II. 8. Expression of glossy leaf and glossy sheath in a liguleless phenotype.
D.R. Clark and R.T. Ramage. Department of Plant Sciences, University of Arizona, Tucson, Arizona 85721, U.S.A.. "R"
A liguleless mutant was obtained by treating barley seed with the chemical mutagen, diethyl sulfate. The liguleless mutant is similar in appearance to the one described by Takahashi et al. (1953): "This variant...is completely deficient not only of the ligule, but also of the auricle on all leaves.... The transition part from leaf-sheath to blade is more elongated without any accessory organ or tissue developed thereof, but it is nevertheless distinct because of the differential epidermal tissues of the sheath and blade." We have not yet allele-tested our mutant with the liguleless mutant reported by Takahashi et al. (1953), but we expect them to be allelic because of their similarity in external appearance. Although it is not readily perceptible, we can visually distinguish a transition zone where the leaf sheath and blade would normally meet. We have not studied the morphology of the epidermal tissues of the sheath and blade but superficial observations have not revealed any gross differences. Therefore, we are not sure what Takahashi et al. (1953) meant by "the differential epidermal tissues of the sheath and blade."
We wanted to know if the absence of wax, as conditioned by the eceriferum mutants 'glossy leaf' and 'glossy sheath', started and stopped at the transition zone from leaf sheath to blade. We crossed our liguleless mutant with the glossy leaf mutant 'gl1' and with a glossy sheath mutant obtained from the same DES-treated population from which the liguleless mutant was isolated. In the F2 of the crosses, liguleless segregants were examined for the expression of the glossy mutants. Liguleless, glossy plants from the cross with glossy leaf had blades that were waxless from the tip to the point where the ligule would normally be. Likewise, liguleless, glossy plants from the cross with glossy sheath had sheaths that were waxless from their point of origin at the node to the area where the ligule would normally be.
These observations bring up many question as to the developmental anatomy of the leaf sheath and blade and to the time of regulation of the genes which control the wax coating found on the epidermis of the sheath and blade.
Reference:
Takahashi, R., J. Yamamoto, S. Yasuda and Y. Itano. 1953. Inheritance and linkage studies in barley. Ber. Ohara Inst 10:29-52.