Adventitious Rooting Of Cuttings Research Articles

IBA and melatonin increase trigonelline and caffeine during the induction and initiation of adventitious roots in Coffea arabica L. cuttings

Caffeine and trigonelline are found in Coffea arabica, and show antioxidant roles and growth and development functions. However, there are no reports on trigonelline and caffeine in relation to coffee rooting. The aim was to evaluate the impact of application of indole-3-butyric acid (IBA) and melatonin on caffeine and trigonelline at different stages of adventitious rooting in cuttings. In addition, to study the correlation between these metabolites and H2O2, phenols, and antioxidant enzymes. Four treatments (Control, melatonin 21 µM (M21), melatonin 43 µM (M43), and IBA 7380 µM (IBA)) were used, with four replications. The growth and biochemical parameters of the antioxidant system were performed in induction, initiation, and extension rooting stages. Higher concentrations of trigonelline and caffeine quantified in the induction and initiation stages were positively correlated with higher percentage of rooted cuttings. Trigonelline and caffeine were positively correlated with H2O2 in all stages of development of adventitious roots. The correlations of trigoneline and caffeine with phenols and antioxidant enzymes reveal different profiles, depending on the phases. The results indicate that IBA and melatonin increase trigonelline and caffeine during the induction and initiation of adventitious roots in Coffea arabica cuttings, which is correlated with a higher percentage of rooted cuttings.

Role of IAA and Primary Metabolites in Two Rounds of Adventitious Root Formation in Softwood Cuttings of Camellia sinensis (L.)

The type of adventitious root formation of tea softwood cuttings is different from that of single node cuttings. In addition to the callus at the base of cuttings, the adventitious roots are also formed in the upper cortex of softwood cuttings. In order to find out the similarities and differences between the above two types of adventitious roots of softwood cuttings and the influencing factors for the differences, an integrated analysis of plant hormones, untargeted metabolomics, and transcriptomics of the softwood cutting stems at different positions is performed. The phytohormone results show that IAA plays a leading role, and a high ratio of in vivo auxin to GA3 or ABA facilitated root formation. The ratios of IAA/GA3 and IAA/ABA in the upper and base rooting parts of cuttings are both higher than the middle non-rooting transition zone. Differences in metabolites indicate that 73 metabolites are involved in the formation of adventitious roots in cuttings. Compared with the middle non-rooting transition zone, most saccharides are downregulated in the upper and base rooting parts of softwood cuttings, and the saccharides in the base rooting parts of cuttings are more consumed than that in the upper rooting parts. Most organic acids in the callus at the base of cuttings show an upward trend, while those in the upper rooting parts show a downward trend. Furthermore, coniferyl alcohol is the key metabolite for adventitious root formation in the upper and base rooting parts of cuttings. Transcriptome results show 1099 differentially expressed genes (DEGs) are obtained, and KEGG enrichment analysis show that these DEGs are significantly enriched in phenylpropanoid biosynthesis, plant hormone signal transduction, and flavonoid biosynthesis pathways. Based on weighted gene co-expression network analysis (WGCNA), two key modules which have a highly positive correlation with IAA are identified. In summary, maintaining the balance of endogenous hormones and sufficient nutritional elements is very important for adventitious root formation in tea plants. Clarifying the material basis of softwood cutting rooting of tea plant is of great significance to improve the cutting survival rate of tea plant (especially difficult rooting varieties) and shorten the breeding cycle.

Adventitious rooting of cuttings from the therapeutic honey plants, Leptospermum polygalifolium and L. scoparium

High demand for therapeutic honey is driving establishment of Leptospermum (Myrtaceae) nectar plantations. Leptospermum seeds are often difficult to extract or germinate, and so methods have been sought to propagate Leptospermum from cuttings. We assessed the amenability of two high-value species, L. polygalifolium and L. scoparium, to propagation as rooted cuttings with or without the application of indole-3-butyric acid (IBA). IBA did not significantly affect average rooting percentages, although IBA occasionally increased the number of adventitious roots per rooted cutting in both species. Average rooting percentages for untreated cuttings were 92%, 88% and 93% for L. polygalifolium clones P6, P9 and P10 and 65% and 76% for L. scoparium clones S9 and S15. The cumulative capacity for plant production from three successive harvests was 95, 126 and 118 rooted cuttings per stock plant for the L. polygalifolium clones and 37 and 53 rooted cuttings per stock plant for the L. scoparium clones. L. polygalifolium and L. scoparium were found to be highly amenable to vegetative propagation, facilitating the establishment of therapeutic-honey plantations.

Vegetative propagation of mate from shoot cuttings induced by coppicing of selected plants

Mate (Ilex paraguariensis A. St.-Hil) is an arboreal species of great economic and socio-environmental importance, which presents difficulties in the adventitious rooting process. The rhizogenic competence of vegetative propagules of mate can be attained by coppicing, but the factors that influence the success of this technique have not yet been elucidated. Therefore, the aim of this study was to evaluate the effects of the stock plant, time of shoot collection, treatment with indolebutyric acid (IBA) and diameter of vegetative propagules in the adventitious rooting of cuttings from shoots induced by coppicing of selected adult plants of mate. Shoots produced from coppiced 13SM01 and 13SM05 stock plants were collected at different times of the year to prepare single-bud cuttings. The cuttings were measured as their diameter in the central portion and treated with 0 and 3000 mg L-1 of IBA. After 60 days, cuttings were evaluated to determine survival and rooting percentages, number of roots, and length of the three largest roots. A completely randomized design was used in a 4 × 2 × 2 × 13 (collection times x stock plants x IBA treatment x diameter classes) factorial scheme with 15 replications. Competence for adventitious rooting was highest for stock plant 13SM05. Cuttings collected in November and February had the highest rooting percentages, without the need of IBA treatment. Cuttings from 13SM01 and 13SM05 with diameters smaller than 0.636 cm (classes 1 to 6) and smaller than 0.712 cm (classes 1 to 7), respectively, had the highest rooting percentages and differed significantly from cuttings with larger diameters. Thus, the results of the present study indicate that stock plants, time of shoot collection, and diameter of vegetative propagules influence adventitious rooting competence of mate cuttings from coppicing adult plants. Rooting of mate cuttings with lower rhizogenic competence is influenced by the application of 3000 mg L-1 of IBA.

The Effect of Biostimulators and Indole-3-Butyric Acid on Rooting of Stem Cuttings of Two Ground Cover Roses

One of the important groups of roses are ground cover roses, used not only as garden plants but also in urban green areas for covering scarps and hill slopes. Roses are mostly propagated in vitro and by budding, grafting, and cuttings however, the latter is feasible only in certain rose groups. To hasten the production of plant material, preparations that stimulate rhizogenesis are used, which are based mainly on auxins and enhance the growth of adventitious roots in cuttings. Other substances capable of stimulating plant growth are biostimulators, which can be an alternative to rooting formulations containing auxins. The goal of this experiment was to compare the effects of the biostimulators AlgaminoPlant and Goteo with that of the synthetic auxin indole-3-butyric acid (IBA) on rooting of cuttings in two ground cover roses Elfrid (‘Kormuse’) and Weisse Immensee (‘Korweirim’). In the preparations, IBA in the form of Rhizopon (1% IBA) or water solution (200 mg L<sup>−1</sup>) was used, whereas the biostimulators were applied at the concentration of 0.2% for foliage spraying. Both biostimulators positively affected the percentage of rooted cuttings, whereas their effect on the degree of rooting was comparable or slightly weaker than that of synthetic auxin. Both biopreparations stimulated the growth of new shoots in cuttings. The use of Goteo resulted in increased content of chlorophyll and total soluble sugars in cuttings, whereas levels of free amino acids and polyphenolic acids were decreased. The synthetic auxin IBA increased the total sugar concentration and the free amino acid contents in cuttings were decreased.

Expression of a Rap2.12 like-1 ERF gene during adventitious rooting of chestnut and oak microshoots

Adventitious rooting of cuttings is a complex developmental process in forest species, with several exogenous and endogenous factors influencing the outcome of the process. In this study we applied an in vitro working system, comprising two lines of microshoots with the same genotype but at a different ontogenetic stages, in two different tree species (chestnut and oak). We analyzed the expression of a gene encoding an AP2/ERF transcription factor from group VII in the initial hours of the adventitious rooting induction, both in rooting competent and incompetent microshoots. The analysis revealed that expression of this gene is related to wounding, ontogenetic stage and auxin in a complex and species-specific manner. Putative induction of the gene by auxin was also analyzed in the presence of naphthyl-phthalamic acid (NPA), an auxin transport inhibitor. In situ expression analysis in chestnut relates the gene activity to cambial divisions and root primordia in rooting competent microshoots, as well as in the root apex. The putative role of the gene during adventitious roots formation is discussed.

Molecular and physiological control of adventitious rooting in cuttings: phytohormone action meets resource allocation.

BackgroundAdventitious root (AR) formation in excised plant parts is a bottleneck for survival of isolated plant fragments. AR formation plays an important ecological role and is a critical process in cuttings for the clonal propagation of horticultural and forestry crops. Therefore, understanding the regulation of excision-induced AR formation is essential for sustainable and efficient utilization of plant genetic resources.ScopeRecent studies of plant transcriptomes, proteomes and metabolomes, and the use of mutants and transgenic lines have significantly expanded our knowledge concerning excision-induced AR formation. Here, we integrate new findings regarding AR formation in the cuttings of diverse plant species. These findings support a new system-oriented concept that the phytohormone-controlled reprogramming and differentiation of particular responsive cells in the cutting base interacts with a co-ordinated reallocation of plant resources within the whole cutting to initiate and drive excision-induced AR formation. Master control by auxin involves diverse transcription factors and mechanically sensitive microtubules, and is further linked to ethylene, jasmonates, cytokinins and strigolactones. Hormone functions seem to involve epigenetic factors and cross-talk with metabolic signals, reflecting the nutrient status of the cutting. By affecting distinct physiological units in the cutting, environmental factors such as light, nitrogen and iron modify the implementation of the genetically controlled root developmental programme.ConclusionDespite advanced research in the last decade, important questions remain open for future investigations on excision-induced AR formation. These concern the distinct roles and interactions of certain molecular, hormonal and metabolic factors, as well as the functional equilibrium of the whole cutting in a complex environment. Starting from model plants, cell type- and phase-specific monitoring of controlling processes and modification of gene expression are promising methodologies that, however, need to be integrated into a coherent model of the whole system, before research findings can be translated to other crops.

Vegetal-Derived Biostimulant Enhances Adventitious Rooting in Cuttings of Basil, Tomato, and Chrysanthemum via Brassinosteroid-Mediated Processes

Plant-derived protein biostimulants exhibit hormone-like activities promoting plant growth and yield, yet detailed investigations on hormonal function have remained limited. This study was conducted to investigate the effects of vegetal-derived-biostimulant on morphological and metabolic changes in cuttings of three herbaceous species demonstrating different rooting ability, basil (Ocimum basilicum L.), tomato (Solanum lycopersicum L.), and chrysanthemum (Chrysanthemum indicum L.), in comparison to auxin. Unrooted cuttings were applied with or without biostimulant (100, 1000, 5000, and 10,000 mg L−1) or auxin [1% indole-3-butyric acid (IBA) plus 0.5% 1-naphthaleneacetic acid (NAA); 100, 200, 300, and 500 mg L−1] as a basal quick-dip, stuck into inert media, and evaluated at 20 days after placement under intermittent mist. Both compounds increased adventitious rooting in all cuttings. Biostimulant required a significantly higher threshold for a series of adventitious rooting responses than auxin, and the maximum effectiveness was achieved at 5000 mg L−1 for biostimulant and 100, 200, and 300 mg L−1 for auxin in basil, tomato, and chrysanthemum, respectively. Adventitious rooting responses (dry mass and length) to biostimulant showed a gradual logarithmic rise as a function of increasing dosages, which was not in agreement with biphasic dose-response of auxin. Biostimulant significantly increased or tended to increase fine roots in all tested cuttings, which was not consistent with auxin. Relatively high levels of endogenous brassinosteroids (BRs) were present in non-treated cuttings of basil, tomato, and chrysanthemum in decreasing order. Both compounds had no effects or concomitantly increased or decreased BR levels in plant tissues, with fewer effects on basil and tomato, containing high BR levels, but more prominent effects on chrysanthemum, containing relatively low BR levels. Contrasting effects of biostimulant and auxin were found in antioxidant activities, which were promoted by biostimulant but inhibited by auxin either in roots or shoots. These results indicate that the hormonal effects of vegetal-derived biostimulant are primarily exerted by BR-mediated processes while involving interaction with auxin. Both the biostimulant-derived BRs and auxin were suggested to modulate endogenous BR pool via overlapping and interdependent regulatory functions, inducing morphological and metabolic changes during adventitious rooting of cuttings in a plant species-specific manner.

Vegetative propagation of native fruit species of páramo <i>Thibaudia floribunda</I> and <i>Cavendishia bracteata</i> by cuttings

Cavendishia bracteata and Thibaudia floribunda (Ericaceae) are wild fruit shrubs native to the Andes region. This study aimed to characterize the rooting potential of basal and apical cuttings using naphthalene acetic acid (NAA) in different concentrations (0, 200, 500, or 1,000 mg L-1). In C. bracteata, the cutting position on the branch affected its sprouting and rooting, with apical cuttings presenting the best performance with auxin application. The rooting of cuttings was more successful in C. bracteata than in T. floribunda. NAA applications between 200 to 500 mg L-1 were more suitable for the propagation of C. bracteata due to the higher percentages of rooting and shoot production. For propagation of T. floribunda, the use of apical cuttings without the application of auxins is recommended. Adventitious roots in cuttings of both species were originated from parenchyma cells of the stem.

Vegetative rescue and cloning of Eucalyptus benthamii selected adult trees

Eu calyptus benthanii presents great aptitude for cultivation in American continent, and due to its origin from western Sydney, NSW, Australia, is especially recommended for regions with cold climates and frequent frosts. Taking their optimal silvicultural performance into account, selected genotypes will certainly represent an excellent alternative for future plantations. The cloning of superior genotypes is accomplished by vegetative propagation of mature trees, and requires physiologically juvenile or rejuvenated material. Special techniques are necessary to reverse the juvenility and adult tree recovery and promote favorable growth and rooting conditions. In the specific case of Eucalyptus sp., the most common vegetative rescue method used by forestry companies to obtain shoots (i.e., propagules) is the coppicing of adult trees, a technique which provides excellent juvenile shoots, favoring the adventitious rooting in cuttings. Cloning techniques are required to vegetative rescue and germoplasm banks formation of selected trees. The present study aimed to evaluate the vegetative rescue after the selection of phenotypes with superior silvicultural characteristics to clone adult trees of E. benthamii, evaluating which technique presented the best cloning result. The cuttings from canopy branches, epicormic shoots from the first (lowest) canopy branches, shoots obtained from girdling and shoots from the pruning of canopy branches were submitted to micropropagation, cutting, and microcutting techniques for each shoot type. Among the key findings for vegetative rescue and cloning, the percentage of in vitro establishment of epicormic shoot (79.2 %), ex vitro rooting (75.0 %) and acclimatization (27.8 %) were suitable. The cuttings of sprouts from girdling stood out as having rooting (18.7 % from greenhouse and 14.3 % from mini-incubator) and acclimation (11.2 % from greenhouse and 9.0 % from mini-incubator). The others vegetative propagations techniques tested did not result in shoot survival, rooting or acclimation.

Adventitious rooting on the Brazilian red-cloak and sanchezia after application of indole-butyric and humic acids

Plant regulators, as well as bioactive fractions of the organic matter, can accelerate the development and increase the efficiency of adventitious rooting in ornamental plants. We evaluated rooting in the Brazilian red-cloak (Megaskepasma erythrochlamys) and sanchezia (Sanchezia nobilis) cuttings in response to application of indole-butyric acid (IBA) and humic acids (HA). Stem cuttings of both species treated with solutions of 0, 250, 500, 1000, 2000 mg/L of IBA and 0, 10, 20, 30, 40 mmol/L of C of HA were placed in 2.0 L plastic pots containing carbonized rice husk, kept in greenhouse. Survival of cuttings, number of leaves and shoot and root fresh and dry matter were evaluated 45 days after. Data were used to run an analysis of variance. We observed the average contrasts, calculated the regression equations and estimated the concentrations that provided the best efficiency in terms of root dry matter. For IBA, 185.4 and 66.8 mg/L were the concentrations that promoted the highest root dry matter accumulation in the Brazilian red-cloak and sanchezia, respectively, with increments of 140 and 22.5% in relation to the control. HA, at 33.6 mmol L-1 of C, increased shoot fresh and dry matter in the Brazilian red-cloak, but reduced root formation compared to the control. In sanchezia, HA at 19.5 mmol L-1 of C promoted increases of 35.9% in root dry matter in relation to the control. We concluded that IBA, in the abovementioned concentrations, increased adventitious rooting in cuttings of both the Brazilian red-cloak and sanchezia, while optimal doses of HA solutions are very likely to improve adventitious rooting in sanchezia, but not in the Brazilian red-cloak.

Transcriptome analysis of indole-3-butyric acid-induced adventitious root formation in nodal cuttings of Camellia sinensis (L.).

Tea (Camellia sinensis L.) is a popular world beverage, and propagation of tea plants chiefly depends on the formation of adventitious roots in cuttings. To better understand potential mechanisms involved in adventitious root formation, we performed transcriptome analysis of single nodal cuttings of C. sinensis treated with or without indole-3-butyric acid (IBA) using the Illumina sequencing method. Totally 42.5 million RNA-Seq reads were obtained and these were assembled into 59,931 unigenes, with an average length of 732 bp and an N50 of 1292 bp. In addition, 1091 differentially expressed unigenes were identified in the tea cuttings treated with IBA compared to controls, including 656 up- and 435 down-regulated genes. Further real time RT-PCR analysis confirmed RNA-Seq data. Functional annotation analysis showed that many genes were involved in plant hormone signal transduction, secondary metabolism, cell wall organization and glutathione metabolism, indicating potential contributions to adventitious rooting. Our study presents a global view of transcriptome profiles of tea cuttings in response to IBA treatment and provides new insights into the fundamental mechanisms associated with auxin-induced adventitious rooting. Our data will be a valuable resource for genomic research about adventitious root formation in tea cuttings, which can be used to improve rooting for difficult-to-root varieties.

The lose of juvenility elicits adventitious rooting recalcitrance in apple rootstocks

For perennial woody plants, softwood cutting is an efficient technique for larger scale propagation and adventitious rooting of cuttings is one of the most crucial steps. To evaluate the significance of juvenility on adventitious rooting, rooting rates was compared between softwood cuttings collected from apomictic seedlings (juvenile), in vitro cultured plants (rejuvenated), suckers (juvenile like) and canopy shoots (adult) of reproductively mature trees in Malus xiaojinensis. After pre-treatment with indole-3-butytric acid (IBA) (3,000 mg L−1) + H2O2 (50 mM), rooting rates in cutting from juvenile, juvenile like and rejuvenated donor plants were significantly higher (>90 %) than that from adult trees. The effects of IBA on adventitious rooting were enhanced significantly by exogenous H2O2. After 15 passages of in vitro subculture, the micro-shoots from adult phase explants were rejuvenated successfully, marked by the elevated expression of miR156 in the leaflets of the micro-shoots. But the rooting ability of rejuvenated micro-shoots was recovered delayed at the 18th or 21st passage of subculture. During the process of rejuvenation, the leaf indole-3-acetic acid contents and the expressions of rooting related genes CKI1, ARRO-1, ARF7 and ARF19 increased significantly. In contrary, the leaf abscisic acid contents decreased. A lack of juvenility is the most important limiting factor governing adventitious rooting of softwood cuttings in apple rootstocks.

Clonal maturation of Corymbia torelliana × C. citriodora is delayed by minimal-growth storage

SummaryMinimal-growth storage may be a simple method to preserve germ plasm while tree varieties undergo clonal selection, but there has previously been little evidence to demonstrate that minimal-growth storage delays maturation. This study assessed the maturation of 10 Corymbia torelliana × C. citriodora clones whose shoots had been stored for 12 months using three different methods: (1) as ex-vitro stock plants in the nursery; (2) in-vitro at 25°C; and (3) in-vitro under minimal-growth conditions at 14°C. Minimal-growth storage increased the subsequent frequency of adventitious rooting in cuttings of 6 of the 10 clones, providing increases in rooted cutting production of between 53% and 163% over ex-vitro nursery storage. Minimal-growth storage also increased adventitious root number in two clones and root mass in four clones. C. torelliana × C. citriodora clones underwent maturation during ex vitro stock plant archiving in the nursery, but in-vitro storage under minimal-growth conditions was highly effective in delaying clonal maturation.

When stress and development go hand in hand: main hormonal controls of adventitious rooting in cuttings

Adventitious rooting (AR) is a multifactorial response leading to new roots at the base of stem cuttings, and the establishment of a complete and autonomous plant. AR has two main phases: (a) induction, with a requirement for higher auxin concentration; (b) formation, inhibited by high auxin and in which anatomical changes take place. The first stages of this process in severed organs necessarily include wounding and water stress responses which may trigger hormonal changes that contribute to reprogram target cells that are competent to respond to rooting stimuli. At severance, the roles of jasmonate and abscisic acid are critical for wound response and perhaps sink strength establishment, although their negative roles on the cell cycle may inhibit root induction. Strigolactones may also inhibit AR. A reduced concentration of cytokinins in cuttings results from the separation of the root system, whose tips are a relevant source of these root induction inhibitors. The combined increased accumulation of basipetally transported auxins from the shoot apex at the cutting base is often sufficient for AR in easy-to-root species. The role of peroxidases and phenolic compounds in auxin catabolism may be critical at these early stages right after wounding. The events leading to AR strongly depend on mother plant nutritional status, both in terms of minerals and carbohydrates, as well as on sink establishment at cutting bases. Auxins play a central role in AR. Auxin transporters control auxin canalization to target cells. There, auxins act primarily through selective proteolysis and cell wall loosening, via their receptor proteins TIR1 (transport inhibitor response 1) and ABP1 (Auxin-Binding Protein 1). A complex microRNA circuitry is involved in the control of auxin response factors essential for gene expression in AR. After root establishment, new hormonal controls take place, with auxins being required at lower concentrations for root meristem maintenance and cytokinins needed for root tissue differentiation.

Adventitious rooting in cuttings of croton and hibiscus in response to indolbutyric acid and humic acid

Adventitious rooting of ornamental plants can be accelerated by the application of growth regulators, such as auxin. Humic acids, organic matter in soil and organic compounds also have a biostimulant effect. This work evaluated the rooting in cuttings of croton (Codianeum variegatum L. Rumph) and hibiscus (Hibiscus rosa-sinensis L) in response to the application of different concentrations of indolbutyric acid (IBA) and humic acid (HA). The experiment was carried out in a greenhouse. Apical stem cuttings were treated with solutions at concentrations of: 0, 250, 500, 1000, 2000 mg L-1 IBA and 0, 10, 20, 30, 40 mmol L-1 HA carbon isolated from vermicomposting. Forty-five days after the applications, the cuttings were removed from the pots containing carbonized rice hull and the following variables were measured: rooting number, length and width of leaves, fresh and dry matter of root and aerial part and root area. The results were subjected to analysis of variance and the qualitative and quantitative effects of the treatments were compared by contrast and regression, respectively. Regression equations were used to determine the maximum efficiency level of root dry matter according to IBA and HA. Higher accumulation of root dry matter was recorded for the treatments with the doses 579 mg L-1 IBA and 14 mmol L-1 HA and 970 mg L-1 IBA and 50 mmol L-1 HA for root cuttings of croton and hibiscus, respectively. It was found that the application of eiher IBA or HA at the indicated doses accelerates rooting in cuttings of croton and hibiscus and contributes to the formation of vigorous plants.

Changes of Soluble Sugars and Enzymatic Activities During Adventitious Rooting in Cuttings of Grewia optiva as Affected by Age of Donor Plants and Auxin Treatments

Changes of Soluble Sugars and Enzymatic Activities During Adventitious Rooting in Cuttings of Grewia optiva as Affected by Age of Donor Plants and Auxin Treatments

Comparative evaluation of oxidative enzyme activities during adventitious rooting in the cuttings of grapevine rootstocks

This study investigated changes in peroxidase (POX) and polyphenol oxidase (PPO) activities through adventitious rooting in hardwood cuttings of grapevine rootstocks. Three grapevine rootstocks with different propensity to produce adventitious roots were selected: recalcitrant (Ramsey), non-recalcitrant (Rupestris du Lot) and intermediate (99R) cultivars. The averages of root number at 65 days were 96 in Lot, 76 in 99R and 30 in Ramsey. Both enzyme activities characteristically increased before adventitious rooting, regardless of rooting ability of the rootstocks, and then decreased. POX activity increased in Ramsey cuttings at 22 days, in Lot and 99R cuttings at 14 days after planting, and then decreased gradually until 51 days. The highest POX activity was determined in Ramsey rootstock with the highest rooting ability and the lowest activity was determined in the rootstocks with the lowest rooting ability. PPO activity gradually increased in Ramsey rootstock cuttings from 10 days to 22 days, in Lot and 99R cuttings at 14 days, and then decreased until 51 days. A significant correlation was identified between high POX activity and adventitious rooting capability in rootstocks, but the same result was not determined with PPO activity. A recalcitrant rooting variety cannot increase POX activity sufficiently before rooting. Therefore applications that could increase POX activity in stem cuttings during rooting may facilitate increased rooting in such rootstocks.

Propagation of Stewartia: Past Research Endeavors and Current Status

Stewartias (Stewartia spp.) are prized for their camellia (Camellia japonica)-like flowers, intense fall color, and exfoliating bark. In spite of having outstanding ornamental value and features, these plants are not readily available for landscaping in the horticulture trade. The primary reason stated is the difficulty of its mass propagation and production. In the last two decades, considerable research has been conducted on various aspects of stewartia propagation such as seed germination, cutting type, light, rooting medium, rooting hormone, cold acclimation, and tissue culture. In this article, we discuss factors that directly influence propagation of stewartia and we highlight results of published studies to propagate stewartia. The evidence indicates success in adventitious rooting of cuttings but at the same time recognizes the continuing challenge associated with overwinter survival. Sexual propagation has also been studied, but its commercial application is limited. To date, there is lack of concrete information on why stewartia remains under-represented in our landscapes. It still remains unclear if it is the lack of consumer demand or existing propagation difficulties that is the cause of under utilization of stewartia. Given the information from most published studies, we suggest further research on the aspect of overwinter survival in addition to a survey of the nursery and greenhouse industry to accurately determine the cause behind the absence of stewartia in horticultural trade.

Influência do estado nutricional de minicepas no enraizamento de miniestacas de eucalipto

O enraizamento adventício de estacas é influenciado por fatores intrínsecos e extrínsecos do material vegetal. O conhecimento sobre o modo de ação desses fatores sobre o enraizamento é fundamental para o sucesso da produção de mudas por miniestaquia. Entre os fatores envolvidos no enraizamento, pode-se destacar a nutrição mineral, pois existe significativa relação entre ela e o enraizamento. No entanto, a importância de vários nutrientes nesse processo ainda não está totalmente esclarecida. Diante do exposto, o objetivo deste trabalho foi avaliar o grau de associação linear entre o estado nutricional das minicepas com o enraizamento de miniestacas de eucalipto. Foram utilizados dados da empresa CENIBRA, entre os quais se analisaram os de enraizamento de miniestacas e dos teores de nutrientes revelados por análises químicas dos tecidos foliares das minicepas. Os dados usados foram originados de minijardim clonal cultivado em leito de areia, com fertirrigação por gotejamento. Com esses dados, foram realizadas análises para avaliar a existência de correlação linear entre as concentrações de macro e micronutrientes nas minicepas e a taxa de enraizamento das miniestacas. Os resultados indicaram que a nutrição mineral desempenha papel importante no enraizamento adventício das miniestacas produzidas pelas minicepas, gerando respostas diferenciadas de acordo com o nutriente considerado. Os resultados evienciaram que a solução nutritiva aplicada no minijardim clonal deve ser específica para cada clone.