Full length ArticleAuxin-cytokinin interaction and variations in their metabolic products in the regulation of organogenesis in two Eucomis species

•Variation in morphology and physiology in two Eucomis species was investigated.•Application of NAA with cytokinins enhanced growth in both species.•Both species demonstrated considerable variations in the levels of phytohormones.•20 isoprenoid and 17 aromatic cytokinin derivatives were quantified in the species.•Four auxin derivatives (IAA, IAAsp, OxIAA and IAGlu) were quantified in the species

In the current study, we evaluated the effect of α-naphthaleneacetic acid (NAA) individually or in combination with different cytokinins (CKs) including benzyladenine (BA), meta-topolin (mT) and isopentenyladenine (iP) on organogenesis, auxin and CK content in Eucomis autumnalis subspecies autumnalis (EA) and Eucomis zambesiaca (EZ). These species were used as model plants due to their ornamental and medicinal properties. Three leaf explants were inoculated in screw-cap jars containing 30 mL Murashige and Skoog (MS) media supplemented with 5 μM NAA alone or in combination with 5 μM CK (BA, mT or iP). After 10 weeks (EA) or 15 weeks (EZ), parameters including shoot and root growth as well as plant fresh weight were recorded. For analysis of auxin and CK content, whole plantlets were harvested, pooled and freeze-dried for the different treatments. In both species, shoot and root proliferation as well as plant biomass were generally higher when NAA was combined with the individual CK than in NAA or CK treatment. The highest concentration of indole-3-acetic acid (IAA, 619 pmol g−1 DW) and 2-oxindole-3-acetic acid (OxIAA, 2381 pmol g−1 DW) were observed in EA-treated with NAA alone while mT treatment (without NAA) had the most abundant indole-3-acetyl-l-aspartic acid (IAAsp, 904 and 582 pmol g−1 DW for EA and EZ, respectively) in both species. A significant concentration of total endogenous CK accumulated in both Eucomis regenerants from mT and mT + NAA when compared to the other treatments. The majority of the detected CKs were of the aromatic CK-type, mainly free bases. The potential physiological roles of these quantified phytohormones in relation to the observed morphological responses are discussed.