Assessing the effect of oxidative enzymes and stem anatomy on adventitious rooting of Olea europaea (L.) leafy cuttings

Abstract

Aim of study: To assess the role of polyphenol oxidase (PPO), peroxidase (POD) and indole-3-acetic acid oxidase (IAAox) during adventitious rooting (Ar) in semi-hardwood cuttings of the easy-to-root olive cv. ‘Arbequina’ and the difficult-to-root cv. ‘Kalamata’. Simultaneously, a histological study was carried out in both cultivars to investigate the tissue related with Ar development.Area of study: The rooting experiments were carried out in ‘Kostelenos’ nurseries (Troizinia, Greece) and in Agricultural University of Athens.Material and methods: Plant material to set up the experiment was collected from current year shoots from 15-year-old mother plants of ‘Arbequina’ and ‘Kalamata’ at three different seasons (summer, autumn and spring). The auxin indole-3-butyric acid (IBA) at 2000 mg L-1 was used as rooting inducer.Main results: Analysis revealed that ‘Kalamata’ had significantly higher enzymatic activities before experiment onset and during Ar compared to ‘Arbequina’. Control cuttings of both cultivars exhibited increased enzymatic activities compared to IBA treated ones. IAAox was on average three times higher in ‘Kalamata’ than in ‘Arbequina’ and exhibited significant peaks during Ar. Similar peaks of POD and PPO activities were also detected. Histological analyses in ‘Kalamata’ revealed a continuous sheath of sclerenchyma ring and increased cortex thickness. Significant cell proliferation occurred in the phloem region in ‘Arbequina’ 15 days after planting and afterwards the root initials started developing in the secondary phloem from cambial cells.Research highlights: The differences in enzymatic activities as well as in stem anatomy could partly justify the different rooting ability of both cultivars.

Azospirillum baldaniorum Sp245 Induces Anatomical Changes in Cuttings of Olive (Olea europaea L., cultivar Leccino): Preliminary Results

“…Transverse sections at the basal portion of semi-hardwood stem cuttings in the Leccino cultivar allowed the detection of cell types and the organization of tissues similar to those described for other olive cultivars [20]. No seasonal differences in stem anatomy were noted, in agreement with Denaxa et al [21]. In Figure 1, the anatomical structure of the stem at the beginning of the trials is reported, when cuttings were just withdrawn (day 0).…”

“…Recently, interesting findings were obtained from the hard-to-root olive cultivar Santa Caterina where a much more successful rooting treatment in comparison with IBA was recorded [13]. The failure of IBA to stimulate rooting, also recorded in hard-to-root cultivars (i.e., Kalamata), suggests that other physiological and/or biochemical factors might be involved in this process [21]. However, auxins remain one of the most important molecules produced by Azospirillum sp.…”

Collection positions in the branch, humic substances and indolebutyric acid in ‘Arbequina’ olive minicuttings

“…Corroborating with this information, Denaxa et al (2019) state that the adventitious root formation of 'Arbequina' olive tree can be affected by auxin interaction, enzymatic activities and anatomical structure.…”

“…On the other hand, Denaxa et al (2019), in an experiment with 'Arbequina' subapical cuttings with concentration of 2,000 mg L -1 of IBA, observed that most of the cuttings rooted without calluses formation, while few formed calluses. Fachinello et al ( 2005) can explained such fact, they state that there is no direct relationship between calluses formation and cuttings rooting and reiterate that although they are independent phenomena, in most cases, calluses formation and the appearance of adventitious roots are influenced by the same factors and can occur simultaneously.…”

Adventitious Root Formation in Plants: The Implication of Hydrogen Peroxide and Nitric Oxide

“…During the induction phase, apart from auxin and carbohydrate accumulation, several other biochemical changes take place, some of which include the local increase in jasmonate as well as of some phenolic compounds, reactive oxygen species (ROS), changes in the levels of other plant growth regulators (especially an increase in ethylene production due to wounding) and changes in the activity of enzymes such as peroxidases (PODs), phenoloxidases, and others [ 10 , 13 , 22 , 23 ]. Peroxidases are heme-containing enzymes with multifunctional roles and various organic substrates [ 30 ], including the endogenous auxin indole-3-acetic acid (IAA), and this is the reason for which they are considered classical rooting markers [ 10 , 11 , 31 , 32 ]. Polyamines have also been implicated in the rooting process since they have been found to promote ARF in some species and improve their response to the external application of auxin [ 11 , 16 , 33 , 34 , 35 , 36 ].…”