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.     

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.     

The Effect of the Ethylene Action Inhibitor 1-Cyclopropenylmethyl Butyl Ether on Early Plant Growth

Increased levels of ethylene in plants are responsible for many deleterious effects such as early senescence, fruit deterioration and inhibition of root elongation. Several cyclopropene derivatives have previously been studied as inhibitors of ethylene action in plants. This study focuses on one such compound, 1-cyclopropenylmethyl butyl ether and its effect on the growth of roots and shoots of canola plants as well as rooting of mung bean seedlings 1-cyclopropenylmethyl butyl ether increased root length in canola plants, but had no significant effect on shoot length. In rooting studies, mung bean seedlings treated with 1-cyclopropenylmethyl butyl ether prior to root excision had fewer numbers of roots than control plants that were not treated with the ethylene action inhibitor. The same rooting study, when repeated in the presence of 1-aminocyclopropane-1-carboxylic acid (ACC), demonstrated an overall increase in the number of roots of inibitor-treated and non-treated plants, however, the inhibitor was still effective in decreasing the number of roots, compared to its non-treated conterpart. Online publication: 7 April 2005     

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。     

Effect of auxins and plant oligosaccharides on root formation and elongation growth of mung bean hypocotyls

The interaction of auxins – IAA, IBA or NAA – with galactoglucomannan oligosaccharides (GGMOs) on adventitious root formation and elongation growth of mung bean hypocotyl cuttings was studied. GGMOs induced adventitious roots in the absence of auxins; however, their effect was lower compared with IBA or NAA. On the other hand, in the presence of auxins, GGMOs inhibited adventitious root induction. Their effect depended on the concentration of oligosaccharides and the type of auxin used. The highest inhibition effect of GGMOs at a concentration of 10⁻⁸ M in the presence of IBA and NAA was observed. In the presence of IAA their inhibition was non-significant in regard to the concentration. The interaction of auxins with GGMOs resulted in the formation of adventitious roots on a shorter part of hypocotyls compared with the effect of auxins alone. However, roots were induced more extensively along the hypocotyls treated with GGMOs compared with the control. GGMOs inhibited the length of induced adventitious roots in the presence of IAA, while in combination with IBA or NAA they were ineffective. The elongation of hypocotyls induced by IAA or IBA was inhibited by GGMOs, too. However, in the presence of NAA or by endogenous growth they were without any significant effect on elongation growth. These findings suggest that GGMOs in certain concentrations might inhibit rooting and the elongation process dependant on auxin used.     

The rooting ability of shoots raised 'in vitro' from the apple rootstock A2 in juvenile and in adult growth phase

The apple rootstock A2 can be readily propagated in vitro both in the juvenile and in the adult growth phase. Shoots were produced by meristem tip culture from the apple rootstock A2 in different growth phases. The influence of growth phases and different concentrations of PG and IBA was investigated as to rooting percentage, survival percentage, number of roots per rooted shoot, root length, shoot length and formation of callus. IBA at 15 μ M without PG gave a significantly lower rooting percentage than 5 and 10 μ M IBA. PG together with IBA stimulated rooting, the optimum concentrations of PG being, however, not the same for the different growth phases. For the adult growth phase, 10⁻⁴ M PG promoted rooting, whereas 10⁻³ M PG markedly inhibited rooting. In the juvenile growth phases, both 10⁻⁴ and 10⁻³ M PG stimulated rooting. PG at 10⁻⁴ M also increased the number of roots. The longest roots were obtained at 10⁻³ M PG and 5 μ M IBA. PG at 10⁻³ M reduced callus formation at all IBA concentrations used. Neither shoot length nor root length influenced the survival percentage.     

Putrescine and polyamine inhibitors in culture medium alter in vitro rooting response of <Emphasis Type="Italic">Decalepis hamiltonii</Emphasis> Wight &amp; Arn.

The influence of polyamine putrescine (PUT), and polyamine inhibitors were tested for in vitro rooting response from micro shoots that initially established on Murashige and Skoog (MS) medium comprising 2.7 µM α-Naphthaleneacetic acid (NAA) and 8.9 µM 6-Benzylaminopurine (BA) by using nodal explants of Decalepis hamiltonii. Incorporation of putrescine alone in rooting medium devoid of auxins supported the best response for in vitro rooting qualitatively and quantitatively. Incorporation of putrescine at 50 µM able to induce 8.62?±?1.93 roots with a maximum root length of 9.10?±?1.65 cm wherein, the root fresh weight was also found to be high compared to all other treatments (5.248?±?1.71 g). Addition of putrescine inhibitor cyclohexylamine (CHA) in medium curtailed rooting response from microshoots. Among the three polyamine inhibitors, CHA in presence of 9.8 µM Indole-3-butyric acid (IBA) outperformed α-DL-difluromethylarginine (DFMA) and α-DL-difluoromethylornithine (DFMO) combination with 9.8?µM IBA. The least response for root number (1.55?±?0.72), root length (1.96?±?0.45 cm), and root weight (1.94?±?0.35 g) was found for IBA?+?PUT?+?DFMA and the best response was noted for IBA?+?PUT?+?CHA (2.6?±?1.1, 2.92?±?0.73 cm, 3.03?±?0.75 g) respectively. Endogenous content of putrescine, spermidine and spermine supported the rooting response from in vitro shoots. These results have clearly demonstrated that putrescine plays a crucial role in rooting of D. hamiltonii. Plantlets were transferred to micro-pots for a short acclimatization stage in greenhouse where they survived at 90?%. This highly reproducible procedure can be adopted for large scale swallow root propagation. Overall, supplementing putrescine in the rooting medium enhances the quantity and quality of roots in D. hamiltonii, thus confirming its role.     

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.     

Promotive effect of chrysanthemic acids on adventitious root formation in some plants

Adventitious root formation in excised cucumber (Cucumis sativus L.) cotyledons was significantly promoted by (±)-cis-chrysanthemic acid at 0.006–1.8 mM. The effect of (±)-cis-chrysanthemic acid on indole-3-acetic acid (IAA)-induced rooting was additive. Rooting in excised cucumber cotyledons was significantly promoted by several isomers of chrysanthemic acid and sodium (±)-cis-chrysanthemate at 0.18 mM. Rooting in mung bean (Phaseolus radiatus L.) hypocotyls was also stimulated by the sodium salt at 0.06–0.6 mM. Rooting of kidney bean (Phaseolus vulgaris L.) hypocotyls was also clearly enhanced by sodium (±)-cis-chrysanthemate at 0.18–6 mM.     

Biochemical and histological changes during in vitro rooting of microcuttings of <Emphasis Type="Italic">Bacopa monnieri</Emphasis> (L.) Wettst.

The present study was conducted to investigate the biochemical changes vis-à-vis histological changes during adventitious rooting of microcuttings of Bacopa monnieri (L.) Wettst. The rooting in these microcuttings was induced on basal MS medium and medium supplemented with different concentrations of indole-3-acetic acid and indole-3-butyric acid (IBA). Presence of lower auxin concentration (1.0 µM) in the medium enhanced rooting and significantly improved number of roots per shoot but maximum root length was observed on basal MS medium. Histological studies were conducted to identify different phases of rooting in these microcuttings. The root meristemoids with distinct polarity become visible after 3 days and mark the beginning of in vitro root initiation phase. It was followed by primordia elongation, root emergence and visible rooting on the 5th day of culture on medium supplemented with auxins. Biochemical studies were also conducted from basal portions of microcuttings cultured on MS medium supplemented with 1.0 µM IBA and control (basal MS medium) from 0 to 7 days. Total carbohydrate content was lower during initial periods (up to day 1) and was found to increase during root initiation and primordia development, which reflects high energy demands for active cell divisions. A significantly higher level of phenols was recorded in microcuttings on medium supplemented with IBA. Polyphenol oxidase, peroxidase (POX), ascorbate peroxidase activities were also found to vary during different phases of rhizogenesis. Early phases were also marked with the lower activities of POX and IAAO. This study revealed significant role of enzymes, sugars and phenols during different phases of rooting.     

Prostaglandin inhibitors and the development of mung bean seedlings

The effect of cortisol and prostaglandin inhibitors on the growth and development of germinating mung bean, Vigna radiata L. Wilzek, cv. Jumbo was investigated. Cortisol, indomethacin, and a mixture of cortisol with aspirin, or benoxaprofen significantly increased radicle length and the number of lateral roots as compared with non-treated controls. A mixture of cortisol and indomethacin significantly increased growth of hypocotyls.     

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     

Differences in the Thermostability and Subunit Species of Cytochrome c Oxidase among Tissues

Cytochrome c oxidase associated with the mitochondrial innermembrane of the overground or underground organs of mung beanwas more stable at 40–55?C than that of the correspondingorgans of pea. In both plants, the enzyme in the overgroundorgans was more resistant to heat inactivation than that inthe underground organs. When the enzyme was solubilized andpartially purified from mung bean hypocotyls or roots, the enzymebecame more labile and was stabilized by exogenous phospholipid.The enzyme partially purified from mung bean hypocotyls wasmore resistant to inactivation than that from its roots eitherin the presence or absence of phospholipid. A subunit (subunitVa) of cytochrome c oxidase in mung bean hypocotyls differedimmunologically from that in the roots. We propose that at leastin mung bean, a nuclear-encoded subunit of cytochrome c oxidaseis synthesized tissue-specifically, which may cause the differencein the thermostability of the enzyme. (Received August 7, 1988; Accepted August 22, 1988)     

Impact of galactoglucomannan oligosaccharides on elongation growth in intact mung bean plants

The impact of exogenously applied galactoglucomannan oligosaccharides (GGMOs) and their structurally modified forms (GGMOs-r—galactoglucomannosyl alditols, GGMOs-g—with reduced galactose content) on the growth of mung bean (Vigna radiata (L.) Wilczek) intact plants cultured in hydroponics has been determined. GGMOs alone or in combination with exogenously added IBA have influenced (with stimulation and/or inhibition effect) hypocotyl and seminal root elongation, adventitious and lateral roots formation and elongation in dependency on their concentration used. The inhibition of elongation growth in hypocotyls as well as in roots was connected with changes of cell wall-associated peroxidases activity and is probably associated with the beginning of cell wall rigidification. Data presented in this paper confirm the hypothesis that exogenously added GGMOs may have antiauxin activity and may interact also with endogenous growth regulators. Certain monosaccharide sequences with terminal galactose in the side chain of GGMOs probably play important role in their biological activity in intact plants as it was demonstrated previously in individual parts of plants.     

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.     

Caffeic acid inhibits in vitro rooting in mung bean [Vigna radiata (L.) Wilczek] hypocotyls by inducing oxidative stress

Caffeic acid (CA), which is ubiquitously present in plants, is a potent phytotoxin affecting plant growth and physiology. The aim of our study was to investigate whether CA-induced inhibition of adventitious root formation (ARF) in mung bean {Vigna radiata (L.) Wilczek [Phaseolus aureus Roxb.]} involves the induction of conventional stress responses. The effect of CA (0–1000 μM) on ARF in mung bean was determined by measuring the generation of reactive oxygen species (ROS) in terms of malondialdehyde and hydrogen peroxide (H₂O₂) content, root oxidizability and changes in levels of antioxidant enzymes. Our results show that CA significantly enhanced MDA content, indicating severe lipid peroxidation, and increased H₂O₂ accumulation and root oxidizability in the lower rooted hypocotylar region (LRHR) of mung bean, thereby inducing oxidative stress and cellular damage. In response to CA, there was a significant upregulation in the activities of scavenging enzymes, such as superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase, catalase and glutathione reductase, in LRHRs of mung bean. Based on these results, we conclude that CA inhibits ARF in mung bean hypocotyls by inducing ROS-generated oxidative stress and upregulating the activities of antioxidant enzymes.     

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.     

Growth and organogenesis in moth bean callus cultures as influenced by triazole growth regulators and gibberellic acid

The triazole plant growth regulators, paclobutrazol and uniconazole, reduced in vitro growth of moth bean callus by 20–25% when added to the culture medium at 1 mg/L (3.4 μM). The addition of 10 mg/L (29 μM) gibberellic acid (GA₃) to the culture medium in combination with the triazoles restored callus growth to a level equivalent to that of the untreated control. GA₃ alone had little effect on callus growth. When added to a regeneration medium at 1 mg/L both paclobutrazol and uniconazole reduced the percentage of cultures that formed roots, as well as the mean number of roots per culture. In contrast, GA₃ increased root formation and counteracted the inhibitory effects of the triazoles on rooting. The addition of triazoles or GA₃ to the regeneration medium reduced the formation of green meristematic nodules, which are precursors of shoots in moth bean callus. When callus was grown in the presence of either paclobutrazol or uniconazole, subsequent root and green meristematic nodule formation were reduced upon transfer to a growth regulator-free regeneration medium. The results of this study indicate that exposure of moth bean callus tissue to micromolar concentrations of triazoles or GA₃ can significantly alter in vitro growth and differentiation.