The Regulation of Citric Acid Accumulation and Carbon Recycling During CAM in Ananas comosus

The carbon balance of shade-grown Ananas comosus was investigatedwith regard to nitrogen supply and responses to high PAR. Netdark CO₂ uptake was reduced from 61.2 to 38.5 mmol CO₂ m^–2in N limited (–N) plants grown under low PAR (60 µmolm^–2 s^–1) and apparent photon yield declined from0.066 to 0.034 (mol 0².mol^–1 photon), although photosyntheticcapacities (measured under 5% CO₂) were similar. Following transferfor 7 d to high PAR (600. µmol m^–2 s^–1), netCO² uptake at night increased by 14% in +N plants, and daytimephotosynthetic capacity was higher, with a maximum value of7.8 µmol m^–2 s^–1. The magnitude of dark CO₂ fixation during CAM was measured asdawn—dusk variations in leaf-sap titratable acidity (H+)and as the proportion of malic and citric acids. The contributionfrom re-fixation of respiratory CO₂ recycling (measured as thedifference between net CO₂ uptake and malic acid accumulation)varied with growth conditions, although it was generally lower(30%) than reported for other bromeliads. Assuming a stoichiometryof 2H+: malate and 3H+: citrate, there was a good agreementbetween titratable protons and enzymatically determined organicacids. The accumulation of citric acid was related to nitrogensupply and PAR regime, increasing from 7.0 mol m–3 (+Nplants) to 18 mol m^–3 (–N plants) when plants weretransferred to high PAR; malate: citrate ratios decreased from13.1 to 2.5 under these conditions. Under the low PAR regime, leaf-sap osmotic pressure increasedat night in proportion to malic acid accumulation. However,following the transfer to high PAR for 7 d, there was a muchgreater depletion of soluble sugars at night which correspondedto a decrease in leaf-sap osmotic pressure. Although a rolefor citric acid in CAM has not been properly defined, it appearsthat the accepted stoichiometry for CAM in terms of gas exchange,titratable acidity, malic acid and osmotic pressure may nothold for plants which accumulate citric acid. Key words: Ananas comosus, CAM, citric acid accumulation, carbon recycling     

Effects of cadmium on the behaviour of citric acid in isolated tomato xylem cell walls

Effects of cadmium on the sorption of citric acid In isolatedxylem cell walls were Investigated. 2.5 nM to 9.5 mM [1.5–¹⁴]crticacid solutions were perfused through columns of xylem cell wallmaterial, isolated from tomato plants (Lycoperslcon esculentumMill, cv. Tiny Tim). The anion exchange potential of the column was estimated byamino acid analysis as approximately 46 meq dm whereas the apparentanion exchange capacity (AEC) was estimated as 1.65±0.1810^–4(citric acId units). This low AEC was attributed toa ‘zipper’ effect, a mutual screening of fixed R^–and A⁺ charges. Pre-loading with ¹¹⁵Cd²⁺ did not affect citric acid sorption,indicating the absence of Cd-effects on the availability offixed A⁺ charges, and the absence of the formation of effectiveR^–-Cd²⁺ and Donnan tree space (DFS) (Cd(cit)H₂]⁺ complexes. Simultaneous application of both citric acid and ¹¹⁵Cd²⁺,⁴⁵Ca²⁺or ²⁸Mg²⁺ resufted in increased sorption of citric acid, probablydue to capacity improvement rather than changes in valence-dependentanion sorption; this may be due to the presence of bulk (M(cit)H₂]⁺,held in the column as [M(cit)H₂]⁺ after protonation in the DFS.Sorption of citric acid was greatest in the presence of Ca²⁺which was discussed in the light of the differences betweenCa, Cd and Mg in their characteristics as co-ordinative M-complexes of citric acid. The overall results indicate the potentialimportance of the presence of metal ions for the xylem transportbehaviour of organic acids in plants. Key words: Cadmium, citric acid, ion exchange, ligand exchange, tomato, xylem cell walls     

Cyclic Nucleotides and In Vitro Plant Cultures: I. INDUCTION OF ORGANOGENESIS IN TOBACCO (NICOTIANA TABACUM CALLUS CULTURES

Mangat, B. S. and Janjua, S. 1987. Cyclic nucleotides and invitro plant cultures. I. Induction of organogenesis in tobacco(Nicotiana tabacum) callus cultures.—J. exp. Bot. 38:2059–2067. The possibility that cyclic nucleotides have a mediatory rolesimilar to cytokinins in plant tissue cultures was examined.Calli obtained from tobacco pith tissue were incubated on growthmedia supplemented with either cyclic AMP, cyclic GMP, adenosineor guanosine, in concentrations ranging from (mg dm^–3)0 to 2·0 together with 2·0 mg dm^–3 of IAA.Results were compared with identical calli grown on media containingcomparable amounts of kinetin and IAA. Increase in callus growthwas observed on all media containing cyclic AMP, cyclic GMP,adenosine, guanosine or kinetin. Adenosine or guanosine didnot promote organogenesis. Low concentrations (0·02 and0·05 mg dm^–3) of kinetin stimulated extensive rootdevelopment. Some root formation was also elicited with higheramounts of cyclic AMP (0·1 and 0·2 mg dm^–3)or cyclic GMP (0·2 and 0·5 mg dm^–3). Bothkinetin and cyclic GMP promoted shoot differentiation. However,in contrast to kinetin, cyclic GMP induced organogenesis atlower concentrations (0·02 and 0·1 mg dm^–3).The addition of 2·0 mg dm ^–3 of cyclic AM P toIAA-free growth media elicited shoot differentiation. This wasalso the case with a similar concentration of kinetin or cyclicGMP. Results suggest cytokinin activity for the two cyclic nucleotides. Key words: Tobacco, Nicotiana tabacum, tissue culture, cyclic nucleotides, cyclic AMP, cyclic GMP organogenesis     

Effect of Chelating Agents and Metal Ions on Growth and Fertility in the Male Clones of the Moss Microdus brasiliensis (Dub.) Ther

The male gametophores of Microdus brasiliensis become fertileafter 48 d on basal medium. EDDH A increases gametophore numberand percentage of fertile gametophores at lower concentrations(10^–8-10^–6 mol dm^–3), whereas EDTA enhancesboth the responses at all levels (10^–8-10^–4 moldm^–3). Their iron salts increase gametophore number aswell as the number of fertile gametophores, and the latter effectis more striking. The number of antheridia per head also increaseswith Fe-EDTA, and at higher concentrations antheridia are induced4 d earlier. EDTA and Fe-EDTA-stimulated antheridia] formationis associated with a corresponding increase in endogenous iron.Copper content increases only at higher levels of EDTA and Fe-EDTA,and there is no correlation with the antheridial induction response.Salicylic acid increases the number of gametophores and thepercentage of fertile gametophores only at lower concentrations(10^–8-10^–6 mol dm^–3), and ferric citrate doesso at all levels. With salicylic acid, antheridia are induced3 d earlier. The number of gametophores as well as the percentageof fertile gametophores increases with the increase in coppersulphate concentration. Co-addition of EDTA (10^–5 moldm^–3) and copper sulphate inhibits both the responsesat higher levels. Among the chelating agents tried, Fe-EDTAis most effective in enhancing antheridial production. Key words: EDDHA, EDTA, Salicylic acid     

Somatic Embryogenesis in Sugarcane (Saccharum officinarum L.): Growth and Plant Regeneration from Embryogenic Cell Suspension Cultures

Embryogenic cell suspension cultures were established from calliderived from young leaves of sugarcane (Saccharum officinarumL.) by placing them in liquid medium containing 5 per cent coconutwater (CW), 2–3 mg 1^–1 2, 4-D and 500 mg 1^–1casein hydrolysate (CH). The cultures were maintained by transferring2.5–5.0 ml of the suspension to 35 ml of fresh mediumevery 4–5 days. Organized structures resembling the earlystages of embryogeny were formed when 2, 4-D in the medium waslowered (0.1–1.0 mg 1^–1) but these did not developbeyond the globular or early scutellar stages. High levels ofsucrose (6–10 per cent) promoted the formation of proembryoids.Plating of the suspension on MS agar medium supplemented with0.25–2.0 mg 1^–1 2, 4-D, 5 per cent CW, 500 mg 1^–1CH, with or without activated charcoal, resulted in the formationof embryogenic calli. A large number of embryoids were formedin media containing lower 2, 4-D concentrations. Transfer ofembryoids to half-strength MS medium with 6 per cent sucroseestablished plantlets which were successfully transferred tosoil. Saccharum officinarumL, sugarcane, suspension culture, embryogenesis, regeneration     

Growth and swainsonine production of Swainsona galegifolia (Andr.) R. Br. untransformed and transformed root cultures

Untransformed and transformed root cultures of Swainsona galegifollawere established for swainsonine production. Transformed rootsgrew faster and produced higher swainsonine levels (62.3 µgg^–1 DW) than untransformed roots (23.6 ,µg g^–1DW) or roots of intact plants (8.7 µg g^–1 DW). Transformationof a number of plant genotypes using A. rhizogenes strain LBA9402 showed that plant genotype Influences swainsonine levelin transformed roots but that a wide range of swainsonine levelscan be induced by separate transformation events in the samegenotype. Enhancement of swainsonine production was attemptedby treatment with sugars and induction of polyploid roots. Key words: Agrobacterium rhizogenes, root cultures, Swainsona galegifolia, swainsonine     

Effects of indoleacetic, p-chlorophenoxyisobutyric and 2,4,6-trichlorophenoxyacetic acids on three phases of rooting in Azukia cuttings

In adventitious root formation of disbudded epicotyl cuttingstaken from light-grown, 5-day-old Azukia angularis seedlings,indoleacetic acid (IAA), 1 x 10^–4 M, applied during thefirst day showed no effect, but enhanced the effect of IAA,1 x 10^–4 M, applied during the second day. Treatment duringthe second day promoted rooting by about 70%, and a combinationof treatments for the first and second days promoted rootingsome 200%. p-Chlorophenoxyisobutyric acid (PCIB), 3 x 10^–4M, and2,4,6-trichlorophenoxyacetic acid (2,4,6-T), 2 x 10^–44M, applied the first day also enhanced the effect of IAA, 2x 10^–4 M, applied the second day. When applied the second day, PCIB, 2 x 10^–4M, increasedthe number of root primordia or clusters of small cells, butnot die number of protruded roots. Formation of the cell clusterwas inhibited by 2,4,6-T, 3 x 10^–4M, applied the secondday. Rooting processes in Azukia cuttings seem to include at leastthree phases: the first phase is induced not only by IAA butalso by PCIB or 2,4,6-T, the second phase is induced by IAAor PCIB and the diird phase depends specifically on IAA. (Received October 28, 1970; )     

In Vitro Culture of Orobanche aegyptiaca

Calli derived from seedlings of the parasitic plant Orobancheaegyptiaca were grown on enriched nutrient agar. Growth wasenhanced by the addition of 0.1 mg 1^–1 NAA and 5 % coconutmilk. The calli developed two kinds of elongated protrusions:thin ones which resemble the young root radicle and thick oneswhich resemble the adventitious roots of Orobanche plants. Bothformed pad-like structures when touching the substrate. In liquidculture, some of the calli were observed to surround isolatedcultured tomato roots. Orobanche aegyptiaca Pers., in vitro culture, germination, coconut milk, root parasite     

Specific Secretion of Citric Acid Induced by Al Stress in Cassia tora L.

A rapid and sensitive assay method for Al-chelating activitywas established to screen Al-chelating substances secreted fromroots of Al-resistant species in response to Al stress. Fromone Al-resistant species, Cassia tora L., an Al-chelating substancewas detected in the root exudates when they were exposed toSO µM Al in 0.5 mM CaCl₂ solution at pH 4.5; the dominantcomponent was identified as citric acid. The secretion of citricacid was very low during the first 4 h after initiation of Altreatment, but increased markedly thereafter. A 3-h pulse with50 µM Al also induced significant secretion of citricacid after 6 h. The lag between Al addition and secretion ofcitric acid suggests that inducible processes are involved.A dose-response experiment showed that the amount of secretedcitric acid increased with increasing external concentrationsof Al. Eight-d treatment of P deficiency did not induce thesecretion of citric acid. Exposure to 50µM of either lanthanum(La³⁺) or ytterbium (Yb³⁺) did not induce the secretion of citricacid either. These findings indicate that the secretion of citricacid is a response specific to Al stress in .C. toraand constitutesa mechanism of Al resistance. (Received April 23, 1997; Accepted June 25, 1997)     

INTERACTION BETWEEN HELIANGINE AND PYRIMIDINES IN ADVENTITIOUS ROOT FORMATION OF PHASEOLUS CUTTINGS

1. Heliangine at 110^–4 M promoted the adventitious rootformation in hypocotyls of cuttings taken from light-grown (1,900lux) Phaseolus mungo seedlings. The promotion was almost completelyreversed by 310^–4 M uracil, uridine, cytidine, oroticacid or 610^–4 M carbamoyl DL-aspartic acid, and partlyby 310^–4 M thymine or thymidine. Neither 310^–4M cytosine, adenine, adenosine, guanine, guanosine nor a combinationof 310^–4 M carbamoyl phosphate and 310^–4 M L-asparticacid reduced the promotion by heliangine.
2. Uracil did not reducethe inhibiting effect of heliangine onthe indoleacetic acidinduced elongation of etiolated Avenacoleoptile sections.
3. Helianginein an aqueous uracil solution was recovered unchangedafter24-hr incubation at room temperature.
4. The root formation ofPhaseolus cuttings was promoted also by2-thiouracil and 5-fluorouracil.The effect was reversed byorotic acid or carbamoyl asparticacid, but not by carbamoylphosphate plus aspartic acid.
5. Ribonucleaseat 100 µg/ml increased the number of rootsprotruded fromhypocotyls of cuttings by about 260%.
6. A possible interpretationfor the promotion of root formationby heliangine is offered.

¹ Contribution No. 15 from the Botanical Gardens, Faculty ofScience, University of Tokyo, Tokyo, Japan. ² Dedicated to Prof. Dr. H. SODING in commemoration of the 70thbirthday.     

Inoculation with Azospirillum lipoferum Affects Growth and Gibberellin Status of Corn Seedling Roots

Maize (Zea mays L., hybrid Cargill 147) seedlings, grown inaseptic conditions, were inoculated with three strains of Azospirillumlipoferum (Al op 33, Al iaa 320, and ATCC 29708) or culturedin different concentrations of indol-3-acetic acid (IAA) orgibberellin A₃ (GA₃). After 48 h, root length, root surfacearea, root dry weight, and shoot dry weight were measured inall treatments. Gibberellin content was evaluated in selectedroots of control and Azospirillum inoculated seedlings by gaschromatography-mass spectrometry-selected ion monitoring withthe use of deuterated gibberellins as internal standards. Thethree strains of A. lipoferum, IAA (2 ng ml^–1), and GA₃(40 to 400 pg ml^–1) significantly enhanced root growth.Improvement of root hair growth and density was obtained mainlywith A. lipoferum strain Al op 33 and GA₃ 40 pg ml^–1.GA₃ was identified by gas chromatography-mass spectrometry (byboth, full scan and selected ion monitoring) in a free acidfraction from roots of the seedlings inoculated with A. lipoferum.In the roots of the non inoculated seedlings GA₃ was found afterhydrolysis of a fraction expected to contain glucosyl conjugates. (Received April 26, 1993; Accepted September 27, 1993)     

Isolation, Culture, and Plant Regeneration of Protoplasts of Two Shrubby Oxalis Species from South America

Protoplasts were successfully isolated from internodal callustissues of both Oxalis glaucifolia and O. rhombeo-ovata whenthey were digested in a solution containing 0.1% (w/v) MacerozymeR-10, 0.5% (w/v) cellulase Onozuka R-10 and 0.3 mmol m^–3sucrose. Protoplasts proliferated to give cell colonies on Gamborget al.'s B5 medium supplemented with 0.3 mmol m^–3 mannitol,0.5 mg dm^–32, 4-D, and 2.0 mg dm^–3 kinetin. Calluswas produced upon transfer of cell colonies to Murashige andSkoog medium containing 2.0 mg dm^–3 l-naphthaleneaceticacid (NAA) and 0.1 mg dm^–3 kinetin for O. glaucifolia,or with 5.0 mg dm^–3 NAA and 0.5 mg dm^–3 6-benzylaminopurine,for O. rhombeo-ovata. Plants were regenerated from O. glaucifoliaprotoplasts on a medium containing 0.1 mg dm–3 NAA, 1.0mg dm^–3 kinetin and 1.0 mg dm^–3 gibberellic acid,but only vascular nodules were differentiated by O. rhombeo-ovataprotoplast-derived calli. Key words: Tissue culture, protoplasts, plant regeneration, Oxalis spp     

Isolation and Characterization of Sodium Chloride-Resistant Callus Culture of Vigna radiata (L.) Wilczek var. radiata

Callus cultures were initiated from seedling root segments ofmungbean (Vigna radiata (L.) Wilczek var. radiata) cv. K 851on modified PC-L2 basal medium. Growing cells were exposed toincreasing concentrations of NaCl in the medium. A concentrationof 300 mol m^–3 NaCl proved completely inhibitory to growthof the calli. On incubation for 25 d, cells which could toleratethis concentration of NaCl grew to form cell clones. Selectedclones were characterized with regard to their growth behaviour,K⁺, Na⁺ and free proline content when grown under stress aswell as on normal media and were compared with the normal sensitivecallus. The selected callus was capable of growing on mediumcontaining NaCl at the inhibitory concentration. The K⁺ contentof the selected callus was lower in the case of the NaCl mediumthan for the normal medium. However, the selected clones maintainedhigher K⁺ and Na⁺ levels, with increased salinization comparedwith the wild-type cells. Salt-selected cells accumulated higherlevels of free proline under NaCl stress compared to wild-typecells. Under normal conditions, however, the amounts of freeproline in selected and non-selected calli were comparable. Key words: Vigna radiata, callus culture, NaCl stress     

L-type voltage-dependent Ca2+ channels in cerebral microvascular endothelial cells and ET-1 biosynthesis

We investigatedthe role of intracellular calcium concentration([Ca²⁺]_i) in endothelin-1 (ET-1) production,the effects of potential vasospastic agents on[Ca²⁺]_i, and the presence of L-typevoltage-dependent Ca²⁺ channels in cerebral microvascularendothelial cells. Primary cultures of endothelial cells isolated frompiglet cerebral microvessels were used. Confluent cells were exposed toeither the thromboxane receptor agonist U-46619 (1 µM),5-hydroxytryptamine (5-HT; 0.1 mM), or lysophosphatidic acid (LPA; 1 µM) alone or after pretreatment with the Ca²⁺-chelatingagent EDTA (100 mM), the L-type Ca²⁺ channel blockerverapamil (10 µM), or the antagonist of receptor-operated Ca²⁺ channel SKF-96365 HCl (10 µM) for 15 min. ET-1production increased from 1.2 (control) to 8.2 (U-46619), 4.9 (5-HT),or 3.9 (LPA) fmol/µg protein, respectively. Such elevated ET-1biosynthesis was attenuated by verapamil, EDTA, or SKF-96365 HCl. Toinvestigate the presence of L-type voltage-dependent Ca²⁺channels in endothelial cells, the [Ca²⁺]_isignal was determined fluorometrically by using fura 2-AM. Superfusionof confluent endothelial cells with U-46619, 5-HT, or LPA significantlyincreased [Ca²⁺]_i. Pretreatment ofendothelial cells with high K⁺ (60 mM) or nifedipine (4 µM) diminished increases in [Ca²⁺]_i inducedby the vasoactive agents. These results indicate that 1)elevated [Ca²⁺]_i signals are involved in ET-1biosynthesis induced by specific spasmogenic agents, 2) theincreases in [Ca²⁺]_i induced by thevasoactive agents tested involve receptor as well as L-typevoltage-dependent Ca²⁺ channels, and 3) primarycultures of cerebral microvascular endothelial cells express L-typevoltage-dependent Ca²⁺ channels.

     

Extraction and Affinity Purification of NADH:Nitrate Reductase from Barley (Hordeum distichum L.) Roots

Conditions suited for the extraction and purification of NADH:nitratereductase (NR) from barley (Hordeum distichum L.) roots wereexamined. The addition of 10 mM EDTA to the extraction mediumproduced an 8-fold increase in the NR activity in the crudeextract, whereas the presence of cysteine in the medium causedan appreciable decrease in this activity. EDTA and FAD stimulatedNR activity in the crude extract; cysteine inhibited it. Theeffect of EDTA seemed to be due to the inhibition of the contaminatingNADH-oxidizing system. The NADH:NR was purified 300-fold by ammonium sulfate fractionationand blue dextran-Sepharose affinity chromatography. The specificactivity was 1,420 nmol nitrite formed min^–1 mg protein^–1at 30?C; the highest specific activity among the NR preparationsobtained thus far from root tissues of higher plants. EDTA,as well as cysteine behaved as an inhibitor for the purifiedNR. (Received January 27, 1982; Accepted June 21, 1982)     

Regeneration of Lasiurus scindicus from Tissue Culture

Embryogenic callus cultures were initiated from mature embryosof Lasiurus scindicus on Murashige and Skoog's medium supplementedwith 6 mg l^–1 2,4-Dichlorophenoxyacetic acid (2,4-D).These cultures were maintained on 2 mg l^–1 2,4-D. Plantletswere regenerated via somatic embryogenesis when the calli weretransferred onto hormone-free MS basal medium. Young plantswere successfully transplanted to pots and grown to maturityin a greenhouse. Grass, Lasiurus scindicus, Thar Desert, drought tolerant, somatic embryogenesis, plant regeneration     

The Effect of Temperature and Light on Gas Exchange and Acid Accumulation in the C3-CAM Plant Clusia minor L

Gas exchange and organic acid accumulation of the C₃-CAM intermediateClusia minor L. were investigated in response to various day/nighttemperatures and two light regimes (low and high PAR). For bothlight levels equal day/night temperatures between 20°C and30°C caused a typical C₃ gas exchange pattern with all CO₂uptake occurring during daylight hours. A day/ night temperatureof 15°C caused a negative CO₂ balance over a 24 h periodfor low-PAR-grown plants while high-PAR-grown plants showeda CAM gas exchange pattern with most CO₂ uptake taking placeduring the dark period. However, there was always a considerablenight-time accumulation of malic acid which increased when thenight-time temperature was lowered and had its maximum (54 mmolm^–2) at day/night temperature of 30/15°C. A significantamount of malic acid accumulation (23 mmol m^–2) in low-PAR-grownplants was observed only at 30/15°C. Recycling of respiratoryCO₂ in terms of malic acid accumulation reached between 2·0and 21·5 mmol m_–2 for high-PAR-grown plants whilethere was no significant recycling for low-PAR-grown plants.Both low and high-PAR-grown plants showed considerable night-timeaccumulation of citric acid. Indeed under several temperatureregimes low-PAR-grown plants showed day/night changes in citricacid levels whereas malic acid levels remained approximatelyconstant or slightly decreased. It is hypothesized that lowand high-PAR-grown plants have different requirements for citrate.In high-PAR-grown plants, the breakdown of citrate preventsphotoinhibition by increasing internal CO₂ levels, whereas inlow-PAR-grown plants the night-time accumulation of citric acidmay function as an energy and carbon saving mechanism. Key words: C. minor, C₃, CAM, citric acid, light intensity     

In Vitro Regeneration from Seedling Organs of Brassica oleracea var. italica Plenck cv. Green Comet I. Effect of Plant Growth Regulators

The calabrese cultivar Brassica oleracea var. italica cv. GreenComet was used in a study of the effects of exogenous hormoneson the growth and differentiation of seedling organs in vitro.Four types of explants were tested: hypocotyl segments, rootsegments, primary leaf discs and cotyledon discs. These explantswere incubated on media containing factorial combinations ofBAP x IBA, BAP x NAA, KN x IBA and KN x NAA (all at 0, 0.1,10 and 10.0mg l^–1). Hypocotyls were the most regenerativeexplants; shoot production was favoured by cytokinin: auxinratios greater than one and was decreased by IBA at 10 mg l^–1when callus was produced. Shoot formation from root explantsoccurred either in the absence of hormones or with low concentrations;no shoot was produced when any hormone was present at 10 mgl^–1. In contrast, shoot production from primary leaf diseswas favoured by high concentrations of both auxin and cytokininwith the combination of BAP and IBA the most effective. Shootproduction from cotyledon discs was sporadic with no consistentresponse on any auxin/cytokinin combination. After further experimentson the optimization of hormone concentration, the followingcombinations were chosen as allowing reliable regeneration:0.1 mg l^–1 BAP+0.1mg l^–1 IBA for hypocotyl segments,0.075 mg l^–1 KN +0.025 mg l^–1 IBA for root segments,and 5.0 mg l^–1 BAP+5.0 mg l^–1 IBA for leaf discs. Brassica oleracea var. italica, calabrese, tissue culture, seedling, auxin, cytokinin     

Effects of 2,3,5-Triiodobenzoic Acid on Plantlet Formation from Cultured Tissues of Taro, Colocasia esculenta (L) Schott (Araceae)

Cultures of a Californian cultivar of Colocasia esculenta varantiquorum, UCI Runner, produced abnormal structures in additionto plantlets on Linsmaier-Skoog (LS) medium supplemented with1 0 mg 1^–1 adenine-N-benzyl-tetrahydro-2H-pyran-2-yl or6-dimethylaminopurine and 0 1 mg 1^–1 napthaleneaceticacid after at least 32 weeks of culture A number of substitutionsand combinations of growth regulators were tested in an attemptto stimulate normal plantlet development These included trialswith 2,4,5-trichlorophenoxyacetic acid, aminocyclopropane-1-carboxylicacid, and 2,3,5-triodobenzoic acid (TIBA) When tissues werecultured on LS medium without hormones, and supplemented with1 mg 1^–1 TIBA, plantlet production occurred in 2 to 4weeks and the number of abnormal structures was reduced Auxin, calloid, callus culture, cytokinins, micropropagation, development     

Effect of Salinity on Growth, Nodulation and Nitrogen Yield of Chickpea (Cicer arietinum L.)

Chickpea cultivar ILC 482 was inoculated with salt-tolerantRhizobium strain Ch191 in solution culture with different saltconcentrations added either immediately with inoculation or5 d later. The inhibitory effect of salinity on nodulation ofchickpea occurred at 40 dS m^–1 (34.2 mol m^–3 NaCl)and nodulation was completely inhibited at 7 dS m^–1 (61.6mol m^–3 NaCl); the plants died at 8 dS m^–1 (71.8mol m^–3 NaCl). Chickpea cultivar ILC 482 inoculated with Rhizobium strain Ch191^spcstrwas grown in two pot experiments and irrigated with saline water.Salinity (NaCl equivalent to 1–4 dS m^–1) significantlydecreased shoot and root dry weight, total nodule number perplant, nodule weight and average nodule weight. The resultsindicate that Rhizobium strain Ch191 forms an infective andeffective symbiosis with chickpea under saline and non-salineconditions; this legume was more salt-sensitive compared tothe rhizobia, the roots were more sensitive than the shoots,and N₂ fixation was more sensitive to salinity than plant growth. Key words: Cicer arietinum, nodulation, N₂ fixation, Rhizobium, salinity