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Cytokinin profiles in ex vitro acclimatized Eucomis autumnalis plants pre-treated with smoke-derived karrikinolide

Aremu, Adeyemi O., Plačková, Lenka, Novák, Ondřej, Stirk, Wendy A., Doležal, Karel, Van Staden, Johannes
Plant cell reports 2016 v.35 no.1 pp. 227-238
Eucomis autumnalis, benzyladenine, biomass, bulbs, cytokinins, leaf area, leaves, micropropagation, naphthaleneacetic acid, plant growth, plant hormones, rooting
KEY MESSAGE : The current evidence of regulatory effect of smoke–water (SW) and karrikinolide (KAR ₁) on the concentrations of endogenous cytokinins in plants partly explain the basis for their growth stimulatory activity. Karrikinolide (KAR₁) which is derived from smoke–water (SW) is involved in some physiological aspects in the life-cycle of plants. This suggests a potential influence on the endogenous pool (quantity and quality) of phytohormones such as cytokinins (CKs). In the current study, the effect of SW (1:500; 1:1000; 1:1500 v/v dilutions) and KAR₁ (10⁻⁷; 10⁻⁸; 10⁻⁹ M) applied during micropropagation of Eucomis autumnalis subspecies autumnalis on the ex vitro growth and CKs after 4 months post-flask duration was evaluated. The interactions of SW and KAR₁ with benzyladenine (BA), α-naphthaleneacetic acid (NAA) or BA+NAA were also assessed. Plants treated with SW (1:500) and KAR₁ (10⁻⁸ M) demonstrated superior growth in terms of the rooting, leaf and bulb sizes and fresh biomass than the control and plants treated with BA and BA+NAA. However, plant growth was generally inhibited with either SW (1:500) or KAR₁ (10⁻⁸ M) and BA when compared to BA (alone) treatment. Relative to NAA treatment, the presence of KAR₁ (10⁻⁷ M) with NAA significantly increased the leaf area and fresh biomass. Both SW and KAR₁-treated plants accumulated more total CKs, mainly isoprenoid-type than the control and NAA-treated plants. The highest CK content was also accumulated in SW (1:500) with BA+NAA treatments. Similar stimulatory effects were observed with increasing concentrations of KAR₁ and BA. The current findings establish that SW and KAR₁ exert significant influence on the endogenous CK pools. However, the better growth of plants treated with SW and KAR₁ treatments was not exclusively related to the endogenous CKs.