Morphological diversity of core Alismatalesтезисы доклада

Дата последнего поиска статьи во внешних источниках: 26 января 2018 г.

Работа с тезисами доклада


[1] Morphological diversity of core alismatales / S. Dmitry, P. Anna, L. Ingrid, R. Margarita // Abstract Book XIX International Botanical Congress. — 2017. — P. 265–265. core Alismatales includes all families of the order except Tofieldiaceae and Araceae. This is a rare example of a group of angiosperm families commonly recognized in pre-molecular era (as subclass Alismatidae) and then fully supported by molecular data in the same circumscription. Aquatic or semi-aquatic habit is of course the most remarkable feature of the group (hence the historical name Helobiae), but in terms of diagnostic characters,the presence of intravaginal squamules and the large storage embryo are the most remarkable. These two features are present in all members of core Alismatales (the squamules of Scheuchzeria are transformed in hairs) and are otherwise very rare among monocots. Both features are present in some Araceae being homoplastic within the family, and the squamules are present in Acorus. Morphological nature of intravaginal squamules is enigmatic. Arber (1923) highlighted that the squamules are attached above the leaf to the base of stem internode. We hypothesize that the squamules are homologous to collateral buds that are characteristic to monocots in general but not to the core Alismatales. The number and morphology of intravaginal squamules are of taxonomic significance in the core Alismatales, for example, distinguishing Potamogeton and former Zannichelliaceae. Leaves of the core Alismatales are diverse in terms of external morphology and anatomy. It is unclear whether they can be considered unifacial in any of the core Alismatales other than Tetroncium (Juncaginaceae). Leaves or leaf petioles have three-dimensional venation in several families, normally with a system of small peripheral vascular bundles. As in angiosperm succulents and halophytes (Ogburn & Edwards,2013), the three-dimensional leaf venation in thick aquatic and helophyte leaves of Alismatales serves to reduce transport distances between veins and photosynthetic cells (Platonova et al., 2016). Like in the eudicot order Caryophyllales (e.g., Melo-de-Pinna et al., 2014), the patterns of orientation of peripheral collateral bundles (with inverted adaxial or abaxial bundles) are unstable in Alismatales. These slender bundles cannot be used for the identification of unifacial leaves. Maundia (Maundiaceae) is remarkable in having similar anatomical structure of foliage leaves and inflorescence peduncles, both with xylem of small peripheral bundles oriented towards periphery of the organ. The similarity is due to their shared function as photosynthetic organs, though functional significance of particular types of bundle orientation remains unclear (Platonova et al., 2016). Compared to many other monocot lineages, the core Alismatales are remarkably diverse in terms of number and position of floral organs and degree and mode of intercarpellary fusion. Floral characters are homoplastic in Alismatales and inferring directions of their transformation is problematic. Patterns of floral diversity in Alismatales can be only partially explained by adaptations to aquatic habitats. In most cases, evolutionary reductions in number of floral organs left no rudiments in the core Alismatales, with notable exceptions in the family Juncaginaceae. The study is supported by the Russian Science Foundation (project 14-14-00250).

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