Relation between Nitrogen Status, Carbohydrate Distribution and Subsequent Rooting of Chrysanthemum Cuttings as Affected by Pre-harvest Nitrogen Supply and Cold-storage

This study investigated the relationship between internal nitrogenand carbohydrate distribution in chrysanthemum cuttings of twocultivars (‘Puma’, ‘Cassa’) when affectedby nitrogen supply to stock plants (0.6, 1.5, or 4.0 g N m^-2week^-1)and different periods (2, 3, or 4 weeks) of dark cold-storage(0.5 or 5°C), and adventitious rooting. Concentrations oftotal nitrogen (N_t) and nitrate in cuttings and the levels ofsugars, starch and fructan in different cutting parts (leaves,upper stem, and basal stem) were studied in relation to subsequentadventitious rooting at natural radiation in a greenhouse. Increasingnitrogen supply resulted in substantially lower starch levelsand higher sucrose concentrations in leaves when cuttings wereexcised. Fructan concentrations were low and decreased withincreasing nitrogen levels. Starch completely disappeared fromleaves and to a large extent from stems within the shorteststorage period. A less pronounced decrease in sugar concentrationwas observed, particularly in low-nitrogen cuttings and thecuttings of ‘Puma’. The number and length of adventitiousroots subsequently formed by unstored and stored cuttings waspositively correlated with initial N_t, and to a lesser extentwith initial nitrate concentrations in cuttings. Whereas rootingwas not limited by pre-rooting concentrations of carbohydratesin the different cutting parts, the generally higher rootingcapability of nitrogen-rich cuttings, a stronger nitrogen responseof ‘Cassa’, and increased rooting at a particularharvest date, were associated with higher sucrose:starch ratiosin leaves at harvest. This reflected an increased assimilateexport. By using this characteristic in a linear regressionmodel, total variability of root numbers, ranging from three–35per cutting, could be predicted to 57% for the unstored andto 40% for all cuttings. Increased basipetal transport of carbohydrates,of nitrogen compounds, and of auxins may be causally involvedin these associations. Copyright 2000 Annals of Botany Company Adventitious rooting, nitrogen, sugars, carbohydrates, source-sink, partitioning, quality, storage, cuttings, stock plants, chrysanthemum, Dendranthema grandiflorum     

A Mechanistic Model of Carbohydrate Dynamics During Adventitious Root Development in Leafy Cuttings

The rooting of vegetatively propagated leafy cuttings involvesthe complex interaction of many processes. For this reason,the influence of carbohydrate status, nutrition, water and hormonalfactors on root formation is poorly understood at a mechanisticlevel. We present a mechanistic model of the growth of pre-formedroot initials on a cutting consisting of leaf, internode androots. The processes represented are leaf photosynthesis, starchmobilization, sugar transport, and sugar utilization for rootgrowth. The model provides a quantitative scheme for understandinghow root development depends on properties of cuttings suchas leaf area, internode length and initial carbohydrate content.The potential of the model to interpret rooting experimentson a whole-cutting basis is illustrated using published datafor cuttings of Triplochiton scleroxylon (a West African hardwood)with different leaf areas. Observed rooting times are reproducedin the model by varying the leaf photosynthetic rate per unitarea. The simulated starch and sugar dynamics during root growthare in qualitative agreement with observations. A sensitivityanalysis is performed to examine the effect of key parameterson the timing or success of rooting. The model provides a frameworkfor examining the role of other factors known to affect rooting,such as nutrient and water status, but requires further parameterisationbefore it can be used as a predictive tool in vegetative propagation. Model, carbohydrates, rooting, vegetative propagation     

Reduced irradiance and applied auxin influence carbohydrate relations in Pinus banksiana cuttings during propagation

Untreated and indole-3-butyrie acid-treated (IBA) cuttings from 90-day-old Pinus banksiana Lamb, stock plants were propagated under normal greenhouse irradiance (max. 900 $$mol m^-2 s^-1) and shade (max. 120 $$mol m^-2 s^-1) to determine effects on adventitious rooting and on reducing sugar and starch concentrations in needles and basal stems. In one experiment, cuttings were assessed at days 15 and 25 of propagation for basal 1-cm stem fresh weight, proportion rooted, number of roots and longest root length. In a second experiment with cuttings, basal 1-cm stem fresh weight and concentrations of reducing sugar and starch in needles and basal stems were measured each day for the first 10 days of propagation. Carbohydrate measurements were also made for seedling stock plants as controls for the second experiment. Carbohydrate data for cuttings were primarily evaluated based on net (cutting minus seedling) concentrations, to correct for changes in cuttings not related to adventitious rooting. Increase of basal stem fresh weight and rooting of cuttings, based on all measured variables, occurred in the order: light + IBA > light > shade + IBA > shade. The best rooting required the greater irradiance. Compared to results from cuttings in the light, shading resulted in lesser accumulations of reducing sugars and starch in needles and basal stems. Reducing sugar: starch concentration ratios were significantly greater in shade- vs light-propagated cuttings, IBA treatment did not offset the effects of shade on rooting or on reducing sugar and starch concentrations or ratios. Overall, the results suggested that decreased reducing sugar and starch concentrations and/or their increased ratios are associated with shade-induced poor rooting of P. banksiana cuttings.     

Auxins or Sugars: What Makes the Difference in the Adventitious Rooting of Stored Carnation Cuttings?

Cold storage of cuttings is frequently applied in the vegetative propagation of ornamental plants. Dianthus caryophyllus was used to study the limiting influences of auxin and sugars on adventitious root formation (ARF) in cuttings stored at 5°C. Carbohydrate levels during storage were modulated by exposing cuttings to low light or darkness. The resulting cuttings were treated (or not) with auxin and planted, and then ARF was evaluated. Carbohydrate levels in the cuttings were monitored and the influence of light treatment on indole-3-acetic acid (IAA) and zeatin (Z) in the basal stem was investigated. Dark storage for up to 4 weeks increased the percentage of early rooted cuttings and the final number and length of adventitious roots, despite decreased sugar levels in the stem base. Light during cold storage greatly enhanced sugar levels, particularly in the stem base where the Z/IAA ratio was higher and ARF was lower than observed in the corresponding dark-stored cuttings. Sugar levels in nonstored and dark-stored cuttings increased during the rooting period, and auxin application enhanced the accumulation of sugars in the stem base of nonstored cuttings. Auxin stimulated ARF most strongly in nonstored, less so in light-stored, and only marginally in dark-stored cuttings. A model of auxin-sugar interactions in ARF in carnation is proposed: cold storage brings forward root induction and sink establishment, both of which are promoted by the accumulation of auxin but not of sugars, whereas high levels of sugars and probably also of cytokinins act as inhibitors. Subsequent root differentiation and growth depend on current photosynthesis.     

Carbohydrate accumulation and partitioning in Pinus banksiana seedlings and seedling cuttings

Tests were conducted to identify possible relations between carbohydrates and callusing-rooting of Pinus banksiana Lamb, cuttings. Terminals, upper stems, and basal (1 cm) stems of 90-day-old untreated seedlings and seedling cuttings were analyzed for sucrose, total soluble reducing sugar, starch and total non-structural carbohydrate during propagation. Seedlings were evaluated in order to determine whether data for cuttings alone properly described carbohydrate-callusing-rooting relations under conditions where stock plants and cuttings were propagated in different environments. Results indicated that seedling terminals and upper stems, but not basal stems, accumulated the measured carbohydrates much like cuttings, though to lesser concentrations. Thus, carbohydrate accumulation by cutting terminals and upper stems would have been overestimated, based on cutting data alone. In terms of rooting, results indicated that: 1) Total carbohydrate accumulation in cutting basal stems was related to callusing-rooting, but a cause-effect relation was not established; 2) The positive relation between callusing-rooting and total carbohydrate accumulation was primarily due to accumulation of reducing sugar and starch, with reducing sugar predominant. 3) Reducing sugar/starch concentration ratios were the most sensitive and convenient indicators of specific carbohydrate differences within and between seedlings and cuttings.     

Rooting and vitality of poinsettia cuttings was increased by arbuscular mycorrhiza in the donor plants

In this paper, we provide evidence that the rooting performance of cuttings can be improved by the arbuscular mycorrhizal (AM) symbiosis of donor plants. Poinsettia stock plants were inoculated with the Glomus intraradices isolate H510 and grown in three different cultivation systems (two organic and one conventional). AM colonization was not related to P availability in the substrate. Decay of the excised cuttings in response to unfavorable postharvest storage conditions was significantly reduced by AM colonization of the stock plants. In most cases, AM significantly promoted the formation of adventitious roots in the stored cuttings. The strongest effect of AM was found when donor plants were grown in a modified organic substrate; then AM-conditioned cuttings showed higher leaf sugar levels and a changed kinetic of carbohydrates during storage. Analyses of N, P, and K in cuttings did not indicate a nutritional effect. The results support the idea that an altered carbohydrate metabolism and plant hormones can contribute to improved rooting performance of cuttings excised from mycorrhizal donor plants.     

Effects of pre-severance light quality on the vegetative propagation ofEucalyptus grandis W. Hill ex Maiden

Two-leaf, two-node cuttings were taken fromEucalyptus grandis stockplants grown under different light qualities (red to far-red ratios of 0.4, 0.7, 1.3, 3.5 and 6.5) at a constant photon flux density (200 μmol m^-2 s^-1). Two experiments tested effects of pre-severance light quality on cutting morphology, post-severance gas exchange, carbohydrate status and rooting of cuttings. The best rooting percentage was achieved by cuttings with longer stems and greater stem volume from stockplants grown at lower red to far-red (R∶FR) ratios. Generally, rooting success was associated with low pre-severance starch and water-soluble sugar concentrations, and a greater total water-soluble carbohydrate (TWSC) content per cutting. Rooting was associated with well maintained stem starch and an increase in stem TWSC during the propagation period. Gas exchange of cuttings was measured between 28 and 33 days after severance. Rooting percentages at 35 days after severance were positively and linearly related to net photosynthetic rate and stomatal conductance. In unrooted cuttings there was a net release of CO₂ which increased significantly with an increase in pre-severance R∶FR ratio. These results demonstrate that stockplant environment may significantly modify the morphology and physiology of subsequent cuttings, and that cutting morphology, and stored and current photosynthates have a significant influence on rooting. ITE is a component of the Edinburgh Centre for Tropical Forestry     

Roles of leaf in regulation of root and shoot growth from single node softwood cuttings of grape (Vitis vinifera)

The role of leaf in regulation of root and shoot growths in single node softwood cuttings of grape (Vitis vinifera) was characterised. Leafy cuttings showed early rooting, vigorous root growth and subsequent shoot development. Defoliation at planting induced early sprouting, but adversely affected rooting and decreased the survival of cuttings irrespective of pre‐planting treatment with 100 μM indole 3‐acetic acid (IAA). Treatment with IAA did not affect the percent rooting of leafy cuttings but increased root and shoot growth. Leaf weight (wt) and leaf area of the cuttings showed a highly significant correlation to root wt of the new plant at 4 wk after planting, while cutting stem + petiole wt was either not or less significantly correlated to root and shoot weights of the subsequent plant. The greater the area or wt of leaf, the better the root and shoot growths, implying that leaf contributed to adventitious root growth. However, retaining the leaf for just 2 days was enough to stimulate rooting in more than 80% of the cuttings, suggesting that leaf tissue could also induce root formation. Root growth increased with the period of leaf retention but leaf removal before 3 wk triggered sprouting leading to high mortality in rooted cuttings. Bringing the leaf closer to the rooting zone by preparing leaf at base (LAB) cuttings delayed rooting and sprouting compared with the standard leaf at top (LAT) cuttings. An inhibitory effect on rooting and sprouting by the exposed upper internode region in LAB cuttings is suggested.     

Relations between carbohydrate, water status and adventitious root formation in leafy pea cuttings rooted under various levels of atmospheric CO2 and relative humidity

Three levels of atmospheric CO₂ and 2 levels of relative humidity (RH) during the rooting period were tested for their effect on several factors presumed to influence adventitious root formation in leafy pea ( Pisum sativum L. cv. Alaska) cuttings. Compared to normal CO₂ levels (350 μl l⁻¹), neither 1800 nor 675 μl l⁻¹ CO₂ affected the rooting percentage or the number of roots per cutting. However, 1800 μl l⁻¹ CO₂ increased root and shoot dry weight, root length, carbohydrate levels in the base of the cuttings and water potential (Ψ_w) of cuttings compared to normal levels of CO₂. Compared to 87% RH. 55% RH decreased all of the above parameters, including the number of roots per cutting. A polyvinyl chloride antitranspirant (which partially blocks stomata and slows photosynthesis) applied simultaneously with 87% RH increased Ψ_w and root length but lowered all of the other above parameters, compared to 87% RH without antitranspirant. Increasing current photosynthate (products of photosynthetic activity after excision), carbohydrate, or Ψ_w either alone or together was associated with increased root system size but not necessarily with increased rooting percentage or root number. The data are consistent with a hypothesis that the number of roots per cutting increased with increasing current photosynthate and carbohydrate until some other factor became limiting. Also, the effect of Ψ_w on rooting percentage and root number was mediated through its effect on current photosynthate and carbohydrate.     

Shoot RNA, cambrial activity and indolebutyric acid effectivity in seasonal rooting of juvenile and mature Ficus pumila cuttings

The seasonal influence on adventitious root formation was studied in woody leaf bud cuttings of Ficus pumila L., creeping fig. Juvenile cuttings rooted easily, whereas only mature cuttings treated with indolebutyric acid (IBA) exceeded 30% rooting. Greater rooting occurred in IBA-treated juvenile and mature cuttings than controls, regardless of the month each experiment was initiated. Seasonal changes influenced rooting in all treatments except IBA treated juvenile cuttings where percentage rooting was not affected. Higher vascular cambial activity and shoot RNA levels occurred in juvenile and mature forms during peak rooting periods. Highest RNA was recorded with juvenile materials during maximum rooting periods, while lowest RNA was observed in mature shoots during low rooting intervals.     

Influence of light on adventitious root formation in birch shoot culturesin vitro

The influence of light of different spectral composition and levels of irradiance (2-40 Wm-²) on adventitious root formation (ARF) in birch shoot segments was investigated. Spontaneous rooting of shoot segments occurred in segments with intact apical or axillary meristems. Concerning ARF shoot meristems could be substituted by application of auxin. The very low rooting percentage of shoot segments in darkness was improved considerably by auxin application. Irradiation of cuttings was a requirement for a high percentage of spontaneous rooting. The promoting effect of light was dependent on its spectral composition and was the highest under red followed by white and blue light. The low rooting response under blue light was enhanced almost to the red light level by shielding the root-forming cutting base from light.     

插壤温度对四倍体刺槐硬枝插条生根过程中生理生化的影响

取四倍体刺槐3年生采穗圃中1年生硬枝插条为材料,研究扦插过程中插壤温度对插穗内源激素含量、酶活性和营养物质含量的影响,揭示四倍体刺槐扦插生根机制。结果表明：四倍体刺槐硬枝扦插过程中,插壤经加热处理,插穗内源IAA含量降低,ABA和ZR含量升高;根原基诱导期插穗内源IAA含量的变化趋势与未加热插穗相反,ABA和ZR含量的变化趋势与未加热插穗相同。插壤经加热处理,插穗IAAO、PPO和POD活性的变化趋势与未加热插穗相同,两处理间插穗IAAO、PPO和POD活性差异不显著。插壤经加热处理,可显著提高插穗可溶性蛋白和可溶性糖含量,而对淀粉和植物总氮含量的影响差异不显著。因此,插壤加热处理,主要是通过降低四倍体刺槐硬枝插穗内源IAA含量,提高插穗可溶性蛋白和可溶性糖含量来促进插条不定根发生。     

Vitis vinifera root and leaf metabolic composition during fruit maturation: implications of defoliation

Grapevine (Vitis vinifera) roots and leaves represent major carbohydrate and nitrogen (N) sources, either as recent assimilates, or mobilized from labile or storage pools. This study examined the response of root and leaf primary metabolism following defoliation treatments applied to fruiting vines during ripening. The objective was to link alterations in root and leaf metabolism to carbohydrate and N source functioning under conditions of increased fruit sink demand. Potted grapevine leaf area was adjusted near the start of véraison to 25 primary leaves per vine compared to 100 leaves for the control. An additional group of vines were completely defoliated. Fruit sugar and N content development was assessed, and root and leaf starch and N concentrations determined. An untargeted GC/MS approach was undertaken to evaluate root and leaf primary metabolite concentrations. Partial and full defoliation increased root carbohydrate source contribution towards berry sugar accumulation, evident through starch remobilization. Furthermore, root myo‐inositol metabolism played a distinct role during carbohydrate remobilization. Full defoliation induced shikimate pathway derived aromatic amino acid accumulation in roots, while arginine accumulated after full and partial defoliation. Likewise, various leaf amino acids accumulated after partial defoliation. These results suggest elevated root and leaf amino N source activity when leaf N availability is restricted during fruit ripening. Overall, this study provides novel information regarding the impact of leaf source restriction, on metabolic compositions of major carbohydrate and N sources during berry maturation. These results enhance the understanding of source organ carbon and N metabolism during fruit maturation.     

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.     

Early steps of adventitious rooting: morphology,hormonal profiling and carbohydrate turnover in carnation stem cuttings

The rooting of stem cuttings is a common vegetative propagation practice in many ornamental species. A detailed analysis of the morphological changes occurring in the basal region of cultivated carnation cuttings during the early stages of adventitious rooting was carried out and the physiological modifications induced by exogenous auxin application were studied. To this end, the endogenous concentrations of five major classes of plant hormones [auxin, cytokinin (CK), abscisic acid, salicylic acid (SA) and jasmonic acid] and the ethylene precursor 1‐aminocyclopropane‐1‐carboxylic acid were analyzed at the base of stem cuttings and at different stages of adventitious root formation. We found that the stimulus triggering the initiation of adventitious root formation occurred during the first hours after their excision from the donor plant, due to the breakdown of the vascular continuum that induces auxin accumulation near the wounding. Although this stimulus was independent of exogenously applied auxin, it was observed that the auxin treatment accelerated cell division in the cambium and increased the sucrolytic activities at the base of the stem, both of which contributed to the establishment of the new root primordia at the stem base. Further, several genes involved in auxin transport were upregulated in the stem base either with or without auxin application, while endogenous CK and SA concentrations were specially affected by exogenous auxin application. Taken together our results indicate significant crosstalk between auxin levels, stress hormone homeostasis and sugar availability in the base of the stem cuttings in carnation during the initial steps of adventitious rooting.     

不同株龄日本落叶松插穗的内源激素含量与生根的关系

研究了日本落叶松母株年龄、插穗内源激素含量与生根之间的关系,以及外源IBA对插穗内源激素含量的影响及其对插穗生根的促进作用。结果表明：不同株龄插穗生根性状及插穗茎和叶中激素含量差异均达极显著水平,叶中激素含量对插穗生根力没有直接影响;插穗茎中生根抑制激素（ABA）含量随株龄增长而增加,生根促进激素与抑制激素的比值（IAA＋GA＋ZR）/ABA却随株龄的增长而递减,与生根力随株龄的变化趋势一致,且该比值与生根性状紧密相关,因此可作为评价母株（无性系）生根力的指标;插后13～32d是插穗愈伤组织形成和不定根诱导的关键期,此期生根促进激素消耗量大,茎中含量大幅度降低,进入根伸长生长阶段,含量上升;外源IBA促进插穗生根的机制在于通过外源激素的刺激,在不定根诱导期,插穗茎中ABA含量大幅度降低,从而有利于不定根的发生和发育。     

Leaf number and position effects on the survival and performance of grape microcuttings in vitro,and the sensitivity of the cut nodal region to the medium

The presence of leaf in microcuttings of grape cvs. Arka Neelamani and Thompson Seedless promoted rooting in vitro (MS, 1 μM IAA, 0.1 μM GA₃, 3% sucrose) but the effect varied depending on the number of leaves and position of the leaf on the cutting. Single node cuttings with a full-length lower internode and a lamina at top (LAT) showed earlier rooting and more root and shoot growth than cuttings with lamina positioned at the middle (LAM), while cuttings with a leaf at the base (LAB) of the cutting and full-length upper internode exhibited a lower percent rooting and sprouting, poor root and shoot growth, and low survival. Partial or complete removal of the upper internodal segment in LAB cuttings improved rooting and sprouting suggesting the possible operation of an inhibitory effect by the upper internode. Retaining an upper leaf in LAB cuttings (LAB+UL) resulted in necrosis of the upper leaf often followed by the lower one. The extent of necrotic damage was influenced by the leaf area and position or age of the cutting on the stock shoot. Retaining the lower internode in LAB and LAB+UL cuttings which held the node–leaf junction away from the medium, or reducing the concentration of MS medium helped significantly in improving the survival and performance of these cuttings. The difference in reaction between LAB and LAT cuttings was attributable mainly to the difference in the sensitivity of the stem part that came in contact with the medium. Removal of the leaf in LAB cuttings reduced this sensitivity. The majority of the LAB and LAB+UL cuttings, as well as non-rooting or delayed rooting LAT and LAM cuttings, exhibited high purple pigmentation of leaf, petiole and stem. Two-leafed cuttings in vitro showed poor survival, less rooting and low plantlet output compared to single-leafed cuttings. This revised version was published online in June 2006 with corrections to the Cover Date.     

Role of ethylene action in ethylene production and poststorage leaf senescence and survival of pelargonium cuttings

This study investigated the role of ethylene action in ethylene production and in poststorage performance of pelargonium cuttings. Cuttings of zonal pelargonium (Pelargonium x hortorum L.H. Bailey) of the cultivars Isabell and Mitzou were treated with ethylene and with the ethylene action inhibitors 1-methylcyclopropene (MCP), silver-thiosulfate (STS) and silver nitrate (SN) and were stored in the dark at different temperatures (5, 12, and 20 °C) for 48 h. Ethylene concentrations in the storage boxes were monitored and poststorage leaf senescence, survival and root formation of cuttings were determined. Applications of MCP resulted in a significant increase of ethylene evolution by cuttings of both cultivars which was more pronounced with increasing storage temperature. After 48 h of storage at 20 °C, ethylene concentrations were more than 20-fold higher for the MCP-treated cuttings as compared to those of the untreated controls. Also preharvest applications of STS and SN increased ethylene evolution by cuttings, even though these effects were less pronounced. However, application of these inhibitors caused severe poststorage leaf injury. Application of ethylene during storage had no effect on subsequent leaf damage. Leaf senescence during rooting and decay of cuttings, which raised with increasing storage temperature, could only partially been reduced by MCP. The results strongly support the conclusion, that in zonal pelargonium cuttings, ethylene production is controlled by autoinhibition, and clearly indicate, that temperature dependent processes other than ethylene action are substantially involved in storage-induced leaf senescence and decay.     

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.     

Comparison of the effects of epibrassinolide and steroidal estrogens on adventitious root growth and early shoot development in mung bean cuttings

Concentrations of 24-epibrassinolide as low as 0.1 μ M consistently inhibited adventitious root formation and elongation in both hypocotyl and epicotyl cuttings from mung bean ( Phaseolus aureus L.). Similar, but less pronounced, inhibitory effects on root elongation were also observed with estrone sulphate and estradiol sulphate. With regards to root number, estrone sulphate enhanced this in both types of cutting, whereas estradiol sulphate was stimulatory in hypocotyl cuttings but inhibitory in epicotyl cuttings. Brassinolide caused a marked stimulation of epicotyl (but not hypocotyl) elongation and a swelling and splitting of the epicotyl in both types of cutting, whereas estrogens varied in their effect from inhibition of epicotyl growth to no effect. Root-applied brassinolide and estrogen sulphates brought about similar morphological abnormalities in shoots viz. epinasty and inrolling of primary leaves and delayed expansion of the first trifoliate leaf.