Cytokinin, auxin and physiological polarity in the aquatic carnivorous plants Aldrovanda vesiculosa and Utricularia australis.
The typical rootless linear shoots of aquatic carnivorous plants exhibit clear, steep polarity associated with very rapid apical shoot growth. The aim of this study was to determine how auxin and cytokinin contents are related to polarity and shoot growth in such plants.



The main auxin and cytokinin metabolites in separated shoot segments and turions of two carnivorous plants, Aldrovanda vesiculosa and Utricularia australis, were analysed using ultra-high-performance liquid chromatography coupled with triple quad mass spectrometry.



In both species, only isoprenoid cytokinins were identified. Zeatin cytokinins predominated in the apical parts, with their concentrations decreasing basipetally, and the trans isomer predominated in A. vesiculosa whereas the cis form was more abundant in U australis. Isopentenyladenine-type cytokinins, in contrast, increased basipetally. Conjugated cytokinin metabolites, the O-glucosides, were present at high concentrations in A. vesiculosa but only in minute amounts in U. australis. N(9)-glucoside forms were detected only in U. australis, with isopentenyladenine-9-glucoside (iP9G) being most abundant. In addition to free indole-3-acetic acid (IAA), indole-3-acetamide (IAM), IAA-aspartate (IAAsp), IAA-glutamate (IAGlu) and IAA-glycine (IAGly) conjugates were identified.



Both species show common trends in auxin and cytokinin levels, the apical localization of the cytokinin biosynthesis and basipetal change in the ratio of active cytokinins to auxin, in favour of auxin. However, our detailed study of cytokinin metabolic profiles also revealed that both species developed different regulatory mechanisms of active cytokinin content; on the level of their degradation, in U. australis, or in the biosynthesis itself, in the case of A. vesiculosa Results indicate that the rapid turnover of these signalling molecules along the shoots is essential for maintaining the dynamic balance between the rapid polar growth and development of the apical parts and senescence of the older, basal parts of the shoots.
Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany AS CR and Faculty of Science of Palacký University, Šlechtitelů 27, CZ-78371 Olomouc, Czech Republic Department of Chemical Biology and Genetics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science of Palacký University, Šlechtitelů 27, CZ-78371 Olomouc, Czech Republic.
Jan
J
Šimura
Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany AS CR and Faculty of Science of Palacký University, Šlechtitelů 27, CZ-78371 Olomouc, Czech Republic Department of Chemical Biology and Genetics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science of Palacký University, Šlechtitelů 27, CZ-78371 Olomouc, Czech Republic.
Lukáš
L
Spíchal
Institute of Botany of the Czech Academy of Sciences, Section of Plant Ecology, Dukelská 135, CZ-37982 Třeboň, Czech Republic.
Lubomír
L
Adamec
Department of Chemical Biology and Genetics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science of Palacký University, Šlechtitelů 27, CZ-78371 Olomouc, Czech Republic.
Aleš
A
Pěnčík
Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany AS CR and Faculty of Science of Palacký University, Šlechtitelů 27, CZ-78371 Olomouc, Czech Republic.
Jakub
J
Rolčík
Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany AS CR and Faculty of Science of Palacký University, Šlechtitelů 27, CZ-78371 Olomouc, Czech Republic.
Ondřej
O
Novák
Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany AS CR and Faculty of Science of Palacký University, Šlechtitelů 27, CZ-78371 Olomouc, Czech Republic miroslav.strnad@upol.cz.
Miroslav
M
Strnad
D059001:Aquatic Organisms; D060435:Carnivory; D003583:Cytokinins / Q000378:metabolism*; D031257:Droseraceae / Q000502:physiology; D007210:Indoleacetic Acids / Q000378:metabolism*; D019684:Magnoliopsida / Q000502:physiology*; D018520:Plant Shoots / Q000378:metabolism
D003583:Cytokinins; D007210:Indoleacetic Acids; C030737:indoleacetic acid; C015950:indoleacetamide
Aldrovanda vesiculosa; Auxin; Utricularia australis; cytokinin; growth polarity; phytohormones; rootless aquatic plants