SciELO - Scientific Electronic Library Online

vol.12 número2Technical and economic feasibility of gradual concentric chambers reactor for sewage treatment in developing countriesA rapid and cheap protocol for preparation of PCR templates in peanut índice de autoresíndice de materiabúsqueda de artículos
Home Pagelista alfabética de revistas  

Servicios Personalizados




Links relacionados


Electronic Journal of Biotechnology

versión On-line ISSN 0717-3458

Electron. J. Biotechnol. v.12 n.2 Valparaíso abr. 2009



Molecular Biology and Genetics

Electronic Journal of Biotechnology ISSN: 0717-3458 Vol. 12 No. 2, Issue of April 15, 2009
© 2009 by Pontificia Universidad Católica de Valparaíso -- Chile Received March 6, 2006 / Accepted August 7, 2008
DOI: 10.2225/vol12-issue2-fulltext-1 How to reference this article

AgNO3 - a potential regulator of ethylene activity and plant growth modulator

Vinod Kumar
Plant Cell Biotechnology Department
Central Food Technological Research Institute
Mysore-570 020, Karnataka State, India

Giridhar Parvatam
Plant Cell Biotechnology Department
Central Food Technological Research Institute
Mysore-570 020, Karnataka State, India

Gokare Aswathanarayana Ravishankar*
Plant Cell Biotechnology Department
Central Food Technological Research Institute
Mysore-570 020, Karnataka State, India
Tel: 91 821 2516501
Fax: 91 821 2517 233

*Corresponding author

Financial support: Department of Biotechnology, Government of India.

Keywords: calcium, ethylene, morphogenesis, polyamines, silver nitrate, somatic embryogenesis.


ACC: 1-Amino-cyclopropane-1-carboxylic acid
ADC: arginine decarboxylase
AgNO3: silver nitrate
AVG: aminoethoxyvinylglycine
BA: 6-benzylaminopurine
DFMA: α-DL-difluromethyl arginine
DFMO: α-DL-difluromethyl ornithine
IAA: indole acetic acid
NAA: α-naphthalene acetic acid
ODC: ornithine decarboxylase
PA: polyamine
Put: putrescine
SAM: S-adenosyl-L- methionine
STS: silver thiosulphate
Spd: spermidine
Spm: spermine

Abstract   Reprint (PDF)

The aim of this review is to critically analyze the role of silver nitrate (AgNO3) in modulating plant growth and development. In recent years, basic studies on ethylene regulation opened new vistas for applied research in the area of micro-propagation, somatic embryogenesis, in vitro flowering, growth promotion, fruit ripening, and sex expression. Silver nitrate has proved to be a very potent inhibitor of ethylene action and is widely used in plant tissue culture. Few properties of silver nitrate such as easy availability, solubility in water, specificity and stability make it very useful for various applications in exploiting plant growth regulation and morphogenesis in vivo and in vitro. Silver ion mediated responses seem to be involved in polyamines, ethylene- and calcium- mediated pathways, and play a crucial role in regulating physiological process including morphogenesis. The molecular basis for regulation of morphogenesis under the influence of silver nitrate is completely lacking. This review compiles published reports of silver nitrate-mediated in vitro and in vivo studies and focuses on fundamental and applied aspects of plant growth modulation under the influence of silver nitrate.

Concluding Remarks
Figure 1
Figure 2
Figure 3
Table 1

In recent years, advances in plant genetic engineering have opened new avenues for crop improvement and various plants with novel agronomic traits have been produced. The success of plant genetic engineering relies on several factors which include an efficient tissue culture system, for regeneration of plants from cultured cells and tissues (Pua et al. 1996). Shoot generation and rooting are important in the realization of the potential of the cell and tissue culture techniques for plant improvement (Purnhauser et al. 1987). Silver ions in the form of nitrate, such as AgNO3, play a major role in influencing somatic embryogenesis, shoot formation and efficient root formation which are the prerequisites for successful genetic transformation (Bais et al. 1999; Bais et al. 2000a; Bais et al. 2000b; Bais et al. 2001a; Bais et al. 2001b; Bais et al. 2001c). Silver ions are also employed in the form of silver thiosulphate in several tissue culture studies (Eapen and George, 1997).

Ethylene is recognized as a ubiquitous plant hormone (Lieberman, 1979; Yang, 1985), which influences growth and development of plants (Abeles, 1973; Yang and Hoffman, 1984; Mattoo and Suttle, 1991). In vitro studies have indicated that ethylene can affect callus growth, shoot regeneration and somatic embryogenesis in vitro (Purnhauser et al. 1987; Songstad et al. 1988; Roustan et al. 1989; Roustan et al. 1990; Biddington, 1992; Pua and Chi, 1993). Thus, by regulating the production or action of ethylene, the growth and development of some tissue cultures can be controlled to a certain extent (Beyer, 1976c; Davies, 1987; Purnhauser et al. 1987; Songstad et al. 1988; Chi and Pua, 1989; Bais et al. 2000a; Giridhar et al. 2003).

AgNO3 has been known to inhibit ethylene action (Beyer, 1976a) and cobaltous ions are known to inhibit ethylene synthesis (Lau and Yang, 1976) (Figure 1). Silver ion is capable of specifically blocking the action of exogenously applied ethylene in classical responses such as abscission, senescence and growth retardation (Beyer, 1976c). These observations led to its application in tissue culture. Addition of AgNO3 to the culture media greatly improved the regeneration of both dicot and monocot plant tissue cultures (Beyer, 1976c; Duncan et al. 1985; Davies, 1987; Purnhauser et al. 1987; Songstad et al. 1988; Chi and Pua, 1989; Veen and Over Beek, 1989; Bais et al. 2000a; Giridhar et al. 2003). The exact mechanism of AgNO3 action on plants is unclear. However, few existing evidences suggest its interference in ethylene perception mechanism (Beyer, 1976c). In recent years, AgNO3 has been employed in tissue culture studies for inhibiting ethylene action because of its water solubility and lack of phytotoxicity at effective concentrations (Beyer, 1976a).


Ethylene is a gaseous plant hormone involved in many aspects of plant life cycle (Figure 1) such as seed germination, root hair development, root nodulation, flower senescence, abscission, and fruit ripening (Johnson and Ecker, 1998; Bleecker and Kende, 2000). Its biosynthesis (Wang et al. 2002) is tightly regulated by internal signals and environmental stimuli from biotic and abiotic stresses, such as pathogen attack, wounding, hypoxia, ozone, chilling, or freezing (Wang et al. 2002). The role of ethylene in morphogenesis has been well documented in an earlier review (Kumar et al. 1998a). Mutants have also been identified that display a constitutive triple response in the absence of ethylene (Kieber et al. 1993). This can be divided into subgroups based on whether or not the constitutive triple response can be suppressed by inhibitors of ethylene perception and biosynthesis, such as silver ions and aminoethoxyvinyl glycine (AVG). Mutants that are unaffected by these inhibitors are termed constitutive triple-response (ctr) mutants, whereas mutants whose phenotype reverts to normal morphology are termed ethylene-overproducer (eto) mutants, which are defective in the regulation of hormone biosynthesis. To date, data is lacking on the molecular basis for silver ion interaction with the mutants, which are insensitive to ethylene.

Ethylene biosynthesis

To understand the role of silver ions in regulating morphogenesis, it is important to know the aspects of ethylene biosynthesis (Figure 1). The biochemistry of ethylene biosynthesis has been a subject of intensive study in plant hormone physiology (reviewed by Wang et al. 2002). In brief, the biosynthesis of ethylene starts with conversion of the amino acid methionine to S-adenosyl-L- methionine (SAM, also called Adomet) by the enzyme Met Adenosyltransferase. SAM is subsequently converted to 1-aminocyclopropane-1-carboxylic-acid (ACC) by the enzyme ACC synthase (ACS). The activity of ACS is the rate-limiting step in ethylene synthesis. The final step requires oxygen and involves the action of the enzyme ACC-oxidase (ACO), formerly known as the ethylene forming enzyme (EFE) (Wang et al. 2002).

A major breakthrough in the ethylene synthesis pathway was the establishment of S-adenosylmethionine (S-AdoMet) and ACC as the precursors of ethylene (reviewed in Yang and Hoffman, 1984; Kende, 1993). On the basis of this knowledge, the enzymes that catalyze these reactions were characterized and purified. The first successes in molecular cloning of the ACC (Sato and Theologis, 1989) and ACO (Hamilton et al. 1991; Spanu et al. 1991) genes led to the demonstration of these enzymes belonging to a multi-gene family and are regulated by a complex network of developmental and environmental signals responding to both internal and external stimuli (reviewed by Johnson and Ecker, 1998). In addition to being an essential building block of protein synthesis, nearly 80% of cellular methionine is converted to S-AdoMet by S-AdoMet synthetase (SAM synthetase) at the expense of ATP utilization (Ravanel et al. 1998). S-AdoMet is the major methyl donor in plants and is used as a substrate for many biochemical pathways, including polyamines and ethylene biosynthesis (Ravanel et al. 1998).

Ethylene signal perception

Ethylene is perceived by a family of five membrane-localized receptors that are homologous to bacterial histidine kinases involved in sensing environmental changes (Figure 2). Ethylene binding occurs at the N-terminal transmembrane domain of the receptors, and a copper co-factor is required for the binding. The system typically consists of a histidine kinase as the sensor that autophosphorylates an internal histidine residue in response to environmental signals, and a response regulator that activates the downstream components upon receiving a phosphate from the histidine residue of the sensor on its aspartate residue (Wurgler-Murphy and Saito, 1997). Five ethylene receptors exist in Arabiodpsis: ETR1, ETR2, ERS1, ERS2, and EIN4 (Chang et al. 1993; Hua et al. 1995; Hua and Meyerowitz, 1998; Sakai et al. 1998). Further characterization of ethylene binding to ETR1 has revealed that it occurs at the hydrophobic pocket located at the N- terminus of the receptors and requires a transition metal, copper, as a co-factor (Figure 2) (Schaller and Bleecker, 1995; Rodriguez et al. 1999; Wang et al. 2002). Further findings indicated that RAN1 is involved in the delivery of copper to the ethylene receptor and that this copper-delivery pathway is required to create functional ethylene receptors in plants (Figure 2) (Wang et al. 2002). Cu ions are also known to form complexes with ethylene (Coates et al. 1968). But the studies of Beyer (1976c) revealed that the effect of silver ions could be explained on the basis that silver ions substitute for Cu ions, thereby interfering with ethylene action. This may be due to the similarity in size, the same oxidation state, and the ability of both Cu ion and Ag ion to form complexes with ethylene (Coates et al. 1968). The possibility of the anti-ethylene property of silver was later well explored in various plant systems. At present there are no concrete evidences to show the involvement of silver ions with signaling networks which leads to down regulation of physiological responses governed by ethylene. Therefore, focus on the elucidation of molecular basis for diverse developmental process in plants such as abscission, flowering, fruit ripening, morphogenesis and sex expression, that are known to be regulated by silver ions, would be interesting.

Possible mechanisms of action of silver nitrate on ethylene action inhibition

Silver ions are capable of generating ethylene insensitivity in plants (Zhao et al. 2002). Ethylene-insensitive mutations (Hall et al. 1999) and silver ions are thought to perturb the ethylene binding sites (Rodriguez et al. 1999). The ethylene receptor, ETR1, contains one ethylene-binding site per homodimer and binding is mediated by a single copper ion (Cu) present in the ethylene-binding site. The replacement of the copper co-factor by silver also serves to lock the receptor into a conformation such that it continuously represses ethylene responses (Zhao et al. 2002).

There are different views and experimental evidences on this subject. According to one view, the ethylene action in plants is inhibited by week antagonists such as CO2 and strong antagonists like silver compounds. This is possibly due to oxidation of ethylene by a metal-ion enzyme system (Abeles, 1973). In Arabidopsis, insensitivity to ethylene is conferred by dominant mutation in receptors (Bleecker et al. 1988). Another hypothesis is that AgNO3 inhibits ethylene action by means of silver ions by reducing the receptor capacity to bind ethylene (Yang, 1985), which would result in higher titers of ethylene in the tissues, thus inhibiting the earlier steps of its own pathway. Miyazaki and Yang (1987) reported the influence of putrescine and AgNO3 on the competitive utilization of SAM. Bais et al. (2000b) also postulated that the utilization of SAM by putrescine for its conversion to spermidine would possibly result in a lower availability of SAM for ethylene biosynthesis (Figure 3). The introduction of ethylene antagonists into the culture media affects the level of ACC, thereby affecting ethylene levels (Gong et al. 2005).


Other important substances responsible for regulation of morphogenesis are polyamines. The polyamines (PAs) are organic compounds having two or more primary amino groups. Polyamines have been implicated in several important cellular processes like cell division, morphogenesis, protein synthesis, DNA replication, and plant response to abiotic stress (Tabor and Tabor, 1984; Smith, 1985; Smith, 1993; Van Den Broeck et al. 1994; Walden et al. 1997; Kumar and Rajam, 2004). They bind to DNA, and are essential for cell viability (Flink and Pettijohn, 1975). Polyamines are also known to be involved in DNA helix stabilization, stabilization of loops in RNA molecules, membrane permeability, DNA replication, cell division, gene expression, regulation of enzyme activities, membrane stabilization, morphogenesis, fruit ripening etc. (Bais and Ravishankar, 2002; Kumar and Rajam, 2004). It has been postulated that polyamines and related compounds are a type of growth regulator or secondary hormonal messenger (Galston, 1983; Davies, 1987). PAs are found in plant cells at significantly higher levels than plant hormones. There is evidence that PAs are taken up by cell suspension cultures (Evans and Malmberg, 1989). Interestingly, it seems that there is a strong link between ethylene, polyamines, and calcium-mediated signaling. This triangle is expected to be a potential target for silver ions. This is because both ethylene and polyamines are metabolically related (Figure 3) and utilize the same precursor, SAM, for their synthesis (Evans and Malmberg, 1989; Bais and Ravishankar, 2002). It has also been suggested that polyamines and ethylene may regulate each other’s synthesis. For instance, ethylene has been shown to inhibit arginine decarboxylase and S-adenosyl methionine decarboxylase activities in pea seedlings (Apelbaum et al. 1985). These enzymes are necessary for polyamine synthesis (Smith, 1985). It has been proved beyond doubt that polyamines play crucial roles in plant growth and development as well as basic biological process (reviewed by Kumar and Rajam, 2004). Since polyamines have been reported to promote embryogenesis (Feirer et al. 1984), the promotive effect of ethylene inhibitors, such as AgNO3, on regeneration was thought to be due to enhanced polyamine synthesis rather than reduced ethylene production. Pua et al. (1996) clearly described the synergistic effect of AgNO3 and putrescine on shoot regeneration in Chinese radish. Miyazaki and Yang (1987) reported the influence of putrescine and AgNO3 on the competitive utilization of SAM. Bais et al. (2000b) postulated that, utilization of SAM by putrescene for its conversion to spermidine would possibly result in a lower availability of SAM for ethylene biosynthesis (Figure 3). On the other hand, Pua and Chi (1993) also reported the same stimulatory effect of AgNO3 feeding on ethylene production and its contribution to increased titers of polyamines in mustard. Polyamines also regulate the growth and secondary metabolism (Bais et al. 1999; Bais et al. 2001b; Bais and Ravishankar, 2002). Reports on somatic embryogenesis in carrot (Roustan et al. 1990; Nissen, 1994) indicate that the potent ethylene action inhibitor, AgNO3, causes the increase of ADC activity, which in turn increases the levels of endogenous polyamines in carrot embryogenic cultures.

Involvement of calcium in polyamine-mediated response

Polyamines are associated with Ca2+ ions in signaling events (Majewska-Sawka et al. 1998). They supported the hypothesis of transportation of spermidine/spermine within protoplasts through a carrier-mediated mechanism (Antognoni et al. 1994, Majewska-Sawka et al. 1997). Majewska-Sawka et al. (1998) found that spermidine/spermine may result in change in distribution of Ca2+ ions. It is reasonable to conclude that Ca2+ ions may be involved in the mechanism of polyamine action in plant cells (Bush, 1995). This aspect is very relevant here because, apart from ethylene regulation, silver nitrate is known to regulate the polyamine pool in plant systems.

Application of silver nitrate in plant tissue culture

So far we have discussed the possible mechanisms of regulation of morphogenesis by silver nitrate. Interestingly, a large number of reports are accumulating on the utility of silver nitrate in tissue culture and other applications, with significant contributions towards the development of plant biotechnology and transgenic research. The following section deals with a brief compilation of published research pertaining to the effect of silver nitrate in plant morphogenesis (Table 1).

Somatic embryogenesis

Theoretically, each living plant cell is capable of forming somatic embryos. Somatic embryos are formed from vegetative plant cells. Applications of this process include: clonal propagation of genetically uniform plant material, elimination of viruses, provision of source tissue for genetic transformation, generation of whole plants from single cells called protoplasts, and development of synthetic seed technology. Plant growth regulators in the tissue culture medium can be manipulated to induce callus formation and subsequently changed to induce embryos from the callus or directly from intact tissues. The ratio of different plant growth regulators required to induce callus or embryo formation varies with the type of plant. The use of silver nitrate improved somatic embryogenesis in several plant species such as buffalograss (Fei et al. 2000), Coffea sp. (Fuentes et al. 2000; Giridhar et al. 2004), carrot (Nissen, 1994), white spruce (Kong and Yeung, 1994), Triticum durum (Fernandez et al. 1999), and Zea mays (Vain Hort and Flament, 1989; Vain Hort et al. 1989; Songstad et al. 1991).

Multiple shoot induction and shoot regeneration

Silver nitrate is known to promote multiple shoot formation in different plants. In vitro shoot formation was improved by incorporating silver nitrate in the culture medium. Ganesh and Sreenath (1996) reported in vitro sprouting of apical buds of Coffea under the influence of AgNO3. The addition of N6-benzyladenine with AgNO3 greatly enhanced the rate of sprouting. At low concentration, AgNO3 was found to cause delayed senescence resulting in improved growth of the proliferated shoots in Coffea canephora (Fuentes et al. 2000). AgNO3 enhanced in vitro shoot growth of C. arabica and C. canephora (Giridhar et al. 2003). Shoot regeneration of Chinese radish Cv Red coat was improved when cultured in media supplemented with 20­30 µM AgNO3 (Pua et al. 1996). Brassica sp. are poorly responsive to tissue culture manipulations (Narasimhulu and Chopra, 1988). B. campestris produces high levels of ethylene causing abnormal growth and development of the plant in tissue culture conditions (Lentini et al. 1988), and also inhibits de novo shoot regeneration in vitro (Chi et al. 1990; Chi et al. 1991; Palmer, 1992; Pua and Chi, 1993). The cotyledons and hypocotyls of 7 cultivars belonging to B. campestris spp. chinensis, spp. pekinensis and spp. parachinensis exhibited improved shoot regeneration on culture media supplemented with growth regulators and AgNO3.

The effects of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), and two inhibitors, silver thiosulfate and aminoethoxyvinylglycine (AVG), were tested in yellow passionfruit (Passiflora edulis) axillary buds cultured in vitro (Reis et al. 2003). The organogenesis was assessed by the number of buds per explant, mean leaf area per explant, and shoot length. ACC-supplemented medium significantly inhibited all evaluated responses. When ethylene action and biosynthesis were inhibited, a significant enhancement of buds and leaf area was observed. The results suggest beneficial effects of silver nitrate on in vitro development of axillary buds.

Inhibition of ethylene action by AgNO3 stimulated regeneration of shoots from cotyledon explants of Helianthus annus (Chraibi et al. 1991). In many plants, the regeneration potential of cultured cells and tissues decreases with increased cycles of subcultures (Ogura and Shimada, 1978; Vasil, 1987). This phenomenon is evident in Pennisetum americanum (Pearl millet) and Plus et al. (1993) effectively addressed this issue by incorporating AgNO3 in the culture medium to restore the regeneration potential. AgNO3 enhanced shoot regeneration frequency in silk tree (Albizzia julibrissin) and Nicotiana plumbaginifolia.

The work done in our laboratory has shown that exogenous feeding of putrescine and silver nitrate influenced morphogenesis in chicory (Chichorium intybus) shoot cultures (Bais et al. 2000b). Putrescine and AgNO3 induced shoot multiplication and in vitro flowering. The chicory plants, which flower biennially, could be forced to flower experimentally for studies on in vitro pollination and seed development (Bais et al. 2000b).

Silver nitrate was found to be beneficial in the regeneration and clonal propagation of several economically important plants (Table 1) such as peanut (Pestana et al. 1999), cowpea (Brar et al. 1999), Brassica sp. (Eapen and George, 1997; Pua et al. 1999), Capscicum sp. (Hyde and Philips, 1996, Kumar et al. 2003a), watermelon (Lim and Song, 1993), Coffea canephora (Kumar et al. 2003b), Cucumber (Mohiuddin et al. 1997), Pomegranate (Naik and Chand, 2003), White marrygold (Misra and Datta, 2001), Cassava (Zang et al. 2001), Petunia (Gavinlertvatana et al. 1980), etc.

In vitro rooting

Decalepis hamiltonii Wight, Arn (swallow root), belonging to Asclepiadaceae, is a monogeneric climbing shrub, native of the Deccan peninsula and forest areas of Western Ghats in India. It is used as a culinary spice due to its aromatic roots. In vitro root formation is a major issue in the tissue culture of this plant. Effects of AgNO3 on in vitro root formation of Decalepis hamiltonii were studied. Addition of 40 µM AgNO3 resulted in root initiation and elongation (Bais et al. 2000a; Reddy et al. 2001).

Vanilla is an important spice crop of commercial value. The effect of AgNO3 on rooting and shooting was elucidated in Vanilla planifolia (Giridhar et al. 2001). Maximum number of shoots and highest shoot length was obtained on medium containing 20 µM AgNO3. AgNO3 not only induced shoot multiplication but also influenced rooting of vanilla explants. The plantlets obtained on medium containing 40 µM AgNO3 exhibited 100% survival. Silver nitrate also induced rooting and flowering in vitro on the rare, rhoeophytic woody medicinal plant, Rotula aquatica Lour. Dipping of the basal end of shoots in NAA (2.69 µM) and silver nitrate (11.7 µM) solution improved rooting efficiency (Sunandakumari et al. 2004).

Modification of sex expression

The inhibition of ethylene action by silver nitrate was employed to suppress the development of female flowers and induce male flowers (Beyer, 1976c; Atsmon and Tabbak, 1979; Takahashi and Jaffe, 1984). Mulberry (Morus alba L.) is a dioecious plant and the male and female flowers are seen in separate plants. Bisexual flowers never occur under natural conditions (Thomas, 2004). By treating the nodal cuttings with silver nitrate, bisexual flowers could be induced in female plants. The histological analysis of these bisexual flowers showed both ovule and anther in the same flower (Thomas, 2004). Bisexual flowers were also induced in cucumber by silver nitrate treatment (Stankovic and Prodanovic, 2002). Ethylene and auxin promote the formation of female flowers whereas gibberellins promote the formation of male flowers (Mohan Ram and Jaiswal, 1970; Saito and Takahashi, 1986). The enhancement of femaleness by auxin possibly occurs through the induction of ethylene biosynthesis (Takahashi and Jaffe, 1984; Trebitsh et al. 1987). Ethylene evolution is highly correlated with sex expression in plants and dioecious plants produce more ethylene than monoecious ones (Rudich et al. 1972; Trebitsh et al. 1987). In view of all these evidences, silver nitrate may possibly be a potent candidate compound to regulate the sex expression in plants.

Fruit ripening

Ethylene plays a crucial role in initiating and accelerating the ripening-related process. Treatment of tomato with silver ions has been shown to inhibit ethylene action and fruit ripening (Hobson et al. 1984). Furthermore, if silver ions were applied at stages of ripeness well after the breaker stage, ripening can be arrested (Tucker and Brady, 1987). The growth regulator 1-methylcyclopropane (1-MCP), like silver ions, is an extremely effective antagonist for plants or harvested plant products (Serek et al. 1995a; Serek et al. 1995b; Serek et al. 1995c; Sisler et al. 1996).

Leaf abscission

Ethylene that stimulated leaf abscission in cotton is blocked by the silver ion (Beyer, 1976c). Without AgNO3, all the leaves had abscised on the 7th day in ethylene. Plants treated with increasing concentrations of AgNO3 and placed in ethylene showed progressively less leaf abscission. Treatment with 25 mg/l of AgNO3 reduced the time required to reach 100% leaf abscission by 2 days. Silver nitrate treatment also reduced the growth retarding effects of ethylene. Other similar experiments with mature cotton plants have demonstrated a similar ability of AgNO3 to prevent young fruit and flower abscission (Beyer, 1976c).

Concluding Remarks

In this review, an attempt has been made to discuss the role of ethylene, polyamines, and silver ions as potent regulators of morphogenesis in plants. The interplay of polyamines, ethylene, and calcium signaling is also discussed. The influence of exogenously applied silver ions in the form of AgNO3 in plant tissue culture media significantly regulates the ethylene activity in most of the plant systems. We have clearly brought out the major physiological effects of AgNO3 in plant systems viz direct or indirect organogenesis, somatic embryogenesis, in vitro rooting of micro shoots, induction of flowering, early flowering, sex expression, and control of leaf abscission. However, there is a gap in information on the molecular mechanisms of interaction between silver ions and the ethylene receptors. Further research on the regulation of morphogenesis through the use of metal ions like silver would throw light on an array of functions of these relatively simple molecules that play a marvelous role in influencing growth, development, and adaptation of plants to the environment. This opens new dimensions in understanding plant morphogenesis. Hence, it is necessary to elucidate the physiological mechanisms at the gene regulation level to find out the actual role of silver ions in signaling and to see how they influence regulation of ethylene action in plants.


VK is grateful to the CSIR, New Delhi for the award of Research Fellowship. Authors thank Mr. Rithesh Narayanpur for his technical assistance in preparation of the manuscript.


ABELES, F.B. Ethylene in plant biology. Academic press New York, 1973. 302 p. ISBN 978-0120414505.        [ Links ]

AL-KHAYRI, J.M. and AL-BAHRANY, A.M. Silver nitrate and 2-isopentyladenine promote somatic embryogenesis in date palm (Phoenix dactylifera L.). Scientia Horticulturae, July 2001, vol. 89, no. 4, p. 291-298. [CrossRef]        [ Links ]

AL-KHAYRI, J.M. and Al-BAHRANY, A.M. Genotype-dependent in vitro response of date palm (Phoenix dactylifera L.) cultivars to silver nitrate. Scientia Horticulturae, February 2004, vol. 99, no. 2, p. 153-162. [CrossRef]        [ Links ]

ANTOGNONI, F.; CASALI, P.; PISTOCCHI, R. and BAGNI, N. Kinetics and calcium-specificity of polyamine uptake in carrot protoplasts. Amino acids, December 1994, vol. 6, no. 3, p. 301-309. [CrossRef]        [ Links ]

APELBAUM, A.; GOLDLUST, A. and ICEKSON, I. Control by ethylene of arginine decarboxylase activity in pea seedlings and its implication for hormonal regulation of plant growth. Plant Physiology, 1985, vol. 79, no. 3, p. 635-640.         [ Links ]

ATSMON, D. and TABBAK, C. Comparitive effects of gibberellin, silver nitrate and aminoethoxyvinyl glycine on sexual tendency and ethylene evolution in the cucumber plant (Cucumis sativus L). Plant Cell Physiology, 1979, vol. 20, no. 8, p. 1547-1555.         [ Links ]

BAIS, H.P.; GEORGE, J. and RAVISHANKAR, G.A. Influence of polyamines on growth of hairy root cultures of witl of chiocory (Chichorium intybus L cv Lucknow local) and formation of coumarins. Journal of Plant Growth Regulation, 1999, vol. 18, no. 1, p. 33-37. [CrossRef]        [ Links ]

BAIS, H.P.; SUDHA, G.; SURESH, B. and RAVISHANKAR, G.A. AgNO3 influences in vitro root formation in Decalepis hamiltonii Wight, Arn. Current Science, 2000a, vol. 79, p. 894-898.         [ Links ]

BAIS, H.P.; SUDHA, G.S. and RAVISHANKAR, G.A. Putrescine and AgNO3 influences shoot multiplication In vitro flowering and endogenous titres of polyamines in Chichorium intybus L cv Lucknow Local. Journal Plant Growth Regulation, 2000b, vol. 19, no. 2, p. 238-248.        [ Links ]

BAIS, H.P.; SUDHA, G.S. and RAVISHANKAR, G.A. Influence of putrescine AgNO3 and polyamine inhibitors on the morphogenetic response in untransformed and transformed tissues of Chichorium intybus and their regenerants. Plant Cell Reports, 2001a, vol. 20, no. 6, p. 547-555. [CrossRef]        [ Links ]

BAIS, H.P.; SUDHA G.S. and RAVISHANKAR, G.A. Putrescine influences growth and production of coumarins in transformed and untransformed root cultures of witloof chicory (Chichorium intybus L cv Lucknow Local). Acta Physiologia Plantarum, 2001b, vol. 23, p. 319-327.        [ Links ]

BAIS, H.P.; VENKATESH, R.T.; CHANDRASHEKAR, A. and RAVISHANKAR, G.A. Agrobacterium rhizogenes mediated transformation of witl of chiocory in vitro shoot regeneration and induction of flowering. Current Science, 2001c, vol. 80, p. 83-87.         [ Links ]

BAIS, H.P. and RAVISHANKAR G.A. Role of polyamines in the ontogeny of plants and their biotechnological applications. Plant Cell Tissue and Organ Culture, 2002, vol. 69, no. 1, p. 1-34. [CrossRef]        [ Links ]

BEYER, E.M. 14C-ethylene incorporation and metabolism in pea seedlings. Nature, 1975, vol. 255, no. 5504, p. 144-147. [CrossRef]        [ Links ]

BEYER, E.M. A potent inhibitor of ethylene action in plants. Plant Physiology, 1976a, vol. 58, no. 3, p. 268-271.         [ Links ]

BEYER, E.M. Ethylene antidote. HortScience, 1976b, vol. 11, no. 3, p. 174-175.         [ Links ]

BEYER, E.M. Silver ion: a potent anti-ethylene agent in cucumber and tomato. HortScience, 1976c, vol. 11, no. 3, p. 175-196.         [ Links ]

BEYER, E.M. Effect of silver ion carbon dioxide and oxygen on ethylene action and metabolism. Plant Physiology, 1979, vol. 63, p. 163-173.         [ Links ]

BIDDINGTON, N.L. The influence of ethylene in plant tissue culture. Plant Growth Regulation, 1992, vol. 11, no. 2, p. 173-178. [CrossRef]        [ Links ]

BLEECKER, A.B.; ESTELLE, M.A.; SOMERVILLE, C. and KENDE, H. Insensitivity to ethylene conferred by a dominant mutation in Arabidopsis thaliana. Science, 1988, vol. 241, no. 4869, p. 1086-1089. [CrossRef]        [ Links ]

BLEECKER, A.B. and KENDE, H. Ethylene: A gaseous signal molecule in plants. Annual Review of Cell and Developmental Biology, 2000, vol. 16, p. 1-18. [CrossRef]        [ Links ]

BRAR, Mohanjeet S.; MOORE, Misty J.; AL KHAYRI, Jameel M.; MORELOCK, Teddy E. and ANDERSON, Edwin J. Ethylene inhibitors promote in vitro regeneration of cowpea (Vigna ungiculata L.). In Vitro Cellular and Developmental Biology-Plant, May 1999, vol. 35, no. 3, p. 222-225. [CrossRef]        [ Links ]

BUSH, D.S. Calcium regulation in plant cells and its role in signaling. Annual Review of Plant Physiology and Plant Molecular Biology, 1995, vol. 46, p. 95-122. [CrossRef]        [ Links ]

CASTILLO, A.M.; EGAÑA, B.; SANZ, J.M. and CISTUE, L. Somatic embryogenesis and plant regeneration from barley cultivars grown in Spain. Plant Cell Reports, 1998, vol. 17, no. 11, p. 902-906. [CrossRef]        [ Links ]

CHANG, C.; KWOK, S.F.; BLEECKER, A.B. and MEYEROWITZ, E.M. Arabidopsis ethylene-response gene ETR1: Similarity of product to two-component regulators. Science, 1993, vol. 262, no. 5133, p. 539-544. [CrossRef]        [ Links ]

CHI, G.L. and PUA, E.C. Ethylene inhibitors enhanced de novo shoot regeneration from cotyledons of Brassica campastris spp in vitro. Plant Science, 1989, vol. 64, p. 243-250. [CrossRef]        [ Links ]

CHI, G.L.; BARFIELD, D.G.; SIM, G.E. and PUA, E.C. Effect of AgNO3 and amino-ethoxyvinylglycine on in vitro shoot organogenesis from seedling explants of recalcitrant Brassica genotypes. Plant Cell Reports, 1990, vol. 9, no. 4, p. 195-198. [CrossRef]        [ Links ]

CHI G.L.; PUA, E.C. and GOH C.J. Role of ethylene on de novo shoot regeneration from cotyledons of Brassica campastris spp Pekinensis(Lour) Olsson in vitro. Plant Physiology, May 1991, vol. 96, no. 1, p. 178-183.         [ Links ]

CHRAIBI, B.K.M.; LATCHE, A.; RAUSTAN, J.P. and FALLOT, J. Stimulation of shoot regeneration from cotyledons of Helianthus annuus by ethylene inhibitors silver and cobalt. Plant Cell Reports, 1991, vol. 10, no. 4, p. 204-207. [CrossRef]        [ Links ]

COATES, G.E.; GREEN, M.L.H. and WADE, K. Organo metallic compounds II. Methuen and Co Ltd London, 1968, p. 1-376.        [ Links ]

CRUZ DE CARVALHO, M.H.; VAN LE, B.; ZUILY-FODIL, Y.; PHAM THI, A.T. and TRAN THANH VAN, K. Efficient whole plant regeneration of common bean (Phaseolus vulgaris L.) using thin-cell-layer culture and silver nitrate. Plant Science, 2000, vol. 159, no. 2, p. 223-232. [CrossRef]        [ Links ]

DAVIES, P.J. The plant hormones: their nature, occurrence, and functions. In: DAVIES P.J. ed. Plant Hormones and Their role in Plant Growth and Development, Ch. Al. Boston: Martinus Nijhoff, 1987.        [ Links ]

DIVYA, K.; ANURADHA, T.S.; JAMI, S.K. and KIRTI, P.B. Efficient regeneration from hypocotyl explants in three cotton cultivars. Biologia Plantarum, 2008, vol. 52, no. 2, p. 201-208. [CrossRef]         [ Links ]

DUNCAN, D.R.; WILLIAMS, M.E.; ZEHR B. and WIDHOLM, J.M. The production of callus capable of plant regeneration from immature embryos of numerous Zea mays genotypes. Planta, 1985, vol. 165, no. 3, p. 322-332. [CrossRef]        [ Links ]

EAPEN, S. and GEORGE L. Plant regeneration from peduncle segments of oil seed brassica species: Influence of AgNO3 and silver thiosulphate. Plant Cell Tissue and Organ Culture, 1997, vol. 51, no. 3, p. 229-232. [CrossRef]        [ Links ]

EL MESKAOUI, A.; DESJARDINS, Y. and TREMBLAY, F.M. Kinetics of ethylene biosynthesis and its effects during maturation of white spruce somatic embryos. Physiologia Plantarum, 2000, vol. 109, p. 333-342. [CrossRef]        [ Links ]

EL-ITRIBY, H.A.; ASSEM, S.K.; HUSSEIN, E.H.A.; ABDEL-CALIL, F.M. and MADKOUR, M.A. Regeneration and transformation of egyptian maize inbred lines via immature embryo culture and a biolistic particle delivery system. In Vitro Cellular and Development Biology-Plant, 2003, vol. 39, no. 5, p. 524-531. [CrossRef]        [ Links ]

EVANS, P.T. and MALMBERG, R.L. Do polyamines have role in plant development? Annual Review of Plant Physiology and Plant Molecular Biology, 1989, vol. 40, p. 235-269. [CrossRef]        [ Links ]

EVANS, J.M. and BATTY, N.P. Ethylene precursors and antagonists increase embryogenesis of Hordeum vulgare L anther culture. Plant Cell Reports, 1994, vol. 13, no. 11, p. 676-678. [CrossRef]        [ Links ]

FEI, S.; READ, P.E. and RIORDAN, T.P. Improvement of embryogenic callus induction and shoot regeneration of buffalo grass by AgNO3. Plant Cell Tissue Organ Culture, 2000, vol. 60, no. 3, p. 197-203. [CrossRef]        [ Links ]

FEIRER, R.P.; MIGNON, G. and LITVAY, J.D. Arginine decarboxylase and polyamines required for embryogenesis in wild carrot. Science, 1984, vol. 223, no. 4643, p. 1433-1435. [CrossRef]        [ Links ]

FERNANDEZ, S.; MICHAUX-FERRIÈRE, N. and COUMANS, M. The embryogenic response of immature embryo cultures of durum wheat (Triticum durum): histology and improvement by AgNO3. Plant Growth Regulation, 1999, vol. 28, no. 3, p. 147-155. [CrossRef]        [ Links ]

FLINK, L. and PETTIJOHN, D.E. Polyamines stabilize DNA folds. Nature, 1975, vol. 253, no. 5486, p. 62-63. [CrossRef]        [ Links ]

FUENTES, S.R.L.; CALHEIROS, M.B.P.; MANETTI-FILHO, J. and VIEIRA, L.G.E. The effects of silver nitrate and different carbohydrate sources on somatic embryogenesis in Coffea canephora. Plant Cell Tissue Organ Culture, 2000, vol. 60, no. 1, p. 5-13. [CrossRef]        [ Links ]

GALSTON, A.W. Polyamines as modulators of plant development. Bioscience, 1983, vol. 33, p. 382-388.         [ Links ]

GANESH, S.D. and SREENATH, H.L. Silver nitrate enhanced shoot development in cultured apical shoot buds of Coffea arabica Cv Cauvery (S4347). Journal of Plantation Crops, 1996, vol. 24, p. 577-580.         [ Links ]

GAVINLERTVATANA, P.; READ, P.E. and RIORDAN, T.P. Control of ethylene synthesis and action by silver nitrate and rhizobitoxine in petunia leaf sections cultured in vitro. Journal of the American Society for Horticultural Science, 1980, vol. 105, p. 304-307.         [ Links ]

GIRIDHAR, P.; OBUL REDDY, B. and RAVISHANKAR, G.A. Silver nitrate influences in vitro shoot multiplication and root formation in Vanilla planifolia Andr. Current Science, November 2001, vol. 81, no. 9, p. 1166-1170.         [ Links ]

GIRIDHAR, P.; INDU, E.P.; VIJAYA RAMU, D. and RAVISHANKAR, G.A. Effect of silver nitrate on in vitro shoot growth of Coffee. Tropical Science, 2003, vol. 43, no. 3, p. 144-146.[CrossRef]        [ Links ]

GIRIDHAR, P.; INDU, E.P.; VINOD, K.; CHANDRASHEKAR, A. and RAVISHANKAR, G.A. Direct somatic embryogenesis from Coffea arabica L and Coffea canephora P ex Fr. under the influence of ethylene action inhibitor-silver nitrate. Acta Physiologiae Plantarum, September 2004, vol. 26, no. 3, p. 299-305. [CrossRef]        [ Links ]

GONG, Y.; GAO, F. and TANG, K. In vitro high frequency direct root and shoot regeneration in sweet potato using the ethylene inhibitor silver nitrate. South African Journal of Botany, 2005, vol. 71, p. 110-113.         [ Links ]

HALL, A.E.; CHEN, Q.G.; FINDELL, J.L.; SCHALLER, G.E. and BLEEKER, A.B. The relationship between ethylene binding and dominant insensitivity conferred by mutant forms of the ETR1 ethylene receptor. Plant Physiology, 1999, vol. 121, no. 1, p. 291-299.         [ Links ]

HAMILTON, A.J.; BOUZAYEN, M. and GRIERSON, D. Identification of a tomato gene for the ethylene-forming enzyme by expression in yeast. Proceedings of the National Academy of Sciences of the United States of America, 1991, vol. 88, no. 16, p. 7434-7437.        [ Links ]

HOBSON, G.E.; NICHOLS, R.; DAVIES, J.N. and ATKEY, P.T. The inhibition of tomato fruit ripening by silver. Journal of Plant Physiology, 1984, vol. 116, no. 1, p. 21-29.         [ Links ]

HUA, J.; CHANG, C.; SUN, Q. and MEYEROWITZ, E.M. Ethylene insensitivity conferred by Arabidopsis ERS gene. Science 1995, vol. 269, p. 1712-1714.         [ Links ]

HUA, J. and MEYEROWITZ, E.M. Ethylene responses are negatively regulated by a receptor gene family in Arabidopsis thaliana. Cell, 1998, vol. 94, no. 2, p. 261-271. [CrossRef]        [ Links ]

HYDE, Camille L. and PHILLIPS, Gregory C. Silver nitrate promotes shoot development and plant regeneration of chili pepper (Capsicum annuum L.) via organogenesis. In Vitro Cellular and Developmental Biology-Plant, April 1996, vol. 32, no. 2, p. 72-80. [CrossRef]        [ Links ]

JHA, A.K.; DAHLEEN, L.S. and SUTTLE, J.C. Ethylene influences green plant regeneration from barley callus. Plant Cell Reports, 2007, vol. 26, no. 3, p. 285-290. [CrossRef]        [ Links ]

JOHNSON, P.R. and ECKER, J.R. The ethylene gas signal transduction pathway: A molecular perspective. Annual Review of Genetics, 1998, vol. 32, p. 227-254. [CrossRef]        [ Links ]

KENDE, H. Ethylene biosynthesis. Annual Review of Plant Physiology and Plant Molecular Biology, 1993, vol. 44, p. 283-307. [CrossRef]        [ Links ]

KHALAFALLA, M.M. and HATTORI, K. Ethylene inhibitors enhance in vitro root formation on faba bean shoots regenerated on medium containing thidiazuron. Plant Growth Regulation, 2000, vol. 32, no. 1, p. 59-63. [CrossRef]        [ Links ]

KIEBER, J.J.; ROTHENBERG, M.; ROMAN, G.; FELDMANN, K.A. and ECKER, J.R. CTR1, a negative regulator of the ethylene response pathway in Arabidopsis, encodes a member of the raf family of protein kinases. Cell, 1993, vol. 72, no. 3, p. 427-441. [CrossRef]        [ Links ]

KONG, L and YEUNG, E.C. Effects of ethylene and ethylene inhibitors on white spruce somatic embryo maturation. Plant Science, 1994, vol. 104, no. 1, p. 71-80. [CrossRef]        [ Links ]

KOTHARI-CHAJER, A.; SHARMA, M.; KACHHWAHA, S. and KOTHARI S.L. Micronutrient optimization results into highly improved in vitro plant regeneration in kodo (Paspalum scrobiculatum L.) and finger (Eleusine coracana (L.) Gaertn.) millets. Plant Cell Tissue and Organ Culture, 2008, vol. 94, no. 6, p. 105-112. [CrossRef]          [ Links ]

KUMAR, P.P.; LAKSHMANAN, P. and THORPE, T.A. Regulation of morphogenesis in plant tissue culture by ethylene. In Vitro Cellular and Developmental Biology-Plant, 1998a, vol. 34, no. 2, p. 94-103. [CrossRef]        [ Links ]

KUMAR, S.; SARKAR, A.K. and KUNHIKANNAN. Regeneration of plants from leaflet explants of tissue culture raised Safed siris (Albizia procera). Plant Cell Tissue Organ Culture, 1998b, vol. 54, no. 3, p. 137-143. [CrossRef]        [ Links ]

KUMAR, V.; GURURAJ, H.B.; PRASAD, B.C.N.; SHARMA, A.; GIRIDHAR, P. RAJASEKARAN, T. and RAVISHANKAR, G.A. In vitro morphogenetic responses and regeneration from pepper (Capsicum annuum) seedling explants. In: Proceedings of 5th International Food Convention. CFTRI, Mysore, India, 2003a, p. 41.         [ Links ]

KUMAR, V.; SATHYANARAYANA, K.V.; INDU, E.P.; SARALA ITTY, S.; GIRIDHAR, P.; CHANDRASHEKAR, A. and RAVISHANKAR, G.A. Stable transformation and direct regeneration in Coffea canephora by Agrobacterium rhizogenes mediated transformation. In: Proceedings of 10th Congress of Federation of Asian and Oceanian Biochemists and Molecular Biologists. 2003b, p. 10.        [ Links ]

KUMAR, S.V. and RAJAM, M.V. Polyamine ethylene nexus: A potential target for post harvest biotechnology. Indian Journal of Biotechnology, 2004, vol. 3, no. 2, p. 299-304.         [ Links ]

KUMAR, V.; RAMAKRISHNA, A. and RAVISHANKAR, G.A. Influence of different ethylene inhibitors on somatic embryogenesis and secondary embryogenesis from Coffea canephora P ex Fr. Plant Cell Tissue and Organ Culture, 2007, vol. 43, no. 6, p. 602-607. [CrossRef]        [ Links ]

LAU, Oi-Lim and YANG, Shang F. Inhibition of ethylene production by cobaltous ion. Plant Physiology, July 1976, vol. 58, no. 1, p. 114-117.         [ Links ]

LENTINI, Z.; MUSSEL, H.; MUTSCHLER, M.A.; and EARLE, E.D. Ethylene generation and reversal of ethylene effects during development of in vitro Brassica compestris life. Plant Science, 1988, vol. 54, no. 1, p. 75-81. [CrossRef]        [ Links ]

LENTINI, Z.; REYES, P.; MARINEZ, C.P. and ROCA, W.M. Androgenesis of highly recalcitrant rice genotypes with maltose and silver nitrate. Plant Science, 1995, vol. 110, no. 1, p. 127-138. [CrossRef]        [ Links ]

LIEBERMAN, N. Biosynthesis and action of ethylene. Annual Review of Plant Physiology, 1979, vol. 30, p. 533-591. [CrossRef]        [ Links ]

LIM, H.T and SONG, Y.N. Effect of explant type and silver nitrate on callus induction and organogenesis organogenesis of watermelon. Journal of Agricultural Sciences, 1993, vol. 5, p. 113-121.         [ Links ]

MAJEWSKA-SAWKA, A.; NIKLAS, A. and JAZDZEWSKA. The effect of polyamines on the development of sugar beet protoplasts. Biologia Plantarum, 1997, vol. 39, no. 4, p. 561-567. [CrossRef]        [ Links ]

MAJEWSKA-SAWKA, A.; BUTOWT, R. and NIKLAS, A. Do polyamines release membrane-bound calcium in sugar beet protoplasts? Journal of Plant Physiology, 1998, vol. 153, no. 1-2, p. 247-250.         [ Links ]

MARTIN, K.P. Plant regeneration protocol of medicinally important Andrographis paniculata (Burm. F.) Wallich ex Nees via somatic embryogenesis. In Vitro Cellular and Development Biology-Plant, 2004, vol. 40, no. 2, p. 204-209. [CrossRef]        [ Links ]

MARTIN, K.P. and MADASSERY, J. Direct and indirect somatic embryogenesis on cotyledon explants of Quassia amara L., an antileukaemic drug plant. In Vitro Cellular and Development Biology-Plant, 2005, vol. 41, no. 1, p. 54-57. [CrossRef]        [ Links ]

MATTOO, A.K. and SUTTLE, J.C. The plant hormone ethylene. CRC press. Boca Raton, Florida, 1991. 337 p. ISBN 0-8493-4566-9.        [ Links ]

MISRA, P. and DATTA, S.K. Direct differentiation of shoot buds in leaf segments of white merigold (Tagetes erecta L). In Vitro Cellular Developmental Biology-Plant, 2001, vol. 37, no. 4, p. 466-470. [CrossRef]        [ Links ]

MIYAZAKI, J.H. and YANG, S.F. The methionine salvage pathway in relation to ethylene and polyamine biosynthesis. Physiologia Plantarum, 1987, vol. 69, no. 2, p. 366-370. [CrossRef]        [ Links ]

MOHAN RAM, H.Y. and JAISWAL, V.S. Induction of female flowers on male plants of Cannabis sativa L. by 2-chloroetahanephosphonic acid. Experientia, 1970, vol. 26, p. 214-216.        [ Links ]

MOHIUDDIN, A.K.M.; CHOWDHURY, M.K.U.; ABDULLA, Z.C. and NAPIS, S. Influence of silver nitrate (ethylene inhibitor) on Cucumber shoot regeneration. Plant Cell, Tissue and Organ Culture, 1997, vol. 51, no. 1, p. 75-78. [CrossRef]        [ Links ]

NAIK, S.K. and CHAND, P.K. Silver nitrate and aminoethoxy venyl glycene promotes in vitro adventitious shoot regeneration of Pomegranate (Punica granatum L). Journal of Plant Physiology, 2003, vol. 160, no. 4, p. 423-430. [CrossRef]        [ Links ]

NARASIMHULU, S.B. and CHOPRA, V.L. Species specific shoot regeneration response of cotyledonary explants of brassicas. Plant Cell Reports, 1988, vol. 7, no. 2, p. 104-106. [CrossRef]        [ Links ]

NISSEN, P. Stimulation of somatic embryogenesis in carrot by ethylene: Effects of modulators of ethylene biosynthesis and action. Physiologia Plantarum, 1994, vol. 92, no. 3, p. 397-403. [CrossRef]        [ Links ]

OGURA, H. and SHIMADA, T. Preliminary report on shoot differentiation from Wheat callus. Wheat information Service, 1978, no. 45, p. 26-28.         [ Links ]

O'KENNEDY, M.M.; SMITH, G. and BOTHA, F.C. Improved regeneration efficiency of a pearl millet (Pennisetum glaucum [L.] R. Br.) breeding line. South African Journal of Botany, 2004, vol. 70, no. 4, p. 502-508.         [ Links ]

OLDACH, K.; MORGENSTERN, A.; ROTHER, S.; GIRGI, M.; O`KENNEDY, M. and LORZ, H. Efficient in vitro plant regeneration from immature zygotic embryos of Pearl millet [Pennisettum glaucum (L) R Br] and Sorgum bicolor (L) Moench. Plant Cell Reports, 2001, vol. 20, no. 5, p. 416-421. [CrossRef]        [ Links ]

OZUDOGRU, E.; OZDEN TOKATLI, Y. and AKCIN, A. Effect of silver nitrate on multiple shoot formation of Virginia-type peanut through shoot tip culture. In Vitro Cellular and Development Biology-Plant, 2005, vol. 41, no. 2, p. 151-156. [CrossRef]        [ Links ]

PALMER, C.E. Enhanced shoot regeneration from Brassica campestris by silver nitrate. Plant Cell Reports, 1992, vol. 11, no. 11, p. 541-545. [CrossRef]        [ Links ]

PATIL, P.; CHANDRA, R.; SANGEETA, K. and RAGHUVEER, P. Influence of polyamines and ethylene inhibitors on somatic embryo induction in chickpea (Cicer arietinum L.). Indian Journal of Plant Physiology, 1999, vol. 3, p. 26-31.         [ Links ]

PESTANA, M.C.; LACORTE, C.; DE FREITAS, V.G.; OLIVEIRA, D.E. and MANSUR, E. In vitro regeneration of peanut (Arachis hypogaea L) through organogenesis: Effect of culture temperature and silver nitrate. In vitro Cellular and Developmental Biology-Plant, 1999, vol. 35, no. 3, p. 214-216. [CrossRef]        [ Links ]

PLUS, J.L.; GEORGE, L.; EAPEN, S. and RAO, P.S. Enhanced plant regeneration in pearl millet (Pennisettum americanum). Plant Cell, Tissue and Organ Culture, 1993, vol. 32, no. 1, p. 91-96. [CrossRef]        [ Links ]

PREM, D.; GUPTA, K. and AGNIHOTRI, A. Effect of various exogenous and endogenous factors on microspore embryogenesis in indian mustard (Brassica juncea (L.) Czern and Coss). In Vitro Cellular and Developmental Biology-Plant, 2005, vol. 41, no. 3, p. 266-273. [CrossRef]        [ Links ]

PUA, E.C. and CHI, G.L. De novo shoot morphogenesis and plant growth of mustard (Brassica juncea) in vitro in relation to ethylene. Physiologia Plantarum, 1993, vol. 88, no. 3, p. 467-474. [CrossRef]        [ Links ]

PUA, E-C.; SIM, G-E.; CHI, G-L. and KONG, L-F. Synergistic effects of ethylene inhibitors and putrescine on shoot regeneration from hypocotyl explants of Chinese radish (Raphanus sativus L. var. longipinnatus Bailey) in vitro. Plant Cell Reports, May 1996, vol. 15, no. 9, p. 685-690. [CrossRef]        [ Links ]

PUA, E.C.; DENG, X. and KOH, A.T.C. Genotypic variability of de novo shoot morphogenesis Brassica oleracea in vitro in response to ethylene inhibitors and Putrescine. Journal of Plant Physiology, 1999, vol. 155, no. 4-5, p. 598-605.         [ Links ]

PURNHAUSER, L.; MEDGYSEY, P.; CZAKO, M.; DIX, J.P. and MARTON, L. Stimulation of shoot regeneration in Triticum aestivum and Nicotiana plumbaginifolia Viv tissue cultures using the ethylene inhibitor silver nitrate. Plant Cell Reports, 1987, vol. 6, no. 1, p. 1-4. [CrossRef]        [ Links ]

RAVANEL, S.; GAKIERE, B.; JOB, D. and DOUCE, R. The specific features of methionine biosynthesis and metabolism in plants. Proceedings of the National Academy of Sciences of the United States of America, 1998, vol. 95, p. 7805-7812.         [ Links ]

REDDY, B.O.; GIRIDHAR, P. and RAVISHANKAR, G.A. In vitro rooting of Decalepis hamiltonii Wight and Arn., an endangered shrub by auxins and root-promoting agents. Current Science, 2001, vol. 81, no. 11, p. 1479-1481.         [ Links ]

REIS, L.B.; PAIVA NETO, V.B.; TOLEDO PICOLI, E.A.; COSTA, M.G.C.; REGO, M.M.; CARVALHO, C.R.; FINGER, F.L. and OTONI, W.C. Axially bud development of passion fruit as affected by ethylene precursor and inhibitors. In Vitro Cellular Developmental Biology-Plant, 2003, vol. 39, no. 6, p. 618-622. [CrossRef]        [ Links ]

RODRIGUEZ, F.I.; ESCH, J.J.; HALL, A.E.; BINDER, B.M.; SCHALLER, G.E. and BLEECKER, A.B. A copper cofactor for the ethylene receptor ETR1 from Arabidopsis. Science, 1999, vol. 283, no. 5404, p. 996-998. [CrossRef]        [ Links ]

ROUSTAN, J.P.; LATCHE, A. and FALLOT, J. Stimulation of Daucus carota somatic embryogenesis by inhibitors of ethylene biosynthesis: cobalt and nickel. Plant Cell Reports, March 1989, vol. 8, no. 3, p. 182-185. [CrossRef]        [ Links ]

ROUSTAN, J.P.; LATCHE, A. and FALLOT, J. Control of carrot somatic embryogenesis by AgNO3 an inhibitor of ethylene action effect on arginine decarboxilase activity. Plant Science, 1990, vol. 67, no. 1, p. 89-95. [CrossRef]        [ Links ]

RUDICH, J.; HALEVY, A.H. and KEDAR, N. Ethylene evolution from cucumber plants as related to sex expression. Plant Physiology, 1972, vol. 49, no. 6, p. 998-999.         [ Links ]

SAITO, T. and TAKAHASHI, H. Role of leaves in ethylene induced femaleness in cucumber plants. Journal of the Japanese Society for Horticultural Science, 1986, vol. 55, no. 4, p. 445-454.         [ Links ]

SAKAI, H.; HUA, J.; CHEN, Q.G.; CHANG, C.; MEDRANO, L.J.; BLEECKER, A.B. and MEYEROWITZ, E.M. ETR2 is an ETR1-like gene involved in ethylene signaling in Arabidopsis. Proceedings of the National Academy of Sciences of the United States of America, 1998, vol. 95, p. 5812-5817.         [ Links ]

SANKHLA, D.; SANKHLA, N. and DAVIS, D.T. Promotion of in vitro shoot formation from excised roots of silktree (Albizzia julibrissim) by an oxime ether derivative and other ethylene inhibitors. Plant Cell Reports, January 1995, vol. 15, no. 1-2, p. 143-146. [CrossRef]        [ Links ]

SATO, T. and THEOLOGIS, A. Cloning the mRNA encoding 1-aminocyclopropane-1-carboxylate synthase, the key enzyme for ethylene biosynthesis in plants. Proceedings of the National Academy of Sciences of the United States of America, 1989, vol. 86, no. 17, p. 6621-6625.         [ Links ]

SCHALLER, G.E. and BLEECKER, A.B. Ethylene-binding sites generated in yeast expressing the Arabidopsis ETR1 gene. Science, 1995, vol. 270, no. 5243, p. 1809-1811. [CrossRef]        [ Links ]

SEONG, E.S.; SONG, K.; JEGAL, S.; YU, C. and CHUNG, I. Silver nitrate and aminoethoxy vinylglycine affect Agrobacterium-mediated apple. Plant Growth Regulation, 2005, vol. 45, no. 1, p. 75-82. [CrossRef]        [ Links ]

SEREK, M.; SISLER, E.C. and REID, M.S. 1-methylcyclopropene a novel gaseous inhibitor of ethylene action improves the life of fruits cut flowers and potted plants. Acta Horticulturae, 1995a, vol. 394, p. 337-347.         [ Links ]

SEREK, M.; SISLER, E.C. and REID, M.S. Effect of 1-MCP on the vase life and ethylene response of cut flowers. Plant Growth Regulation, 1995b, vol. 16, no. 1, p. 93-97. [CrossRef]        [ Links ]

SEREK, M.; SISLER, E.C.; TIROSH, T. and MAYAK, S. 1-methylcyclopropene prevents bud flower and leaf abscission of Geraldton Wax flower. Hortscience, 1995c, vol. 30, no. 6, p. 1310.         [ Links ]

SISLER, E.C.; SEREK, M. and DUPILLE, E. Comparison of cyclopropene 1 methylcyclopropene and 1-3 dimethyl cyclopropene as ethylene antagonists in plants. Plant Growth Regulation, 1996, vol. 18, no. 3, p. 169-174. [CrossRef]        [ Links ]

SMITH, T.A. Plant polyamines metabolism and function Polyamine synthesis. In: FLORES, H.E.; ARTECA, R.N. and SHANNON, J.C. eds. Polyamines and ethylene: biochemistry, physiology and interaction. American Society of Plant Physiologists, Rockville, Md, 1985. p. 1-23.        [ Links ]

SMITH, T.A. Amines. In: HARBORNE, J.B. and DEY, P.M. eds. Methods in Plant Biochemistry (Alkaloids and Sulphur compounds). Academic Press, 1993, p. 17-49.        [ Links ]

SONGSTAD, D.D.; DUNCAN, D.R. and WIDHOLM, J.M. Effect of 1-aminocycopropane-1-carboxilic acid silver nitrate and norbornadiene on plant regeneration from maize callus cultures. Plant Cell Reports, 1988, vol. 7, no. 4, p. 262-265. [CrossRef]        [ Links ]

SONGSTAD, D.D.; ARMSTRONG, C.L. and PETERSEN, W.L. Silver nitrate increase type II callus production from immature embryos of maize inbred B73 and its derivatives. Plant Cell Reports, 1991, vol. 9, no. 12, p. 699-702. [CrossRef]        [ Links ]

SPANU, P.; REINHARDT, D. and BOLLER, T. Analysis and cloning of the ethylene-forming enzyme from tomato by functional expression of its mRNA in Xenopus laevis oocytes. EMBO Journal, 1991, vol. 10, no. 8, p. 2007-2013.         [ Links ]

STANKOVIC, L. and PRODANOVIC, S. Silver nitrate affects on sex expression in cucumber (Cucumis sativus). II Balkan symposium on Vegetables and Potatoes. Acta Hortoculturae, 2002, vol. 579, p. 203-206.         [ Links ]

STEINMACHER, D.A.; CANGAHUALA-INOCENTE, G.C.; CLEMENT, C.R. and GUERRA, M.P. Somatic embryogenesis from peach palm zygotic embryos. Plant Cell Tissue and Organ Culture, 2007, vol. 43, no. 2, p. 124-132. [CrossRef]        [ Links ]

SUNANDAKUMARI, C.; MARTIN, K.P.; CHITHRA, M. and MADHUSOODANAN, P.V. Silver nitrate induced rooting and flowering in vitro on rare rhoeophytic woody medicinal plant, Rotula aquatica Lour. Indian Journal of Biotechnology, July 2004, vol. 3, no. 3, p. 418-421.         [ Links ]

TABOR, C.W. and TABOR, H. Polyamines. Annual Review of Biochemistry, 1984, vol. 53, p. 749-790. [CrossRef]        [ Links ]

TAKAHASHI, H. and JAFFE, M.J. Further studies of auxin and ACC induced feminization in cucumber plant using ethylene inhibitors. Phyton, July 1984, vol. 44, no. 1, p. 81-86.         [ Links ]

THOMAS, T.D. In vitro modification of sex expression in Mulberry (Morus alba) by ethrel and silver nitrate. Plant Cell Tissue Organ Culture, 2004, vol. 77, no. 3, p. 277-281. [CrossRef]        [ Links ]

TREBITSH, T.; RIOV, J. and RUDICH, J. Auxin, Biosynthesis of ethylene and sex expression in cucumber (Cucumis sativus). Plant Growth Regulation, 1987, vol. 5, no. 2, p. 105-113. [CrossRef]        [ Links ]

TSAO, C.W.V. and REED, B.M. Gelling agents, silver nitrate, and sequestrene iron influence adventitious shoot and callus formation from Rubus leaves. In Vitro Cellular and Developmental Biology-Plant, 2002, vol. 38, no. 1, p. 29-32. [CrossRef]         [ Links ]

TUCKER, G.A. and BRADY, C.J. Silver ions interrupt tomato fruit ripening. Journal of Plant Physiology, 1987, vol. 127, no. 1-2, p. 165-169.         [ Links ]

VAIN HORT, Y.P. and FLAMENT, P. Role of ethylene in embryogenic callus initiation and regeneration in Zea mays L. Journal of Plant Physiology, 1989, vol. 135, no. 5, p. 537-540.         [ Links ]

VAIN HORT, Y.P.; YEAN, H. and FLAMENT, P. Enhancement of production and regeneration of embryogenic type II callus in Zea mays L by AgNO3. Plant Cell Tissue Organ Culture, 1989, vol. 18, no. 2, p. 143-142. [CrossRef]        [ Links ]

VALDEZ-ORTIZ, A.; MEDINA-GODOY, S.; VALVERDE, M.E. and PAREDES-LOPEZ, O. A transgenic tropical maize line generated by the direct transformation of the embryo-scutellum by A. tumefaciens. Plant Cell Tissue and Organ Culture, 2007, vol. 91, no. 3, p. 201-214. [CrossRef]        [ Links ]

VAN DEN BROECK, D.; VAN DEN STRAETEN, D.; VAN MONTAGUE, M. and CAPLAN, A. A group of chromosomal proteins is specifically released by spermine and loses DNA-binding activity upon phosphorylation. Plant Physiology, 1994, vol. 106, no. 2, p. 559-566.         [ Links ]

VASIL, I.K. Developing cell and tissue culture system for the improvement of cereal and grass crops. Journal Plant Physiology, 1987, vol. 128, no. 3, p.193-218.         [ Links ]

VEEN, H. and OVER BEEK, J.H.M. The action of silver thiosulphate in carnation petals. In: CLIGSTERS, H.D.; PROFT, M.; MARCELLE, R. and VAN POUCKE, M. eds. Biochemical and physiological aspects of ethylene production in lower and higher plants. Kluwer Academic Publication. Dordedrecht, The Netherlands, 1989, p. 109-117.        [ Links ]

WALDEN, R.; CORDEIRO, A. and TIBURIO, A. Polyamines: Small molecules triggering pathways in plant growth and development. Plant Physiology, 1997, vol. 113, no. 4, p. 1009-1013.         [ Links ]

WANG, K.L.C.; HAI, L. and ECKER, J.R. Ethylene biosynthesis and signaling networks. Plant Cell, 2002, S131-S151 Supplement.         [ Links ]

WANG, G.L. and XU, Y.N. Hypocotyl-based Agrobacterium-mediated transformation of soybean (Glycine max) and application for RNA interference. Plant Cell Reports, 2008, vol. 27, no. 7, p. 1177-1184. [CrossRef]        [ Links ]

WOESTE, Keith E. and KIEBER, Joseph J. A strong loss-of-function mutation in RAN1 results in constitutive activation of the ethylene response pathway as well as a rosette-lethal phenotype. Plant Cell, 2000, vol. 12, p. 443-455.        [ Links ]

WU, L.M.; WEI, Y.M. and ZHENG, Y.L. Effects of silver nitrate on the tissue culture of immature wheat embryos. Russian Journal of Plant Physiology, 2006, vol. 53, no. 4, p. 530-534. [CrossRef]        [ Links ]

WURGLER-MURPHY, S.M. and SAITO, H. Two-component signal transducers and MAPK cascades. Trends in Biochemical Sciences, 1997, vol. 22, no. 5, p. 172-176. [CrossRef]        [ Links ]

YANG, S.F. and HOFFMAN, N.E. Ethylene biosynthesis and its regulation in higher plants. Annual Review of Plant Physiology, 1984, vol. 35, p. 155-189. [CrossRef]        [ Links ]

YANG, S.F. Biosynthesis and action of ethylene. HortScience, 1985, vol. 20, no. 1, p. 41-45.        [ Links ]

YU, Y.; WANG, J.; ZHU, M.L. and WEI, Z.M. Optimization of mature embryo-based high frequency callus induction and plant regeneration from elite wheat cultivars grown in China. Plant Breeding, 2008, vol. 127, no. 3, p. 249-255. [CrossRef]        [ Links ]

ZANG, P.; PHANSIRI, S. and KAERLAS, J.P. Improvement of cassava shoot organogenesis by the use of AgNO3 in vitro. Plant Cell Tissue Organ Culture, 2001, vol. 67, no. 1, p. 47-54. [CrossRef]        [ Links ]

ZHAO, X.C.; QU, X.; MATHEWS, D.E. and SCHALLER, G.E. Effect of ethylene-pathway mutations upon expression of the ethylene receptor ETR1 from Arabidopsis. Plant Physiology, 2002, vol. 130, no. 4, p. 1983-1991.         [ Links ]

Note: Electronic Journal of Biotechnology is not responsible if on-line references cited on manuscripts are not available any more after the date of publication.

Supported by UNESCO / MIRCEN network

Creative Commons License Todo el contenido de esta revista, excepto dónde está identificado, está bajo una Licencia Creative Commons