Early changes in auxin and ethylene production in vine cuttings before adventitious rooting

Node cuttings of in vitro cultured grapevine were rooted in absence of any growth regulator, before the onset of the axillary bud. There were two peaks of ethylene production at 2 and 10–12 h, well marked in the top and bottom portions of the cuttings for the former. The level of IAA increased in the basal portions of the cuttings only, from the 4th hour, and culminated at the 24th hour. The wound ethylene of the first rise might be initiating the sequence of reactions leading to root formation. The second ethylene rise might result from the beginning of the increase of the IAA level.     

Endogenous auxin levels in terminal stem cuttings of Chrysanthemum morifolium during adventitious rooting

Free and ester-bound IAA were determined in Chrysanthemum morifolium Ramat cv. 'Yellow Galaxy' by means of a solid phase enzyme immunoassay. In shoots, free auxin decreases basipetally whereas ester IAA reaches a maximum in the middle part. After making the cuttings, a strong increase in both free and ester IAA (or total IAA, respectively) is found up to the time when the first adventitious roots become visible. Only prolonged irradiance of stock plants at high light intensities (40 W m⁻²) delays this increase in the cuttings, concomitantly with a lower number of roots compared to the controls (4.5 W m⁻²), although root growth as determined by measuring root length or fresh weight is not affected. A distinct relation is found between IAA content of stock plants at the time when cuttings are taken and the number of adventitious roots formed by the cuttings 20 days later.     

Multiple factors influence adventitious rooting in carnation (<Emphasis Type="Italic">Dianthus caryophyllus</Emphasis> L.) stem cuttings

Efficient propagation of uniform starting material is a critical requirement for mass production of most ornamental plants, including carnation. For some elite cultivars, the production of young plantlets is limited by poor adventitious root formation from stem cuttings. We previously characterized the molecular signature during adventitious rooting in two carnation cultivars, 2101-02 MFR and 2003 R 8, which were selected because of their contrasting rooting performance. To determine additional factors that contribute to the differences observed in adventitious rooting during the commercial scaling-up of this species, we characterized rooting performance and endogenous hormone levels in stem cuttings of these two cultivars during one production season. We found that stem cutting production declined during the harvest season in a cultivar-dependent manner. In addition, the initiation of adventitious roots in the stem cutting base depended on its endogenous auxin and cytokinin levels at harvest time, while their subsequent growth and development was mainly influenced by the physiological status of the mother plant at harvest time and of the stem cutting during the rooting process.     

Origin and basipetal transport of the IAA responsible for rooting of carnation cuttings

The origin and transport of the IAA responsible for rooting was studied in carnation (Dianthus caryophyllus L.) cuttings obtained from secondary shoots of the mother plants. The presence of mature leaves in the cuttings was essential for rooting. Removal of the apex and/or the youngest leaves did not reduce the rooting percentage as long as mature leaves remained attached. Removal of mature leaves inhibited rooting for a 24-day period during which the basal leaves grew and reached maturity. After this period rooting progressed as in intact cuttings. Auxin (NAA + IBA) applied to the stem base of defoliated cuttings was about 60% as effective as mature leaves in stimulating rooting. Application of NPA to the basal internode resulted in full inhibition of rooting. The view, deduced from these results, that auxin from mature leaves is the main factor controlling the rooting process was reinforced by the fact that mature leaves contained IAA and exported labelled IAA to the stem. The distribution of radioactivity after application of (5-3H)-IAA to mature leaves showed that auxin movement in the stem was basipetal and sensitive to NPA inhibition. The features of this transport were studied by applying 3H-IAA to the apical cut surface of stem sections excised from cuttings. The intensity of the transport was lower in the oldest node than in the basal internode, probably due to the presence of vascular traces of leaves. Irrespective of the localization of the sections and the carnation cultivar used, basipetal IAA transport was severely reduced when the temperature was lowered from 25 to 4 degrees C. The polar nature of the IAA transport in the sections was confirmed by the inhibition produced by NPA. Local application of IAA to different tissues of the sections revealed that polar auxin transport was associated with the vascular cylinder, the transport in the pith and cortex being low and apolar. The present results strongly support the conclusion that IAA originating from the leaves and transported in the stem through the polar auxin transport pathway was decisive in controlling adventitious rooting.     

Nitric oxide modulates specific steps of auxin-induced adventitious rooting in sunflower

Present work on indole-3-acetic acid (IAA)-induced adventitious rooting in sunflower hypocotyl highlights a clear demarcation of nitric oxide (NO)-dependent and NO-independent roles of auxin in this developmental process. Of the three phases of adventitious rooting, induction is strictly auxin-dependent though initiation and extension are regulated by an interaction of IAA with NO. A vital role of auxin-efflux transporters (PIN) is also evident from 1-napthylphthalamic acid (NPA)-triggered suppression of adventitious roots (AR). Use of actin depolymerizing agent, latrunculin B (Lat B), has demonstrated the necessity of functional actin filaments in auxin-induced AR response, possibly through its effect on actin-mediated recycling of auxin transporter proteins. Thus, evidence for a linkage between IAA, NO and actin during AR formation has been established.Key words: adventitious roots, auxin, sunflowerAdventitious roots (AR) are post-embryonic roots known to originate from stem, leaf petiole and non-pericycle tissue of old roots. In young stem, AR commonly arise from the interfascicular parenchyma while they appear from vascular rays near the cambium in older stem. Formation of AR begins with re-differentiation of predetermined cells which switch from their morphogenetic path to act as mother cells for initiation of root primordia.¹ The process of AR formation consists of three physiologically interdependent phases: induction, initiation and extension.¹ Induction phase comprises of various molecular and biochemical events but no morphologically visible changes appear during this phase. Formation of multilayered cells and conception of root primordia occurs during initiation phase. During expression phase, root primordia exhibit intra-stem growth and their emergence through epidermis. Various environmental and endogenous factors, such as temperature, light, hormones (particularly auxin), sugars and mineral salts, act as cues for promoting redifferentiation of predetermined cells resulting in root induction.The three phases of AR formation are known to be regulated by alterations in the endogenous level of auxin.² A transient increase in auxin concentration has been reported during induction phase, which is followed by a decrease and again an increase during expression phase.³ Auxin transport to and from the responding region is essential for root organogenesis. Acropetal transport of auxin occurs through the vascular cylinder and the basipetal transport takes place through the epidermal and subtending cortical cells.⁴ Polar transport of auxin from the shoot apical meristem to the rooting region is primarily facilitated by auxin-influx (AUX1) and -efflux (PIN) transporters. Asymmetric localization of these transporter proteins in the vascular cambium cells is responsible for differential distribution of auxin in a particular zone of cells.⁵ Polar auxin transport is known to be inhibited by 1-napthylphthalamic acid (NPA, a phytotropin). This inhibition is mediated through a binding of NPA molecule to putative NPA-binding protein (NBP), which is functionally associated with PIN proteins.⁶ Efflux transporters exhibit rapid turnover in plasma membrane.⁷ High affinity of NBP for actin filaments,^8,9 suggests its involvement in the cycling and polar distribution of PIN proteins.¹⁰ Organization of actin filaments is known to be rapidly, reversibly and specifically disrupted by Latrunculin B (Lat B), a macrolide toxin isolated from Latrunculia magnificia, a red sea sponge.¹¹ Lat B associates with actin monomers in 1:1 ratio, thereby preventing their repolymerization into filaments, resulting in a complete shift from F-actin to G-actin.¹² Owing to its well-understood and simple mode of action and low effective dosage, Lat B has supplanted the classic actin-depolymerizing drug cytochalasin D¹³ in pharmacological investigations. In the past few years, significant work has been done on NO as a signaling molecule in a variety of plant developmental processes.¹⁴ Nitric oxide is known to play a crucial role in root development.¹⁵Using sunflower as a model system, present work has been undertaken to investigate the possible role of NO during IAA-induced adventitious rooting in hypocotyl explants. Since auxin action is principally based on PIN-regulated polar transport of IAA molecules, and PIN proteins are known to exhibit actin-asssisted rapid recycling in the target cells, attempts have been made in the present work to find a correlation between auxin transport, actin and NO, using specific pharmacological agents. Additionally, effect of Cyclosporin A (CsA), an inhibitor of nitric oxide synthase (NOS) in animal systems,¹⁶ has also been investigated. These specific agents have been used to monitor root initiation at the target sites in our attempts to decipher a signaling cascade for AR.Seeds of Sunflower (Helianthus annuus L. cv. Morden) were germinated on moist germination sheets at 25 ± 2°C under continuous illumination of 4.3 Wm⁻². Hypocotyls from 4 d old seedlings and with similar growth rate, were excised up to 6 cm below the cotyledonary node. Hypocotyl explants with apical meristem intact but cotyledons excised were selected for the present work with a view to provide a continuity of the endogenous auxin source. Similar explants were also recently used by Huang et al.¹⁷ to investigate indole-3-butyric acid (IBA)-induced AR formation in mung bean (Phaseolus radiatus L.). Using IAA instead of IBA for such investigations was preferred for the present work keeping in view that the two auxins seem to employ different transport proteins for their polar transport.¹⁸ Freshly harvested explants were put upright in glass vials with their proximal cut ends dipped in 1 ml of different concentrations (1, 5, 10 and 15 µM) of IAA, thus bathing the hypocotyls up to 5 mm of their lower ends. Explants were maintained in dark during the course of experiments. The number of AR visible on hypocotyl surface was recorded daily up to 4 days of incubation. Concentration of IAA thus observed optimal for rooting (10 µM) was used for all further experiments. Similarly, various concentrations of other test solutions, namely NPA (auxin efflux blocker; 1 and 10 µM), Lat B (an inducer of actin depolymerization; 25, 50 and 100 nM), CsA (an inhibitor of cyclophilins; 1, 5 and 10 µM), sodium nitroprusside (SNP; NO donor; 1, 5, 10 and 100 µM) and 2-phenyl-4,4,5,5-tetramethyllimidazoline-1-oxyl-3-oxide (PTIO; NO scavenger; 1 and 1.5 mM), were initially used to select their respective optimal concentrations. Based on these preliminary experiments NPA, Lat B, CsA, SNP and PTIO were used at 10 µM, 100 nM, 10 µM, 100 µM and 1.5 mM, respectively, for all subsequent experiments. Some other treatment combinations, namely NPA (10 µM) + IAA (10 µM); LatB (100 nM) + IAA (10 µM); CsA (10 µM) + IAA (10 µM); SNP (100 µM) + NPA (10 µM) and PTIO (1.5 mM) + IAA (10 µM) were also used to investigate their effects on adventitious rooting. Hypocotyl explants incubated in distilled water served as control. Morphological observations of rooting response were imaged after 7 days of incubation, using Nikon digital camera fitted on a stereomicroscope (Stemi 2000, Zeiss, Germany). Detailed evaluation of root initiation was observed after clearing by immersing the explants in a 3:1 solution of ethanol: acetic acid overnight. They were then transferred to 2 N NaOH solution, left overnight, washed once with distilled water and stained with safranin solution for 2–3 min. Excess stain was removed by repeated washing in distilled water. The lower 2 cm region of hypocotyl explants was then cut and mounted on a glass slide to examine endogenous root initials, using a stereomicroscope (Stemi 2000, Zeiss, Germany) fitted with a Nikon camera.Root initiation and extension in the basal region of hypocotyl explants maintained in distilled water indicates the expected basipetal transport of the inducing factor (endogenous IAA) from the intact meristem, as also reported earlier.¹⁹ Treatment with IAA (10 µM) elicited two effects on hypocotyl explants in comparison to those subjected to distilled water treatment: (1) Formation of greater number of root initials, (2) Greater extension of the initiated roots (Figs. 1 and ​and22). A response similar to that evoked by IAA is also evident in hypocotyl explants treated with 100 µM of SNP (Figs. 1 and ​and22). Recently SNP (NO donor) has been reported to evoke dose-dependent response on AR formation in marigold.²⁰ In the present work, treatment with variable concentrations of SNP, ranging from 1–100 µM, lead to a gradual increase in the number and extension growth of AR till 100 µM. Pagnussat et al.²¹ and Liao et al.²⁰ have used 10 µM and 50 µM as effective SNP concentration in cucumber and marigold, respectively. Thus, optimal concentration of SNP for AR formation is species-dependent. In presence of PTIO (1.5 mM; a specific NO scavenger), complete suppression of AR was evident in sunflower, as also reported earlier in mung bean.¹⁷ Combination of PTIO with IAA lead to root initiation only (no extension growth). NPA (10 µM) blocked AR initiation by endogenous (distilled water treatment) and exogenous IAA (Fig. 1). Application of NPA inhibits polar auxin transport, thus reducing the optimal concentration of IAA required for AR formation at the hypocotyl base (zone of AR formation). Thus, no evidence of root initials was evident in presence of NPA, which is also reported in cucumber²² and loblolly pine,²³ respectively. Though NO is expected to act downstream of IAA²⁴ but a treatment of SNP in combination with NPA (present work) lead to complete suppression of AR formation. Our unpublished observations have indicated the expression of NO in the interfascicular cells after induction phase (i.e., during AR iniation and extension). Thus, it can be proposed that IAA is involved in induction phase of adventitious rooting independent of NO, while initiation and extension phases appear to involve IAA-NO interaction. CsA-cyclophilin complex is known to inhibit calcineurin (a protein phosphatase) and NOS activity in animal systems.²⁵ Treatment of hypocotyl explants with CsA (10 µM) lead to formation of fewer number of roots which exhibited extension growth. Oh et al.²⁶ reported a significant reduction in the number of roots in the presence of CsA in hypocotyl explants from tomato. Subjecting hypocotyl explants with a combination of CsA and IAA lead to formation of fewer number of root initials, reaffirming the involvement of NO in auxin action in the developmental process under investigation (AR). However, further investigations on the role of cyclophilins and NOS in auxin-modulated AR formation are required to pinpoint their specific sites of action in this developmental process. Treatment with Lat B (+ and − IAA) lead to complete AR suppression in sunflower hypocotyl explants. Actin-mediated polar localization of PIN proteins is responsible for polar auxin transport and disruption of microfilaments by Lat-B would thus, directly affect IAA transport leading to the observed AR suppression. These observations indicate a convergence of the effect of IAA with that of NO and a role of a well organized actin in the responding cells.Open in a separate windowFigure 1Effect of IAA and various other pharmacological agents on adventitious rooting in hypocotyl explants. Morphological observations of rooting response (A and C). Evaluation of endogenous root initiation and elongation observed in cleared explants stained with safranin (B and D). Scale bar represents 3 mm.Open in a separate windowFigure 2Quantitative analysis of AR initiation in presence of distilled water, IAA and various pharmacological agents in hypocotyl explants of sunflower. Each datum presents a mean and standard error from at least three observations.To sum up, present investigations provide evidence for a linkage between auxin-induced AR response in seedling hypocotyls and NO (Fig. 3). Both endogenous and exogenous IAA-mediated AR induction seem to depend on actin. Significance of actin in this developmental response has become evident via its role in the cycling of auxin efflux proteins (PIN). The three phases of AR formation can be differentiated from each other in terms of their sensitivities to IAA and NO. AR induction phase seems to be governed by auxin alone, independent of NO. NO seems to become operative in this auxin-modulated response (AR) during initiation and extension phase only. Investigations are being undertaken in the author''s laboratory to visualize and quantitate the NO signal in the IAA-responding hypocotyl explants so that the phasing of the role of NO during AR formation can be precisely predicted.Open in a separate windowFigure 3Schematic presentation of the probable events associated with NO-mediated adventitious rooting.     

Activity and isoforms of peroxidases, lignin and anatomy, during adventitious rooting in cuttings of Ebenus cretica L

Adventitious rooting of Ebenus cretica cuttings was studied in order to examine a) the rooting ability of different genotypes in relation to electrophoretic patterns of peroxidases. b) the activity and electrophoretic patterns of soluble and wall ionically bound peroxidases, the lignin content and anatomical changes in the control and IBA treated cuttings of and genotypes in the course of adventitious root formation. In addition, a fraction of soluble cationic peroxidases was separated by gel filtration chromatography from the total soluble peroxidases of a genotype. No rooting occurred in cuttings without IBA-treatment. In both genotypes, electrophoretic patterns of soluble anionic peroxidases revealed two common peroxidase isoforms, while a fast-migrating anionic peroxidase isoform (A3) appeared only in genotypes. Both genotypes showed similar patterns of soluble, as well as wall ionically bound cationic peroxidase isoforms. The number of isoforms was unchanged during the rooting process (induction, initiation and expression phase) but an increase in peroxidase activity (initiation phase) followed by decrease has been found in IBA-treated cuttings. During initiation phase the lignin content was almost similar to that on day 0 in genotype while it was reduced at by about 50% in genotype at the respective time. Microscopic observations revealed anatomical differences between genotypes. According to this study, the and genotypes display differences in anatomy, lignin content, activity of soluble peroxidases and the electrophoretic patterns of soluble anionic peroxidase isoforms. The A3-anionic peroxidase isoform could be used as biochemical marker to distinguish and genotypes of E. cretica and seems to be correlated to lignin synthesis in rooting process.     

Response to auxin changes during maturation-related loss of adventitious rooting competence in loblolly pine (Pinus taeda) stem cuttings

Hypocotyl cuttings (from 20- and 50-day-old Pinus taeda L. seedlings) rooted readily within 30 days in response to exogenous auxin, while epicotyl cuttings (from 50-day-old seedlings) rarely formed roots within 60 days. Responses to auxin during adventitious rooting included the induction of cell reorganization and cell division, followed by the organization of the root meristem. Explants from the bases of both epicotyl and hypocotyl cuttings readily formed callus tissue in response to a variety of auxins, but did not organize root meristems. Auxin-induced cell division was observed in the cambial region within 4 days, and later spread to the outer cortex at the same rate in both tissues. Cells at locations that would normally form roots in foliated hypocotyl cuttings did not produce callus any differently than those in other parts of the cortex. Therefore, auxin-induced root meristem organization appeared to occur independently of auxin-induced cell reorganization/division. The observation that N-(1-naphthyl)phthalamic acid (NPA) promoted cellular reorganization and callus formation but delayed rooting implies the existence of an auxin signal transduction pathway that is specific to root meristem organization. Attempts to induce root formation in callus or explants without foliage were unsuccessful. Both the cotyledon and epicotyl foliage provided a light-dependent product other than auxin that promoted root meristem formation in hypocotyl cuttings.     

Nauclea diderrichii: rooting of stem cuttings,clonal variation in shoot dominance,and branch plagiotropism

Summary Nauclea diderrichii (De Wild, and Th. Dur.) Merill (Rubiaceae), an indigenous hardwood of West Africa, is increasingly being grown commercially. This study investigates the potential for vegetative propagation and clonal selection, and raises some fundamental questions about the physiology of apical dominance and of plagiotropism. Rooting ability was high, with up to 100% rooting in 2–4 weeks, when different Indole-3-butyric acid (IBA) concentrations and leaf areas were tested. Auxin applications greatly increased the numbers of roots per cutting. The decapitation of unbranched plants revealed clonal variation in apical dominance and also in the establishment of outright dominance by the two shoots formed from the outgrowth of the axillary buds of the opposite leaves at the top node. Regression analysis of the Dominance Ratio (length of dominant: length of the sub-dominant shoot at the time of achieving dominance) against overall lateral bud activity (r = 0.82), showed that when the two top shoots co-dominate they provide a more powerful source of Correlative Inhibition than when one of the top shoots dominates the other. The imposition of plagiotropism in the axillary bud occurred over a period of a few days as the terminal and axillary buds emerged from the stipule. Growth of accessory buds on intact plants and debranched cuttings was orthotropic. These results are discussed with regard to the role of the leaf in root formation and the understanding of dominance relationships, branching and crown development in trees.     

Stimulation of adventitious root formation in non-woody stem cuttings by uridine

Uridine strongly stimulated adventitious root formation in stem cuttings of sunflower (Helianthus annuus L.), mung bean (Vigna radiata L.) and common bean (Phaseolus vulgaris L.). A dose response curve of uridine induced rooting showed that the optimum concentration of uridine was 0.1 µM. At all concentrations employed, uridine had no significant effect on root elongation. The rooting response of stem cuttings to the optimal concentration of indole-3-butyric acid (10 µM) in combination with 0.1 µM uridine did not significantly differ from their response to either of these compounds when applied alone. However, the rooting response of the cuttings to sub-optimal IBA (0.01 µM) was significantly stimulated by uridine. These findings suggested that uridine may have stimulated rooting by increasing the sensitivity of the rooting tissue to auxin.     

The effect of native and ACC deaminase-containing Azospirillum brasilense Cd1843 on the rooting of carnation cuttings

Carnation cuttings treated with non-transformed and 1-aminocyclopropane (ACC) deaminase-containing Azospirillum brasilense Cd1843 produced significantly more roots than untreated controls and fewer roots than cuttings treated with 0.1% indolebutyric acid (IBA). The roots produced by cuttings treated with ACC deaminase-containing Azospirillum brasilense Cd1843 were the longest roots resulting from any of the treatments, followed by non-transformed Azospirillum brasilense Cd1843, 0.1% IBA, and treatment with water. The results are interpreted in terms of a previously proposed model of bacterial promotion of plant growth by ACC deaminase and indoleacetic acid, and may have implications for the use of plant growth-promoting bacteria in the flower industry.     

Metabolic changes during rooting in stem cuttings of five mangrove species

Vegetative propagation through rooting in stem cuttings in five tree mangroves namely Bruguiera parviflora, Cynometra iripa, Excoecaria agallocha, Heritiera fomes, and Thespesia populnea using IAA, IBA and NAA was reported. Spectacular increase in the root number was noted in the cuttings of H. fomes and C. iripa treated together with IBA (5000 ppm) and NAA (2500 ppm). The highest number of roots was obtained with IBA (2500 ppm) and NAA (500 ppm) in E. agallocha. B. parviflora and T. populnea responded better to IAA and IBA treatment. The species specific variation in the rooting response to exogenous application of auxins was reflected in the metabolic changes during initiation and development of roots in cuttings. Biochemical analysis showed increase of reducing sugar in the above-girdled tissues at initiation as well as subsequent development of roots which was further enhanced by the use of auxins. Decreases in the total sugar, total carbohydrate and polyphenols and increase in total nitrogen were recorded in the girdled tissues and the high C/N ratio at the initial stage helped in initiation of roots in all the species. Interaction of IBA and NAA promoted starch hydrolysis better than IAA and IBA during root development and subsequently reduced the C/N ratio and increased the protein-nitrogen activity during root development which suggest the auxin influenced mobilization of nitrogen to the rooting zone.Abbreviations IAA Indole-3-acetic acid - IBA Indole-butyric acid - NAA A-naphthalene acetic acid     

Effect of auxins on adventitious rooting from stem cuttings of candidate plus tree Pongamia pinnata (L.), a potential biodiesel plant

Pongamia pinnata, commercially important tree species used to produce biofuels, is known for its multipurpose benefits and its role in agro-forestry. Present study examines the amenability of vegetative propagation and effect of maturation in candidate plus tree P. pinnata through rooting of stem cuttings treated with varying concentrations and combinations of auxins. The performance of the cuttings was evaluated using SAS GLM software and the data were analyzed as a one-way classified data with and without sub sampling for inferring auxin concentration that can be included in programmes aimed at genetic improvement of the tree species. All auxin treatments promoted sprouting and at lower concentrations triggered/enhanced rooting of cuttings. The effectiveness was in the order of IBA > NAA > IAA when applied singly. IBA at 4.92 mM was found to be most effective where rooting percentage and number of roots were significantly higher (P < 0.01) than in control. However higher concentrations of auxins above 7 mM in general inhibited the rooting of cuttings. The interaction among auxins was found to be effective in root induction and differentiation and the most stimulating effects were observed in three-component mixture. The effect of other cutting characteristics such as juvenility and cutting position on rooting is also discussed.     

RNA and protein metabolism during adventitious root formation in stem cuttings of Phaseolus aureus

Indole-3-butyric acid (IBA, 10⁻⁴ M ), spermine (7 × 10⁻⁵ M ) and vitamin D₂ (6.3 × 10⁻⁵ M ), all of which enhance rooting in mung bean cuttings ( Phaseolus aureus Roxb. cv. Berkin), influence RNA metabolism. Total and poly (A)⁺-RNA synthesis within the hypocotyl is inhibited by each of these chemicals within 24 h. These changes precede induced cell division and are therefore associated with the so-called inductive period of regeneration during which some cells in the hypocotyl undergo dedifferentiation. However, following subsequent transfer of cuttings to borate, which is an essential prerequisite for development of root primordia in these cuttings, RNA synthesis is enhanced by pretreatments with IBA, spermine or vitamin D₂. Furthermore, IBA inhibits synthesis and turnover of protein within the hypocotyl.     

Metabolic changes during rooting in stem cuttings of Casuarina equisetifolia L.: effects of auxin, the sex and the type of cutting on rooting

Rooting in terminal shoot and lateral shoot cuttings from 10-year-old elite trees of Casuarina equisetifolia L. in different sex groups was achieved after 20 days when the basal ends of the cuttings were dipped for 3 h in 20 ppm indole-3-butyric acid (IBA). Shoots derived from male plants rooted better than their female and monoecious counterparts, and the lateral shoots were more responsive to rooting than the terminal shoots. During rooting, the metabolic activities varied in both lateral shoot and terminal shoot cuttings derived from plants under different sex groups. Peroxidase and polyphenoloxidase activities were high during root initiation and showed a sharp decline thereafter. The polyphenoloxidase activity was higher in the lateral shoot than the terminal shoot cuttings. The rooted plantlets survived and established well in the field.Abbreviations IAA indole-3-acetic acid - IBA indole-3-butyric acid - NAA 1-naphthaleneacetic acid - PVP polyvinylpyrrolidone     

Maturation-related loss in rooting competence by loblolly pine stem cuttings: The role of auxin transport, metabolism and tissue sensitivity

A comparison of rooting ability of stem cuttings made from hypocotyls and epicotyls from 50-day-old seedlings of loblolly pine ( Pinus taeda L. ) reveals a dramatic decline by epicotyl cuttings, which do not root at all in 20–30 days in the presence or absence of auxin. In contrast, almost all the hypocotyls root during this time, but only in the presence of exogenously applied auxin. The failure of epicotyls to root does not appear to be due to differences in [¹⁴C]-labeled auxin uptake, transport, metabolism, or tissue distribution in the two types of cuttings. At the cellular level, initial responses to auxin, such as differentiation of the cambium into parenchyma, occur in both types of cuttings, but localized rapid cell division and root meristem organization are not observed in epicotyls. Autoradiography revealed that radioactivity from a -naphthalene acetic acid is bound in the cortex but not concentrated at sites of root meristem organization prior to the organization of the meristem in hypocotys. During the development of the epicotyl. cellular competence to form roots appears to be lost. Although this loss in competence is not associated with a concurrent loss in ability to transport auxin polarly, the latter process appears to play a key role in rooting other than to move auxin to the site of root formation. The phytotropin N-(1-naphthyl)phthalamic acid inhibits rooting if applied during the first 3 days after the cutting is made, but does not affect auxin concentration or metabolism at the rooting site.     

Etiolation of stock plants affects adventitious root formation and hormone content of pea stem cuttings

Stock pea plants (Pisum sativum L.) were etiolated fully or partially at the third internode that acted as the cutting base. The etiolation started the fifth day after sowing and lasted till cutting preparation. Cuttings derived from partially etiolated plants rooted more than non-etiolated ones while fully etiolated ones rooted more only after treatment with 1% sucrose solution for 4 days. Endogenous IAA in the base of etiolated cuttings was higher during the first 24 h after cutting preparation than in the control. Z/ZR did not show significant differences while iAde/iAdo was higher in the control. Ethylene was increased 24 h after cutting preparation and the increase was greater from partially etiolated cuttings. The results showed that besides IAA and cytokinins, which played a role in the rooting of cuttings, sucrose influenced rooting in the case of fully etiolated stock plants.     

Nitrogen- and storage-affected carbohydrate partitioning in high-light-adapted Pelargonium cuttings in relation to survival and adventitious root formation under low light

BACKGROUND AND AIMS: The aim of this study was to determine the role of nitrogen- and storage-affected carbohydrate availability in rooting of pelargonium cuttings, focusing on the environmental conditions of stock plant cultivation at low latitudes, transport of cuttings, and rooting under the low light that prevails during the winter rooting period in Central European greenhouses. METHODS: Carbohydrate partitioning in high-light-adapted cuttings of the cultivar 'Isabell' was studied in relation to survival and adventitious root formation under low light. Effects of a graduated supply of mineral nitrogen to stock plants and of cutting storage were examined. KEY RESULTS: Nitrogen deficiency raised starch levels in excised cuttings, whereas the concentrations of glucose and total sugars in leaves and the basal stem were positively correlated with internal total nitrogen (Nt). Storage reduced starch to trace levels in all leaves, but sugar levels were only reduced in tissues of non-nitrogen deficient cuttings. Sugars accumulated in the leaf lamina of stored cuttings during the rooting period, whereas carbohydrates were simultaneously exhausted in all other cutting parts including the petioles, thereby promoting leaf senescence. The positive correlation between initial Nt and root number disappeared after storage. Irrespectively of storage, higher pre-rooting leaf glucose promoted subsequent sugar accumulation in the basal stem and final root number. The positive relationships between initial sugar levels in the stems with cutting survival and in leaves with root formation under low light were confirmed in a sample survey with 21 cultivars provided from different sources at low latitudes. CONCLUSIONS: The results indicate that adventitious rooting of pelargonium cuttings can be limited by the initial amount of nitrogen reserves. However, this relationship reveals only small plasticity and is superimposed by a predominant effect of carbohydrate availability that depends on the initial leaf sugar levels, when high-light adaptation and low current light conditions impair net carbon assimilation.     

Interaction of abscisic acid and auxins in rooting of cuttings

Abscisic acid (ABA) at optimum concentrations promoted rootingof Phaseolus aureus ROXB. and Lycopersicon esculentum MILL,stem cuttings. In combination with IAA (indole-3-acetic acid)ABA has mostly given additive effects. Synergistic effect ofABA was noted on IBA (-indolebutyric acid)-induced rooting ofLycopersicon cuttings. Rooting of Phaseolus vulgaris L. cuttingscompletely failed when ABA (50 mg/liter) was applied in combinationwith IBA or NAA (-naphthaleneacetic acid). The results suggestthat abscisic acid may be an important natural regulator ofrooting in cuttings. (Received March 19, 1970; )     

A relationship between irradiation, carbohydrates and rooting in cuttings of Pisum sativum

Rooting ability was studied for cuttings derived from pea plants ( Pisum sativum , L. cv. Alaska) grown in controlled environment rooms. When the cuttings were rooted at 70 μmol m⁻² s⁻, ¹ (photosynthetic photon flux density) or more, a stock plant irradiance at 100 μmol m⁻² s⁻¹ decreased rooting ability in cuttings compared to 5 μmol m⁻², s⁻¹, However, cuttings rooted at 160 μmol m⁻² s⁻¹ formed more roots compared to 5 (μmol m⁻² s⁻¹. Although a high irradiance increased the number of roots formed, it could not overcome a decreased potential for root formation in stock plants grown at high irradiance. Light compensation point and dark respiration of cuttings decreased by 70% during the rooting period, and the final levels were strongly influenced by the irradiance to the cuttings. Respiratory O₂ uptake decreased in the apex and the base of the cutting from day 2 onwards, whereas a constant level was found in the leaves. Only the content of extractable fructose, glucose, sucrose and starch varied during the early part of the rooting period. We conclude that the observed changes in the cuttings are initiated by excision of the root system, and are not involved in the initiation of adventitious roots.