Auxin effects on rooting in pea cuttings

Light-grown stem cuttingss of Pisum sativum L. cv. Weibull's Marma were rooted in a nutrient solution. The presence of 10 μ M indolylacetic acid (IAA) in the solution for 24 h or longer periods decreased the number of roots subsequently formed to about 50% of control, provided IAA was present in the solution during any of the 4 first 24 h periods. Treatment for 6 h or shorter periods caused no or small response. IAA did not appreciably change the time needed for root formation, the time course of root appearance or the pattern of root distribution along the basal internode. IAA at 100 μ M usually increased the number of roots although variable results were obtained with this IAA concentration.
The number of roots was strongly increased by treatment with indolylbutyric acid (IBA) or 2,4-dichlorophenoxyacetic acid (2,4-D). None of these or other synthetic auxins decreased the number of roots in suboptimal concentrations. Experiments with 10 μ M IBA showed that stimulation of rooting was obtained only if the auxin was present in the rooting solution for several days. Simultaneous treatment with IAA decreased the stimulating effect of IBA to some extent, whereas no such response was obtained if IAA was combined with 2,4-D.
IAA applied in lanolin to the stem of intact cuttings decreased the number of roots formed. Decapitation and debudding of the cuttings decreased the number of roots formed. If at least 2 leaves were left this decrease was efficiently counteracted by an optimal IAA dose applied to the upper part of the stem. A five times higher dose was less effective, indicating a negative effect on rooting also by IAA applied to the shoots.     

Factors affecting the inhibitory effect of indolylacetic acid on root formation in pea cuttings

Indol-3yl-acetic acid (IAA) present in the rooting solution for 1–4 days appreciably decreased the number of roots subsequently formed in pea stem cuttings. Removal of the lowest 10 mm of the cutting base after IAA treatment abolished the inhibitory effect of IAA almost completely. The number of roots formed from the remaining part of the base internode after excision of the basal centimeter of the internode 4 days after the cuttings were taken was similar to that of the control. It is concluded that the first root primordia, which develop near the cut surface, have an inhibitory influence on development of further roots. The inhibitory effect of IAA may be explained as a strengthening of this dominance phenomenon.
Addition of charcoal to the rooting solution delayed the appearance of roots but increased the number of roots developed during a standard rooting period. Adsorption of stimulatory and inhibitory compounds at the surface of the cutting base is believed to be the reason for these results as no evidence of accumulation of inhibitory compounds in the solution was obtained. Charcoal reversed the inhibitory effect of IAA if added after the IAA treatment. This reversal was almost complete if the IAA treatment lasted for one day only but decreased drastically if the IAA treatment was extended over 4 days.     

Seasonal Rhythm of Rooting of Salix atrocinerea cuttings

The response of rooting and the content of growth substances in Salix atrocinerea cuttings were studied every month throughout the whole year. To study the rooting response 100 cuttings were put into a rooting mist-propagator frame and the results were observed 30 days later. The hormone content was studied with the same type of cuttings by means of methanol extraction, fractionating into acid, basic and neutral substances and chromatographic analysis on paper and bioassays. Salix atrocinerea cuttings have three rooting phases: one very active in January, February, March and April with plentiful roots, not ramified, originating at the base of the cutting; a second lesser phase from May to August with numerous small and very ramified roots formed at a more ample area on the stalk. Both peaks are separated by a sharp fall in June. From September to December the third phase of rooting takes place. Response is practically nil and the few small roots formed are originated at the base of the stalk, again, as in the first phase. In the histograms a remarkable activity in the acid fraction at Rf = 0.30–0.50 was found and IAA was identified. The rooting capacity of these cuttings and the IAA content show some correlation but not exact enough to assert that the root response is governed by an optimum hormonal content. In Salix atrocinerea cuttings inhibitors are absent during the whole year which support the hypothesis that root formation might in some cases be influenced also by the presence or absence of inhibitory growth substances.     

Dynamics of extractable carbohydrates in Pisum sativum. III. The effect of IAA and temperature on content and translocation of carbohydrates in pea cuttings during rooting

The number of roots formed in cuttings of pea ( Pisum sativum L. cv. Alaska) was regulated both by the temperature and by IAA, whereas the time to the appearance of the first roots was regulated only by the temperature. Cuttings treated with 10^-3 M IAA had a smaller content of extractable carbohydrates than the control ones irrespective of the temperature. In the bases of cuttings rooted at 25°C the content of extractable carbohydrates was lower than in those rooted at 15°C. Cuttings treated with IAA showed up to elevenfold increase of extractable carbohydrates in the bases at day 3. This increase of soluble sugars was not correlated with the number of roots formed or the speed of rooting. It is concluded that IAA affects the accumulation of carbohydrates, and this is not connected with the rooting ability of the cuttings.     

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

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

Effect of Photoperiod, Auxins and Gibberellic Acid on Rooting of Stem Cuttings of Bryophyllum tubiflorum

Photoperiod controls the initiation and development of roots on cuttings of Bryophyllum tubiflorum. Root initiation occurred when either the mother plant or the cuttings were exposed subsequently to SD conditions. Cuttings from LD plants exposed to LD did not root at all even after 4 weeks showing that short days are necessary for rooting of cuttings of this plant. The short day requirement can be substituted by IAA or IBA as roots were initiated in cuttings from LD plants when treated with the auxins under LD conditions. GA stimulates rooting of cuttings under SD conditions but does not replace the SD requirement. It failed to induce rooting under LD conditions.     

Patterns of adventitious root formation in English ivy

Adventitious root formation by debladed petiole cuttings of English ivy (Hedera helix L.) proceeds via a direct rooting pattern for the easy-to-root juvenile phase, while the difficult-to-root mature phase roots through an indirect rooting pattern. Juvenile petiole cuttings treated with α-naphthaleneacetic acid (NAA, 100 μM) plus the polyamine biosynthesis inhibitor, difluoromethylarginine (DFMA, 1 mM), formed an increased number of roots per cutting initiated by the indirect rooting pattern. The increased root formation and change in rooting pattern were reversed by the addition of putrescine (1 mM). Delaying auxin application to petiole cuttings for 15 days also induced juvenile petioles to root by the indirect pattern. This could be reversed by rewounding the base of the cutting prior to auxin application after day 15. The data support the use of the terms “competent root-forming cells” and “induced competent root-forming cells” to describe the target cells for the initial events of root formation for the direct and indirect rooting patterns, respectively.     

The course of root differentiation from root primordia in poplar stems

Upon rooting of poplar stem cuttiags the total inductive stimulation does not take place, but the individual root primordia maintain a relative independence. This becomes evident by various time parameters of their differentiation. Under experimental conditions, in dormant cuttings from one year individuals of the hybrid I 214 the activation of the first root primordia occurs after 24 h, the pre-emergent development of the roots formed was completed after 72 h. The activated root primordium is divided into two regions. In the distal region with the predominating cell division the root apex with histogens is formed by the action of initials. From peripheral cell layers of the distal region the so-called “Wurzeltasche” develops which covers the root cap. Due to cell elongation in the proximal region the root apex is pushed up towards the stem surface. The beginning differentiation of the connective vascular tissue is a preparative step for the connection of the vascular system of the developing root with the secondary vascular system of the maternal stem. Following the penetration of the root through the peripheral stem tissues this connection is realized with progressing development. In the developed root the protoxylem elements differentiate continuously and acropetally in direct continuity with tracheids of the basal connective region.     

The effect of indole-3-acetylaspartic acid on adventitious root formation on bean cuttings

The influence of indole-3-acetylaspartic acid (IAAsp) on rooting of stem cuttings from bean plants (Phaseolus vulgaris L.) of different ages, cultivated at different temperatures (17°, 21° and 25°C) was studied and compared to that of indole-3-acetic acid (IAA). At a concentration of 10^–4 M, IAAsp only nonsignificantly stimulated adventitious root formation, approximately to the same level as IAA in all treatments. IAAsp at 5×10^–4 M further enhanced rooting, by up 200% of control values, with little influence of temperature conditions and stock plant age. This concentration of IAA usually stimulated rooting more than the conjugate. The largest differences between the effects of IAAsp and IAA occured at the highest cultivation temperature of 25°C where stock plant age also influenced the response. The number of roots produced in comparison with the control, was enhanced from 350% on cuttings from the youngest plants to more than 600% on cuttings from the oldest. In contrast to the conjugate, 5×10^–4 M IAA induced hypocotyl swelling and injury of the epidermis at the base of cuttings, in all treatments.     

Auxin Synergists in Rooting of Cuttings

Leafy cuttings of Eranthemum tricolor were treated with tannic acid, gallic acid, p-hydroxybenzoic acid and salicylic acid at the concentrations of 1000, 100, 10 and 1 nig/1 for 24 hours, whereafter they were dipped quickly in a 1000 mg/l solution of IAA, IBA and NAA for ten seconds. None of the phenolics showed any root promoting effect when used singly. In combination with NAA and IBA tannic acid promoted rooting, however, with IAA there was no effect to be seen. Gallic acid also markedly increased the number of roots of cuttings treated with NAA and IBA. Even in this case there was no effect with IAA. Synergism was also recorded between p-hydroxybenzoic acid and IAA or NAA but not with IBA. Salicylic acid greatly promoted rooting in combination with both IAA, IBA and NAA.     

Juvenile stockplant material enhances root development through higher endogenous auxin level

Stockplants with various physiological characteristics were compared in a propagation experiment with leafy cuttings of ornamental cherry Prunus subhirtella ‘Autumnalis’. At the time of severance, cuttings harvested from juvenile 3-year-old in vitro-derived plants contained in their bases nearly twice as much IAA (indole-3-acetic acid) as cuttings derived from mature 40-year-old trees. Juvenile cuttings showed better rooting success in the propagation season. They developed a significantly higher number of primary roots and grew better than physiologically older cuttings. IAA time-course levels in cutting bases in the days after severance were similar in both cuttings types. They decreased over the first day (rooting late initiation phase) after severance until the third day after severance when the levels increased again (rooting induction phase and beginning of the root developing phase). At the time of severance, juvenile cuttings also contained higher concentrations of IAAasp (indole-3-acetyl aspartic acid) in their bases than mature cuttings. IAAasp time-course levels were similar to those measured for IAA.     

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。     

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 abscisic acid on endogenous IAA, auxin protector levels and peroxidase activity during adventitious root initiation in Vigna radiata cuttings

Endogenous levels of free and conjugated IAA, auxin protectors (Prs) and peroxidase (PER) activity and their relation to adventitious root initiation (ARI) were investigated at the potential sites of adventitious rooting in relation to exogenous application of 250 μM ABA during the first 120 h after treatment. Cuttings from 7-day-old mung bean [Vigna radiata (L.) Wilcz.] seedlings were treated with 125, 250, and 500 μM ABA for 24 h. ABA significantly stimulated ARI but extremely inhibited epicotyl growth as compared to control. Free and conjugated IAA were measured by reversed-phase high performance liquid chromatography while Prs and PER activities were measured spectrophotometrically. The present results also indicate that endogenous free IAA levels peaked later in ABA-treated cuttings than that in control, suggesting that ABA extended the length of the induction phase of rooting process in treated cuttings and that might explain the significant delay of the appearance of roots at the treated cuttings. Higher level of IAA conjugates was found in ABA-treated cuttings than that in untreated ones. Pr level also peaked later in ABA-treated cuttings than that in control, indicating that ABA extended the period of Pr activity. An initial temporary decrease of PER activity was found in associating with high levels of free IAA and Prs during most of the primary events, while the opposite occurred during the secondary events of adventitious rooting process in both treated and untreated cuttings. Thus, ABA may stimulate ARI in mung bean Vigna radiata cuttings by regulating the concentration and /or activities of endogenous IAA, Prs, and PER activity in favor of inducing a large number of adventitious roots at their potential sites of adventitious rooting.     

SUCROSE-INDOLE-3-ACETIC ACID INTERACTIONS ON ROOT REGENERATION BY PINUS LAMBERTIANA EMBRYO CUTTINGS

Interactions affecting root formation by IAA and sucrose, supplied to Pinus lambertiana embryo cuttings through their cotyledons, were explored. The sucrose optimum for rooting and dry weight increase is approximately 8 %. Osmotic substitutes for sucrose, applied alone or concomitantly with sucrose, were unable to duplicate its effects on regeneration. One μM IAA increased the number of roots per cutting with all sucrose concentrations. However, with suboptimal sucrose concentrations it only increased the total number of cuttings forming roots. Because IAA accumulates at the site of root formation, the possibility that it mobilizes sucrose or its derivatives to the site of root formation was explored. No evidence was found for hormone-directed transport of sucrose in this system. IAA had no effect on either the basal accumulation or transport of label derived from U-¹⁴C-sucrose.     

Seasonal changes in adventitious root formation in hypocotyl cuttings of Pinus sylvestris: Influence of Photoperiod during stock plant growth and of indolebutyric acid treatment of cuttings

Seedlings of Pinus sylvestris were grown for 6 weeks under natural light conditions in a temperature controlled environment room. Cuttings from these plants were rooted in tap water or in indolebutyric acid (IBA) solutions for 60 days at an irradiance of 16 W m^-2. Experiments were performed at 3-week intervals during two growth seasons. — Seasonal changes in root formation were found in control cuttings as well as in IBA treated cuttings. The number of roots and the percentage of cuttings that rooted were high during early spring and autumn. During the summer period hardly any roots were formed. Stimulation of root formation by IBA occurred manily during spring and autumn when cuttings already possessed the ability to form roots. — The influence of photoperiod during stock plant growth was also investigated. Shorter photoperiod resulted in an increase in the number of roots and rooting percentage. The period during summer where rooting was inhibited under natural light conditions was considerably shortened when stock plants were grown at a photoperiod of only 4 h. The results demonstrate the importance of the growing conditions for stock plants for subsequent root formation. The results are discussed with special reference to the role of irradiance.     

Regulation of root formation by auxin-ethylene interaction in pea stem cuttings

The possibility was investigated that the inhibition of rooting in pea ( Pisum sativum L. cv. Weibull's Marma) cuttings caused by low indol-3yl-acetic acid (IAA) concentrations is due to ethylene produced as a result of IAA treatment. Treatment with 10 uμ IAA reduced the number of roots to about 50% of the control and increased ethylene production in the stem bases by about 20 times the control value during the two first days of treatment. Ethylene-releasing compounds (ethephon and 1-amino-cyclopropane-1-carboxylic acid, ACC), in concentrations giving a similar ethylene release, inhibited rooting to the same extent or more strongly than IAA. These results indicate that IAA-induced ethylene is at least responsible for the negative component in IAA action on root formation in pea cuttings. A higher IAA concentration (100 μ) and indol-3yl-butyric acid efficiently counteracted the negative effect of ethylene on root formation.     

几种木本植物插穗生根与内源IAA,ABA的关系

迄今为止,传统的插条繁殖仍是林业和园林工作者获得良种无性系和培育苗木的重要途径。在影响插穗不定根形成内外因素中,植物内源激素水平和生长调节剂应用占有重要地位。已知第一个根原基细胞的分裂依赖于内源生长素或外源的生长调节剂(Hartmann 1983,Haissig 1974),低浓度的ABA(1.26～20μg/ml)能促进     

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.     

Distribution of indole-3-acetic acid in Petunia hybrida shoot tip cuttings and relationship between auxin transport, carbohydrate metabolism and adventitious root formation

To determine the contribution of polar auxin transport (PAT) to auxin accumulation and to adventitious root (AR) formation in the stem base of Petunia hybrida shoot tip cuttings, the level of indole-3-acetic acid (IAA) was monitored in non-treated cuttings and cuttings treated with the auxin transport blocker naphthylphthalamic acid (NPA) and was complemented with precise anatomical studies. The temporal course of carbohydrates, amino acids and activities of controlling enzymes was also investigated. Analysis of initial spatial IAA distribution in the cuttings revealed that approximately 40 and 10 % of the total IAA pool was present in the leaves and the stem base as rooting zone, respectively. A negative correlation existed between leaf size and IAA concentration. After excision of cuttings, IAA showed an early increase in the stem base with two peaks at 2 and 24 h post excision and, thereafter, a decline to low levels. This was mirrored by the expression pattern of the auxin-responsive GH3 gene. NPA treatment completely suppressed the 24-h peak of IAA and severely inhibited root formation. It also reduced activities of cell wall and vacuolar invertases in the early phase of AR formation and inhibited the rise of activities of glucose-6-phosphate dehydrogenase and phosphofructokinase during later stages. We propose a model in which spontaneous AR formation in Petunia cuttings is dependent on PAT and on the resulting 24-h peak of IAA in the rooting zone, where it induces early cellular events and also stimulates sink establishment. Subsequent root development stimulates glycolysis and the pentose phosphate pathway.