COMPETENCE OF CEREAL LEAF-CELLS .1. PATTERNS OF PROLIFERATION AND REGENERATION CAPABILITY INVITRO OF THE INFLORESCENCE SHEATH LEAVES OF BARLEY, WHEAT AND TRITORDEUM

We have studied the patterns of proliferation in vitro and the regenerative capability of the inflorescence sheath leaves (the last five leaves produced by a tiller) of three cereal species, wheat, barley and tritordeum. The leaves were dissected out from the tillers, cut individually into 1-mm segments and placed on medium in sequence according to their original position in the tiller. Callus induction was achieved in the presence of 2,4-D, while hormone-free medium was used for plant regeneration. All five inflorescence sheath leaves of wheat and tritordeum showed the ability to proliferate in vitro, while barley leaf segments did not proliferate. In both wheat and tritordeum, proliferative and regenerative ability were differentially affected by the explant age. Wheat leaves more than 0.5 cm long maintained their proliferative ability but their regenerative potential was strongly reduced and limited to the basal regions, while quite mature leaves of tritordeum still contained competent cells able to proliferate and to regenerate with similar efficiency to that of young leaves. The results clearly demonstrate that cereal leaf cells capable of plant regeneration are not confined to basal meristematic regions and that tritordeum inflorescence sheath leaves in particular contain large regions of tissue able to be induced to proliferate and regenerate.