INVESTIGATION OF THE ACIDIC ALLOMONE OF THE GASTROPOD MOLLUSC PHILINE APERTA BY MEANS OF ION CHROMATOGRAPHY AND HISTOCHEMICAL LOCALISATION OF SULPHATE AND CHLORIDE IONS

Improved methods of collection of acidic allomones from theskin of the gastropod mollusc Philine aperta minimised contaminationby the anions of sea water and of blood. Neat allomone extractsremained stable in the laboratory for up to 15 months at 5–8°C,having a pH value of 2–3. Diluted extracts (1: 9 or 1:99) gradually lost their activity. Analyses by the Dionex H.P.ion chromatography apparatus showed that organic ions were presentonly in trace quantities in the allomone samples, and the principalinorganic anions were chloride and sulphate (their concentrationsapproached parity in the purest preparations). Measurementsof Cl^– varied in different samples from 2062 to 3989 p.p.million, and of SO₄^2–from 1272 to 3152 p.p. million. TheSO₄^2- CI^- ratios varied from 0.62 to 0.84. New observations are presented on the rate of in situ precipitationof BaSO₄ in preparations of the skin of Philine. The rate ofpenetration of BaCl₂ into the skin was approximately linear,even when the animal had become moribund (30 min). BaSO₄ crystalgrowth increased during the first 30 min of exposure, but laterdeclined, for reasons that are not clear. The method yieldedclear outlines of the acid sacs in histological preparations. A silver nitrate irrigation method was devised in order to investigatechloride ions in the acidic epithelium of Philine. The advanceof AgNO₃ into the tissue was usually smooth-fronted, but siteswere evident where the acid sacs had acted as channels for penetration.The silver deposits took the form of uniform small particles,often precipitated against the inner wall of an acid sac, butsometimes forming a central cluster. The method was of valuein building up a picture of structural relations as well asthe chemical composition of the acid sacs of Philine (Received 18 February 1985;     

Physiological and Ecological Studies in the Analysis of Plant Environment: VII. An Analysis of the Differential Effects of Light Intensity on the Net Assimilation Rate, Leaf-Area Ratio, and Relative Growth Rate of Different Species

Since relative growth rate is the product of net assimilationrate and leaf-area ratio (leaf area/plant weight), it followsthat if the effects of shading on both net assimilation rateand leaf-area ratio can be expressed mathematically, then therelationship between light intensity and relative growth ratecan be derived from the product of the two mathematical expressions. For all the ten species investigated in field and pot cultureexperiments, it has been found that during the early vegetativephase both the changes in leaf-area ratio and net assimilationrate, over the range of 0·1 to full daylight, are linearlyrelated to the logarithm of the light intensity. In consequence,the relationship between relative growth rate and the logarithmof light intensity—being the product of the two linearregressions—is curvilinear. For species of shady habitats (Geum urbanum, Solamun dulcamara)neither the levels of assimilation rate nor the ‘compensation-point’values are very different from those of the eight species fromopen situations (e.g. Hordeum vulgare, Pisum sativum, Fagopyrumesculentum). Nevertheless the intensity at which growth rateis maximal varies between species: it is 0•5 for G. urbanum,0•7 for H. annuus, full daylight for F. esculentum, whilefor Trifolium subterraneum the calculated value is 1·8daylight. Such specific differences can be largely accountedfor in terms of the differences in leaf-area ratio at the differentlight levels. On the basis of this analysis of the light factor, a ‘shade’plant is best redefined as a species in which a reduction ofthe light intensity causes a rapid rise in the leaf-area ratiofrom an initial low value in full daylight: for a ‘sun’plant the converse definition holds.     

Growth and Dry-weight Distribution in Callistephus chinensis as Influenced by Lighting Treatment

Plants of two cultivars of Callistephus chinensis (Queen ofthe Market and Johannistag) were grown in 8 h of daylight perday with one of the following treatments given during the 16h dark period: (a) darkness—‘uninterrupted night’,(b) I h of light in the middle of the dark period—a ‘nightbreak’, (c) I min of light in every hour of the dark period—‘cycliclighting’, (d) light throughout—‘continuouslight’. The plants receiving uninterrupted dark periods remained compactand rosetted in habit with small leaves, while leaf expansion,stem extension, and flower initiation were promoted in all threeillumination treatments (b, c, d). Although these three treatmentsproduced similar increases in leaf area, continuous light wasthe most effective for the promotion of both stem growth andflower initiation while cyclic lighting was generally more effectivethan a I-h night break. Continuous light also caused more dry matter to be divertedto stems at any given vegetative dry weight and it was shownthat the stem weight ratio of both varieties was correlatedwith stem length.     

Plant Growth-promoting Rhizobacteria and Soybean [ Glycine max (L.) Merr.] Growth and Physiology at Suboptimal Root Zone Temperatures

Application of plant growth-promoting rhizobacteria (PGPR) hasbeen shown to increase legume growth and development under optimaltemperature conditions, and specifically to increase nodulationand nitrogen fixation of soybean [Glycine max (L.) Merr.] overa range of root zone temperatures (RZTs). Nine rhizobacteriaapplied into soybean rooting media were tested for their abilityto reduce the negative effects of low RZT on soybean growthand development by improving the physiological status of theplant. Three RZTs were tested: 25, 17.5, and 15 °C. At eachtemperature some PGPR strains increased plant growth and development,but the stimulatory strains varied with temperature. The strainsthat were most stimulatory at each temperatures were as follows:15 °C—Serratia proteamaculans 1–102; 17.5 °C—Aeromonashydrophila P73, and 25 °C—Serratia liquefaciens 2–68.Because enhancement of plant physiological activities were detectedbefore the onset of nitrogen fixation, these stimulatory effectscan be attributed to direct stimulation of the plant by thePGPR rather than stimulation of plant growth via improvementof the nitrogen fixation symbiosis. Legume; nitrogen fixation; nodulation; root zone temperature; PGPR     

The In Vitro Flowering of Kalanchoe blossfeldiana Poellniz: I. ROLE OF CULTURE CONDITIONS AND NUTRIENTS

Dickens, C. W. S. and Van Staden, J. 1988. The in vitro floweringof Kalanchoe blossfeldiana Poellniz. 1. Role of culture conditions.—J.exp. Bot. 39: 461—471. Nodal explants of Kalanchöe blossfeldiana Poellniz. werecultured in vitro on a low nutrient hormone-free medium. Floweringwas achieved in response to short-day inductive cycles. Thissystem was used to test the influence, on the flowering response,of a variety of culture conditions and media. Reduced vesseland medium volume both inhibited flowering, as did renderingthe vessel impervious to gasses. Nitrogen in the form of NH₄NO₃and KNO₃ promoted flowering and vegetative growth in differentways. Increasing sucrose content in the medium caused some increasein the flowering response and in leaf anthocyanin production,but inhibited most aspects of vegetative growth. All of theseaspects are discussed in relation to the induction and evocationof flowering. Key words: Kalanche, flowering, in vitro     

Glycosylation sites identified by solid-phase Edman degradation: O-linked glycosylation motifs on human glycophorin A

The human red blood cell sialoglycoprotein, glycophorin A (GpA),contains a ‘mucin-like’ extensively O-glycosylatedextracellular domain which carries the MN blood group antigens.We have revised the sites of O-glyccsylation in the extracellulardomain of GpA by automated solid-phase Edman degradation, whichallowed positive identification and quantitation of O-glycosylatedSer and Thr residues, as well as the single N-glycosylationsite. One N-linked and 16 O-linked sites were identified. Carbohydratewas absent on Ser 1, Ser14, Ser15, Ser23, Thr28 and Thr58 inGpA. We propose that the glycosyltransferases present in erythrocytesrecognize specific flanking sequences around potential O-glycosylationsites. All 16 O-glycosylation sites are explained on the basisof four motifs. Three motifs are associated with Thr-glycosylation:Xaa—Pro—Xaa—Xaa where at least one Xaa = Thr;Thr—Xaa—Xaa—Xaa where at least one Xaa = Thr;Xaa—Xaa—Thr—Xaa where at least one X = Argor Lys. The fourth motif is associated with Ser-glycosylation:Ser—Xaa—Xaa—Xaa where at least one Xaa = Ser.These simple rules explain the glycosylation (or lack of it)on 21 of 22 Ser/Thr in the extracellular domain of GpA. glycophorin A O-glycosylation motif solid-phase Edman degradation     

The Effect of Root Temperature on Growth and Uptake of Ammonium and Nitrate by Brassica napus L. in Flowing Solution Culture: I. GROWTH

Macduff, J. H., Hopper, M. J. and Wild, A. 1987. The effectof root temperature on growth and uptake of ammonium and nitrateby Brassica napus L. in flowing solution culture. I. Growth.—J.exp. Bot. 38: 42–52 Oilseed rape (Brassica napus L. cv. Bien venu) was grown for49 d in flowing nutrient solution at pH 6?0 with root temperaturedecrementally reduced from 20?C to 5?C; and then exposed todifferent root temperatures (3, 5, 7, 9, 11, 13,17 or 25?C)held constant for 14 d. The air temperature was 20/15?C day/nightand nitrogen was supplied automatically to maintain 10 mmolm^–3 NH₄NO₃ in solution. Total dry matter production wasexponential with time and similar at all root temperatures givinga specific growth rate of 0?0784 g g^–1 d^–1. Partitioningof dry matter was influenced by root temperature; shoot: rootratios increased during treatment at 17?C and 25?C but decreasedafter 5 d at 3?C and 5?C. The ratio of shoot specific growthrate: root specific growth rate increased with the ratio ofwater soluble carbohydrates (shoot: root). Concentrations ofwater soluble carbohydrates in shoot and root were inverselyrelated to root temperature; at 3, 5 and 7?C they increasedin stem + petioles throughout treatment, coinciding with a decreasein the weight of tissue water per unit dry matter. These resultssuggest that the accumulation of soluble carbohydrates at lowtemperature is the result of metabolic imbalance and of osmoticadjustment to water stress. Key words: Brassica napus, oilseed rape, root temperature, specific growth rate     

THE AMINO ACID COMPOSITION OF FRESHWATER MOLLUSC SHELLS IN RELATION TO PHYLOGENY AND ENVIRONMENT

Quantitative thin layer chromatography of structural amino acidswas standardized for the study of shell proteins of 13 speciesof freshwater mollusc. There was slight intraspecific variationbetween individuals, particularly for tyrosine concentrations.No external periostracum was chemically identifiable in theshell of Lymnaea peregra (Müller) and this species showedsome amino acid heterogeneity in different parts of the shell.Despite these intraspecific variations, analysis of variancesuggested interspecific variation in concentrations for almostall the amino acids tudied. Cluster and principal componentsanalysis indicated that the amino acid composition did reflectphylogenetic affinity but that environmental factors were probablymore-important. (Received 5 August 1982; revised 5 August 1982;     

Reproduction rates and secondary production of three species of the rotifer genus Synchaeta in the estuarine Potomac River

Rotifers are a relatively well-studied component of lacustrinesystems but their role is only poorly understood in estuaries.Three species of the genus Synchaeta—S. baltica, S. triophthalmaand S.cecilia—dominate the cold-water assemblage of rotifersin Chesapeake Bay. Laboratory experiments were conducted todetermine the temperature dependence of egg development time(EDT) for each species; EDT varied over an approximate rangeof 90–9 h as temperature (T) varied from 2 to 22°C.The EDT/temperature relationships could be closely fitted bya simple polynomial equation of the form log(EDT) = a + b(logT) + c(log T)² for each species. Natural populations of thesethree rotifers were sampled during a cruise in the Potomac River(7–11 March 1983). Estimates of specific reproductiverates (b) were calculated based on the previously defined EDT/temperaturerelationship and the observed ratio of eggs/rotifers for eachspecies. The two most abundant species, S.triophthalma and S.cecilia,showed a clear dependence of b on the observed chlorophyll aconcentrations. Maximum reproductive rates ({small tilde}0.015h^–1) were attained only at relatively high phytoplanktondensities within a bloom of Heterocapsa triquetra where thechlorophyll a concentrations exceeded 10 µg l^–1.Estimates of secondary production suggest that Synchaeta spp.may contribute to the trophic flow of carbon in this systemwith a significance at least similar to that of the planktoniccopepods.     

The Effects of Light Intensity and External Potassium Level on Root/Shoot Ratio and Rates of Potassium Uptake in Perennial Ryegrass (Lolium perenne L.)

Loliun perenne L. (cv.S. 23) was grown on vermiculite in winterin a heated greenhouse for 8 weeks under factorial combinationsof two potassium regimes (nominally 6 parts/10⁶ and 156 parts/10⁶in Hewitt's solution) and three densities of artificially supplementedvisible radiation flux (36.1, 7.3, and 2.2 W m^–2). Growthand potassium uptake were studied through the calculation ofvarious growth functions from fitted curves. There was little effect of potassium treatment but the experimentalmaterial responded markedly to light. Leaf-area ratio in thethree treatments showed extreme plasticity in increasing from2–3 x 10^–2 through 6 x 10^–2 to 8–9 x10^–2 m² g^–1 as light intensity decreased. Correspondingdecreases in unit leaf rate, however, caused over-all reductionsin relative growth rate. Specific absorption rates for potassium (A_K, dry-weight basis)were strongly reduced at the lower light intensities but alsodisplayed complex ontogenetic drifts. Values of the allometricconstant, k (the ratio of root and shoot relative growth rates),decreased from c. 0.7 at 36.1 W m^–2 through c. 0.3 at7.3 W m^–2 to a value not significantly different fromzero (P < 0.05) at 2.2 W m^–2. In material grown under the two higher light intensities a constantinverse relationship was found between the mass ratio of rootand shoot and the corresponding activity ratio. The resultsconform to this model: Mass ratio = –0.001+45.0 (1/activityratio) where activity ratio is expressed as specific absorptionrate for potassium (in µg g root^–1 h^–1)/unitshoot rate (rate of increase of whole-plant dry weight per unitshoot dry weight, in mg g shoot^–1 h^–1). The implicationsof this relationship are discussed.     

Phosphorus utilization by Asterionella formosa Hass

Observations have been made on the relationship in Lake Windermerebetween the growth of Asterionella formosa and the concentrationof dissolved phosphate. Asterionellaformosa has also been grownin culture and the amount of phosphorus required by this organismhas been determined. These experiments have shown that: (1) Asterionella can take up and store in reserve phosphorusfrom concentrations below those found in phosphorus-poor lakes(i.e. below 1 µg.P/l.). (2) Growth can continue in phosphorus-deficient media by makinguse of such reserves, cell phosphorus being steadily reduced. (3) The limiting requirement per cell of phosphorus is veryminute—about 0—06µg P/10⁶ cells/1, so thatinitial concentrations as low as rog.P/l. can theoreticallyproduce a population of some i6 x io6 cells/l. before limitationby phosphorus deficiency. This has been realized in culture.The behaviour of Asterionella formosa growing in nature hasbeen found to conform with that found in culture. It is concludedfrom such observations that phosphorus deficiency is unlikelyto provide a limit to growth of Asterionella in Windermere,despite the very low initial concentration of dissolved phosphate.Further experiments have shown that Asterionella cells low inphosphorus can rapidly take up added phosphate from lake waterbut not from distilled water. Some factors which affect therate of phosphate uptake of depleted cells are investigated,and attempts have ben made to throw some light on the natureof the apparent difference between lake water on the one handand distilled water and a number of artificial lake waters onthe other. No conclusion is reached on the reason why Asterionellacells behave differently in lake water and in artificial media.     

Growth and decline of a diatom spring bloom phytoplankton species composition, formation of marine snow and the role of heterotrophic dinoflagellates

During the spring of 1994, we determined the factors responsiblefor the decline of the seasonal diatom bloom in the Gullmarfjord, on the west coast of Sweden. Four species constituted>75% of the biomass—Detonula confervacea, Chaetocerosdiadema, Skeletonema costatum and Thalassiosira nordenskioeldii—reachingconcentrations of 4900, 350, 8200 and 270 cells ml^–1,respectively. Growth of phytoplankton was exponential (growthrate = 0.12 day^–1) from 3 to 21 March, after which a galewith winds >15 m s^–1 caused massive aggregation. Amaximum of 130 p.p.m. (v/v) of marine snow aggregates was observedby in situ video at the peak of the bloom. Critical concentrations(Jackson, Deep-Sea Res., 37, 1197–1211, 1990) were similarto observed showing that coagulation theory could explain thesudden decline of the bloom. The heterotrophic dinoflagellateGyrodinium cf. spirale increased exponentially after the peakof the bloom with maximum (temperature-adjusted) growth rates.After the rapid aggregation and sedimentation of the bloom,they were able to control any further growth of diatoms. Nitrateand silicate were never depleted, but phosphate may have beenlimiting by the end of the study period. We conclude that massaggregation during a gale marked the end of the bloom, and thatintense grazing by heterotrophic dinoflagellates prevented anysubsequent increase of diatoms.     

Water Relations of Sitka Spruce Seedlings After Root Damage

Sitka spruce[Picea sitchensis(Bong.) Carr] seedlings were subjectedto varying degrees of root damage in a growth room, rangingfrom careful transplanting to exposure of the root system toair for up to 3 h. After replanting, transpiration (E), leafwater potential (₁) and growth of the shoot and root were measuredand observations made on plant survival. Some plants in the root exposure treatments died 20–85days after planting. In plants which eventually died, E wasdepressed directly after treatment, but ₁ showed a variableresponse. In some plants ₁ decreased from —8·0x 10⁵ to —30 x 10⁵ Pa after only 10 days but in othersthere was little change in ₁ for 50 days. In spite of the maintenanceof a high water potential in some of the latter plants for longperiods, no root or shoot growth occurred. In plants which lived, the root damage reduced root and shootgrowth relative to untreated controls, and most treatments stronglydepressed E but had little or no effect on ₁. The changes of E and ₁ in treated plants suggest that the suppressionof E was often independent of ₁ although water stress eventuallydeveloped in some of the severely treated plants. Sitka spruce, Picea sitchensis (Bong.)Carr, water relations, root damage, transpiration, leaf water potential     

Nitrogen Utilization in N-limited Barley During Vegetative and Generative Growth: III. POST-ANTHESIS KINETICS OF NET NITRATE UPTAKE AND THE ROLE OF THE RELATIVE ROOT SIZE IN DETERMINING THE CAPACITY FOR NITRATE ACQUISITION

Barley (Hordeum vulgare L., cvs Golf, Mette, and Laevigatum)was grown under nitrogen limitation in solution culture untilnear maturity. Three different nitrogen addition regimes wereused: in the ‘HN’ culture the relative rate of nitrate-Naddition (RA) was 0·08 d^–1 until day 48 and thendecreased stepwise to, finally, 0·005 d^–1 duringgrain-filling; the ‘LN’ culture received 45% ofthe nitrogen added in HN; the ‘CN’ culture was maintainedat RA 0·0375 d^–1 throughout. Kinetics of net nitrateuptake were measured during ontogeny at 30 to 150 mmol m^–3external nitrate. V_max (which is argued to reflect the maximuminflux rate in these plants) declined with age in both HN andLN cultures. A pronounced transient drop was observed just beforeanthesis, which correlated in time with a peak in root nitrateconcentration. Similar, but less pronounced, trends were observedin CN. The relative V_max (unit nitrogen taken up per unit nitrogenin plants and day) in all three cultures declined from 1·3–2·3d^–1 during vegetative growth to 0·1–0·7d^–1 during generative growth. These values are in HN andLN cultures 15- to more than 100-fold in excess of the demandset by growth rates throughout ontogeny. Predicted balancingnitrate concentrations (defined as the nitrate concentrationrequired to support the observed rate of growth) were below6·0 mmol m^–3 in HN and LN cultures before anthesisand then decreased during ontogeny. In CN cultures the balancingnitrate concentration increased during grain-filling. Apartfrom the transient decline during anthesis, most of the effectof ageing on relative V_max can be explained in terms of reducedcontribution of roots to total biomass (R:T). The loss in uptakeper unit root weight is largely compensated for by the declinewith time in average tissue nitrogen concentrations. The quantitativerelationships between relative V_max and R:T in ageing plantsare similar to those observed for vegetative plants culturedat different RAs. The data support the contention that the capacity for nitrateacquisition in N-limited plants is under general growth control,rather than controlled by specific regulation of the biochemicalpathway of nitrate assimilation. Key words: Barley, nitrogen concentration, root: total plant biomass ratio, V_max     

Mineral nutrition, of cultured chlorophyllous cells of tobacco VII. Effects of the NH4/NO3 ratio and of Cl in the media on the growth and ionic balance of cells

NG, a strain of cultured tobacco cells of Nicotiana glutinosahad high growth rates and carboxylate contents (C—A) of100 to 130 meq/100 g of dry cells on media containing 42 meqNO₃/liter as the sole N source. (C—A) is the amount ofinorganic cations minus inorganic anions in meq per 100 g ofdry cells. NG, cultured on media containing NH₄ 10+NO₃ 42 in meq/liter,had lower growth rates and lower (C—A) values as comparedwith NG on media containing NO₃ as the sole N source. NG, cultured on media containing NH₄ 30+NO₃ 42 in meq/liter,had high growth rates and (A—C) values of 22 to 53 meq/100gof dry cells. In this case, the (A—C) content may correspondto organic cations, basic organic N compounds such as free asprotein-bound basic amino acids. The easily absorbed Cl mayhave been required maintain good growth conditions such as ionicbalance and a favorable pH in the cells. Thus cultured cells of Nicotiana glutinosa may have physiologicaladaptability against variations in a relatively wide range of|C—A| contents [|C—A| being the absolute valuesof (C—A)]. (Received May 15, 1980; )     

PROMOTING ACTIVITY OF TERPENIC LACTONES IN PHASEOLUS ROOTING AND THEIR REACTIVITY TOWARD CYSTEINE

Sesquiterpenoids which contain exomethylenes conjugated to -lactonecarbonyl-heliangine, helianginol, pyrethrosin and cyclopyrethrosinacetate—promoted the adventitious root formation on hypocotylsof cuttings taken from light-grown (1900 lux) 6-day old Phaseolusmungo seedlings, but their derivatives in which the methylene-lactone systems are reduced-to the saturated lactones—dihydroheliangine,hexahydro-heliangine, dihydrohelianginol, dihydrocyclopyrethrosinacetate and tetrahydrocyclopyrethrosin acetate—showedno effect on the root formation. As far as the present experiment is concerned, every substancewhich showed promoting activity in Phaseolus rooting reactedwith cysteine and formed an adduct, but any of the substancesincapable of promoting root formation did not react with cysteine.The correlation of promoting activity of terpenic lactones inPhaseolus rooting with their reactivity toward SH groups maythus be demonstrated. ¹ Contribution No. 14 from the Botanical Gardens, Faculty ofScience, University of Tokyo, Tokyo.     

Photoadaptation in Antarctic phytopfankton: variations in growth rate, chemical composition and P versus I curves

The response of phytoplankton to variations in the light regimewas studied during the VULCAN and ACDA cruises in the Antarctic.Unenriched batch cultures of 12–19 days' duration reachedchl concentrations of 10–50 µg^–1 and exhibitedexponential growth rates, with the maximal rate being 0.41 doubl,day^–1. Ice edge algae exhibited maximum growth rates atphoton flux densities (PFD) of 30–100 µE m^–2S^–1and the growth rate was reduced by about 30% at 500–1000µE m^–2S^–1 The chl/C ratio ranged between 0.004and 0.018, with the lowest ratios at PFDs above 500 µEm^–2S^–1 chl/C ratios were also below maximum at PFDsbelow 40–50 µE m^–2S^–1 The C:N:P ratioswere close to the Redfield ratios; the Si/C ratio averaged 0.16(atoms), and the ATP/C ratio averaged from 0.0024 to 0.0050in different culture senes. When thawed after having been frozenfor 10 days, shade-adapted cultures were in a much better conditionthan sun-adapted ones. P versus I data showed that the maximumassimilation number varied from 0.75 to 4.4 µg C (µgchl)^–1h^–1. It varied inversely with the chl/C ratio;therefore the maximum carbon turnover rate varied little betweensamples (0.024/0.035 h^–1). Low biomass communities exhibitedrelatively high values for (the initial slope of P versus Icurves), low values for 1_sat (160–330 µE m^–2S^–1),and they were susceptible to photoinhibition. In contrast, communitiesdominated by Odontella weissflogii exhibited low values for, a high value for I_sat (560 µE m^–2S^–1 andthey tolerated high PFDs. The photo-adaptational status of thephytoplankton in natural water samples is discussed relativeto the profile of water column stability and mixing processes.     

The Influence of Stress Conditions on Chlorophyll Content of Two Range Grasses with Contrasting Photosynthetic Pathways

The influence of various treatments and temperature regimeson total chlorophylls and on the chlorophyll a:b ratio of westernwheatgrass and blue grama plants was investigated at differenttime intervals during the 120-day growth period. Western wheatgrass,a C₃ species, accumulated greater amounts of chlorophyll thandid blue grama plants, a C₄ species. Maximum concentrations(mg gd wt^–1) of chlorophylls in western wheatgrass andin blue grama were recorded at the lower (13/7°C) and higher(30/18°C) temperature regimes. Nitrogen fertilizer alonedecreased the chlorophyll content in both species. The chlorophylla:b ratio in blue grama ranged from an average of 2·00under irrigated plus fertilized conditions to 3·00 undercontrol and fertilized conditions. On the other hand, the chlorophylla:b ratio in western wheatgrass remained constant at 3·00throughout the growing season under various treatments and temperatureregimes.     

Initiation and Growth of Callus and Cell Suspensions of Theobroma cacao L

Callus and suspension cultures of Theobroma cacao L., initiatedfrom immature cotyledons of beans from pods harvested 120–130days after pollination were established. A modified B-5 or Murashige—Skoogagar medium sustained growth of callus without loss of vigourafter each sub-culture. A 15-fold weight increase occurred duringthe 4 week culture periods at 30 ± 1 °C. Coconutwater improved callus growth substantially. The optimum hormonalconcentrations for growth of suspensions were 0.5 mg 1^–1of 2, 4-dichlorophenoxyacetic acid and 0.1 mg I^–1 of kinetinin a Murashige—Skoog basal medium liquid medium. The optimumtemperature for growth of suspensions was 25–30 °C.The cell number and cell mass of suspensions increased 20-foldin 14 days. No organogenesis or embryogenesis was observed. Theobroma cacao L., acao, cell culture, suspension culture, tissue culture.     

Analysis of the Promoter of the Auxin-Inducible Gene, parC, of Tobacco

The auxin-responsive region (AuxRR) in the promoter of the parCgene was analyzed in transgenic tobacco plants in which the5' flanking region of the parC promoter was placed upstreamof the gene for rß-glucuronidase (GUS). The AuxRRwas located between nucleotides (nt) –226 and –54.Detailed dissection of this segment revealed that the presenceof the non-contiguous sequences from nt –226 to –151and from nt –84 to –54 was required for the expressionof the auxin responsiveness of the parC promoter. The sequencefrom nt –226 to –151 was found to contain a sequencewhich resembles the as-1 element in the 35S promoter of cauliflowermosaic virus (CaMV). Although it has been reported that theas-1 element is involved in auxin responsiveness [Liu and Lam(1994) J. Biol. Chem. 269: 668], we showed that introductionof a point mutation into the as-1-like sequence completely eliminatedauxin responsiveness, a result that suggests that the sequenceis indispensable for auxin responsiveness. However, the presenceof the as-1-like sequence alone was not sufficient for auxinresponsiveness, since the segment (nt –226 to –84)that included the as-1-like sequence failed to confer auxinresponsiveness on the core promoter. It is possible that thetwo separately located sequences play specific roles in interactionswith trans-factors that are required for the expression of theauxin responsiveness of the parC promoter. (Received March 11, 1996; Accepted July 9, 1996)