Portal de Periódicos da CAPES

Artigo Produção Nacional Revisado por pares

BIBTEX RIS

Intriguing thigmonastic (sensitive) stamens in the Plains Prickly Pear Opuntia polyacantha (Cactaceae)

2013; Elsevier BV; Volume: 208; Issue: 5-6 Linguagem: Inglês

10.1016/j.flora.2013.04.009

1618-0585

J. Hugo Cota‐Sánchez, Odair José Garcia de Almeida, Denver J. Falconer, Hyeok Jae Choi, Lewis Bevan,

Plant Diversity and Evolution

a b s t r a c t The movement of sensitive stamens in flowers of the Plains Prickly Pear (Opuntia polyacantha) is described in detail along with the external and internal filament anatomy. The goals of this investigation were: (1) to provide a synthesis of floral phenology and determine whether this rather unique stamen movement is nastic or a tropism and (2) to conduct macro- and micro-morphological analyses of filaments to deter- mine if there are anatomical traits associated with this movement. To better understand the internal and external structure in sensitive filaments of O. polyacantha, we performed comparative anatomical analyses in two additional species from the Opuntioideae with stamens lacking such sensitivity. The con- sistent unidirectional movement of stamens, independent of the area stimulated, indicates a thigmonastic response. This movement serves multiple purposes, from enhancing pollen presentation to facilitating cross-pollination, protecting pollen and preventing insects from robbing pollen. Anatomically, the sen- sitive and non-sensitive filaments exhibit different tissue organization. Cuticle thickness, presence of capsular structures, two layers of curved cells, and more and larger intercellular spaces are characteristic of sensitive filaments. A thin unicellular epidermal layer is characteristic in sensitive filaments versus 2-3 epidermal layers in non-sensitive filaments. Another striking feature in sensitive filaments is the pres- ence of papillae and capsular structures. We believe that these elements are related to water mobility with subsequent contraction during the thigmonastic response. Capsular structures might have a role in fluid mobility according to the stimulus of the filaments. We hypothesize that the thigmonastic response is controlled by cells with elastic properties, as evidenced by the plasmolyzed curved and contracted cells in the filaments and the fact that the movement is activated by changes in cell turgor followed by contraction as a result of plasmolysis.