Estudio morfo-anatómico de aquenios de Centaurea soltitialis. L

JOSÉ L. ESCANDÓN; LILIA I. LINDSTRÖM; OSVALDO A. FERNÁNDEZ

Tandil, Buenos Aires

Congreso; X Congreso Argentino de Ciencias Morfológicas; 2006

Sociedad Argentina Ciencias Morfológicas

Morpho–Anatomical Studies on the achenes of Centaurea soltitiallis L. Escandón. J. L1,2; Lindström. L; and Osvaldo A. Fernández2 1 Fellowship, Embassy of Belgica, Quito, Ecuador, 2CERZOS and Departamento de Agronomía, Lab. de Morfología Vegetal. Universidad Nacional del Sur, 8000 Bahía Blanca, Argentina escandon@criba.edu.ar   Centaurea soltitialis is a weed of the family Asteraceae with isolated (solitary) cinarocefalos heads, and two types of achenes. The achenes located in the center are clear and posses pappus, while those in with periphery are dark in color without pappus. In the present work was studied if the dimorphism of the achenes was associated with anatomical differences of the pericarp.Ten μm cutting of the pericarp were studied using conventional optical microscopy. Additional information was obtained by analyzing part of the material by electronic microscopy. The pericarp of the achenes with pappus was 25 to 30 μ thick, characterized by the presence of an external epidermis of elongated cells, with thick and tangential external walls. One of the ends of these cells was acute sharp, while the other was rounded and superimposed with the next cell. Below appeared two strata of elongated parenchyma cell with deposits of phytomelanin (?¿), followed by one or two layers of fiber. The axis of these set of successive layers was parallel to the longitudinal alignment of the fruit. Finally, next to the seed tegument (a cap of macroesclereidas) was recorded a layer of equidimensional cells with crystal of calcium oxalate, whose compositions was studied by EDX method. The pericarp of the achenes without pappus differentiated by being thicker, 50 to 60 μm, and by showing epidermal cells with thin walls, their ends were straight and the external surface slightly concave. Two additonal strata of parenchyma were registered, also larger proportion of phytomelanin and a deposit of of epicuticular wax.