Circumscription of the genus Medicago (Leguminosae) by seed characters

Abstract

Delimitation of Medicago from its close relatives in tribe Trifolieae subtribe Trigonellinae remains controversial. Scanning electron microscope studies of the seed surface of Medicago, Trigonella, and Melilotus showed consistent differences between Medicago and the other two genera. Smooth and rough seeds occur in all three genera, the rough seeds proving taxonomically useful. The roughness of Medicago seeds is due to rugose surface bumps (usually wrinkled, always with rounded sides), except in the monotypic section Orbiculares. The roughness of seeds of Trigonella, Melilotus, and Medicago section Orbiculares is due to tuberculate surface bumps. The structure of the Malpighian layer shows completely parallel taxonomic differences. The Malpighian cells are traversed by the light line, and the length of the portion of the cell above the light line (a) and that below the light line (b) distinguishes smooth, rugose, and tuberculate seeds. In smooth seeds (of Medicago, Melilotus, and Trigonella), a and b are constant. In rugose seeds (in Medicago only), a is constant while b is greater under the testa bumps, varying with the height of the portion of the bump occupied. In tuberculate seeds (in Medicago section Orbiculares, and in Trigonella and Melilotus), b is constant while a is greater under the testa bumps. These studies confirm the appropriateness of circumscribing Medicago in a wide sense, except for the inclusion of Medicago section Orbiculares.

Morfoanatomia de la cubierta seminal en siete especies de Passiflora L., subgénero Passiflora (Passifloraceae)

“…Para el estudio anatómico de la cubierta seminal en secciones transversales se consideraron los siguientes atributos: grosor de la cubierta seminal, número de capas, tipo de capa, tipo de alargamiento radial de las células de cada capa (Rodríguez 1976, Lindorf et al 1985, Buth et al 1987, Haridasan & Mukherjee 1988, Kaur & Pal 1989, Corral et al 1989, Small et al 1990, Escala 1994, las mediciones se realizaron en 25 campos por especie con un microscopio óptico calibrado (Nikon Opthifot 2). El material vegetal fue ablandado en una mezcla de etanol 70% y glicerina 40% en relación 1:1 por un período de 15 días; luego se hidrató en agua destilada por 24 horas y fue conservado en etanol 70% por 48 horas (Jha & Pandey 1989, C. Sánchez, datos no publicados).…”

A synopsis of the genus Medicago (Leguminosae)

“…Plants indigenous to Eurasia and North Africa. Invariably separable from allied genera by the floral pollination syndrome described above (and in more detail in Small et al 1987), and by the presence of hemolytic saponins (Jurzysta et al 1988); and almost invariably separable from allied genera by seed characters (Small et al 1990).…”

Comparative study on the morphology, palynology and essential oil composition of three trigonella L. species (Fabaceae) from Iran

“…One of them, T. foenumgraecum L. is commonly grown as a vegetable (Grossheim, 1945;Hamzehee, 2000;Hedge, 1970). Many bioactive compounds such as protodioscin, trigoneoside, diosgenin, yamogenin have been isolated from fenugreek seeds (Giradon et al, 1986;Kabilan et al, 2002;Murakami et al, 2000;Pandita et al, 1991;Small et al, 1990;Yoshikawa et al, 1992). The important chemical constituents are saponins, coumarin, fenugreekine, nicotinic acid, phytic acid, scopoletin and trigonelline (Ullah Khan et al, 2009).…”