Galati Beatriz G, Monacci Federico, Gotelli Marina M, Rosenfeldt Sonia
Depto. Biodiversidad y Biología Experimental, Universidad de Buenos Aires, Pab. II, Ciudad Universitaria, C1428EHA, Buenos Aires, Argentina.
Ann Bot. 2007 Apr;99(4):755-63. doi: 10.1093/aob/mcm011. Epub 2007 Mar 12.
Although orbicular functions are still a matter of debate, they are considered by most authors to be exclusively formed by a secretory tapetum. However, the presence of orbicules on a peritapetal membrane associated with a plasmodial tapetum has been described for Abutilon pictum (Malvaceae) in a previous study. Thus, studies on other species of Malvaceae are necessary to corroborate the presence of such bodies in other members of the family. Pollen and microsporangium development of Modiolastrum malvifolium has been studied in this work.
Anthers at different stages of development were processed for transmission electron microscopy and light microscopy. Membranes and pollen walls resistant to acetolysis were isolated from whole anthers.
Microspore tetrads have a tetrahedral arrangement. Pollen grains are shed at the bicellular stage. The tapetum is invasive, non-syncytial and a peritapetal membrane with orbicules is formed.
This is the first report of the presence of orbicules on a peritapetal membrane in a species with a tapetum of an invasive, non-syncytial type. Taking into consideration all the information on the subject, it can be concluded that the presence of orbicules is not a stable criterion to differentiate between a secretory or plasmodial, or intermediate invasive, non-syncytial tapetum.
尽管小孢子周壁的功能仍存在争议，但大多数作者认为其仅由分泌型绒毡层形成。然而，在之前的一项研究中，已报道在金铃花（锦葵科）中，与变形绒毡层相关的周缘膜上存在小孢子周壁。因此，有必要对锦葵科的其他物种进行研究，以证实该科其他成员中是否存在此类结构。本研究对杨叶肖槿的花粉和小孢子囊发育进行了研究。
对不同发育阶段的花药进行透射电子显微镜和光学显微镜观察。从整个花药中分离出抗乙酰解的膜和花粉壁。
小孢子四分体呈四面体排列。花粉粒在二细胞阶段散落。绒毡层为侵入型、非合胞体，且形成了带有小孢子周壁的周缘膜。
这是关于侵入型、非合胞体类型绒毡层的物种中，周缘膜上存在小孢子周壁的首次报道。综合考虑关于该主题的所有信息，可以得出结论，小孢子周壁的存在并非区分分泌型或变形型，或中间侵入型、非合胞体绒毡层的稳定标准。
