Search Results (156)

Efficient adventitious root formation is crucial for Lavandula angustifolia Mill. propagation. This study evaluated the effects of continuous and short-duration pulse applications (1 min, 1 h, and 1 day) of the auxin dichlorprop (DCP) and its prodrug dichlorprop-2-ethylhexyl ester (DCPE) at varying concentrations on adventitious rooting and callus formation. DCPE generally proved more effective than DCP in promoting rooting, especially at lower concentrations, with continuous application of 0.1 µM DCPE yielding the highest number of adventitious roots. Notably, a brief 1 min pulse of 2.5 µM DCPE induced superior rooting, including high root number and weight, while minimizing callus formation compared to longer exposures. In contrast, 1 h pulse treatments showed a positive correlation between auxin concentration and root number but led to substantial callus development. These findings highlight DCPE’s potential as an efficient auxin source for lavender propagation, likely due to its rapid hydrolysis to active DCP within plant tissues, facilitating systemic distribution. The enhanced rooting achieved with short pulse treatments offers significant implications for optimizing commercial propagation for this economically important aromatic plant. Full article

Cinnamomum parthenoxylon (Jack) Meisner is an important spice tree species in southern China. In in vitro cultures of C. parthenoxylon, the young stem explants can differentiate into adventitious buds and roots under different exogenous growth regulator conditions. However, the underlying regulatory mechanisms governing this differentiation process remain unclear. In this study, physiological and biochemical characteristics were measured, and transcriptomic sequencing was performed in different differentiation processes. Significant changes in physiological and biochemical parameters were observed during the differentiation of the young stems. Soluble sugars, soluble proteins, malondialdehyde (MDA), zeatin riboside (ZR), abscisic acid (ABA), gibberellin (GA) content, the (IAA + GA + ZR)/ABA ratio, and polyphenol oxidase (PPO) activity displayed contrasting expression patterns during the formation of adventitious buds and roots. The RNA-seq result revealed that the differentiation direction of young stems is regulated by the synthesis of endogenous hormones and associated signaling pathways. At the same time, phenylpropanoid metabolism and glucose metabolism pathways acted as auxiliary pathways, facilitating the formation of adventitious buds and roots. Furthermore, quantitative real-time PCR (qRT-PCR) results were highly consistent with transcriptome sequencing results. This study lays the foundation for exploring the directional differentiation of young stems in C. parthenoxylon. Full article

Poplar (Populus spp.) is an economically and ecologically important temperate tree species known for its rapid growth. Clonal propagation has facilitated genetic advancements, but it remains challenging due to substantial variations in rooting capacity among poplar species and clones. Poplar clones were divided into two groups based on their rooting ability (high or low), and their transcriptome was analyzed for 3 weeks following stem-cutting propagation to investigate the rooting mechanisms of a hybrid of two fast-growing poplar species (Populus alba × P. tomentiglandulosa). The root length and area of the high-rooting group were 668.7% and 198.4% greater than those of the low-rooting ability group, respectively (maximum p < 0.001). Compared to week 0, genes involved in auxin signaling, cell wall organization, and secondary metabolite biosynthesis were consistently upregulated at 1, 2, and 3 weeks after planting, respectively. The expression of genes associated with cell wall differentiation and flavonoid biosynthesis was greater in the high- than in the low-rooting group at week 2. MYB and AP2/ERF transcription factors, which regulate flavonoid biosynthesis, as well as chalcone isomerase, a key enzyme in early flavonoid biosynthesis and root formation, were upregulated in the high-rooting group. The flavonoid biosynthesis pathway is important in rooting after stem cutting of Populus alba × P. tomentiglandulosa hybrids. Full article

Triadica sebifera, an economically and medicinally valuable tree species native to China, was investigated for its in vitro regeneration potential using leaf explants from nodal cuttings of young stems and sprouts. This study evaluated the effects of basal media, plant growth regulators (PGRs), explant sources, and incision methods on adventitious shoot induction, supplemented by histological analysis. The highest shoot regeneration frequency (98.89%) and maximum shoot number (72) were achieved via direct organogenesis using sucker-derived nodal cuttings cultured on MS medium with 2 mg/L 6- benzyladenine (6-BA), 0.3 mg/L kinetin (KT), and 0.2 mg/L α-naphthaleneacetic acid (NAA). Under identical conditions, branch-derived explants showed lower regeneration (84.44%, 64 shoots). Transverse midvein incision proved most effective, with sucker-derived leaves exhibiting superior regeneration. Shoots elongated completely (100%) on Murashige and Skoog (MS) medium containing 0.3 mg/L 6-BA, 0.03 mg/L NAA, and activated charcoal. Rooting was optimal on MS medium with 0.3 mg/L indole-3-butyric acid (IBA), yielding a 98% acclimatization survival rate. Histological analysis revealed de novo meristem formation from parenchyma cells, confirming direct organogenesis without callus intermediation, further validating the enhanced regenerative capacity of sprout-derived explants. This efficient in vitro regeneration system provides a foundation for large-scale propagation and germplasm conservation of T. sebifera, while offering insights for woody plant regeneration studies. Full article

In plants, the transition from the juvenile to adult stage involves physiological and anatomical changes initiated and partially controlled by evolutionarily conserved microRNAs. This process is of particular significance for the successful propagation of woody plant species that have transitioned to vegetative maturity and are recalcitrant to propagation. Conserved miRNAs differentially expressed between rejuvenated and mature Ilex paraguariensis plants were identified using high-throughput sequencing of small RNA libraries. The expression of miR156/miR157/miR528 was high in the leaves of juvenile plants and gradually decreased as the plant transitioned from juvenile to adult stages. In contrast, miR172 was predominantly expressed in adult plants. This variation confirmed that adults transitioned back to a juvenile phase after serial-rooted cuttings, allowing the plants to regain juvenile characteristics. Rejuvenation promotes the formation of adventitious roots and improves root structure, which supports the overall growth of the plant and results in greater vigour. The results will offer insights for further investigation into the molecular mechanisms regulating vegetative phase change in I. paraguariensis and other recalcitrant woody plant species. This knowledge could facilitate the earlier identification of rejuvenated material by analysing a wider range of genotypes and maturation stages, enhancing the efficiency of Ilex paraguariensis mass propagation. Full article

The Multi-Parent Advanced Generation Inter-Cross (MAGIC) population is a powerful tool for dissecting the genetic architecture controlling natural variation in complex traits. In this work, the natural variation available in Arabidopsis thaliana MAGIC lines was evaluated by mapping quantitative trait loci (QTLs) for primary root length (PRL), lateral root number (LRN), lateral root length (LRL), adventitious root number (ARN), and adventitious root length (ARL). We analyzed the differences in the root structure of 139 MAGIC lines by measuring PRL, LRN, LRL, ARN, and ARL. Through QTL mapping, we identified new potential genes that may be responsible for these traits. Furthermore, we detected single-nucleotide polymorphisms (SNPs) in the coding regions of candidate genes in the founder accessions and the recombinant inbred lines (RILs). We identified a significant region on chromosome 1 associated with AR formation. This region encompasses 316 genes, many of which are involved in auxin and gibberellin signaling and homeostasis. We discovered SNPs in the coding regions of these candidate genes in the founder accessions that may contribute to natural variation in AR characteristics. Additionally, we found a novel gene that encodes a protein from the hydroxyproline-rich glycoprotein family, which exhibits differential SNPs in accessions with contrasting AR formation. This study provides genetic insights into the natural variation in AR numbers using MAGIC lines linked to hormone-related genes. Full article

Cinnamomum bodinieri is a tree species highly valued for its superior-quality timber and ecological benefits. However, its large-scale propagation is hindered by the low efficiency of adventitious root (AR) formation. This study investigated the physiological and molecular mechanisms underlying AR formation in C. bodinieri. The results revealed that ARs originate from callus tissue, with the root primordium classified as a latent type. During AR formation, concentrations of soluble protein and soluble sugar decreased, while the activities of superoxide dismutase (SOD), peroxidase (POD), and indole-3-acetic acid oxidase (IAAO) peaked 20 days after cutting (CB2), with polyphenol oxidase (PPO) activity exhibiting an “N”-shaped trend. These findings indicate that substantial nutrient consumption is required for AR formation, with SOD, POD, PPO, and IAAO positively regulating the process. Indole-3-acetic acid (IAA) levels significantly decreased during the early stages of cutting but increased thereafter, whereas the concentration of abscisic acid (ABA) continuously rose. Similar trends were observed for zeatin riboside (ZR) and gibberellic acid (GA). Transcriptome analysis identified 28 key genes involved in plant hormone signal transduction pathways. Furthermore, weighted gene co-expression network analysis (WGCNA) pinpointed 14 hub genes, including CYP94B3 and NAC82, linked to hormone-associated traits. Furthermore, quantitative real-time PCR (qRT-PCR) confirmed the accuracy of the transcriptome sequencing results. This analysis uncovered critical interactions between hormonal signaling pathways and pivotal gene networks. Overall, the findings highlight the central regulatory role of endogenous hormones in AR formation, with IAA serving as the predominant regulator. Full article

Mei (Prunus mume Sieb. et Zucc.) is a rare woody species that flowers in winter, yet its large-scale propagation is limited by the variable ability of cuttings to form adventitious roots (ARs). In this study, two cultivars were compared: P. mume ‘Xiangxue Gongfen’ (GF), which roots readily, and P. mume ‘Zhusha Wanzhaoshui’ (ZS), which is more recalcitrant. Detailed anatomical observations revealed that following cutting, the basal region expanded within 7 days, callus tissues had appeared by 14 days, and AR primordia emerged between 28 and 35 days. Notably, compared to the recalcitrant cultivar ZS, the experimental cultivar GF exhibited significantly enhanced callus tissue formation and AR primordia differentiation. Physiological analyses showed that the initial IAA concentration was highest at day 0, whereas cytokinin (tZR) and gibberellin (GA1) levels peaked at 14 days, with ABA gradually decreasing over time, resulting in increased IAA/tZR and IAA/GA1 ratios during the rooting process. Transcriptomic profiling across these time points identified significant upregulation of key genes (e.g., PmPIN3, PmLOG2, PmCKX5, PmIAA13, PmLAX2, and PmGA2OX1) and transcription factors (PmWOX4, PmSHR, and PmNAC071) in GF compared to ZS. Moreover, correlation analyses revealed that PmSHR expression is closely associated with IAA and tZR levels. Overexpression of PmSHR in tobacco further validated its role in enhancing lateral root formation. Together, these findings provide comprehensive insights into the temporal, hormonal, and genetic regulation of AR formation in P. mume, offering valuable strategies for improving its propagation. Full article

The natural rooting rate and speed of cuttings of Camellia sinensis var. Assamica cv. Hainan-dayezhong (HD) are relatively low. To investigate the mechanisms by which growth regulators promote adventitious root (AR) formation in this tea variety, this study examined the effects of exogenous indene-naphthaleneacetic acid (ABT-1) and indole-3-butyric acid (IBA) treatments on the AR formation of cuttings, using water as a control. Systematic measurements and comparisons were carried out on the changes and differences in nutrient content, oxidase activity, and endogenous hormone levels and ratios during the AR formation process under the influence of exogenous hormone treatments. The relationships between these factors and the progression of AR formation in HD were analyzed. Both ABT-1 and IBA treatments significantly accelerated the AR formation process and improved the AR formation rate and AR formation index. Among them, IBA treatment showed a more pronounced promoting effect, increasing the AR formation rate by 21.58% and achieving an AR formation index of 32.14% compared with the control. During the AR formation process, both ABT-1 and IBA treatments increased the soluble sugar content and polyphenol oxidase (PPO) activity during the callus induction phase while decreasing peroxidase (POD) and indole-3-acetic acid oxidase (IAAO) activity during the callus induction and adventitious root initiation phases. Additionally, both treatments accelerated the consumption of endogenous hormones such as indole-3-acetic acid (IAA) and abscisic acid (ABA) and amplified fluctuations in cytokinin (CTK) levels and IAA/ABA ratios. Notably, IBA treatment resulted in greater changes in the soluble protein content and IAA/ABA ratio, with an increase of 49.22% and 80.87%, respectively. The two peaks of PPO activity occurred earlier, on days 10 and 40 after cutting, with IBA treatment having 6.85% and 40.35% higher activity than ABT-1 treatment at the corresponding time points, thereby maintaining relatively higher levels throughout callus induction and adventitious root initiation phases. Furthermore, IAAO activity decreased more significantly on days 10 and 30 after cutting, with decreases of 35.45% and 40.75%, respectively, which favored the formation of adventitious roots more. Both treatments promoted AR formation by regulating physiological balance, but IBA demonstrated superior efficacy in accelerating HD cutting rooting. These findings highlight IBA’s potential as a targeted growth regulator for improving HD propagation efficiency. Full article

This study presents the optimal light spectrum and medium composition for the in vitro induction of adventitious bulbs in T. tarda Stapf. Bulb scales, used as explants, were cultivated on 100% MS solid media with 3% or 6% sucrose and 0 or 0.5 µM BAP (6-benzyl-aminopurine) under a 16 h photoperiod and different fluorescent light treatments (white, red, blue). Darkness was used as a control. The cultures were maintained at 20 ± 2 °C for 12 weeks. The obtained results revealed that white light combined with 6% sucrose yielded the highest adventitious bulb formation, with an average of 12.1 ± 1.3 bulbs per explant. The bulbs formed directly on the surface of the explants. Red light combined with 3% sucrose and 0.5 µM BAP completely inhibited bulb formation, while darkness promoted leaf development, with a maximum of 1.3 ± 0.1 leaves per bulb, under darkness on medium with 6% sucrose. The addition of BAP, in most cases, was essential for root formation, with a maximum of 2.9 ± 0.6 roots per bulb under the influence of white light. This study demonstrates that it is possible to obtain an effective and efficient method for T. tarda propagation from bulb scales treated with 6% sucrose under white light condition. This method offers the potential for the commercial cultivation of this ornamental species. Full article

Quercus robur L., also referred to as “summer oak” or “English oak”, is an esthetically pleasing species, making it an excellent choice for street trees and gardens. Raising Quercus presents several challenges, including its long growth period, delayed germination, and inconsistent emergence. The shoot proliferation and adventitious root formation of Q. robur are crucial for establishing a tissue culture regeneration system and are vital for the successful transplantation of seedlings. To address this, experiments were conducted to assess shoot proliferation and adventitious root formation in Q. robur using various media. The shoot proliferation time, shoot proliferation coefficient, number of rooting strips, and length indicators of roots were recorded. The results indicated that a combination of 0.3 mg/L 6-Benzylaminopurine (6-BA) and 100 mg/L cefotaxime (Cef) was optimal for shoot propagation, while a solution of 0.1 mg/L 1-Naphthaleneacetic acid (NAA) and 1/2 Murashige and Skoog Medium (1/2MS) medium was most effective for root induction. This study has identified the optimal conditions for adventitious root formation and shoot proliferation in Q. robur, providing a basis for further research into propagation, germplasm conservation and genetic transformation techniques. Full article

Tree peony (Paeonia ostii T. Hong et J. X. Zhang) is an important medicinal and ornamental plant. It would be useful to propagate this plant in tissue culture, but it is difficult to induce root formation. Auxin plays a pivotal role in adventitious root formation, and ABCB transporter proteins are involved in auxin transport. To elucidate the function of the ABCB transporter family in P. ostii, we identified members of the ABCB gene family in the P. ostii genome and analyzed the functional characteristics of the putative proteins. In total, 29 ABCB genes were identified in P.ostii, distributed on five chromosomes. In a phylogenetic analysis, the PoABCBs were grouped into four subfamilies, with the largest being Subfamily I, characterized by their MDR structure. PoABCB genes in the same subfamily exhibited similar intron/exon arrangements and motif composition. The promoters of PoABCBs contained cis-acting elements associated with the photoresponse and hormone signaling. qRT-PCR analyses showed that, after treatment of tissue-cultured P. ostii seedlings with auxin, five PoABCB gene family members (PoABCB6, PoABCB10, PoABCB11, PoABCB12, and PoABCB16) were significantly upregulated during adventitious root development. These genes may play roles in the auxin response and adventitious root development of P. ostii in vitro. Full article

A study was conducted to access the effectiveness of exogenous application of indole-3-butyric acid (IBA) on adventitious root formation in kiwifruit semi-hardwood stem cuttings (SCs) from Actinidia deliciosa rootstock and Actinidia arguta female scion. Treatment comprised IBA concentrations of 0, 10, 100, 1000, 10,000 and 100,000 ppm. Parallel experiments for A. deliciosa and A. arguta’s treatment were arranged in a randomised complete block design, with 12 replications. In A. deliciosa, treatments had significant (p ≤ 0.05) effects in rooting percentage, number of roots, root length, size of callus formation and callus percentage, except for dry root mass. In A. arguta, treatments showed significant (p ≤ 0.05) effects in rooting percentage, number of roots, root length and dry root mass. No callus formation was observed in A. arguta. Relative to the control, in A. deliciosa, the highest (42%) rooting percentage and lengthy (0.301 cm) roots, were observed at 10,000 ppm IBA concentration, whereas the most (0.295) number of roots were produced at 100,000 ppm IBA concentration. Calli percentage (94%) was highest at 100 ppm IBA, while the size of callus formation was the biggest (2.8) at IBA concentration of 100,000 ppm, when compared to the control. In A. arguta, the highest (100%) rooting percentage was achieved at the control (0 ppm), 100 ppm and 10,000 ppm IBA concentrations, whereas the greatest (0.9815) number of roots were observed at the IBA concentration of 10 ppm. Lengthy (1.0839 cm) roots were achieved at IBA concentration of 100 ppm, whereas the greatest (0.1061 g) dry root mass was attained at IBA concentration of 10,000 ppm. In conclusion, the use of growth regulator IBA was effective for root formation in SCs of A. deliciosa rootstock. In A. arguta female scion, IBA application improved the quality of rooting (more and longer roots). IBA application showed its potential in stimulating root development at 10,000 ppm IBA. Full article

Efficient adventitious root formation is essential in micropropagation. Auxin prodrugs, inactive precursors that convert into active auxins within the plant, offer potentially improved rooting control and reduced phytotoxicity. This study investigated the efficacy of dichlorprop ester (DCPE), commercialized as Corasil^® and Clemensgros^® (originally intended to increase grapefruit size), in promoting in vitro root initiation in the model plant Populus × canadensis, compared to its hydrolyzed form DCP and the related compound C77. DCPE displayed a stronger root-inducing effect than DCP, especially at lower concentrations (0.01 and 0.1 µM). Notably, at 1 µM, both DCP and DCPE induced abundant aerial root formation, a phenomenon not previously observed in poplar with traditional auxin treatments. Metabolite analysis revealed distinct patterns. DCPE treatment resulted in rapid hydrolysis to DCP, leading to faster and more systemic distribution of the active auxin throughout the plant, compared to direct DCP application. C77 treatments showed slower uptake and limited translocation combined with slow metabolism to DCP. These results highlight the potential of auxin prodrugs like DCPE as an effective and controllable auxin source for optimizing in vitro rooting protocols in woody plant species. Full article

Adventitious root (AR) formation in plants originates from non-root organs such as leaves and hypocotyls. Auxin signaling is essential for AR formation, but the roles of other phytohormones are less clear. In Arabidopsis, at least two distinct mechanisms can produce ARs, either from hypocotyls as part of the general root architecture or from wounded organs during de novo root regeneration (DNRR). In previous reports, gibberellin acid (GA) appeared to play reverse roles in both types of ARs, since GA treatment blocks etiolation-induced AR formation from hypocotyls, whereas GA synthesis and signaling mutants apparently displayed reduced DNRR from detached leaves. In order to clarify this contradiction, we employed the GA biosynthesis inhibitor paclobutrazol (PBZ) and found that PBZ had positive effects on both types of AR formation in Arabidopsis. Consistently, GA treatment had negative effects on both AR formation mechanisms, while loss of GA synthesis and signaling promoted DNRR under our conditions. Our results show that PBZ treatment can rescue declined AR formation in difficult-to-root leaf explants such as erecta receptor mutants. Furthermore, transcriptional profiling revealed that PBZ treatment altered GA, brassinosteroids, and auxin responses, which included the up-regulation of LBD16 that is well known for its pivotal role in AR initiation. Full article