Heavy-metal-induced ethylene production in Arabidopsis thaliana

Different plant parts varied in copper sulfate (CuSO(4)) and cadmium sulfate (CdSO(4))-induced ethylene production, inflorescences showed the greatest induction, while all other plant parts tested produced significantly less. Leaf age had a dramatic effect on CuSO(4) and CdSO(4)-induced ethylene production with the youngest leaves showing the greatest stimulation and as the age of the leaf increased there was a reduction in their ability to produce ethylene. However, there was no significant difference in CuSO(4), CdSO(4) and wound-induced ethylene production when whole rosettes were taken from plants that were 7, 14 or 21-day-old. The highest amount of CuSO(4) and CdSO(4)-induced ethylene production was produced in the root tip with regions below this producing less. CuSO(4) and CdSO(4)-induced ethylene production was also greatest from the tip of the inflorescence to 2cm below the tip and from this point down there was a reduction in ethylene production. When inflorescence stalks or leaves were treated with CuSO(4) or CdSO(4) over a range of concentrations from 0 to 800microM, there was an increase in ethylene production starting at 50microM with increasingly greater responses up to 400microM. There was no further increase at the 800microM CuSO(4) concentration; however, there was a slight decline with 800microM CdSO(4). Inflorescence stalks or leaves treated with either 400microM CuSO(4) or CdSO(4) exhibited a dramatic increase in ethylene production 2h following treatment initiation and remained high over a 24-h period with a decline in ethylene production after this time in inflorescence stalks but not the leaves. It was found that light caused a dramatic decrease in CuSO(4), CdSO(4) and wound-induced ethylene production in both inflorescence stalks and leaves. When inflorescence stalks or leaves were treated at 43 degrees C, there was a dramatic effect on CuSO(4), CdSO(4) and wound-induced ethylene production in each.     

Brassinosteroid-induced exaggerated growth in hydroponically grown Arabidopsis plants

The effects of root application of brassinolide (BL) on the growth and development of Arabidopsis plants ( Arabidopsis thaliana ecotype Columbia [L.] Heynh) were evaluated. Initially, all leaves were evaluated on plants 18, 22, 26 and 29 days old. The younger leaves were found to exhibit maximal petiole elongation and upward leaf bending in response to BL treatment. Therefore, based on these results leaves 6, 7 and 8 on 22–24-day-old plants were selected for all subsequent studies. Elongation along the length of the petiole in response to BL treatment was uniform with the exception of an approximately 4 mm region next to the leaf where upward curvature was observed. Both BL and 24-epibrassinolide (24-epiBL) were evaluated, with BL being more effective at lower concentrations than 24-epiBL. The exaggerated growth induced by 0.1 μ M BL was not observed in plants treated with 1 000-fold higher concentrations of GA₃, IAA, NAA or 2,4-D (100 μ M ). In addition, no exaggerated growth effects were observed when plants were treated with 200 ppm ethylene or 1 m M ACC. All treatments with BL, NAA, 2,4-D, IAA or ACC promoted ethylene and ACC production in wild type Arabidopsis plants, but only BL triggered exaggerated plant growth. BL also promoted exaggerated growth and elevated levels of ACC and ethylene in the ethylene insensitive mutant etr1-3 , showing that the effect of BR on growth is independent of ethylene. This work provides evidence that BR-induced exaggerated growth of Arabidopsis plants is independent of gibberellins, auxins and ethylene.     

Effects of natural and synthetic auxins on the gravitropic growth habit of roots in two auxin-resistant mutants of Arabidopsis, axr1 and axr4: evidence for defects in the auxin influx mechanism of axr4.

The partially agravitropic growth habit of roots of an auxin-resistant mutant of Arabidopsis thaliana, axr4, was restored by the addition of 30-300 nM 1-naphthaleneacetic acid (NAA) to the growth medium. Neither indole 3-acetic acid (IAA) nor 2,4-dichlorophenoxyacetic acid (2,4-D) showed such an effect. Growth of axr4 roots was resistant to IAA and 2,4-D, but not at all to NAA. The differential effects of the three auxins suggest that the defects of axr4 result from a lower auxin influx into its cells. The partially agravitropic growth habit of axr1 roots, which was less severe than that of axr4 roots, was only slightly affected by the three auxins in the growth medium at concentrations up to 300 nM; growth of axr1 roots was resistant to all three of the auxins. These results suggest that the lesion of axrl mutants is different from that of axr4.     

The effect of brassinosteroid on auxin-induced ethylene production by etiolated mung bean segments

Brassinosteroid, an analogue of brassinolide, (BR) (2α, 3α, 22β, 23β-tetrahydroxy-24β-methyl-B-homo-7-oxa-5α-cholestan-6-one), was tested in conjunction with indole-3-acetic acid (IAA), naphthaleneacetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D), indole-3-butyric acid (IBA), indole-3-propionic acid (IPA), indole-3-pyruvic acid (IPyA), indole-3-aldehyde (IAld), indole-3-carbinol (ICB) or tryptophan (TRP) for its effects on ethylene production by etiolated mung bean (Vigna radiata (L.) Rwilcz cv. Berken) hypocotyl segements. The enhancement of ethylene production due to BR was greatest in conjunction with 1 μM IBA, 2,4-D, IAA, or NAA (these increases were 2580, 2070, 890, and 300%, respectively). When increasing concentrations of IBA, 2,4-D, IAA, or NAA were used, there was a decrease in the percentage stimulation by BR. Both IPyA and IPA had different optimal concentrations than the other auxins tested. Their BR-enhanced maximum percentage stimulations (1430 and 1580%) were greatest with 5 μM IPya and 10 μM IPA, respectively. There was a marked reduction in the percentage stimulation by BR with either 100 μM IPyA or IPA. The inactive indoles (IAld, ICB, or TRP) did not synergize with BR at any of the concentrations tested. Four hours following treatment those segments in contact with 1 μM BR with or without the addition of 10 μM IAA began to show a stimulation in ethylene production above the control and this stimulation became greater over the following 20 h. It was necessary for BR to be in continual contact with the tissue to have a stimulatory effect on auxin-induced ethylene production. When segments excised from greater distances below the hypocotyl hook, were treated with either IAA alone or in combination with BR, there was a decrease in ethylene production with increasing distance. There was no effect of hypocotyl length on BR stimulation of auxin-induced ethylene production; however, there was a definite decrease in ethylene production when IAA was applied alone.     

Effects of Natural and Synthetic Auxins on the Gravitropic Growth Habit of Roots in Two Auxin-Resistant Mutants of Arabidopsis, axr1 and axr4: Evidence for Defects in the Auxin Influx Mechanism of axr4

Arabidopsis thaliana, axr4 , was restored by the addition of 30–300 nM 1-naphthaleneacetic acid (NAA) to the growth medium. Neither indole-3-acetic acid (IAA) nor 2,4-dichlorophenoxyacetic acid (2,4-D) showed such an effect. Growth of axr4 roots was resistant to IAA and 2,4-D, but not at all to NAA. The differential effects of the three auxins suggest that the defects of axr4 result from a lower auxin influx into its cells. The partially agravitropic growth habit of axr1 roots, which was less severe than that of axr4 roots, was only slightly affected by the three auxins in the growth medium at concentrations up to 300 nM; growth of axr1 roots was resistant to all three of the auxins. These results suggest that the lesion of axr1 mutants is different from that of axr4. Received 9 June 1999/ Accepted in revised form 16 August 1999     

The massugu1 mutation of Arabidopsis identified with failure of auxin-induced growth curvature of hypocotyl confers auxin insensitivity to hypocotyl and leaf.

Unilateral application of indole-3-acetic acid (IAA) in a lanolin base to hypocotyls of partially etiolated seedlings of wild-type Arabidopsis thaliana induced growth curvature in a dose-dependent manner. The effects of IAA in concentrations from 1 to 1000 microM were studied, with maximum IAA-induced curvature at 100 microM. Three IAA-insensitive mutants were isolated and are all in the same locus, massugu1 (msg1). They did not undergo hypocotyl growth curvature at any of the IAA concentrations tested. msg1 is recessive and is located on chromosome 5. msg 1 hypocotyl growth is resistant to 2,4-dichlorophenoxyacetic acid (2,4-D), but the roots are as sensitive to 2,4-D as the wild type. Growth of the hypocotyl was inhibited to essentially the same extent as the wild type by 6-benzylaminopurine, abscisic acid, and 1-aminocyclopropane-1-carboxylate, an ethylene precursor. The msg1 leaves were also resistant to 2,4-D-induced chlorosis. The gravitropic response of the msg1 hypocotyl takes much more time to initiate and achieve the wild-type degree of curvature, whereas the msg1 roots responded normally to gravity. The mature plants and the etiolated seedlings of msg1 were generally wild type in appearance, except that their rosette leaves were either epinastic or hyponastic. msg1 is the first auxin-insensitive mutant in which it effects are mostly restricted to the hypocotyl and leaf, and msg1 also appears to be auxin specific.     

Ethylene production by auxin-deprived, suspension-cultured pear fruit cells in response to auxins, stress, or precursor

Auxin-deprived, mannitol-supplemented, suspension-cultured pear (Pyrus communis L. Passe Crassane) fruit cells produce large quantities (20-40 nanoliters ethylene per 10⁶ cells per hour) of ethylene in response to auxins, CuCl₂ or 1-amino-cyclopropane-1-carboxylic acid (ACC). Maximum rates of production are achieved about 12 hours after the addition of optimal amounts of indoleacetic acid (IAA), naphthalene acetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D), 4 to 5 hours after the addition of CuCl₂ and 1 to 2 hours after the addition of ACC. Supraoptimal concentrations of IAA result in a lag phase followed by a normal response. High concentrations of NAA and 2,4-D result in an early (4-5 hours) stress response and injury.

Continuous protein and RNA synthesis are essential for elaboration of the full IAA response; only protein synthesis is necessary for the response to CuCl₂ and ACC. Based on polysomal states and rates of amino acid incorporation, CuCl₂ partially inhibits protein synthesis while nonetheless stimulating ethylene production. In general, ethylene production by the pear cells resembles that of other plant systems. Some differences may reflect the sensitivity of the cells and are discussed. The relatively high levels of ethylene produced and the experimental convenience of the cultured cells should make them especially suitable for further investigations of ethylene production and physiology.

     

Inhibition of IAA-induced ethylene production in etiolated mung bean hypocotyl segments by 2,3,5-triiodobenzoic acid and 2-(p-chlorophenoxy)-2-methyl propionic acid

The effect of two auxin antagonists, 2,3,5-triiodobenzoic acid (TIBA) and 2-( p -chlorophenoxy)-2-methyl propionic acid (CMPA) on IAA-induced ethylene production in etiolated mung bean hypocotyl ( Vigna radiata L. Rwilcz cv. Berken) segments was studied. Both TIBA and CMPA inhibited IAA-induced ethylene production and CO₂ production at concentrations from 0.001 m M to 0.1 m M and 0.01 m M to 1.0 m M , respectively. The optimum concentration for inhibition of ethylene production by TIBA was 0.05 m M and CMPA was 0.5 m M . At the optimum concentration of TIBA and CMPA, there was a significant decrease in IAA-induced ethylene production without a decrease in respiration rates below control levels. After 18 h, mung bean hypocotyl segments treated with 0.05 m M TIBA for 6 h or 0.5 m M CMPA for 8 h showed a maximum inhibition of IAA-induced ethylene production. Treatments longer than 8 h caused no further inhibition. The uptake of [¹⁴C]-naphthaleneacetic acid by mung bean segments was greatly reduced by the addition of either TIBA (0.05m M ) or CMPA (0.5 m M ) to the incubation media. The results of treatment sequences showed that TIBA needed to be applied prior to IAA in order to inhibit IAA-induced ethylene production, but CMPA caused the same inhibitory effect whether applied before or after IAA treatment. These findings provide evidence that TIBA inhibits auxin-induced ethylene production in etiolated mung bean hypocotyl segments by blocking auxin movement into the tissue whereas CMPA may work on both auxin transport and action.     

Regulation of organogenesis and somatic embryogenesis by auxin in melon,Cucumis melo L.

Various tissues of seeds and seedlings of melon were cultured in vitro to study the effects of auxin concentration on organogenesis and embryogenesis. Adventitious shoots and somatic embryos were formed from explants of cotyledons of mature seeds, hypocotyls of seedlings, and leaves and petioles of young plantlets. Expanded cotyledons of seedlings formed only adventitious shoots. All tissues responded similarly to the 2,4-D concentration in the media, that is, adventitious shoots were formed at low concentration, callus proliferated without differentiation at intermediate concentration and somatic embryos were induced at high concentration. Cotyledons of mature seeds formed both adventitious shoots and somatic embryos more efficiently than any other tissues cultured.Effects of three auxins, 2,4-D, NAA and IAA, on organogenesis and embryogenesis were compared using cotyledons of mature seeds. Adventitious shoots were formed at low level of auxins (0 to 0.01 mg/l 2,4-D; 0 to 0.1 mg/l NAA; 0 to 1.0 mg/l IAA), and embryos were formed at high level of auxins (1.0 to 2.0 mg/l 2,4-D; 3.0 to 10.0 mg/l NAA; 20.0 to 100.0 mg/l IAA). IAA gave more efficient shoot formation and embryogenesis than the other auxins.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - NAA -naphthaleneacetic acid - IAA 3indoleacetic acid - BA 6-benzylaminopurine - MS Murashige and Skoog     

Effect of glyphosate on ethylene production in tobacco callus

Glyphosate (N-phosphonomethylglycine) caused a significant decrease or a slight increase in ethylene production in tobacco callus (Nicotiana tabacum L.) depending on the concentration of indole-3-acetic acid (IAA) present in the medium. IAA stimulated ethylene production, but a pretreatment with glyphosate greatly reduced the IAA-induced ethylene production. Inasmuch as glyphosate treatment promoted the metabolism of IAA, the decrease in ethylene production induced by glyphosate is attributed to the rapid loss of free IAA in the treated tissue.     

Morphogenesis in leaf,hypocotyl and root explants of Digitalis thapsi L. cultured in vitro

The effects of the auxins 2,4-D, NAA and IAA either alone or in combination with kinetin or BA were investigated to assess the morphogenetic potential of leaf, root and hypocotyl explants of Digitalis thapsi. Calluses were obtained from the three explants in basal medium without the addition of growth regulators and in leaves, the calluses formed roots. Application of 2,4-D, NAA or BA increased callus formation. The presence of NAA induced root formation and that of BA induced shoot formation via callus interphase. Indole-3-acetic acid alone only induced the generation of roots in the hypocotyl callus. Kinetin was ineffective in all the explants tested. Combinations of NAA with kinetin or BA were more effective in inducing organogenesis in leaf explants. Optimum responses were obtained in hypocotyl and root explants by using IAA in combination with BA, the highest rate of shoot regeneration being observed in hypocotyl explants.Rooting of the differentiated shoots was readily achieved in media without growth regulators. Regenerated plantlets were transferred to soil and grew with a survival rate of 70%.Abbreviations BA benzyladenine - 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indoleacetic acid, Kin-kinetin - NAA naphthaleneacetic acid     

The effect of indole-3-Acetic acid on ethylene formation in wheat seedlings

Isoperoxidase B 1 isolated from winter wheat (Triticum aestivum L., cv. Jubilar) seedlings was shown to catalyze ethylene formation from α-keto, γ-methylmercaptobutyric acid (KMBA). In the presence of Mn²⁺, indole-3-acetic acid (IAA), andp-coumaric acid, the kinetics by isoperoxidase B 1 catalyzed conversion of KMBA into ethylene and other products was similar to that of IAA oxidation. The reaction rate was therefore controlled by IAA through its electrondonating properties. Exogenous IAA induced ethylene formation in the segments of etiolated wheat coleoptiles. IAA-induced ethylene production was enhanced by L-methionine and mitomycin C. Aminoethoxy-analogue of rhizobitoxine, ferulic acid, sodium benzoate, cycloheximide and actinomyoin D exhibited significant inhibitory effects. These data indicate that the overall reaction mechanism in coleoptile segments involves RNA and protein synthesis. The site of IAA action is not specific; 2,4-dichlorophenoxyacetic, α-naphthylacetic and indole-3-butyric acids, respectively, possessed comparable inductive effect as IAA. Indole-3-propionic acid, indole, L-tryptophan and glucobrassicin had only low inductive efficiency, and moreover indole and L-tryptophan slowed down IAA-induced ethylene formation.     

The Effects of Plant Growth Substances on Rind-Regeneration after Girdling in Solanum melongena cv. esculantum

This paper deals with the effects of four plant growth substances, ic. IAA, NAA, 2,4-D and GA and their different concentration on rind-regeneration after girdling in Solanum melongen var. esculantum. The formation of callus was promoted by IAA, NAA and GA, but retarded by 2,4-D in early stage. The initiation of vascular cambium in callus was retarded by all these substances. However, an increase in amount of xylem was promoted by IAA at low concentrations. The different concentrations of NAA and GA affected a decrease in amount of xylem. The formation of "bundled" vascular tissue was impelled by NAA, GA and 2,4-D. The initiation of phellogen was promoted by IAA and NAA at high concentrtion. In addition, the nest-like tracheid mass was induced in callus by IAA and NAA frequently.     

Effects of auxins and cytokinins on growth and rosmarinic acid formation in cell suspension cultures of Anchusa officinalis

Cell suspension cultures of Anchusa officinalis required exogenous phytohormones for their normal growth. Cell lysis was observed at the third passage in a hormone-free medium. Using hormone — depleted cells, the effects of auxins (2,4-D, NAA, IAA and CFP) and cytokinins (BA, kinetin, and zeatin) on cell growth and RA production were investigated. All auxins tested could maintain growth and integrity of the cells whereas cytokinins alone could not, suggesting that this culture is auxindependent. Among the auxins tested, NAA had a pronounced effect on RA production. The total RA content obtained at optimum NAA concentration (0.25 mg/l) reached 1.7 g/l (12% of dry weight). The kinetics of growth and RA production suggested that the increase in final RA content was due to both an increase in the rate of RA synthesis and initiation of the period of synthesis in the exponential rather than the linear growth phase.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - NAA 1-naphthaleneacetic acid - IAA indoleacetic acid - CFP 2-chloro-4-fluorophenoxyacetic acid - BA 6-benzyladenine - RA rosmarinic acid     

Effect of diclofop-methyl and 2,4-D on transmembrane proton gradient: a mechanism for their antagonistic interaction

The site of action of the postemergence graminicide, diclofop-methyl (DM), in susceptible plants is possibly the plasmalemma. Indole-acetic acid (IAA)- and fusicoccin (FC)-induced net proton excretion in Avena coleoptiles was inhibited by the free acid, diclofop. However, net proton excretion recovered within 2 h when 2,4-dichlorophenoxy acid (2,4-D) was added simultaneously with diclofop. Diclofop depolarized the membrane potential (Em) within 12 min but the Em recovered within 30 min when diclofop was removed and replaced with either IAA or 2,4-D. The inhibition of IAA-induced coleoptile growth by DM and the membrane effects of its acid, diclofop, were partially reversed by 2,4-D if it was added shortly after treatment of the tissue. These results are consistent with the reversal of DM injury in whole plants with 2,4-D.     

Regulation of Inflorescence Growth in Cuttings of the Grape Vine (Vitis vinifera L.)

In woody cuttings of the grape vine inflorescences of fertilebuds usually atrophy soon after bud burst. Inflorescences areretained if leaves are removed from the elongating shoot, butremoval of apices and roots does not affect inflorescence growthif leaves are present. With defoliated cuttings, inflorescencegrowth is stimulated by removal of apices but depressed by removalof roots. Applications of indole acetic acid to the petiolestumps of defoliated cuttings did not replace the effect ofleaves and induce atrophy of inflorescences. Inflorescence growthin defoliated cuttings was inhibited by 2,4-dichlorophenoxyaceticacid (2,4-D), but concentrations which depressed inflorescencegrowth produced toxicity symptoms. Applications of 2,3,5-tri-iodobenzoicacid to petioles and leaf laminae were without effect on inflorescencegrowth. Treatment of inflorescences with the cytokinin 6-(benzylamino)-9-(2-tetrahydropyranyl)-9H-purine(SD 8₃₃₉) promoted inflorescence growth in both the presenceand the absence of leaves. Inhibitory effects of 2,4-D on inflorescencegrowth were partially reversible by application of SD 8₃₃₉.Response of inflorescences to gibberellic acid required eitherremoval of leaves or addition of SD 8₃₃₉.     

Effects of Brassinolide and IAA on Ethylene Production and Elongation in Maize Primary Roots

We examined the effects of brassinolide (BL) and/or an auxin (indole-3-acetic acid) on ethylene production and elongation in the primary roots of maize (Zea mays). When these two hormones were applied exogenously, both increased ethylene production. Before the tenth hour after treatment began, the influence of IAA was more evident than that of BL; the reverse was found beyond 10 h. When these hormones were treated simultaneously, the increase in level of ethylene was greater than the sum of effects by each hormone. Such a positive interaction was also recorded for changes in the activity of ACC synthase and the expression of its gene. For ACC oxidase, however, the two hormones had no apparent influence. When applied separately, neither affected root elongation nor proton extrusion. However, when given in combination, both phenomena occurred. Our results suggest that BL interacts with IAA to promote ethylene biosynthesis and elongation in roots. Therefore, it is possible that brassinolide acts by inducing auxin, which then stimulates both ethylene production (at the early stage) and root development.     

Enhancement of ethylene biosynthesis and germination with thidiazuron and some selected auxins in Striga asiatica seeds

Witchweed [ Striga asiatica (L.) Kuntze], an economically important parasitic weed on several poaceous crops, is difficult to control. In nature, germination and subsequent morphogenesis of Striga are cued to specific host-derived chemical signals. Seeds (approximately 2.4 mg) treated with thidiazuron (TDZ) or the auxins 2,4-dichlorophenoxy-acetic acid (2,4-D), 1-naphthalene acetic acid (NAA), or 2-(4-chloro- o -tolyloxy) propionic acid (MCPP) produced little ethylene (66-138 nl l⁻¹). Combinations of TDZ with the auxins increased ethylene production by 4- to 18-fold. Ethylene production was strongly inhibited (86–92%) by aminoethoxyvinylglycine (AVG), inhibitor of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase. Ethylene evolved from seeds treated with TDZ in combination with 2,4-D increased after a lag period and was promoted by a pretreatment in 2,4-D. TDZ or any of the auxins, at the rates tested, effected negligible to low levels of germination (0 to 16%), whereas mixtures of TDZ with the above auxins stimulated 38 to 84% germination. Test solutions containing TDZ and indole-3-acetic acid (IAA) were, however, less effective. TDZ/auxin-induced germination was inhibited by AVG and the ethylene action inhibitor silver thiosulfate (STS). The inhibitory effect of the former was reversed by treatment with ACC. In vitro studies revealed negligible germination (< 1%) on control medium. Seeds germinating on media containing TDZ alone developed into seedlings with distinct shoots and rudimentary roots. Seeds germinating on media containing 2,4-D, irrespective of TDZ concentration, were induced to form calli. The results are consistent with a model in which both germination and subsequent morphogenesis in Striga are associated with exogenous and endogenous phytohormones.     

Relationships in actions of indoleacetic acid, benzyladenine and abscisic acid in ethylene production

The relationships between IAA and ABA, and between BA and ABAin their effects on ethylene production were examined with etiolatedmungbean hypocotyl segments. When ABA and IAA were simultaneouslyapplied to the tissues, ABA inhibited IAA-induced ethylene productionand the degree of inhibition was solely determined by the ABAconcentrations. Increasing concentrations of BA did not affectABA inhibition. Low concentrations of ABA slightly increasedendogenous ethylene production. When ABA and BA were appliedtogether in the presence of IAA, the degree of ABA inhibitionwas again determined by the ABA concentrations regardless ofthe BA concentrations. BA did not recover ABA inhibition andABA did not inhibit the stimulative effect of BA on both endogenousand IAA-induced ethylene production. Almost the same resultswere obtained with ABA and BA pretreatment of the tissues. Thisindicates that in the processes of IAA-induced ethylene production,IAA and ABA act in series, but that the actions at their respectivesites are independent. ¹ This research was partly supported by grants from the Ministryof Education (C-956037) and the Ministry of Agriculture (49–1330)of Japan, and by the Asahi Press. (Received June 14, 1975; )     

Plant regeneration through somatic embryogenesis from mature seed and young inflorescence of wild rice (Oryza perennis Moench)

Somatic embryogenesis in the wild rice species (Oryza perennis) was induced from cultured mature seeds and young inflorescences. Murashige and Skoog's (MS) medium supplemented with 2 mg/l 2,4-D and 0.2 mg/l BAP was used for induction of a compact, white nodular callus and somatic embryos. Plant regeneration occurred with the tranfer of the nodular callus to MS basal medium containing 0.5 mg/l IAA, 0.5 mg/l NAA, 4 mg/l BAP and 500 mg/l casein hydrolysate. The embryogenic nature of the callus from both explants was maintained over 10 subcultures for about 12 months. Plant regeneration with respect to the number of calli plated from the 6th to 10th passage varied from 80% to 60% for young inflorescence derived callus and from 75% to 69.8% for seed-derived callus.Abbreviations MS Murashige and Skoog medium - BAP 6-benzylaminopurine - 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indole-3-acetic acid - NAA naphthalene acetic acid - CH casein hydrolysate