Unusual developmental morphology and anatomy of vegetative organs in Utricularia dichotoma\u2014leaf, shoot and root dynamics

Markus S Reut,Bartosz J Płachno

doi:10.1007/s00709-019-01443-6

Abstract

The terrestrial carnivorous species Utricularia dichotoma is known for a great phenotypic plasticity and unusual vegetative organs. Our investigation on 22 sources/populations revealed that after initiation of a leaf and two bladders on a stolon, a bud was formed in the proximal axil of the leaf, developing into a rosette with up to seven organs. The first two primordia of the bud grew into almost every possible combination of organs, but often into two anchor stolons. The patterns were generally not population specific. The interchangeability of organs increased with increasing rank in the succession of organs on stolon nodes. A high potential of switching developmental programs may be successful in a fluctuating environment. In this respect, we were able to show that bladders developed from anchor stolons experimentally when raising the water table. Anatomical structures were simple, lacunate and largely homogenous throughout all organs. They showed similarities with many hydrophytes, reflecting the plant’s adaptation to (temporarily) submerged conditions. The principal component analysis was used in the context of dynamic morphology to illustrate correlations between organ types in the morphospace of U. dichotoma, revealing an organ specific patchwork of developmental processes for typical leaves and shoots, and less pronounced for a typical root. The concept and methods we applied may prove beneficial for future studies on the evolution of Lentibulariaceae, and on developmental morphology and genetics of unusual structures in plants.

Highlights

The current study focuses on the terrestrial U. dichotoma Labill. of subgenus Polypompholyx Lehm. section Pleiochasia, since (a) Polypompholyx is considered to have the closest morphological affinity to the Genlisea-Utricularia ancestor
We investigated anatomical structures of stolons, leaves and bladder stalks of U. dichotoma to contribute to the overall understanding of the nature of these vegetative organs, and all data was analysed based on the principal component analysis (PCA) approach
The initial pattern of a first foliage leaf and two flanking bladders seems to differ from other Utricularia species outside of subgenus Polypompholyx, the initiation of further organs on the stolon node is on the same side of the leaf in various members of subg

Summary

Introduction

Due to the very special plant architecture, the genus Utricularia L. (Lentibulariaceae) has been and still is a popular subject to study developmental morphology (e.g. Darwin 1875; Goebel 1891, 1898, 1905; Lloyd 1942; Chormanski and Richards 2012; Rutishauser 2016), embryology (e.g. Kamieński 1877; Merz 1897; Lang 1901; Kondo et al 1978; Płachno and Świątek 2010, 2011; Płachno 2011), histology/ ultrastructure (e.g. Fineran 1980; Płachno et al 2017a, 2017b), and molecular phylogeny/genetics (e.g. Jobson and Albert 2002; Carretero-Paulet et al 2015a, 2015b; IbarraLaclette et al 2011, 2013; Silva et al 2018).Handling Editor: Peter NickAs a fascinating ambassador of the ‘carnivorous syndrome’ (Juniper et al 1989), Utricularia had evolved small bladders with an extremely fast suction mechanism to trap organisms in the water or wet soil (e.g. Poppinga et al 2015). As a fascinating ambassador of the ‘carnivorous syndrome’ (Juniper et al 1989), Utricularia had evolved small bladders with an extremely fast suction mechanism to trap organisms in the water or wet soil Mature plants of the sister genus Genlisea A.St.-Hil. have a less complex vegetative body with rosulate foliage leaves and leaf-like invers Y-shaped ‘rhizophylls’ showing homologies with the Utricularia bladder and functioning like an eel-trap in wet substrate (Lloyd 1942; Reut 1993; Fleischmann 2018). In contrast to Genlisea and Utricularia, the third genus within the family, Pinguicula L., traps the prey on its generally rosulate and sticky foliage leaves above ground, and grows roots into the soil (Fleischmann and Roccia 2018).

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