Abscisic acid promotes root system development in birch tissue culture: a comparison to aspen culture and conventional rooting‐related growth regulators

Abstract

The research aim was to assess the effects of the plant hormone abscisic acid (ABA) and the growth regulator paclobutrazol (PBZ) on root system development during the in vitro culture of different birch and aspen genotypes. The studied genotypes involved two aspen (Populus tremula and Populus tremuloides × P. tremula) and two silver birch (Betula pendula) trees, with one of the birches characterized by its inability to root in vitro. For experiments, apical shoot segments were cultured on nutrient medium enriched with either ABA or PBZ. Additionally, the analysis of the endogenous hormones in shoots developed on hormone‐free medium was conducted by high‐performance liquid chromatography. The endogenous concentration of auxin indole‐3‐acetic acid was much higher in the aspens than that in the birches, while the highest concentration of ABA was found in the root‐forming birch. The culturing of this birch genotype on medium enriched with ABA resulted in an increased root length and a higher number of lateral roots without any negative effect on either shoot growth or adventitious root (AR) formation, although these two processes were largely inhibited by ABA in the aspens. Meanwhile, PBZ promoted AR formation in both aspen and birch cultures but impaired secondary root formation and shoot growth in birches. These results suggest the use of ABA for the in vitro rooting of birches and PBZ for the rooting of aspens.

Effect of Ethylene and Abscisic Acid on Steroid and Triterpenoid Synthesis in Calendula officinalis Hairy Roots and Saponin Release to the Culture Medium

“…In another study, ABA was applied in conditions of water deficiency and enhanced UVB radiation to improve the acclimation of grapevine ( Vitis vinifera ) to cultivation at high heights, and the treatment resulted in more than six-fold increased accumulation of squalene—the precursor of triterpenoids [ 36 ]. In plant in vitro cultures, ABA is used to enhance the production of phenolic acids in Salvia miltiorrhiza Bunge [ 29 ]; however, more often, it has been reported as a factor applied in various tissue culture systems to promote somatic embryogenesis, enhance somatic embryo quality or promote root system development [ 37 , 38 ]. The results obtained in the present study indicated that ABA can act as an efficient enhancer of the triterpenoid productivity in plant in vitro cultures.…”

An HD‐ZIP transcription factor, MxHB13, integrates auxin‐regulated and juvenility‐determined control of adventitious rooting in Malus xiaojinensis

“…Other hormone signaling pathways are also known to affect rooting. For example, ABA is known to promote root development in birch ( Betula pendula ) and aspen ( Populus tremula ) (Vaiciukyne et al., 2019). We found many ABA‐related DEGs with low expression in Mx‐A cuttings compared with Mx‐J cuttings, which was inconsistent with the previous report (Saito et al., 2019).…”

Adventitious Rooting in Populus Species: Update and Perspectives

“…The role of gibberellins (GAs) in AR formation is still unclear but a few studies have demonstrated that exogenous applications of gibberellic acid are inhibitors of AR formation in Populus . In the aspen P. tremula , the application of paclobutrazol (PBZ), an inhibitor of GA biosynthesis, was found to promote AR formation, whereas GA treatment had a negative effect on AR development in in vitro culture cuttings ( Žiauka and Kuusiene, 2010 ; Vaičiukynė et al, 2019 ). Moreover, transgenic hybrid aspen P. tremula × P. tremuloides overexpressing GA20ox1 , one of the genes that catalyzes the final step in the synthesis of bioactive GAs, had poor rooting efficiency, whereas overexpression of the GIBERELLINS INSENSITIVE ( GAI ) gene, which is a repressor of GA signaling, increased the number of ARs ( Eriksson et al, 2000 ; Busov et al, 2006 ; Mauriat et al, 2014 ).…”

“…Moreover, gene expression of ARF6 and ARF8 , positive regulators of adventitious rooting, was increased, whereas the expression of ARF17 , a negative regulator of adventitious rooting, was significantly lower at the base of the stem cuttings ( Tomiyama et al, 2020 ). In Populus , Vaičiukynė et al (2019) measured the content of ABA in in vitro cultured shoots of two aspens ( P. tremula , and P. tremuloides × P. tremula ) with different rooting abilities. No differences in ABA content were found between the two genotypes, suggesting that the endogenous content of ABA in the shoots is not correlated with the rooting ability of these two genotypes.…”