Achene dimorphism in Bidens pilosa L. (Asteraceae) as determined by germination test

Abstract

The germination of achenes of Bidens pilosa L. was analyzed during the life span of the mother plant. Decrease in the range of achene size was monitored until the senescence of the mother plant when the shortest achenes were harvested. The analysis of the germination percentage confirmed the presence of two distinct classes, formerly defined as short and long ones. Because length can not be used for the separation of those classes, the morphological characteristics of the tegument, specially of the ornament must be used for separation of the achenes with verrucose tegument (formerly named as short achenes) and achenes without ornament of the tegument (formerly named as long achenes). The achenes with verrucose tegument presented dormancy and light sensitivity, and the achenes without ornament of the tegument presented no dormancy and no light sensitivity for the germination process.

Phytochrome controls achene germination in Bidens pilosa L. (Asteraceae) by very low fluence response

“…Achenes of B. pilosa without ornaments presented no light sensitivity and achenes with ornament in the tegument presented low germination under dark and high germination under W as reported by Amaral and Takaki (1998); however, FR was not efficient to inhibit achene germination of this batch of achenes (Figure 2). Fenner (1980) observed that the light requirement is dependent on the conditions of achenes maturation and drying, indicating that because shade light induced light requirement, phytochrome was present and control germination.…”

“…The achenes were separated by morphological characteristics with and without verrucose ornament of tegument (Amaral & Takaki, 1998). The germination tests were carried out using 30 achenes on two layers of water moistened filter paper in each of four 90mm Petri dishes (Amaral & Takaki, 1993).…”

“…Valio et al (1972) described that light had no effect on achenes germination. Amaral and Takaki (1998) proposed dimorphism was present in B. pilosa and that achenes without ornament of the tegument (formerly named as long achenes) had no phytochrome controlling the germination process. However, in achenes with verrucose ornament (formerly named as short achenes) phytochrome controls the germination.…”

Picão-preto: uma planta daninha especial em solos tropicais

“…Amaral & Takaki (1998) (Carmona & Villas Bôas, 2001), chegando a 35 o C se enterradas a 1,0 cm de profundidade (Chivinge, 1996;Rios et al, 1989). …”

Desenvolvimento de plantas e germinação em cipselas dimórficas de Synedrella nodiflora (L.) Gaertn. (Asteraceae)

“…Em outras espécies também há um heteromorfismo morfológico, formado por diásporos de diferentes tamanhos, contudo, com relação às respostas fisiológicas há a presença de apenas dois tipos (AMARAL & TAKAKI, 1998).…”