The Net Orientation of Wall Microfibrils in the Outer Periclinal Epidermal Walls of Seedling Leaves of Wheat

Use of the dichroic stain chlor-zinc-iodine revealed that the net orientation of cellulose wall microfibrils in the outer paradermal wall of the epidermis of seedling wheat leaves is principally transverse in the extension zone. The net orientation of microfibrils changes abruptly to principally longitudinal at the end of cell elongation. The net angle of orientation of microfibrils in the extension zone was not a function of Rht-dosage (number of dwarfing alleles), and neither leaf extension rate nor estimated maximum relative elemental rate of elongation were functions of microfibril orientation. The results indicate that elongation rates are not regulated by the net angle of orientation of microfibrils and support the concept that leaf extension rate is regulated by the length of the extension zone.