Vrijdaghs A, Goetghebeur P, Smets E, Muasya A M
Laboratory of Plant Systematics, Institute of Botany and Microbiology, K.U.Leuven, Kasteelpark Arenberg 31, B-3001 Leuven, Belgium.
Ann Bot. 2006 Sep;98(3):619-30. doi: 10.1093/aob/mcl138. Epub 2006 Jun 28.
In 1976 the monotypic genus Hellmuthia was placed in the Hypolytreae s.l., but was subsequently ascribed to the Mapanioideae, tribe Chrysitricheae, mainly because of the presence in Hellmuthia of two lateral, mapanioid-like floral scales with ciliated keels, the anatomy of the nutlet, the embryo and the inflorescence. Recently, based on cladistic analyses and supported by pollen ontogenetic evidence, Hellmuthia was transferred to a Cyperaceae, tribe Cypereae, clade mainly consisting of Ficinia and Isolepis. In this study, the floral ontogeny in Hellmuthia was investigated and compared with the floral ontogeny in Paramapania, with special attention for the floral scales.
Freshly collected inflorescences of Hellmuthia membranacea and Paramapania parvibractea were investigated using scanning electron and light microscopy.
In the conical 'spikelet' in Hellmuthia, proximal bracts occur, each axillating an axis with empty glume-like structures, or a reduced spikelet. Hence, it is a reduced partial inflorescence. In Hellmuthia, the stamen primordia originate before the primordia of the perianth-gynoecium appear. Moreover, a third adaxially positioned 'floral scale' was observed for the first time. The position and relative time of appearance of the floral scales in Hellmuthia are typical for perianth parts in Cyperoideae. The basal position of Hellmuthia within a clade of species with usually perianthless flowers, allows the presence of rudiments of a perianth in Hellmuthia to be interpreted as a primitive state. Development of the lateral 'scales' in Paramapania follows a different pattern. Therefore, it was decided that the lateral 'scales' in Paramapania are different from the lateral perianth parts in Hellmuthia. The pollen grains in Hellmuthia are cyperoid, with one polar and five lateral apertures, of which the membrane is covered with sexinous bodies. The pollen surface is granulate and perforate with microspines.
The floral ontogeny in Hellmuthia occurs according to the general cyperoid pattern. The lateral scales in Hellmuthia are perianth parts, and they are not homologous to the lateral 'scales' in Paramapania.
1976年，单型属Hellmuthia被归入广义的Hypolytreae族，但随后被归入Mapanioideae亚科、Chrysitricheae族，主要是因为Hellmuthia具有两枚具纤毛龙骨状的侧生、类似Mapanioideae亚科的花鳞片，以及小坚果、胚和花序的解剖结构。最近，基于分支系统学分析并得到花粉个体发育证据的支持，Hellmuthia被转移到莎草科Cypereae族，该分支主要由Ficinia和Isolepis组成。在本研究中，对Hellmuthia的花个体发育进行了研究，并与Paramapania的花个体发育进行了比较，特别关注花鳞片。
使用扫描电子显微镜和光学显微镜对新鲜采集的膜质Hellmuthia和小叶Paramapania的花序进行了研究。
在Hellmuthia的圆锥形“小穗”中，有近端苞片，每个苞片腋生一个具空颖状结构的轴或一个简化的小穗。因此，它是一个简化的部分花序。在Hellmuthia中，雄蕊原基在花被 - 雌蕊原基出现之前就已产生。此外，首次观察到第三个位于近轴面的“花鳞片”。Hellmuthia中花鳞片的位置和相对出现时间是莎草亚科花被部分的典型特征。Hellmuthia在通常无花被花的物种分支中的基部位置，使得Hellmuthia中花被残迹的存在被解释为一种原始状态。Paramapania中侧生“鳞片”的发育遵循不同的模式。因此，确定Paramapania中的侧生“鳞片”与Hellmuthia中的侧生花被部分不同。Hellmuthia中的花粉粒为莎草型，有一个极孔和五个侧孔，其膜覆盖有刺状突起。花粉表面具颗粒状且有微刺穿孔。
Hellmuthia的花个体发育按照一般的莎草型模式进行。Hellmuthia中的侧生鳞片是花被部分，它们与Paramapania中的侧生“鳞片”不同源。
