Аннотация:The unifacial leaves of the investigated Senedo species are terete (S. citriformis, S. radicans, S. spiculosus), ensiform (S.ficoides), and linear pseudo-bifacial (S. serpens). Each has a very short bifacial leaf base and an unifacial blade. All leaf primordia generated at the flat shoot-apex are transversely flattened. Therefore, adaxial and abaxial sides and the margin in between are clearly discernible in the primordium. We consider those margins as provisionary. The primordium tip remains throughout the leaf development to become the tip of the mature leaf. No secondary tip arises to cause an unifacial design of the mature leaf. Unifacial leaf design establishes after the primordium has differentiated into Unterblatt and Oberblatt. The former retains its provisionary sides and its margin to develop the leaf base. Thus, the provisionary sides and margin of the leaf primordium become definite in the bifacial leaf base. The Oberblatt transversely rounds in both, terete and ensiform leaves, to cause the provisionary margin to disappear. Thereupon, the unifacial part arises and gives rise to the unifacial definite leaf blade. The Oberblatt remains flattened in the pseudo-bifacial leaf, but a new margin develops on its provisionary adaxial side and becomes the definite leaf margin. It delimits definite adaxial and definite abaxial sides. The latter consists of the whole provisionary abaxial part of the Oberblatt and most of its provisionary adaxial side. Thus, the basal bifacial part of the Oberblatt and its distal unifacial one differentiate. Later, the unifacial part grows to a pseudo-bifacial, linear blade. Then, the facial design of the leaf changes during leaf development.
Keywords: unifacial leaf, terete leaf, ensiform leaf, pseudo-unifacial leaf, leaf development, Senedo, leaf morphology