6-Benzylaminopurine and kinetin modulations during in vitro propagation of Quercus robur (L.): an assessment of anatomical, biochemical, and physiological profiling of shoots

Abstract

For many woody species, such as Quercus robur, cytokinins in the culture medium are required to maintain in vitro plant material. Among synthetic cytokinins, 6-benzylaminopurine (BAP) and kinetin (KIN) are the most frequently used. In addition to inducing shoots, cytokinins can cause morphophysiological disorders. Therefore, we aimed to investigate the anatomical, biochemical, and physiological alterations and pro les of Q. robur shoots exposed to two cytokinins, applied alone and in combination. Shoots previously established in vitro were transferred to WPM culture media supplemented with BAP at concentrations of 0, 1.25, and 3.50 µM combined with KIN at concentrations of 0, 0.62, and 1.25 µM totaling 9 treatments. Anatomical, physiological, and biochemical analyses were performed after 40 d of culture. BAP induced the formation of new buds with anatomically underdeveloped leaves; induced shoot-tip necrosis, which is considered a response to the ine cient transport of water and nutrients; reduced the thickness of the cell walls of phloem bers; and decreased the content of phenolic compounds and photosynthetic pigments. These responses were less pronounced with co-exposure to KIN. In contrast, KIN alone stimulated a larger area of secondary xylem and more ligni ed cell walls. BAP can induce shoots with underdeveloped anatomical and biochemical characteristics. Shoots that grew with KIN alone had stem and leaf anatomical characteristics, indicating greater commitment to cellular differentiation than proliferation. When both cytokinins are combined, KIN can partially mitigate the deleterious effects of BAP on in vitro growth.

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“…From the present investigations, we found that optimum cytokinin concentrations, i.e., MS + 2.0 mg/l KIN + 2.0 mg/l BAP, demonstrated the highest growth responses (average shoot length, number of leaves per shoot, FW, and DW). Martins et al (2022) found that the combination of two cytokinins can be more advantageous than using only one, which is consistent with our findings. In our studies, also the combination of auxins (MS + 0.5 IAA mg/l + 0.5 IBA mg/l + 1.0 mg/l NAA) promoted the root initiation, elongation, and number of roots per shoot.…”

“…Cytokinins and auxins were commonly used in culture media to influence physiological reactions that led to promotion of the growth of shoots, roots, and whole plant. A number of researchers have investigated the impact of auxins (NAA, IAA) and cytokinins (BAP, KIN) on in vitro growth and secondary metabolites from the plant ( Amoo and Staden, 2012 ; Martins et al., 2022 ). The highest concentrations of cytokinins offered the best outcomes, which may be due to the ability of BAP to promote cell proliferation and lateral bud development.…”

“…BAP exhibits a more sustained stimulation of cell division due to its stable nature and resistance to oxidation characteristics. In addition, it cannot easily broken down by plants ( Komakech et al., 2020 ; Okello et al., 2021 ; Martins et al., 2022 ).…”