Ecophysiological Traits of Terrestrial and Aquatic Carnivorous Plants: Are the Costs and Benefits the Same?

Identification of trade-offs among physiological and morphological traits and their use in cost-benefit models and ecological or evolutionary optimization arguments have been hallmarks of ecological analysis for at least 50 years. Carnivorous plants are model systems for studying a wide range of ecophysiological and ecological processes and the application of a cost-benefit model for the evolution of carnivory by plants has provided many novel insights into trait-based cost-benefit models. Central to the cost-benefit model for the evolution of botanical carnivory is the relationship between nutrients and photosynthesis; of primary interest is how carnivorous plants efficiently obtain scarce nutrients that are supplied primarily in organic form as prey, digest and mineralize them so that they can be readily used, and allocate them to immediate versus future needs. Most carnivorous plants are terrestrial – they are rooted in sandy or peaty wetland soils – and most studies of cost-benefit trade-offs in carnivorous plants are based on terrestrial carnivorous plants. However approximately 10% of carnivorous plants are unrooted aquatic plants. In this Forum paper, we ask whether the cost-benefit model applies equally well to aquatic carnivorous plants and what general insights into trade-off models are gained by this comparison. Nutrient limitation is more pronounced in terrestrial carnivorous plants, which also have much lower growth rates and much higher ratio of dark respiration to photosynthetic rates than aquatic carnivorous plants. Phylogenetic constraints on ecophysiological trade-offs among carnivorous plants remain unexplored. Despite differences in detail, the general cost-benefit framework continues to be of great utility in understanding the evolutionary ecology of carnivorous plants. We provide a research agenda that if implemented would further our understanding of ecophysiological trade-offs in carnivorous plants and also would provide broader insights into similarities and differences between aquatic and terrestrial plants of all types.Organismic and Evolutionary BiologyOther Research Uni

Phylogeny of the "orchid-like" bladderworts (gen. Utricularia sect. Orchidioides and Iperua : Lentibulariaceae) with remarks on the stolon-tuber system

Background and Aims The "orchid-like" bladderworts (Utricularia) comprise 15 species separated into two sections: Orchidioides and Iperua. These robust and mostly epiphytic species were originally grouped within the section Orchidioides by the first taxonomical systems. These species were later split into two sections when sect. Iperua was proposed. Due to the lack of strong evidence based on a robust phylogenetic perspective, this study presents a phylogenetic proposal based on four different DNA sequences (plastid and nuclear) and morphology to test the monophyly of the two sections. Methods In comparison with all previous phylogenetic studies, the largest number of species across the sections was covered: 11 species from sections Orchidioides and Iperua with 14 species as an external group. Maximum likelihood and Bayesian inferences were applied to DNA sequences of rps16, trnL-F, matK, the internal transcribed spacer (ITS) and three morphological characters: (1) the crest of the corolla; (2) the primary organs in the embryo; and (3) tubers. Additionally, a histochemical analysis of the stolons and tubers is presented from an evolutionary perspective. Key Results The analyses showed the paraphyly of sect. Iperua, since Utricularia humboldtii is more related to the clade of sect. Orchidioides. Utricularia cornigera is grouped in the sect. Iperua clade based on chloroplast DNA sequences, but it is nested to sect. Orchidioides according to ITS dataset. Morphological characters do not support the breaking up of the 'orchid-like' species into two sections, either. Moreover, the stolon-tuber systems of both sections serve exclusively for water storage, according to histological analyses. Conclusions This study provides strong evidence, based on DNA sequences from two genomic compartments (plastid and nucleus) and morphology to group the Utricularia sect. Orchidioides into the sect. Iperua. The tubers are important adaptations for water storage and have been derived from stolons at least twice in the phylogenetic history of 'orchid-like' bladderworts

Quite a few reasons for calling carnivores "the most wonderful plants in the world"

A plant is considered carnivorous if it receives any noticeable benefit from catching small animals. The morphological and physiological adaptations to carnivorous existence is most complex in plants, thanks to which carnivorous plants have been cited by Darwin as ‘the most wonderful plants in the world’. When considering the range of these adaptations, one realizes that the carnivory is a result of a multitude of different features. Scope: This review discusses a selection of relevant articles, culled from a wide array of research topics on plant carnivory, and focuses in particular on physiological processes associated with active trapping and digestion of prey. Carnivory offers the plants special advantages in habitats where nutrient supply is scarce. Counterbalancing costs are the investments in synthesis and the maintenance of trapping organs and hydrolysing enzymes. With the progress in genetic, molecular and microscopic techniques, we are well on the way to a full appreciation of various aspects of plant carnivory. Conclusions: Sufficiently complex to be of scientific interest and finite enough to allow conclusive appraisal, carnivorous plants can be viewed as unique models for the examination of rapid organ movements, plant excitability, enzyme secretion, nutrient absorption, food-web relationships, phylogenetic and intergeneric relationships or structural and mineral investment in carnivory

Th e infl uence of prey capture on photosynthetic rate in two aquatic carnivorous plant species

Abstract Photosynthetic (P N ) and dark respiration rate (RD) were measured in two species of aquatic carnivorous plants, Aldrovanda vesiculosa and Utricularia australis, growing with or without prey in an outdoor growth experiment. After 7-14 days, the positive growth effect of feeding on prey (apical growth rate, plant size, branching) was evident in both species. Tissue N content in young leaf whorls of both species fed on prey was significantly lower (by 54% in Aldrovanda, by 86% in Utricularia) than that in unfed variants, while tissue P content was about the same. In both species, chlorophyll a content was consistent with tissue N content and RD in fed and unfed variants was very similar. However, P N was significantly greater in fed plants of Aldrovanda, while lower in Utricularia. It is possible to conclude that feeding on prey in aquatic carnivorous plants leads to neither an increase of shoot tissue N content nor P N per unit biomass. Thus, the main physiological effect of catching prey is not enhancement of P N , but to provide N and P for essential growth processes in juvenile tissues.

Characteristics of turion development in two aquatic carnivorous plants: Hormonal profiles, gas exchange and mineral nutrient content

Abstract Turions are vegetative, dormant, and storage overwintering organs formed in perennial aquatic plants in response to unfavorable ecological conditions and originate by extreme condensation of apical shoot segments. The contents of cytokinins, auxins, and abscisic acid were estimated in shoot apices of summer growing, rootless aquatic carnivorous plants, Aldrovanda vesiculosa and Utricularia australis, and in developing turions at three stages and full maturity to reveal hormonal patterns responsible for turion development. The hormones were analyzed in miniature turion samples using ultraperformance liquid chromatography coupled with triple quadrupole mass spectrometry. Photosynthetic measurements in young leaves also confirmed relatively high photosynthetic rates at later turion stages. The content of active cytokinin forms was almost stable in A. vesiculosa during turion development but markedly decreased in U. australis. In both species, auxin content culminated in the middle of turion development and then decreased again. The content of abscisic acid as the main inhibitory hormone was very low in growing plants in both species but rose greatly at first developmental stages and stayed very high in mature turions. The hormonal data indicate a great strength of developing turions within sink–source relationships and confirm the central role of abscisic acid in regulating the turion development

Vascular tissue in traps of Australian carnivorous bladderworts (Utricularia) of the subgenus Polypompholyx

Utricularia (bladderworts) are rootless carnivorous plants forming small suction traps which are hollow discoid bladders. There is some controversy surrounding the understanding of trap vascularization in Utricularia species and most of the knowledge in the literature is based on aquatic Utricularia from section Utricularia. In this study, we investigated trap vascularization in 9 Utricularia species or clones from the subgenus Polypompholyx using several light microscopy staining techniques. Both xylem and phloem elements were found in the traps of all investigated species or clones. The pattern of trap vascular bundles from the subgenus Polypompholyx was similar to that reported for subgenus Bivalvaria, but different from that of aquatic U. vulgaris from the subgenus Utricularia. The system of trap vascularization in the members of the subgenus Polypompholyx was different from that found in the traps of Genlisea, which is a closely related genus (both Lentibulariaceae). The structure of trap vascular bundles was, however, similar in Genlisea and Polypompholyx. Possible utilization of xylem elements in Utricularia traps is discussed

Alternative or cytochrome? Respiratory pathways in traps of aquatic carnivorous bladderwort Utricularia reflexa

Carnivorous plants of the genus Utricularia (bladderwort) form modified leaves into suction bladder traps. The bladders are metabolically active plant tissue with high rates of mitochondrial respiration (RD). In general, plants possess two mitochondrial electron transport pathways to reduce oxygen to water: cytochrome and an alternative. Due to the high metabolic rate in the bladders, it is tempting to assume that the bladders prefer the cytochrome c oxidative pathway. Surprisingly, we revealed that alternative oxidase (AOX), which yields only a little ATP, is much more abundant in the bladders of Utricularia reflexa in comparison with the shoots. This pattern is similar to the carnivorous plants with passive pitcher traps (e.g. Sarracenia, Nepenthes) and seems to be widespread across many carnivorous taxa. The exact role of AOX in the traps of carnivorous plants remains to be investigated