Caffeic acid affects early growth, and morphogenetic response of hypocotyl cuttings of mung bean (Phaseolus aureus)

Caffeic acid (CA) is one of the most common cinnamic acids ubiquitously present in plants and implicated in a variety of interactions including allelopathy among plants and microbes. This study investigated the possible interference of CA with root growth and the process of rhizogenesis in hypocotyl cuttings of mung bean (Phaseolus aureus=Vigna radiata). Results indicated that CA (0-1000 microM) significantly suppressed root growth of mung bean, and impaired adventitious root formation and root length in the mung bean hypocotyl cuttings. Further investigations into the role of CA in hampering root formation indicated its interference with the biochemical processes involved in rooting process at the three stages - root initiation (third day; RI), root expression (fifth day; RE), and post-expression (seventh day; PE) - of rhizogenesis. CA caused significant changes in the activities of proteases, peroxidases (PODs), and polyphenol oxidases (PPOs) during root development and decreased the content of total endogenous phenolics (TP) in the hypocotyl cuttings. The enhanced activity of PODs and PPOs, though, relates to lignification and/or phenolic metabolism during rhizogenesis; yet their protective role to CA-induced stress, especially during the PE phase, is not ruled out. At 1000 microM CA, where rooting was significantly affected, TP content was very high during the RI phase, thus indicating its non-utilization. The study concludes that CA interferes with the rooting potential of mung bean hypocotyl cuttings by altering the activities of PODs and PPOs and the endogenous TP content that play a key role in rhizogenesis.     

Ferulic acid impairs rhizogenesis and root growth,and alters associated biochemical changes in mung bean (Vigna radiata) hypocotyls

The present study investigated the effect of ferulic acid (FA; 0–1000 µM) on early growth, and rhizogenesis in mung bean (Vigna radiata) hypocotyls and associated biochemical changes. FA severely affected the radicle elongation and number of secondary roots after 72 h. The root and shoot length, number and length of secondary roots, and seedling dry weight of one-week-old seedlings of mung bean were decreased by 64%. The rooting potential (percent rooting, number and length of adventitious roots) of mung bean hypocotyls under in vitro conditions was significantly inhibited in response to 1–100 µM FA. At 1000 µM there was complete cessation of rooting. FA caused a reduction in the contents of water-soluble proteins and endogenous total phenolics, whereas the activities of proteases, peroxidases, and polyphenol peroxidases increased. The study concludes that FA inhibits root growth and development, and in vitro rooting process in mung bean by interfering with biochemical processes that are crucial for root formation.     

Effects of 2-benzoxazolinone on the germination, early growth and morphogenetic response of mung bean (Phaseolus aureus)

2‐Benzoxazolinone (BOA), a type of hydroxamic acid present in cereals and implicated in allelopathy, is now being viewed as a potential candidate for the development of natural herbicides. A study was conducted to determine the effect of BOA on mung bean (Phaseolus aureus) through a multitude of bioassays to understand its physiological and biochemical action. It was observed that BOA significantly decreased the germination of mung bean and its early growth (measured in terms of seedling length and dry weight). A typical dose–response relationship was observed with BOA treatment, and I₅₀ values (concentrations at which 50% inhibition occurs) for germination, seedling length and seedling dry weight were calculated to be 4.3, 0.71 and 0.77 mM , respectively. There was therefore a greater inhibitory effect on seedling growth than on germination. Treated seedlings were characterised by a loss of chlorophyll and decreased respiratory activity, indicating a possible adverse effect of BOA on photosynthetic and respiratory metabolism. Mitotic activity in root‐tip cells of onion (Allium cepa) was completely arrested in response to BOA treatment, and the cells exhibited abnormality in shape and size. BOA also adversely affected rhizogenesis in hypocotyl cuttings of mung bean, indicating an impact on morphogenetic potential. It was associated with significant changes in the protein content and activities of proteases and polyphenol oxidases during the root development phase. This study concludes that BOA interfered with essential biochemical processes in mung bean. Such studies provide useful information on the biochemical and physiological modes of actions of BOA, with a view to its use as a herbicidal compound.     

Plant growth regulators and adventitious root development in relation to auxin

Adventitious root formation in stem cuttings of mung bean was enhanced by ethrel, which had an additive effect when employed simultaneously with indolebutyric acid (IBA). Abscisic acid (ABA) did not influence the number of roots per cutting whereas gibberellic acid (GA₃) and kinetin were without effect on rooting at lower concentrations but were inhibitory at higher concentrations. Nevertheless, all three of these chemicals showed synergistic interactions with IBA and/or indol-3-ylacetic acid (IAA) and thereby significantly promoted root formation. A localised application of morphactin to the epicotyl of cuttings totally inhibited root production irrespective of which of the foregoing growth regulators were suppliedvia the hypocotyl. Morphactin application also prevented root formation in cuttings treated with vitamin D₂. The various growth regulators employed had differing effects on growth of roots but there was no simple relationship between their effects on root formation and subsequent root growth.     

Polyamines and root formation in mung bean hypocotyl cuttings : I. Effects of exogenous compounds and changes in endogenous polyamine content

The effect of several polyamines (putrescine, spermidine, and spermine), their precursors (l-arginine and l-ornithine), and some analogs and metabolic inhibitors (l-canavanine, l-canaline, and methylglyoxal-bis [guanylhydrazone]) on root formation have been studied in mung bean (Vigna radiata [L.] Wilczek) hypocotyl cuttings.     

Hydrogen Peroxide Is a Second Messenger in the Salicylic Acid-Triggered Adventitious Rooting Process in Mung Bean Seedlings

In plants, salicylic acid (SA) is a signaling molecule that regulates disease resistance responses, such as systemic acquired resistance (SAR) and hypertensive response (HR). SA has been implicated as participating in various biotic and abiotic stresses. This study was conducted to investigate the role of SA in adventitious root formation (ARF) in mung bean (Phaseolus radiatus L) hypocotyl cuttings. We observed that hypocotyl treatment with SA could significantly promote the adventitious root formation, and its effects were dose and time dependent. Explants treated with SA displayed a 130% increase in adventitious root number compared with control seedlings. The role of SA in mung bean hypocotyl ARF as well as its interaction with hydrogen peroxide (H₂O₂) were also elucidated. Pretreatment of mung bean explants with N, N’-dimethylthiourea (DMTU), a scavenger for H₂O₂, resulted in a significant reduction of SA-induced ARF. Diphenyleneiodonium (DPI), a specific inhibitor of membrane-linked NADPH oxidase, also inhibited the effect of adventitious rooting triggered by SA treatment. The determination of the endogenous H₂O₂ level indicated that the seedlings treated with SA could induce H₂O₂ accumulation compared with the control treatment. Our results revealed a distinctive role of SA in the promotion of adventitious rooting via the process of H₂O₂ accumulation. This conclusion was further supported by antioxidant enzyme activity assays. Based on these results, we conclude that the accumulation of free H₂O₂ might be a downstream event in response to SA-triggered adventitious root formation in mung bean seedlings.     

脱落酸对绿豆下胚轴不定根发生的影响

以10^-4 mol/L脱落酸(ABA)处理绿豆种子24 h,在幼苗下胚轴长6 cm时,切除根部作为插条,研究ABA对插条不定根发生及插条基部细胞周期时相的影响。结果表明,ABA可促进下胚轴插条不定根发生,增加生根数和生根范围;ABA提高插条基部细胞色氨酸转氨酶、吲哚丙酮酸脱羧酶和吲哚乙醛脱氢酶的比活性,增加吲哚乙酸含量,同时进入细胞周期S期的基部细胞数目增加,促进DNA合成,有利于不定根的发生。     

Caffeine affects adventitious rooting and causes biochemical changes in the hypocotyl cuttings of mung bean (<Emphasis Type="Italic">Phaseolus aureus</Emphasis> Roxb.)

Caffeine (1,3,7-trimethylxanthine), a purine alkaloid found naturally in over 100 plant species, has recently been viewed as a safe chemical for management of pests including molluscs, slugs, snails, bacteria, and as a bird deterrent. It possesses phytotoxicity against plant species, yet the mechanism of action is lacking. A study was conducted to determine the effect of caffeine on the rooting of hypocotyl cuttings of mung bean (Phaseolus aureus) and the associated biochemical changes. At lower concentrations (<1,000 μM) of caffeine, though rooting potential was not affected, yet there was a significant decrease in the number of roots and root length. At 1,000 μM caffeine, there was a 68% decrease in the number of roots/primordia per cutting, whereas root length decreased by over 80%. However, no root formation occurred at 2,000 μM caffeine. Further investigations into the biochemical processes linked to root formation revealed that caffeine significantly affects protein content, activities of proteases, polyphenol oxidases (PPO) and total endogenous phenolic (EP) content, in the mung bean hypocotyls. A decrease in rooting potential was associated with a drastic reduction in protein content in the lower rooted portion, whereas the specific activity of proteases increased indicating that caffeine affects the protein metabolism. Activity of PPO decreased in response to caffeine, whereas EP content increased significantly indicating its non-utilization and thus less or no root formation. Respiratory ability of rooted tissue, as determined through TTC (2,3,5-triphenyl tetrazolium chloride) reduction, was impaired in response to caffeine indicating an adverse effect on the energy metabolism. The study concludes that caffeine interferes with the root development by impairing protein metabolism, affecting activity of PPO (and thus lignification), and EP content, which are the crucial steps for root formation.     

Stimulation of Adventitious Rooting in Cuttings of Four Herbaceous Species by Piperazine

Piperazine, a chemical used as buffer component, greatly promotedadventitious root formation in cuttings of sunflower (Helianthusannuus L.), pea (Pisum sativum L.), mung bean (Vigna radiataL.) and to a lesser extent in bean (Phaseolus vulgaris L.) seedlings.Piperazine was more effective in acidic pH. The studies withpiperazine analogues showed that any substantial modificationof the structure caused the chemical to be less effective, oreven inhibitory. Histological studies in sunflower hypocotylsdemonstrated that piperazine did not alter the timing of theinitial cell division. In the presence of piperazine, sunflowerhypocotyls failed to develop primary phloem fibres. Piperazineat the concentrations that promote rooting did not kill or damagethe tissue at the base of the hypocotyl. Compared to controls,piperazine treatment did not alter the proportion of primordiathat eventually developed into actively elongating roots. Sixdays after treatment 45% of the control roots in the basal sectionwere actively growing, compared to 51% in the piperazine. Therewas little evidence suggesting that the piperazine-induced promotionof rooting was caused by the removal of basal dominance in whichpiperazine killed the basal part of hypocotyl.Copyright 1995,1999 Academic Press Helianthus annuus, Phaseolus vulgaris, Pisum sativum, Vigna radiata, adventitious roots, mung bean, pea, piperazine, sunflower     

Enhancement of adventitious root formation in mung bean cuttings by 3,5-dihalo-4-hydroxybenzoic acids and 2,4-dinitrophenol

3,5-Dihalo-4-hydroxybenzoic acids enhanced adventitious root formation in mung bean (Vigna radiata L.) cuttings. 3,5-Diiodo-4-hydroxybenzoic acid was more active than 3,5-dichloro-4-hydroxybenzoic acid, increasing the number of roots formed by about 4-fold. 2,4-Dinitrophenol also enhanced significantly adventitious root formation in mung bean cuttings. The phenolic compounds were active with or without indole-3-acetic acid. The possible mechanism by which these phenolic compounds enhance rooting is discussed.Abbreviations CCCP carbonyl cyanide 3-chlorophenylhydrazone - DIHB 3,5-diiodo-4-hydroxybenzoic acid - DNP 2,4-dinitrophenol     

Interaction of auxins with growth-retarding, -inhibiting and ethylene-producing chemicals in rooting of cuttings

The growth retarding chemical Cycocel significantly synergizedIAA- and IBA-induced rooting of mung bean and IBA-induced rootingof tomato cuttings. In marigold, Cycocel and B-Nine promotedrooting when applied alone but did not synergize auxin-inducedroot formation. Chlorflurenol, a growth-inhibiting morphactin,antagonized auxin-induced rooting of all three species; inhibitionwas especially marked in the presence of IBA. The ethylene-producingchemical Amchem promoted rooting of mung bean and marigold cuttingswhen applied alone. In tomato cuttings, Amchem significantlysynergized IAA-induced root formation. (Received July 5, 1972; )     

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.     

甘蔗废糖蜜对绿豆插条下胚轴生根的影响

本文研究甘蔗废糖蜜对绿豆插条下胚轴生根的影响,结果表明,1000~7000mg/L浓度范围内的甘蔗废糖蜜能明显增加绿豆插条下胚轴不定根的数目、根长、根干重及生根范围,并促进不定根内可溶性糖含量和不定根系活力提高。     

Promotion of adventitious root formation by 4-chlororesorcinol: A polyphenol oxidase inhibitor

The extent of rooting in cuttings of Phaseolus vulgaris L., and Vigna radiata Wilcz. was affected by 4-chlororesorcinol, a polyphenol oxidase inhibitor. More root primordia and more roots were formed after 4-chlororesorcinol treatment both with and without 10^-5M Indole butyric acid. Promotion of rooting was observed also in cuttings of Elaeagnus pungens, Gypsophilia elegans and Kalanchoe blossfeldiana. The enhancement in bean and mung bean was accompanied by a concomitant wider spatial distribution of the primordia and the resulting adventitious roots. The formation of primordia in the treated cuttings was delayed by 12–24 hours, compared to untreated cuttings. The treatment was effective only when given during the first hours after the preparation of the cutting of bean and mung bean, suggesting involvement in the initiation stage. Hypocotyl extracts of mung bean cuttings, pretreated with 4-chlororesorcinol, exhibited reduced polyphenol oxidase activity. The inhibition was not reversed by washing of the treated extract in 50% acetone or by an overnight dialysis, suggesting tight or maybe even irreversible binding of the inhibitor to the enzyme.Abbreviations 4-CR 4-chlororesorcinol - IBA Indole butyric acid - PPO polyphenol oxidase     

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.     

Abscisic acid and Ethrel abolish the inhibition of adventitious root formation of paclobutrazol-treated bean primary leaf cuttings

Paclobutrazol (PB), a triazole growth retardant and an inhibitor of gibberellin biosynthesis, reduced at 17 μM concentration the adventitious root formation of bean primary leaf cuttings. Treatments with 5 μM ABA or 4 μM Ethrel, an ethylenereleasing compound, restored the rooting of PB-treated cuttings. Ethylene production and the content of the precursor 1-aminocyclopropane-l-carboxylic acid (ACC) were enhanced in root-forming tissues of PB-treated petioles 48 h after ABA application. The effect of ABA could be abolished by 10 μM CoCl₂, an inhibitor of ACC oxidase. Thus, ABA might stimulate rooting through its effect on ethylene release. 2 mM silver thiosulphate, an inhibitor of ethylene action, decreased the rooting of PB-treated cuttings similarly to Co²⁺, but failed to negate the ABA effect. These data indicate that the effect of PB on rhizogenesis is not associated directly with the inhibition of the biosynthesis of gibberellins Acknowledgements: We are grateful to Gabriella Biró. This work was supported by the Hungarian National Science Research Foundation (OTKA), Project No. 462.     

Influence of ethylene on adventitious root formation in mung bean hypocotyl cuttings

The relationship between ethylene and adventitious root formation in mung bean hypocotyl cuttings was studied.Ethephon, an ethylene-releasing compound, at 5 x 10 -5 M increased root number and root dry weight on hypo-cotyl cuttings. When ethephon was applied to hypocotyl at different times after excision, there were two effectivetimes for root production i.e. between 06 h and 18-24 h. These two time periods correspond to the induction phase and the late initiation phase of root development, respectively. After excision, three peaks of ethylene productionwere observed. The first peak commencing at 6 h started the sequence of reactions leading root formation, the second peak appearing at 12 h coincided with the beginning of the increase of the IAA level during primordia initiation, and the third peak showing at 48 h played a role in root differentiation and growth. Ethylene stimulated rooting by enhancing the increase in auxins. Thus it appears that the IAA-induced ethylene production may be a factor involved in the stimulation of adventitious root formation.     

Interaction of paclobutrazol and indole-3-butyric acid in relation to rooting of mung bean (Vigna radiata) cuttings

Paclobutrazol (PB) only slightly stimulated the rooting of mung bean cuttings but, interestingly, the number of adventitious roots formed was dramatically increased when PB was used together with indole-3-butyric acid (IBA). Application of PB in the first phase of root formation, when root initials are induced, caused the greatest enhancement of the promotive effect of IBA on rooting. Investigation of the effect of PB on uptake, transport and metabolism of [5^-3H]-IBA in mung bean cuttings revealed some changes in the rate of metabolism of IBA in comparison with control cuttings. PB was found to be involved in the partitioning of carbohydrates along the cuttings. Application of sucrose, like PB to the base of IBA-treated cuttings enhanced the effect of IBA. The patterns of the effects of PB and IBA, separately and together, on rooting were similar in defoliated and intact cuttings, however the number of roots was much lower in the defoliated cuttings, which lacked a source of assimilates. PB counteracted the effect of GA₃ in the upper regions of the cuttings and seemed to increase the sink capacity at the base of the cuttings. The results of the present study clearly demonstrated the enhancing influence of PB on IBA stimulation of the rooting of mung bean cuttings. It is suggested that PB may affect the rate of metabolism of IBA during rooting and the status of the local sink, in the base of the cuttings, thus partially contributing to the enhancement of the rooting-promotive effect of IBA.     

Effect of Ethephon, Indole Butyric Acid, and Treatment Solution pH on Rooting and on Ethylene Levels within Mung Bean Cuttings

Light-grown mung bean (Phaseolus aureus Roxb.) cuttings were treated with buffered and nonbuffered solutions of Ethephon, indole butyric acid (IBA), and the combination of both. Ethephon treatment resulted in increased tissue ethylene levels with increasing solution pH, but had no effect on rooting. IBA treatment had no effect on tissue ethylene levels, but strongly promoted rooting. Combinations of Ethephon and IBA had no effect on rooting of mung bean cuttings beyond that obtained by IBA alone.     

Abscisic-acid-stimulated rooting of stem cuttings

Summary Abscisic acid (ABA) has been found to stimulate rooting of stem cuttings of mung beans and English ivy. ABA partially overcame the inhibitory effect of gibberellic acid on root formation of mung bean cuttings but at the concentrations used did not overcome the inhibitory effect of kinetin on root formation.