Abstract
The development of adventitious roots is affected by several factors, including the age of the cutting donor plant, which negatively affects rooting capacity. Eucalyptus globulus quickly loses rooting capacity of cuttings as the donor plant ages, although the molecular and biochemical mechanisms behind this process are still unclear. To better understand the bases of rooting competence loss in E. globulus, the time required for a significant decline in rhizogenic ability without exogenous auxin was determined in microcuttings derived from donor plants of different ages after sowing. Tip cuttings of donor plants were severed before and after loss of rooting competence of microcuttings to test the hypothesis that auxin and carbohydrate homeostasis regulate rooting competence decline. There were no significant changes in concentration of carbohydrates, flavonoids, or proteins before and after the loss of rooting capacity. Peroxidase (EC 1.11.1.7) total activity increased with loss of rooting competence. Auxin concentration showed the opposite pattern. In good agreement, TAA1, a key gene in auxin biosynthesis, had lower expression after loss of rooting capacity. The same applied to the auxin receptor gene TIR1, suggesting reduced auxin sensitivity. On the other hand, genes associated with auxin response repression (TPL, IAA12) or with the action of cytokinins, the rhizogenesis inhibitor-related ARR1, showed higher expression in plants with lower rooting competence. Taken together, data suggest that age negatively affects E. globulus rooting by a combination of factors. Decreased endogenous auxin concentration, possibly caused by less biosynthesis, lower auxin sensitivity, higher expression of genes inhibiting auxin action, as well as of genes related to the action of cytokinins, appear to play roles in this process.
Highlights
Eucalyptus globulus Labill. is considered one of the top species for the paper industry due to its high quality cellulose pulp, low lignin and lipid content, and high syringyl/guaiacyl (S/G) ratio (Cruz et al, 2006; Rencoret et al, 2007; Barbosa et al, 2008; Neiva et al, 2014)
adventitious root (AR) development starts with the induction phase, that involves the reprograming of target cells to new meristematic cells but absence of any visible cell divisions leading to the formation of internal root meristems
Progressive loss of adventitious rooting capacity of microcuttings derived from aging donor plants was evident, becoming significant around 1.5 to 2 months after sowing
Summary
Eucalyptus globulus Labill. is considered one of the top species for the paper industry due to its high quality cellulose pulp, low lignin and lipid content, and high syringyl/guaiacyl (S/G) ratio (Cruz et al, 2006; Rencoret et al, 2007; Barbosa et al, 2008; Neiva et al, 2014). Is considered one of the top species for the paper industry due to its high quality cellulose pulp, low lignin and lipid content, and high syringyl/guaiacyl (S/G) ratio (Cruz et al, 2006; Rencoret et al, 2007; Barbosa et al, 2008; Neiva et al, 2014) This is a rooting recalcitrant species (Le Roux and Van Staden, 1991; Fett-Neto et al, 2001), Adventitious Rooting Decline in Eucalypt sometimes making adventitious root (AR) development and vegetative propagation difficult. AR expression involves the growth of root primordia through the stem tissues and establishment of vascular connections. Induction phase is followed by the formation of dome-shaped root primordia (initiation phase), establishment of vascular connections and root emergence (expression phase) (Da Costa et al, 2013; Guan et al, 2015; Druege et al, 2016)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
