Adventitious Root Formation In Cuttings Research Articles

The Rooting of Stem Cuttings and the Stability of uidA Gene Expression in Generative and Vegetative Progeny of Transgenic Pear Rootstock in the Field.

Adventitious rooting plays an important role in the commercial vegetative propagation of trees. Adventitious root formation is a complex biological process, but knowledge of the possible unintended effects induced by both the integration/expression of transgenes and in vitro conditions on the rooting is limited. The long-term stability of transgene expression is important both for original transformants of woody plants and its progeny. In this study, we used field-grown pear rootstock GP217 trees transformed with the reporter ß-glucuronidase (uidA) genes with and without intron and re-transformed with the herbicide resistance bar gene as model systems. We assessed the unintended effects on rooting of pear semi-hardwood cuttings and evaluated the stability of transgene expression in progeny produced by generative (seedlings) and vegetative (grafting, cutting) means up to four years. Our investigation revealed that: (1) The single and repeated transformations of clonal pear rootstocks did not result in unintended effects on adventitious root formation in cuttings; (2) stability of the transgene expression was confirmed on both generative and vegetative progeny, and no silenced transgenic plants were detected; (3) yearly variation in the gene expressions was observed and expression levels were decreased in extremely hot and dry summer; (4) the intron enhanced the expression of uidA gene in pear plants approximately two-fold compared to gene without intron. The current study provides useful information on transgene expression in progeny of fruit trees under natural environmental conditions.

Endogenous hormone levels and activities of IAA-modifying enzymes during adventitious rooting of tree peony cuttings and grafted scions

During rooting of both cuttings and grafted scions of tree peony (Paeonia suffruticosa Andr.) cultivar ‘Fengdanbai’, the anatomical structure, the contents of endogenous hormones (indole acetic acid, IAA; zeatin, ZT; gibberellin, GA3; and abscisic acid, ABA), and the activities of IAA oxidase (IAAO), peroxidase (POD), and polyphenol oxidase (PPO) were observed. The results showed that the rooting processes in cuttings and grafted scions were similar, but that the critical period of rooting in cuttings was earlier than in grafts (cuttings: 18–20 days; scions: 38–40 days). IAA content showed a direct correlation with rooting, with the peak value appearing as the adventitious roots were breaking through the epidermis in both cuttings and grafts (cuttings: 20 days; scions: 38 days). ZT and GA3 promoted adventitious rooting, and ABA inhibited it. The peak values of the IAA:ABA and IAA:ZT ratios appeared at the same time as the IAA peak (cuttings: 20 days; scions: 38 days), which indicated that these values were closely related to the occurrence of adventitious roots. Changes in the activities of IAAO, POD, and PPO, which modify IAA levels, indicated that there were no direct relationships between these three enzymes and adventitious root formation in cuttings or grafts. These results provide a basis for further study of adventitious root formation in the ornamental tree peony.

Petunia as model for elucidating adventitious root formation and mycorrhizal symbiosis: at the nexus of physiology, genetics, microbiology and horticulture.

Adventitious root formation in cuttings and establishment of arbuscular mycorrhizal symbiosis reflect the enormous plasticity of plants and are key factors in the efficient and sustainable clonal propagation and production of ornamental crops. Based on the high importance of Petunia hybrida for the European and US annual bedding plant markets and its suitability as a model for basic plant sciences, petunia has been established as an experimental system for elucidating the molecular and physiological processes underlying adventitious root formation and mycorrhizal symbiosis. In the present review, we introduce the tools of the Petunia model system. Then, we discuss findings regarding the hormonal and metabolic control of adventitious rooting in the context of diverse environmental factors as well as findings on the function of arbuscular mycorrhiza related to nutrient uptake and resistance to root pathogens. Considering the recent publication of the genomes of the parental species of P. hybrida and other tools available in the petunia scientific community, we will outline the quality of petunia as a model for future system‐oriented analysis of root development and function in the context of environmental and genetic control, which are at the heart of modern horticulture.

Comprehensive Analysis of R2R3-MYB Genes During Adventitious Root Formation in Cuttings of Morus alba

Mulberry is a widespread and important economic crop in China. Cutting is a suitable method for large-scale propagation of fine cultivars, but it is limited by the low rate of adventitious root (AR) formation. Currently, we found large variations of R2R3-MYB genes during AR formation in Morus alba. There are a few studies on this issue, and therefore a systematic research is needed to improve the cuttage technique. The Hidden Markov Model (HMM) was built and applied in searching MYB genes. Phylogenetic relationships with subtribe designations and clustering expression of R2R3-MYB proteins were obtained referring to the transcriptome sequencing data in the normal cutting process. In addition, hormone trials with exogenous hormone treatment were performed to observe R2R3-MYB gene expression levels by quantitative real-time PCR (qRT-PCR) along with physiological changes during AR formation. In this study, we first identified 116 R2R3-MYB family genes of 247 MYB genes in mulberry (M. alba). They are clustered into 51 subtribes according to the structures of motifs and phylogenetic classes. On the basis of data analysis, the majority of R2R3-MYB genes play roles as activating transcription factors in the cortex during AR formation, which synchronously participate in many related signal pathways. Our results showed the R2R3-MYB genes have a detailed classification and express differently in the process of cutting, indicating that this gene family plays important roles during AR formation and functions differently in response to the corresponding signal pathways.

Plant Hormone Homeostasis, Signaling, and Function during Adventitious Root Formation in Cuttings.

Adventitious root (AR) formation in cuttings is a multiphase developmental process, resulting from wounding at the cutting site and isolation from the resource and signal network of the whole plant. Though, promotive effects of auxins are widely used for clonal plant propagation, the regulation and function of plant hormones and their intricate signaling networks during AR formation in cuttings are poorly understood. In this focused review, we discuss our recent publications on the involvement of polar auxin transport (PAT) and transcriptional regulation of auxin and ethylene action during AR formation in petunia cuttings in a broad context. Integrating new findings on cuttings of other plant species and general models on plant hormone networks, a model on the regulation and function of auxin, ethylene, and jasmonate in AR formation of cuttings is presented. PAT and cutting off from the basipetal auxin drain are considered as initial principles generating early accumulation of IAA in the rooting zone. This is expected to trigger a self-regulatory process of auxin canalization and maximization to responding target cells, there inducing the program of AR formation. Regulation of auxin homeostasis via auxin influx and efflux carriers, GH3 proteins and peroxidases, of flavonoid metabolism, and of auxin signaling via AUX/IAA proteins, TOPLESS, ARFs, and SAUR-like proteins are postulated as key processes determining the different phases of AR formation. NO and H2O2 mediate auxin signaling via the cGMP and MAPK cascades. Transcription factors of the GRAS-, AP2/ERF-, and WOX-families link auxin signaling to cell fate specification. Cyclin-mediated governing of the cell cycle, modifications of sugar metabolism and microtubule and cell wall remodeling are considered as important implementation processes of auxin function. Induced by the initial wounding and other abiotic stress factors, up-regulation of ethylene biosynthesis, and signaling via ERFs and early accumulation of jasmonic acid stimulate AR formation, while both pathways are linked to auxin. Future research on the function of candidate genes should consider their tissue-specific role and regulation by environmental factors. Furthermore, the whole cutting should be regarded as a system of physiological units with diverse functions specifically responding to the environment and determining the rooting response.

Influence of light and shoot development stage on leaf photosynthesis and carbohydrate status during the adventitious root formation in cuttings of Corylus avellana L.

Adventitious root formation in plant cuttings is influenced by many endogenous and environmental factors. Leaf photosynthesis during rooting of leafy cuttings in hard to root species can contribute to supply carbohydrates to the intensive metabolic processes related to adventious root formation. Light intensity during rooting is artificially kept low to decrease potential cutting desiccation, but can be limiting for photosynthetic activity. Furthermore, leafy cuttings collected from different part of the shoot can have a different ability to fuel adventitious root formation in cutting stem. The aim of this work was to determine the role of leaf photosynthesis on adventitious root formation in hazelnut (Corylus avellana L) (a hard-to-root specie) leafy cuttings and to investigate the possible influence of the shoot developmental stage on cutting rooting and survival in the post-rooting phase. Cutting rooting was closely related to carbohydrate content in cutting stems during the rooting process. Cutting carbohydrate status was positively influenced by leaf photosynthesis during rooting. Non-saturating light exposure of leafy cuttings can contribute to improve photosynthetic activity of leafy cuttings. Collection of cuttings from different part of the mother shoots influenced rooting percentage and this appear related to the different capability to concentrate soluble sugars in the cutting stem during rooting. Adventitious root formation depend on the carbohydrate accumulation at the base of the cutting. Mother shoot developmental stage and leaf photosynthesis appear pivotal factors for adventitious roots formation.

Transcript profiling analysis reveals crucial genes regulating main metabolism during adventitious root formation in cuttings of Morus alba L.

Mulberry is an important economic crop spread widely in China for long time, and cutting is the most suitable method for good varieties in large scale propagation, which is limited by the low adventitious rooting rate. Currently, the regulation mechanisms in adventitious roots (AR) formation of mulberry (Morus alba L.) are not completely known. A genome-wide gene expression profiling was conducted by Solexa sequencing at pivotal stages. Differentially expressed annotated genes were obtained from the analysis of Gene Orthology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and Orthology (KO). Some related genes were selected to confirm the altered expression levels by quantitative real-time PCR (qRT-PCR). By transcript profiling analysis we found differentially expressed genes associated with common pathways including hormone signal transduction, cell cycle, carbohydrate metabolism and energy metabolism that play important roles in AR formation (M. alba L), which were found more obvious in the period of root primordia formation, not initial formation of callus. In addition, the qRT-PCR confirmations agreed well with the results. The period of root primordia formation was verified to be more important during the whole procedure of AR formation in cuttings, mainly regulated by several critical signal pathways of hormones and effected by other genes in cell cycle and energy metabolism.

Stem Anatomy and Adventitious Root Formation in Cuttings of Angophora, Corymbia and Eucalyptus

Many plantation eucalypts are difficult to propagate from cuttings, and their rooted cuttings often possess very few adventitious roots. We microscopically examined the stem anatomy of cuttings from 12 species of eucalypts and we determined whether adventitious root formation in auxin-treated cuttings of four species was limited to particular positions around the vascular tissue. Most species contained a central pith that was arranged in a four-pointed stellate pattern. The surrounding vascular tissue was also arranged in a stellate pattern near the shoot apex but it developed a more rectangular shape at the outer phloem as the stems enlarged radially. Adventitious roots formed at, or slightly peripheral to, the vascular cambium, and they formed at both the corners and the sides of the rectangular-shaped vascular tissue. The study highlighted that auxin-treated eucalypt cuttings can produce roots at multiple positions around the vascular tissue and so propagation methods can aim to produce more than four adventitious roots per rooted cutting. Higher numbers of adventitious roots could improve the root system symmetry, stability, survival and growth rate of clonal eucalypt trees.

Effect of Indole 3-Butyric Acid and Media Type on Adventitious Root Formation in Sheanut Tree (<i>Vitellaria paradoxa</i> C. F. Gaertn.) Stem Cuttings

Shea nuts play an important role in food security for rural folks within sub-Sahara Africa, serving as the main source of income for many people living in Northern Ghana. Unfortunately, the full economic potential of the Sheanut tree has not been fully realized due to the difficulty involved in its domestication. This difficulty in vegetatively propagating sheanut trees has greatly hindered its cultivation and the realization of its true economic potential. Two experiments were conducted to investigate the effects of rooting media and varying indole 3-butyric acid (IBA) concentrations on adventitious root formation in cuttings taken from coppiced sheanut trees. Results indicated that 3000 ppm produced significantly (p 0.05) better rooting (57.5%) than 5000 ppm (30%), 7000 ppm (45.0%) and the control (7.5%). Although the levels of soluble sugars (SS) and total free phenols (TFP) in the cutting were significantly (p 0.05) higher at the end of the experiment (after IBA treatment) compared to the start (prior to IBA treatment), the SS and TFP trends observed did not clearly explain the rooting differences found between the IBA levels investigated. Callus formation was significantly (p 0.05) higher (35.0%) in the control (no IBA). Generally, callus formation decreased with increasing IBA concentration. In the rooting media experiment, rooting was significantly (p 0.05) higher in the rice husk medium (35.0%) compared to that in the palm fiber (18.3%), saw dust (14.1%) and top soil (16.7%) media.

Nitrogen absorption, growth of stock plants, and adventitious rooting of Pelargonium × hortorum cuttings as affected by the form and dosage of nitrogen

SummaryEffective modern production of young Pelargonium hortorum L.H. Bailey plants requires a reliable rooting response of shoot tip cuttings from stock plants. This study was conducted to explore the N demand and the influence of the form and dosage of N on the growth of stock plants in aerated nutrient solutions (A, C) and thin-layer peat substrates (B). The effects of three N dosages at 1, 7, and 13 mmol N l–1 (A) or 0.5, 1.5, and 4.0 g N m–2 week–1 (B) were examined. Futhermore, at uniform dosages of 7 mmol N l–1, graduated substitutions of NO3– by NH4+ were investigated using six NH4+:NO3– ratios of 0:100, 20:80, 40:60, 60:40, 80:20, and 100:0 (C). The quality, survival and rooting capacity of cuttings were determined in response to NH4+ or NO3– alone (A), NH4+ and NO3– fertigation (B), or the NH4+:NO3– ratio (C). Natural irradiation and different shading regimes during Spring and Summer cultivation ensured adequate light [photosynthetic photon flux density (PPFD) = 314 µmol m–2 s–1], while limiting light during Autumn (PPFD = 135 µmol m–2 s–1) interfered with the N treatments. The N status, survival rate, and rooting of cuttings were examined in samples of cuttings provided by propagators worldwide. In solution-culture, NH4+:NO3– ratios of 20:80 and 40:60 provided optimised growth and quality of cuttings at 7 mmol N, regardless of light level. Compared with NO3–-only nutrient solutions, these ratios enhanced the branching of stock plant roots, NO3– absorption in shoot tissues, overall cutting yield, and adventitious root formation in cuttings. Although NH4+:NO3– ratios above 60:40 impaired fresh weight and the number of tip cuttings per plant, the rooting capacity of such cuttings was promoted further, as long as adequate light was available. We hypothesise that the ratio of N form shifts hormone levels and carbon fluxes which, in turn, influence the root and shoot morphology of stock plants, as well as the rooting of cuttings. Cultivation in peat substrate resulted in the highest yields and best rooting of cuttings at weekly N doses of 1.5 g N m–2. The high dose of N (4 g) did not enhance yield, but rather reduced the rooting of cuttings at adequate light levels.This dose also resulted in increased NO3–-N and salt accumulation in the peat. Moreover, while reduced rooting at a low N dose (i.e., 0.5 g) indicated N limitation, the impaired rooting seen at a high N dose may have been induced by osmotic stress to the stock plants.

Effect of branch position and auxin treatment on clonal propagation of Tectona grandis Linn. f.

The main objective of our clonal propagation program is the production of high quality timber and faster tree growth. Teak (Tectona grandis Linn. f.) is an important plantation species in the tropics but the demand of teak timber is increasing globally. Teak planting stock is still produced from seeds of unselected elite genotypes which may lead to poor stand establishment. The number of seeds per fruit and their germination ability are also variable and limited by several factors. Therefore an alternative method i.e., clonal propagation is required for mass multiplication of elite trees. It is an established fact that the clonal propagation or adventitious root formation in cuttings is markedly affected by several external and internal factors. Considering these, an experiment was conducted on leafy soft wood shoot cuttings of 3-year-old hedged teak stock plants grown in a hedge garden to study the effects of branch position and auxin treatment on adventitious root formation. A factorial completely randomized design was used for experimentation. Coppice shoots were collected from basal, middle and upper positions of the hedge garden; and mono-nodal leafy cuttings were prepared. These cuttings were treated with different concentrations of IBA and NAA; and were cultured in a mist chamber for rooting where the relative humidity was maintained at 85 ± 2% with maximum and minimum day-night temperature at 32 ± 1°C and 26 ± 1°C respectively. After 45 days the cuttings were removed from the rooting medium and observations were made. It was observed that the rooting parameters viz., percent rooting and percent sprouting, mean number of leaves, mean number of shoots and length, and mean number of roots and length per cutting were significantly influenced by the branch position and auxin treatment. Treatment with 4000 ppm IBA increased percent rooting and percent sprouting whereas NAA suppressed it. Treatment with 4000 ppm IBA also increased the mean number of leaves and shoots, and the length, and the mean number of roots per cutting. The highest mean number of roots and length were observed in cuttings taken from the branch emerging at the upper position followed by branches of middle and lower position. Cuttings of branches at a middle position showed the highest values of percent rooting, percent sprouting, mean number of leaves and shoots and mean shoot length per cutting. Furthermore, the interactive effect of branch position and auxin treatment on rooting and sprouting response was also found to be significant. Overall, the findings of this investigation suggest that middle branch position in hedge plants and 4000 ppm IBA can be made to induce maximum rooting and to produce high quality planting stock material for clonal forestry program of teak.

Piriformospora indica promotes adventitious root formation in cuttings

Adventitious root formation in excised plant shoots is a crucial process in the vegetative propagation of many plant species, and insufficient rooting causes substantial losses in the propagation industry. Based on the various physiological effects on whole plants described for the basidiomycete Piriformospora indica, it was hypothesized that inoculation of the substrate with this endophyte should promote the generation and growth of adventitious roots in cuttings. Inoculation experiments were conducted to study the effects of P. indica on adventitious rooting in three plant species. Inoculation with P. indica dramatically enhanced the number and length of the adventitious roots in pelargonium and poinsettia. Root colonization parameters suggest that the interaction between the endophyte and cuttings had already occurred before physical contact. In contrast, petunia showed no rooting response to P. indica inoculation. Very fast root formation in this plant indicates that a minimum time period for the fungus–plant interaction is required for establishment of a promoting effect. P. indica-based biotechnology is proposed as a new tool for improving plant propagation systems of plant species or cultivars with low to moderate capacity of adventitious root formation.

The Effects of Ascorbate on Root Regeneration in Seedling Cuttings of Tomato

The changes in ascorbate (ASC) and dehydroascorbate (DHA) levels and the activities of ascorbate metabolising enzymes were examined during adventitious root formation in cuttings of tomato (Lycopersicon esculentum Mill. cv. Paw) seedlings. The effects of ASC, DHA and the immediate ascorbate precursor – galactono-γ-lactone (GalL) supplemented to the culture medium on the rooting response, ascorbate content and the activities of the ASC-metabolising enzymes were also investigated. The cuttings treated with abovementioned compounds formed more roots then control plants. However, in contrast to the number of regenerated organs, the elongation of newly formed roots was markedly inhibited. Treatment with auxin (IAA) resulted in a similar phenotype. The inhibitor of auxin polar transport-TIBA (2,3,5-triiodobenzoic acid) effectively blocked rooting. The inhibitory effect of TIBA was reversed by auxin and ASC treatments, while DHA and GalL were ineffective. Both auxin and ASC stimulated cell divisions in an area of pericycle layer of TIBA-treated rooting zones, that enabled cuttings to form roots in the presence of the inhibitor of auxin polar transport. It has been found that the first stages of rooting, preceding the emergence of roots, are accompanied by an increase in endogenous content of ASC with a peak in the 3rd day of rooting. Subsequent stages, when elongation of newly formed roots occurs, are characterised by low level of ASC. The activities of the ascorbate peroxidase (APX), ascorbate oxidase (AOX), ascorbate free radical reductase (AFRR) and dehydroascorbate reductase (DHR) increased in the first 3 days of root formation. The initial period of rooting was also accompanied by the increase of the hydrogen peroxide content and the activities of catalase (CAT) and guaiacol peroxidase (GPX) in the rooting zones. IAA, ASC, DHA as well as Gal stimulated the APX activity, however the rise of the enzyme's activity induced by ASC, DHA and Gal was reversed by TIBA, which was found to inhibit APX. Only exogenous IAA was able to maintain the high level of APX activity in the TIBA-treated cuttings. AOX was strongly affected by ASC and GalL – treatments, its activity increased in the cuttings grown on the media containing ASC in the absence as well as in the presence of TIBA. On the other hand, GalL-dependent stimulation of its activity was suppressed if TIBA was present in a rooting medium.

Methyl gallate and its 3-glucoside promote rooting in bean cuttings

Methyl gallate stimulated adventitious root formation in cuttings of bean (Phaseolus vulgaris L.). This polyphenol was quickly metabolized into 3-glucosyl methyl gallate to such an extent that 4 h after application no methyl gallate was detected. The isolated glucoside when supplied exogenously at 0.5 mM also enhanced rooting; the effect was 2-fold greater than that of methyl gallate. The glucoside persisted in the cuttings for 72 h after treatment. Because methyl gallate is rapidly transformed to a stable glucoside, we suggest that the root stimulation effect could be ascribed to its glucoside.

Adventitious root formation in cuttings of Backhousia citriodora F. Muell : 2. Seasonal influences of temperature, rainfall, flowering and auxins on the stock plant

A 2-year study was carried out on established trees at two sites in southeastern Queensland, Australia, to identify environmental factors that influenced rooting of Backhousia citriodora from cuttings. Complex interactions of rainfall events above 20 mm from the preceding month and mean maximum temperature on stock plants resulted in a correlation with rooting success of r=0.81 and 0.74 for sites at The University Of Queensland, Gatton Campus, and Cedar Glen, respectively. A more detailed investigation under controlled environmental conditions showed that maintaining stock plants at temperatures between 10 and 30 °C had no direct effect on rooting capacity. However, temperature was correlated with growth, which may have an indirect effect on root formation. In spring, floral initiation was found to only delay rooting and had no effect on the final rooting percentage. A series of seasonal experiments demonstrated that application of the auxins indole-3-acetic acid, indole-3-butyric acid and napthaleneacetic acid over a range of concentrations (1000–8000 μg/ml) did not significantly increase rooting compared to the control and there is no practical advantage in applying auxins. Seasonal results and the temperature experiment also suggest that under a glasshouse environment with higher temperatures in winter and an adequate supply of water, B. citriodora cuttings can be successfully rooted over the whole year.

Adventitious root formation in cuttings of Backhousia citriodora F. Muell2. Seasonal influences of temperature, rainfall, flowering and auxins on the stock plant

A 2-year study was carried out on established trees at two sites in southeastern Queensland, Australia, to identify environmental factors that influenced rooting of Backhousia citriodora from cuttings. Complex interactions of rainfall events above 20 mm from the preceding month and mean maximum temperature on stock plants resulted in a correlation with rooting success of r=0.81 and 0.74 for sites at The University Of Queensland, Gatton Campus, and Cedar Glen, respectively. A more detailed investigation under controlled environmental conditions showed that maintaining stock plants at temperatures between 10 and 30 °C had no direct effect on rooting capacity. However, temperature was correlated with growth, which may have an indirect effect on root formation. In spring, floral initiation was found to only delay rooting and had no effect on the final rooting percentage. A series of seasonal experiments demonstrated that application of the auxins indole-3-acetic acid, indole-3-butyric acid and napthaleneacetic acid over a range of concentrations (1000–8000 μg/ml) did not significantly increase rooting compared to the control and there is no practical advantage in applying auxins. Seasonal results and the temperature experiment also suggest that under a glasshouse environment with higher temperatures in winter and an adequate supply of water, B. citriodora cuttings can be successfully rooted over the whole year.

Adventitious root formation in cuttings of Backhousia citriodora F. Muell : 1. Plant genotype, juvenility and characteristics of cuttings

Backhousia citriodora is a commercially valuable Australian woody species that has a reputation for being recalcitrant in forming adventitious roots from cuttings. A study was carried out to determine whether maturation and plant genotype influenced rooting. It also tried to establish whether genotypic differences in rooting ability were related to characteristics of the cutting material. The rooting of cuttings in B. citriodora declines after maturation and is strongly influenced by genotype. The cutting characteristics of actively growing axillary buds, wide stems and mature leaves are associated with rooting and survival but not related to genotype. Furthermore, the 8–24 weeks required by B. citriodora to form roots from cuttings makes it difficult to distinguish between the characteristics that increase rooting and those characteristics that enhance survival. A subsequent disbudding experiment demonstrated that axillary buds per se have an inhibitory effect on rooting. This suggests that the presence of actively growing axillary buds are an indication of overall growth and condition of the stock plant unrelated to the formation of adventitious rooting. The effects of other cutting characteristics on rooting are also discussed.

Immunohistochemical localisation of ubiquitin and the proteasome in sunflower (Helianthus annuus cv. Giganteus).

This study provides an immunohistochemical demonstration of the involvement of the ubiquitin- and proteasome-dependent pathway during differentiation and organogenesis in plants. The localisation of ubiquitin and the proteasome was studied in meristems, leaves, stems and roots of sunflower (Helianthus annuus L. cv. Giganteus). By using a new technique that enhances very low antigen signals, we obtained information on the structural distribution of the ubiquitin- and proteasome-dependent pathway, and of the importance of this pathway during organogenesis and plant development. Ubiquitin and the proteasome showed overall similarities in their cellular localisation. The highest antigenic signal was observed in the root and shoot apical meristems, in leaf primordia and vascular tissue. The cambium showed less expression than the apical meristems. During adventitious root formation in cuttings, no sign of increased expression was observed within dedifferentiating tissue, but as organogenesis progressed, the antigenic signal of ubiquitin and the proteasome gradually increased in the developing roots. Comparison of immunochemical results and Western blots demonstrated that important changes in the cellular antigen signal could only be detected by immunochemistry.

Adventitious root formation in cuttings of loblolly pine (Pinus taeda L .): developmental sequence and effects of maturation

Adventitious root formation in cuttings from fascicular shoots in loblolly pine (Pinus taeda L.) consists of four more or less discontinuous stages: (1) proliferation of cells at the base of the cutting, (2) differentiation of wound vascular tissue and periderm, (3) dedifferentiation of a zone near the wound cambium and wound phloem to form a root initial, and (4) formation of a root meristem. Anatomical changes during adventitious root initiation are described in cuttings from donors of different types and ages. Cuttings from seedlings and 3- to 7-year-old hedged stock plants rooted better than cuttings from 3-year-old tree form donors. It is concluded that the loss of rooting capacity in loblolly pine can be arrested by shearing loblolly pine stock plants to low hedges. The process of root initiation, however, was similar in cuttings from all sources and is apparently not the cause for the rapid decline of rooting potential with increasing age of the donor plant.

Adventitious root formation in cuttings of loblolly pine (

Adventitious root formation in cuttings of loblolly pine (