Anatomical Studies of the Luzulae Group of Cyperus (Cyperaceae)

Abstract

The systematic relationships of the Luzulae group of Cyperus are elucidated by anatoridtal studies of the achenes and leaves. Epidermal patterns of the achenes are distinctive, consistent for each taxon, and useful in clarifying instances of interspecific hybridization; variation of the epidermal cells is most evident with respect to the size of the cell, the number, thickness, and sinuosity of the anticlinal walls per cell, and the shape and nature of the apex of the silica body found in the center of each cell. Leaf anatomical data support the present classification of the Luzulae group. Leaf epidermal patterns as well as the structure of the vascular bundles and the arrangements of sclerenchyma, mesophyll, and air spaces observed in leaf transverse sections are mostly uniform among the taxa. The most variable leaf anatomical characters are the number of vascular bundles per leaf (correlated with leaf width) and the occurrence of bulliform cells. The study confirms the use of achene epidermal features at the varietal or specific level, and the use of leaf anatomical features at the sectional, generic, or familial level. Anatomical data are frequently useful in characterizing species or species complexes within a genus and in determining evolutionary relationships (Stant 1973; Forbes 1980; Standley 1981). In reference to Cyperaceae, Metcalfe (1969) stated that the important and significant anatomical characters have proved to be those of the leaf epidermis and those evident from leaf transverse sections. Extensive studies in Cyperaceae have substantiated the usefulness of anatomical data, especially of the leaves but also of the inflorescences, flowers, and fruits (Koyama 1966, 1967; Kukkonen 1967; Govindarajalu 1969; Schuyler 1971; Toivonen and Timonen 1976; Forbes 1980; Standley 1981). Some of the earlier anatomical studies, based only on a few taxa within a large genus, have sometimes resulted in erroneous statements about the extent of variation present. For example, Metcalfe (1969) stated that there are only minor anatomical differences between the species of Carex L. Standley (1981), however, has shown that leaf anatomy demonstrates distinct and sometimes major variations between taxa classified in the same section of Carex. Thorough documentation of all species of several sections of large cyperaceous genera will likely reveal patterns of variation not known or expected because prior studies were based on such small samples. After an initial taxonomic study of the taxa included in the Luzulae group of Cyperus L. (Denton 1978), several questions concerning species relationships persisted. To elucidate the systematic relationships of the 15 taxa included in this New World group, a comparative, anatomical analysis of the achenes and leaves was undertaken. Descriptions and illustrations of pertinent anatomical features are presented for all taxa in the Luzulae group.