Physiological and Biochemical Responses of Merwilla plumbea Cultured In Vitro with Different Cytokinins After 1 Year of Growth Under Ex Vitro Conditions
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Since their discovery in the 1950s, cytokinins (CKs) have become integral, almost indispensable, components of plant growth media in in vitro propagation. However, despite the extensive use of exogenous CKs in plant tissue culture systems, there is a paucity of knowledge on the longevity of their physiological effect post in vitro. The objective of this study was to evaluate the long-term physiological effect of CKs (including a novel meta-topolin derivative) applied during in vitro propagation of Merwilla plumbea after 1 year of ex vitro growth. Ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) was used for the quantification of endogenous auxins and phenolic compounds in the 1-year-old M. plumbea plants. Compared to the control, exogenous CKs had a significant carry-over effect on ex vitro growth of M. plumbea plants after 1 year growing under ex vitro conditions. M. plumbea plants treated with the novel CK 6-(3-hydroxybenzylamino)-9-(tetrahydropyran-2-yl)purine (mTTHP, 1.0 µM) had significantly higher leaf area per plant, total leaf fresh weight and bulb diameter. Varying concentrations of free indole-3-acetic acid (IAA), oxindole-3-acetic acid (OxIAA) and indole-3-acetyl-l-aspartic acid (IAA-Asp) were detected in leaves of plants originally treated with exogenous CKs, whereas these compounds were absent in leaves of plants without exogenous CKs. Likewise, a CK-type and concentration-dependent response was observed for hydroxybenzoic acids, hydroxycinnamic acids, flavonoids and antioxidant activity of the extracts. The current study showed the influence of type and concentration of exogenous CKs used in vitro on production of phytochemical compounds during ex vitro growth. Taken together, the study provides significant insights on the residual effect of exogenous CKs on the regulation of auxin homeostasis and phenolic acid and/or flavonoid metabolism in 1-year-old M. plumbea plants growing under ex vitro conditions.
KeywordsAsparagaceae Auxins Cytokinins Flavonoids Phenolic acids
The National Research Foundation and University of KwaZulu-Natal, South Africa provided financial support. This work was also financed by the Ministry of Education, Youth and Sports, Czech Republic (Grant LO1204 from the National Program of Sustainability). We thank Mrs Alison Young (UKZN Botanical Garden, Pietermaritzburg, South Africa) and her staff for their assistance in maintaining the greenhouse facilities.
M.M., S.O.A. and A.O.A. conceived research idea and designed the experiments. L.P. and K.D. synthesized the meta-topolins and prepared 6-(3-hydroxybenzylamino)-9-(tetrahydropyran-2-yl)purine. J.G. and M.S. quantified the phenolic compounds while AP conducted the auxin analysis. M.M., A.O.A., S.O.A., A.P., J.G. and M.S. analysed the data. M.M. wrote the draft manuscript with help from S.O.A. and A.O.A. K.D. and J.V.S. contributed research facilities/reagents/materials and supervised the research. All authors read and edited the final manuscript.
- Aremu AO, Plačková L, Gruz J, Bíba O, Šubrtová M, Novák O, Doležal K, Van Staden J (2015) Accumulation pattern of endogenous cytokinins and phenolics in different organs of one-year-old cytokinin pre-incubated plants: implications for conservation. Plant Biol 17:1146–1155CrossRefPubMedGoogle Scholar
- Jones B, Gunnerås SA, Petersson SV, Tarkowski P, Graham N, May S, Dolezal K, Sandberg G, Ljung K (2010) Cytokinin regulation of auxin synthesis in Arabidopsis involves a homeostatic feedback loop regulated via auxin and cytokinin signal transduction. Plant Cell 22:2956–2969CrossRefPubMedPubMedCentralGoogle Scholar
- Karioti A, Hadjipavlou-Litina D, Mensah ML, Fleischer TC, Skaltsa H (2004) Composition and antioxidant activity of the essential oils of Xylopia aethiopica (Dun) A. Rich. (Annonaceae) leaves, stem bark, root bark, and fresh and dried fruits, growing in Ghana. J Agric Food Chem 52:8094–8098CrossRefPubMedGoogle Scholar
- Makara A, Rubaihayo P, Magambo M (2012) Carry-over effect of thidiazuron on banana in vitro proliferation at different culture cycles and light incubation conditions. Afr J Biotechnol 9:3079–3085Google Scholar
- Nordström A, Tarkowski P, Tarkowska D, Norbaek R, Åstot C, Dolezal K, Sandberg G (2004) Auxin regulation of cytokinin biosynthesis in Arabidopsis thaliana: a factor of potential importance for auxin–cytokinin-regulated development. Proc Natl Acad Sci USA 101:8039–8044CrossRefPubMedPubMedCentralGoogle Scholar
- Szüčová L, Spíchal L, Doležal K, Zatloukal M, Greplová J, Galuszka P, Kryštof V, Voller J, Popa I, Massino FJ, Jørgensen J-E, Strnad M (2009) Synthesis, characterization and biological activity of ring-substituted 6-benzylamino-9-tetrahydropyran-2-yl and 9-tetrahydrofuran-2-ylpurine derivatives. Bioorg Med Chem 17:1938–1947CrossRefPubMedGoogle Scholar