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.     

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。     

The effect of ethylene on adventitious root formation in mung bean (Vigna radiata) cuttings

A promotive effect of ethylene on the formation of adventitious roots by mung bean cuttings was demonstrated using a recirculating solution culture system to apply dissolved ethylene. The number of roots increased in proportion to the length of exposure to the gas. Mean root numbers per cutting for a 4-day exposure to ethylene and an air control were 45 and 19, respectively. The tissue was most sensitive to a 24-h ethylene “pulse” 2–3 days after taking cuttings. Rooting was maximal at a concentration of 13 μl 1^?1 ethylene. The ethylene treatment inhibited the growth of roots and terminal buds. Application of Ag⁺, as silver thiosulfate, reversed the effect of ethylene on the two growth responses but had no effect on root numbers. Norbornadiene, another inhibitor of ethylene action, reversed all three ethylene responses.     

Hydrogen peroxide acts as a signal molecule in the adventitious root formation of mung bean seedlings

Hydrogen peroxide (H₂O₂), an active oxygen species, is widely generated in many biological systems and mediates various physiological and biochemical processes in plants. In this study we demonstrated that the exogenous H₂O₂ was able to promote the formation and development of adventitious roots in mung bean seedlings. Treatments with 1–100 mM H₂O₂ for 8–18 h significantly induced the formation and development of adventitious roots. Catalase (CAT) and ascorbic acid, which are H₂O₂ scavengers or inhibitors, eliminated the adventitious root-promoting effects of exogenous H₂O₂. H₂O₂ may have a downstream signaling function in the auxin signaling pathway and be involved in auxin-induced adventitious root formation. 2,3,5-Triiodobenzoic acid (TIBA), an inhibitor of auxin polar transport, strongly inhibited adventitious rooting of mung bean seedlings; however, the inhibiting effects of TIBA on adventitious rooting can be partially reversed by the exogenous IBA or H₂O₂. Diphenylene iodonium (DPI) strongly inhibits the activity of NADPH oxidase, which is one of the main sources of H₂O₂ formation in plant cells. DPI treatment strongly inhibited the formation of adventitious roots in mung bean, but the inhibitory effects of DPI on rooting can be partially reversed by the exogenous H₂O₂ or IBA. This indicates that the formation of adventitious roots was blocked once the generation of H₂O₂ through NADPH oxidase was inhibited, and H₂O₂ mediated the IBA-induced adventitious root formation. Furthermore, a rapid increase in the endogenous level of H₂O₂ was detected during incubation with water 12–36 h after the primary root removal in mung bean seedlings. Three hours after the primary root removal, the generation of endogenous H₂O₂ was markedly induced in IBA-treated seedlings in comparison with water-treated seedlings. This implies that IBA induced overproduction of H₂O₂ in mung bean seedlings, and that IBA promoted adventitious root formation via a pathway involving H₂O₂. Results obtained suggest that H₂O₂ may function as a signaling molecule involved in the formation and development of adventitious roots in mung bean seedlings.     

Triadimefon stimulates rooting in bean hypocotyl

Triadimefon, a broad spectrum fungicide and an inhibitor of gibberellic biosynthesis, whitened, thickened, and shortened the roots of bean ( Phaseolus vulgaris L. cv. Spring Green) seedlings and stimulated the development of root primordia along the hypocotyl. In a comparative study, triadimefon, IAA, spermidine, putrescine and spermine all stimulated adventitious root growth, but triadimefon was more effective than the other 4 compounds. Equimolar concentrations of gibberellic acid (GA₃) completely eliminated the stimulatory effect of triadimefon. Stimulation of root development by triadimefon was accompanied by inhibition of ethylene biosynthesis followed by removal of basal dominance and an increase in polyamine levels, both of which occurred after rooting had begun. Although triadimefon was effective in stimulating rooting, its mechanism of action is apparently not mediated via the control of ethylene and polyamine biosynthesis.     

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.     

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.     

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.     

Involvement of ethylene in the rooting of seedling shoot cultures of <Emphasis Type="Italic">Bixa orellana</Emphasis> L.

Using seedlings derived from the shoot apex of annatto (Bixa orellana L. cv. Bico-de-Pato) we observed the rooting frequency of B. orellana, the number and length of roots and the rate of ethylene production during 30 d in culture. The rhizogenesis response was affected by auxins (NAA or IBA) and by both the ethylene biosynthesis precursor 1-aminocyclopropane-1-carboxylic acid (ACC) and the inhibitor 2-aminoethoxyvinylglycine (AVG). Auxin supplementation to the medium resulted in root induction, ethylene production, and an undesirable callusing in the epidermal and cortical tissues. Irrespective of the presence of auxins, supplementing the medium with ACC promoted ethylene biosynthesis and callusing, which resulted in increased cell proliferation mainly in the cortical and vascular tissues, while the epidermis was mostly unaltered. In both ACC and auxin-supplemented medium, increased ethylene production and callusing occurred, suggesting a synergistic effect between these two responses. ACC was capable of inducing adventitious root formation, but the roots produced had a wrinkled appearance when compared to normal roots. Conversely, AVG reduced ethylene production and callusing, while the epidermis, cortex, and inner tissues remained unaltered, regardless of the presence of auxins. AVG was beneficial in these aspects, although its application led to a reduction in the number of roots and in the average root length. In conclusion, it was not possible to establish a direct relation between ethylene and rooting, but we hypothesize that, under the experimental conditions described, ethylene may enhance tissue sensitivity to auxin. However, ethylene did not seem essential to the rhizogenesis process in annatto.     

The effect of ethylene on adventitious root formation in mung bean (Vigna radiata) cuttings

A promotive effect of ethylene on the formation of adventitious roots by mung bean cuttings was demonstrated using a recirculating solution culture system to apply dissolved ethylene. The number of roots increased in proportion to the length of exposure to the gas. Mean root numbers per cutting for a 4-day exposure to ethylene and an air control were 45 and 19, respectively. The tissue was most sensitive to a 24-h ethylene pulse 2–3 days after taking cuttings. Rooting was maximal at a concentration of 13 l 1^–1 ethylene. The ethylene treatment inhibited the growth of roots and terminal buds. Application of Ag⁺, as silver thiosulfate, reversed the effect of ethylene on the two growth responses but had no effect on root numbers. Norbornadiene, another inhibitor of ethylene action, reversed all three ethylene responses.     

Ethylene and in vitro rooting of rose shoots

Effects of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC), ethylene biosynthesis inhibitor, (CoCl₂), and inhibitor of ethylene binding to receptors, 1-methylcyclopropene (1-MCP), on ethylene production and rooting in shoot culture of Rosa hybrida L. cv. Alba meidiland were studied. Additionally, effect of ethylene removal by KMnO₄ and HgClO₄ on rooting was tested. ACC increased ethylene production and delayed root formation, decreased the number of roots per shoot and inhibited root growth. In contrast, inhibition of ethylene production by CoCl₂ accelerated root emergence, and increased the number of roots per shoot. Likewise, removing ethylene from the ambient atmosphere improved root emergence and, increased root number of per shoot and markedly inhibited root growth. Blocking the ethylene receptors by 1-MCP increased ethylene level in the ambient atmosphere and increased both emergence and root formation. Both ethylene biosynthesis and action are involved in the control of rooting. Ethylene concentration in glass jars was too high for root emergence and formation, but was appropriate for root growth. CoCl₂ or 1-MPC can be recommended for regulation of rooting in rose shoot culture, since both emergence and number of roots were improved but root growth was not inhibited.     

铁核桃根与叶水浸提液对果园间作绿肥植物的化感作用及其生理机制

以西南地区具有代表性的16种绿肥植物为受体材料,采用培养皿药膜法研究了铁核桃(Juglans sigillata)根水浸提液对受体种子发芽率及幼苗鲜重、干重的化感效应;并进一步研究了铁核桃根、叶水浸提液和胡桃醌对化感效应存在明显差异的4种绿肥植物(绿豆、红三叶、白三叶、花生)种子萌发与幼苗生长以及抗氧化酶特性的影响,以筛选适宜中国西南地区核桃园种植的绿肥植物,探讨核桃根和凋落物对绿肥作物的化感作用机制。结果表明:(1)铁核桃根水浸提液对绿豆的发芽率没有影响,但对绿豆幼苗鲜重和干重有显著抑制作用,而对其他15种绿肥的发芽率和鲜重、干重均有抑制作用。(2)胡桃醌显著抑制绿豆种子萌发,而铁核桃根或叶水浸提液对绿豆种子萌发没有影响。(3)铁核桃根或叶水浸提液以及胡桃醌对绿肥植物幼苗生长的化感效应趋势一致,但核桃根或叶水浸提液的化感效应强于胡桃醌。(4)绿豆幼苗在铁核桃根或叶水浸提液以及胡桃醌处理下,超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)的活性均高于其他3种(红三叶、白三叶、花生)受体幼苗,表明绿豆清除活性氧能力高,细胞受损害程度较低,受化感作用影响最弱。研究认为,绿豆为适宜中国西南地区幼龄核桃园种植的间作绿肥植物。     

Root Formation in Ethylene-Insensitive Plants

Experiments with ethylene-insensitive tomato (Lycopersicon esculentum) and petunia (Petunia x hybrida) plants were conducted to determine if normal or adventitious root formation is affected by ethylene insensitivity. Ethylene-insensitive Never ripe (NR) tomato plants produced more below-ground root mass but fewer above-ground adventitious roots than wild-type Pearson plants. Applied auxin (indole-3-butyric acid) increased adventitious root formation on vegetative stem cuttings of wild-type plants but had little or no effect on rooting of NR plants. Reduced adventitious root formation was also observed in ethylene-insensitive transgenic petunia plants. Applied 1-aminocyclopropane-1-carboxylic acid increased adventitious root formation on vegetative stem cuttings from NR and wild-type plants, but NR cuttings produced fewer adventitious roots than wild-type cuttings. These data suggest that the promotive effect of auxin on adventitious rooting is influenced by ethylene responsiveness. Seedling root growth of tomato in response to mechanical impedance was also influenced by ethylene sensitivity. Ninety-six percent of wild-type seedlings germinated and grown on sand for 7 d grew normal roots into the medium, whereas 47% of NR seedlings displayed elongated tap-roots, shortened hypocotyls, and did not penetrate the medium. These data indicate that ethylene has a critical role in various responses of roots to environmental stimuli.     

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.     

l-DOPA (l-3,4-dihydroxyphenylalanine) affects rooting potential and associated biochemical changes in hypocotyl of mung bean, and inhibits mitotic activity in onion root tips

A study was undertaken to explore the effect of l-DOPA (l-3,4-dihydroxyphenylalanine) on the rooting potential of hypocotyl cuttings of mung bean (Phaseolus aureus Roxb. var. SML-32) and related biochemical changes at the post-expression phase. At lower concentrations of (0.0001–0.1 mM) l-DOPA, there was no change in rooting potential, though the average number of roots per cutting and root length were significantly decreased (except at 0.0001 mM). However, at 1.0 mM concentration, a 50% inhibition in rooting potential was noticed and the root number and length were severely reduced. In contrast, at 2.5 mM l-DOPA, none of the hypocotyl cutting rooted. The decrease in rooting potential was associated with a significant effect on the biochemical changes measured in terms of protein and carbohydrate metabolism and activity of peroxidases. In the l-DOPA treated hypocotyl cuttings, there was a significant reduction in the protein and carbohydrate content, whereas activities of associated enzymes proteases and amylases decreased, particularly at higher treatment concentration (>1.0 mM). It indicated negative effect of l-DOPA on these two important metabolic processes. Likewise, activity of peroxidases also decreased in the l-DOPA treated hypocotyl mung bean cuttings thereby indicating its role in suppressing rhizogenesis as the enzyme is involved in lignification process during cell division. l-DOPA suppressed mitotic activity in the root tip cells of onion indicating thereby its interference with the cell division, which is required for the formation of new meristematic tissue during rhizogenesis. Based on the obtained results, it is concluded that l-DOPA interferes with the various biochemical processes in the mung bean hypocotyl cuttings thereby affecting their rooting potential.     

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     

人参皂苷对4种栽培作物早期根系发育的化感效应

人参、西洋参能通过根系分泌三萜皂苷等化感物质,严重影响后茬人参的生长,但对人参以外的植物是否具有化感效应尚不清楚。本实验研究了不同质量浓度的人参皂苷对小麦、白菜、黄瓜及绿豆4种常见栽培作物早期根系发育的影响,结果发现人参皂苷处理液（25、50和100mg·L-1）对4种作物主根及不定根的发育影响不尽相同。随着处理质量浓度的升高,小麦、白菜、黄瓜根系活力分别比同组CK明显降低,根长、根鲜重也呈降低趋势。各浓度人参皂苷处理对黄瓜和绿豆下胚轴不定根的数量、根长、根鲜重及根系活力的影响均未达到显著水平,但二者抗氧化酶的活性都微有升高。总之,人参皂苷对4种栽培作物的主根发育均有抑制作用,尤其对小麦、黄瓜主根生长的抑制作用较强;但对黄瓜和绿豆不定根发育的影响不明显。     

人参皂苷对4种栽培作物早期根系发育的化感效应

人参、西洋参能通过根系分泌三萜皂苷等化感物质,严重影响后茬人参的生长,但对人参以外的植物是否具有化感效应尚不清楚.本实验研究了不同质量浓度的人参皂苷对小麦、白菜、黄瓜及绿豆4种常见栽培作物早期根系发育的影响,结果发现人参皂苷处理液(25、50和100 mg· L-1)对4种作物主根及不定根的发育影响不尽相同.随着处理质量浓度的升高,小麦、白菜、黄瓜根系活力分别比同组CK明显降低,根长、根鲜重也呈降低趋势.各浓度人参皂苷处理对黄瓜和绿豆下胚轴不定根的数量、根长、根鲜重及根系活力的影响均未达到显著水平,但二者抗氧化酶的活性都微有升高.总之,人参皂苷对4种栽培作物的主根发育均有抑制作用,尤其对小麦、黄瓜主根生长的抑制作用较强;但对黄瓜和绿豆不定根发育的影响不明显.