short EZ, and slow elongation rate. Cell production rates increase more on the adaxial than on the abaxial surface. Cells spend equal periods of time elongating in dwarf and tall plants, but relative elemental growth rates start to decline sooner in the dwarf. GA increased the rate at which longitudinal wall area increased because the increased axial growth more than compensated for reduced radial growth. In dwarf leaves, increased radial expansion was detected in basal parts of the EZ before cortical microtubules lost transverse orientation in the distal elongation zone. We conclude that loss of microtubule orientation is not required for low GA levels to reduce growth anisotropy.