El androsporangio, la androsporogénesis y la androgametogénesis de Cayaponia citrullifolia, C. bonariensis y Cucurbitella duriaei (Cucurbitaceae)

POZNER, R.

DARWINIANA

Instituto de Botánica Darwinion

Lugar: Buenos Aires; Año: 1993 p. 109 - 123

0011-6793

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> This paper deals with the androsporangium development, androsporogenesis and androgametogenesis of 3 Argentine species of Cucurbitaceae, with emphasis in the mechanism of anther dehiscence and the possible physical link between the gametogenic cell and the siphonogenic nucleous within the androphyte (pollen grain). The following are the main conclusions: a) The androsporangium walls develops according to the basic type established by Davis (1966), with 2 or 3 middle layers in different areas of the same androsporangium wall. The tapetum is of the secretory type with unicleate cells. Sporogenous cells of Cayaponia citrullifolia (Griseb.) Cogn. and C. bonariensis (Mill.) Mart. Crov. show different ability to divide mitotically before meiosis. Meiotic cytokinesis is simultaneous and produces tetrahedric tetrads. Androphytes are 2-celled when shed. b) Endothecium cells exhibit ringed or spiralled fibrous thickenings on their tangential walls, like a folding hood. During the dehiscence, the endothecial cells compress along their tangential axis. In Cayaponia citrullifolia and C. bonariensis the epidermal cells also compress under endothecial pressure and the sporangium wall contracts over itself. But in Cucurbitella duriaei (Naudin) Cogn. the epidermal cells resist endothecial pressure and the androsporangium wall contracts more on its inner side than on the outer one, bending towards the loculus. Both dehiscence mechanisms are in relation to the androecium structure. c) The androgametogenesis suggests some kind of physical link between the gametogenic cell and the siphonogenic nucleus, which together form the male germ unit (Owens, 1992). This linkage could be established during or immediately after the mitosis of the androspore. According to some figures published in the literature, the gametogenic cell seems to be linked to the siphonogenic nucleus in other species of Cucurbitaceae, and it is also possible that the male gametes could be linked to the siphonogenic nucleus within the pollen tube.