Stigma and pollen dimorphisms in Limonium sinense (Plumbaginaceae)
Date Issued
2010
Date
2010
Author(s)
Lai, Guan-Chung
Abstract
Many species of Plumbaginaceae are distyly, with long-styled morph and short-styled morph occurred in the same species. Furthermore, some distylous species have dimorphic stigmatic cells and pollen exine. Only pollination between two morphs (intermorph) is compatible, and this circumstance terms heteromorphic self-incompatibility. Previous researches in Plumbaginaceae hypothesized that the species with monomorphic stigma and pollen exine as well as self-incompatibility appeared first, and then the species with dimorphic stigma and pollen exine associated with self-incompatibility, forming heteromorphic self-incompatibility later. Limonium sinense, a perennial herb in Plumbaginaceae, is non-distylous but dimorphic in stigma and pollen exine. However, there was no report indicating the existence of hetermorphic self-incompatibility in this species, and the differentiation of morphological development between two morphs remained unclear.
In this study, SEM observation indicated that the number and shape of floral primodia and the developmental processes in early floral development stage of Morph A and Morph B in L. sinense were similar. Dimorphic stigmas and pollen grains appeared in later stage of floral development. Through observation of TEM, sparse procolumellae formed on tetraspore membrane of Morph A in the later tetrad stage of microsporogenesis and then developed into lophate exine in mature stage, while dense procolumellae deposited on tetraspore membrane of Morph B in the later tetrad stage of microsporogenesis and then forming reticulate exine in mature stage. At the same time, stigma primordial of Morph A developed into cob shape, while stigma primordia of Morph B differentiated into papillate shape. Field investigation of L. sinense revealed the positions of stigmas in Morph A were higher than that in Morph B, but the positions of anthers between two morphs were similar. The intermorph pollination had pollen grains germinated and pollen tube elongated normally, but the fruit set produced in Morph A was lower than that in Morph B. Pollination in the same morph (intramorph) displayed few pollen grains germinated and pollen tube elongated seldom into styles. The fruit set produced by intramorph pollination was low in both Morph A and Morph B. Selfing in L. sinense showed that no pollen grain germinated and no fruit produced.
The results of this study on L. sinense revealed that the stigma positions of Morph A and Morph B are different, that stigmas and pollen grains of these two Morphs had their differentiated developments starting from the late tetrad stage of microsporogenesis showed differentiated development, and that self-incompatibility is strong in intrafloral selfing but unstable in monomorphic interfloral pollination. The results were coinciding with the presumption of previous research on the evolutionary sequences of heteromorphic self-incompatibility system in Plumbaginaceae, with self-incompatibility first, then dimorphic stigmas and pollen grains, and finally heteromorphic self-incompatibility.
Subjects
pollen / stigma dimorphisms
microsporogenesis
Plumbaginaceae
distyly
Type
thesis
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