Collapse of Peroxide-Scavenging Systems in Apple Flower-Buds Associated with Freezing Injury

Changes in the metabolic activities of peroxide-producing systemsand peroxide-scavenging systems after freezing and thawing inflower buds of the apple, Malus pumila Mill., were studied withspecial reference to freezing injury. In flower buds of the‘McIntosh’ apple that were frozen below lethal temperatures,the activity of NADH-Cyt c reductase (EC 1.6.99.3 [EC] ), one of theenzymes in the electron-transport chains that are related tothe peroxide-producing systems, decreased slightly, while thatof Cyt c oxidase (EC 1.9.3.1 [EC] ) hardly changed. By contrast, theactivities of glucose-6-phosphate dehydrogenase (EC 1.1.1.49 [EC] ),dehydroascorbate reductase (EC 1.8.5.1 [EC] ) and ascorbate peroxidase(EC 1.11.1.11 [EC] ), which are involved in the peroxide-scavengingsystems, decreased to very low levels. The activity of glyceraldehyde-3-phosphatedehydrogenase (EC 1.2.1.12 [EC] ) also decreased markedly. However,little change was observed in the activities of hexokinase (EC2.7.1.1 [EC] ), glucosephosphate isomerase (EC 5.3.1.9 [EC] ), glutathionereductase (EC 1.6.4.2 [EC] ) and glutathione peroxidase (EC 1.11.1.9 [EC] ).Examination of substrates involved in the peroxide-scavengingsystems revealed that the levels of glucose-6-phosphate andfructoses-phosphate decreased to approximately 10^–4 to10^–5 M and 10^–5 M, respectively, and the levelsof GSH decreased to about 10^–5 M or became barely detectable.A decrease in the levels of GSSG also occurred while levelsof ascorbate rose slightly. Similar results were observed withflower buds from ‘Starking Delicious’ and ‘Jonathan’apple trees. These results suggest that the freezing injury to apple flower-budsis closely related to the collapse of the peroxide-scavengingsystems that are coupled with the pentose phosphate cycle. Theresults also suggest that the dysfunction of these peroxide-scavengingsystems is caused by H₂O₂, which may be produced during freezingand thawing. (Received March 14, 1992; Accepted June 5, 1992)     

Effect of malformin on the major constituents of Phaseolus vulgaris

Malformin inhibits wet and dry weight, nitrogen accumulation,and cell wall, RNA, DNA and protein synthesis in Phaseolus vulgaris.The relative proportion of dry matter and nitrogen in malformedtissues is increased in the ethanol soluble fraction and decreasedin the residue remaining after hydrolysis with 0.5 N HCl. Inhibitionof cell wall and protein synthesis was generally greater thaninhibition of nitrogen accumulation and RNA and DNA synthesis.The effects of malformin on the composition of P. vulgaris aresimilar to alterations in composition reported for ethylene,and opposite to those reported for gibberellic acid. ¹This research was supported by grant GB-7158 from the NationalScience Foundation and grant E-146-F from the American CancerSociety. ²Journal Paper No. 3509 of the Purdue Agricultural ExperimentStation. (Received October 23, 1968; )     

The Regulation of the Starch-Malate Balances during Volume Changes of Guard Cell Protoplasts

The enzymatic activities of phosphoenolpyruvate carboxylase(EC 4.1.1.31 [EC] ), ‘malic enzyme’ (EC 1.1.1.40 [EC] ), phosphofmctokinase(EC 2.7.1.11 [EC] ) and fructosebisphosphatase (EC 3.1.3.11 [EC] ) weremeasured during the swelling and shrinking of isolated and purifiedguard cell protoplasts (Vicia faba) in darkness. The volumeincrease was accompanied by the activation of phosphofructokinaseand a short stimulation of phosphoenolpyruvate carboxylase,at the same time the ‘malic enzyme’ and fructosebisphosphatasewere inhibited. However, during the shrinkage of guard cellprotoplasts these two enzymes were activated in contrast tophosphoenolpyruvate carboxylase and phospho-fructokinase. Becauseof the dramatic increase of phosphoenolpyruvate carboxylaseactivity during the swelling, this enzyme was assumed to actas a trigger for the swelling phase.     

Auxin-promoted Transport of Metabolites in Stems of Phaseolus vulgaris L.: SOME CHARACTERISTICS OF THE EXPERIMENTAL TRANSPORT SYSTEMS

Indol-3yl-acetic acid (IAA) applied to sterns of Phaseolus vulgarisseedlings, decapitated above primary leaves, enhanced the mobilizationof ¹⁴C-metabolites to the treated stumps and this effect wasapparent within 3–6 h of applying the hormone. More than90 per cent of the total ¹⁴C-activity transported to the stumpswas detected in the alcohol-soluble extracts. In all treatments,less than 5 per cent of the ¹⁴C-photosynthate exported fromthe primary leaves was translocated upwards. Accumulation of¹⁴C-activity was also increased when the IAA was applied laterallyto intact internodes. This effect was obtained when ¹⁴C wassupplied either above or below the point of hormone application.By selective heat girdling, it was shown that the auxin affected¹⁴C transport when either the root ‘sink’ was removedor transpiratory flow of water through the treated internodewas maintained. Decapitated stems treated with plain lanolinfor 3 d were found to retain their responsiveness to auxin interms of enhanced metabolite transport. Heat-girdling experimentsand estimates of ¹⁴C transport velocity suggested that mostof the ¹⁴C movement was restricted to the phloem of treatedstumps. Similar effects of IAA on a transport in excised stemsegments of Phaseolus vulgaris were observed.     

Physiological Changes in Phaseolus vulgaris in Response to Long-term Ozone Exposure

The effects of ozone on Phaseolus vulgaris cv. Lit were investigatedusing open-top chambers (OTCs) ventilated with charcoal andPurafil filtered air (CF treatments), ambient air (NF treatments)and ambient air to which low, medium or high concentrationsof ozone were added (NFL, NFM and NFH). Ozone additions of 8,16 and 23 nl l^–1 were made during phase 1 of the experiment(0–44 d after emergence, DAE), and additions of 15, 30and 47 nl l^–1 were made during phase 2 (45–99 DAE).Ozone was added to the chambers between 1100 and 1800 h GMT,for 3 or 4 consecutive days each week. The seasonal 7-h meanozone concentrations were 8, 21, 27, 33 and 38 nl l^–1in the CF, NF, NFL, NFM and NFH treatments, respectively. No visible symptoms of ozone injury or significant physiologicalchanges were detected in P. vulgaris during phase I of the experiment.In phase 2, the photosynthesis (Pn) and stomatal conductance(gs) of NFH-plants were inhibited by 73% and 86%, respectively,during ozone exposure, and recovered to pre-exposure valueson the following day. These observations were made prior tothe appearance, 60 DAE, of bronze lesions on the leaves of NFH-plants.The photosynthetic capacity and gs of NFH-leaves decreased asthe severity of ozone injury increased. Rates of weight lossfrom excised leaves also increased with increasing ozone injury.Microscopic investigations of the bronzed regions revealed extensivecellular breakdown, including tonoplast and chloroplast enveloperupture, and the aggregation of the cytoplasmic contents towardsone end of the cell. Severely damaged leaves abscised from the plants, resultingin premature canopy senescence in the NFM and NFH treatments.This, coupled with the lower photosynthetic capacity of existingleaves led to 25 % lower yield in the NFH than the NF treatment(P < 0.05). Phaseolus vulgaris, green bean, ozone, symptom development, photosynthesis, cell ultrastructure     

Activation Energies of Reactions Catalyzed by the Nitrate Reductase from Chlorella vulgaris

The thermal dependence of two of the reactions catalyzed bythe nitrate reductase from Chlorella vulgaris was determined.The activation energies for NADH:nitrate oxidoreductase (EC1.6.6.1 [EC] ) and NADH:Cytochrome c oxidoreductase (EC 1.6.99.3 [EC] )are 42.1 kJ?mol^–1 and 21.5 kJ?mol^–1, respectively.Since the thermal dependency of the two enzymes is different,ratios of the activities will vary with temperature. The importanceof both rigorous thermal control during nitrate reductase assaysas well as the need to specify the temperature at which theratio of activities for the enzyme are clearly established. ¹Present Address: Cropping Systems Research Laboratory, USDA-ARS,Route 3, Box 215, Lubbock, TX 79401, U.S.A. (Received November 25, 1987; Accepted March 2, 1988)     

Responses of CO2 assimilation to changes in irradiance: laboratory and field data and a model for beans (Phaseolus vulgaris L.)

The responses of net CO₂ assimilation to sudden changes in irradiancewere studied in Phaseolus vulgaris L. in the laboratory andthe field. For irradiance changes between 50 µmol m^–2s^–1 to 350 µmol m^–2 s^–1 in the laboratory,assimilation rate increased with half-times of 2.7 and 4.1 minin well-watered and water-stressed plants, respectively. Ina field experiment with a change in irradiance from 400 to 1200µmol m^–2 s^–1 the response was faster (half-time=c.1.2 min). In all cases when irradiance was returned to a lowvalue, assimilation declined rapidly with a half-time of approximately1 min, which approached the time resolution of the gas-exchangesystem. The corresponding changes in stomatal conductance in responseto both increasing and decreasing irradiance were much slowerthan the assimilation responses, indicating that biochemicalprocesses, rather than CO₂ supply, primarily determined theactual rate of assimilation in these experiments. The conceptof stomatal limitation to photosynthesis is discussed in relationto these results. A simple model for assimilation in a fluctuating light environmentis proposed that depends on a steadystate light response curve,an ‘induction lag’ on increasing irradiance, andan induction-state memory. The likely importance of taking accountof such induction lags in natural canopy microclimates is considered. Key words: Models, Phaseolus vulgaris, photosynthetic induction, CO₂ assimilation, stomatal limitation, sunflecks, water stress     

ERRATA

Effects of coupled solute and water flow in plant roots withspecial reference to Brouwer's experiment. Edwin L. Fiscus. p. 71 Abstract: Line 3 delete ‘interval’ insert‘internal’. p. 73 Materials and Methods: line 6: delete ‘diversion’ insert ‘division’ line 9 equation should read J_v=L_p P–RT(C⁰–C¹). 74 Last line of figure legend: 10^–1 should read 10^–11. 75 Line 11: delete ‘seems’ insert ‘seem’. le 1 column heading—10⁶ should read 10¹¹. 77 delete ‘...membrane in series of...’ insert ‘membranein series or...’ Delete final paragraph.     

Late Transplanting and the Yield of Phaseolus vulgaris L.

The prediction that very high seed yields of dry beans (Phaseolusvulgaris L.) would be produced by the delayed transplantingof large plants has been tested in a factorial experiment withfour dates of transplanting and eight plant populations. Therewere significant differences in yield between transplantingdates and between population densities, and there was a significantdate-density interaction. At low plant densities (up to about30 plants m^–2) the three transplanted treatments yieldedless than the hand-sown controls, and late transplanting yieldedless than early. At the highest density the situation was reversed;all three transplanted treatments out-yielded the controls andlate transplanting tended to out-yield plants transplanted early.The biggest yield was 340 g seed m^–2 from a transplantedcrop grown at 35 plants m^–2. The data on yield fitted a modified rectangular hyperbola ofthe form where y is yield per unit area, p is the number of plants perunit area, t is the number of days between sowing and transplanting,and B_o, n, m, and p are arbitrary parameters. This equationaccounted for 91 per cent of the variation in yield with t andp. It is suggested that late transplanting had adverse effects,due to transplanting ‘shock’ and which were mostmarked at low plant densities; and beneficial effects, ascribableto an effect on plant ‘plasticity’, which were mostmarked at high plant densities. Possible physiological mechanismsof these effects are discussed. Phaseolus vulgaris, yield, density, transplanting     

A Cytochrome P450 Mediated Naringenin 3'-Hydroxylase from Sweet Orange Cell Cultures

A microsomal flavonoid 3'-hydroxylase (F3'H) catalyzing themetabolism of naringenin to eriodictyol in Citrus sinensis (L.)Osbeck cv. ‘Hamlin’ cell suspension cultures wasshown to be a cytochrome P450 enzyme. This reaction requiredO₂ and NADPH and was inhibited by CO, with partial reversalof CO-inhibition by light at 450 nm. Cytochrome P450 contentranged from 10–20 pmol (mg microsomal protein)^–1.The F3'H reaction was shown to be linear in regard to proteinconcentration between 2.5 and 25 µg of microsomal protein.The optimum pH for the reaction was 7.4–7.6 and the temperatureoptimum was between 30 and 37°C. The apparent K_m and V_maxfor naringenin were 24 µM±3.2 and 81.4±7.9pmol eriodictyol min^–1 (mg protein)^–1, respectively.The microsomal F3'H was also capable of forming dihydroquercetinfrom dihydrokaempferol (40 pmol min^–1 (mg protein)^–1)and of quercetin from kaempferol (3.25 pmol min^–1 (mgprotein^–1). Cytochrome c and ketoconazole were the bestinhibitors of WH activity followed by piperonyl butoxide anda-naphthoflavone. Light was shown to be an inducer of the F3'Halmost doubling the specific activity and increasing the microsomalcytochrome P450 content by 30% over that of dark grown cells.F3'H activity was also confirmed in microsomal preparationsof young (new flush) leaves from ‘Hamlin’ treesand flavedo of ‘Hamlin’ oranges, ‘Marsh’grapefruit, and ‘Lisbon’ lemon. No activity wasobserved in older, hardened leaves and albedo of all the fruittested. Initiation of embryogenesis in the ‘Hamlin’cell suspension cultures by switching from a sucrose mediumto a glycerol-based medium resulted in the down-regulation ofF3'H. ¹Mention of a trademark, warranty, proprietary product, or vendordoes not constitute a guarantee by the U.S. Department of Agricultureand does not imply its approval to the exclusion of other productsor vendors that may also be suitable.     

The Apparent Induction of Nitrate Uptake by Chara corallina Cells following Pretreatment with or without Nitrate and Chlorate

Nitrate provision has been found to regulate the capacity forChara corallina cells to take up nitrate. When nitrate was suppliedto N sufficient cells maximum nitrate uptake was reached after8 h. Prolonged treatment of the cells in the absence of N alsoresulted in the apparent ability of these cells to take up nitrate.Chlorate was found to substitute partially for nitrate in the‘induction’ step. The effects on nitrate reductionwere separated from those on nitrate uptake by experiments usingtungstate. Tungstate pretreatment had no effect on NO^–₃uptake ‘induced’ by N starvation, but inhibitedNO^–₃ uptake associated with NO^–₃ pretreatment. Chloridepretreatment similarly had no effect on NO^–₃ uptake ‘induced’by N deprivation, but inhibited NO^–₃ uptake followingNO^–₃ pretreatment. The data suggest that there are atleast two mechanisms responsible for the ‘induction’of nitrate uptake by Chara cells, one associated with NO^–₃reduction and ‘induced’ by CIO^–₃ or NO^–₃and one associated with N deprivation. Key words: Nitrate, Chlorate, Chara corallina, Induction     

Potential toxicity of chrysophytes affiliated with Poterioochromonas and related 'Spumella-like' flagellates

The chrysophyte genera Poterioochromonas and Ochromonas andtheir heterotrophic analogons, i.e. the ‘Spumella-like’flagellates, account for a significant and often dominatingfraction of the pelagic nanoplankton. Even though several osmotrophicallyand autotrophically grown strains of Ochromonas and Poterioochromonasare assumed to produce toxins, the potential toxicity has beeninvestigated neither for its association with bacterivorousnutrition nor within the related exclusively heterotrophic ‘Spumella-like’flagellates. We investigated the toxic potential of severalflagellate strains using cultures of flagellates, cell extractsand filtrate of flagellate cultures. The effect on potentialpredators was exemplarily tested for the cladoceran Daphniamagna and the rotifer Platyias sp. All tested heterotrophicand mixotrophic flagellate strains were toxic to zooplanktonat abundances exceeding 10⁴ flagellates mL^–1. For therotifers, survival on any of the flagellate strains was significantlylower than that in the control treatment (P < 0.001) alreadyafter 24 h. We conclude that (i) ‘Spumella-like’flagellates can be toxic to zooplankton, (ii) all tested flagellates,i.e. heterotrophic and mixotrophic flagellates, feeding phagotrophicallycan be toxic to zooplankton and (iii) sublethal effects maybe observed at typical field abundances, even though acute toxicityseems to be restricted to flagellate abundances observed onlyat peak events.     

Effects of Deoxygibberellin C (DGC) and 16-Deoxo-DGC on Gibberellin 3{beta}-Hydroxylase and Plant Growth

Deoxygibberellin C (DGC), a C/D ring-rearranged isomer of GA₂₀,was shown to inhibit the conversion of [2,3-³H₂]GA₉ to [2-³H]GA₄by gibberellin 3ß-hydroxylase from immature seedsof Phaseolus vulgahs. Deoxygibberellin C inhibited the promotionof growth by exogenously applied GA₂₀ of rice (Oryza sativaL.) seedlings. Evidence is also presented that DGC is a competitiveinhibitor of the 3ß-hydroxylase from P. vulgaris.However, DGC only weakly inhibited the conversion catalyzedby the 3ß-hydroxylase from Cucurbita maxima at highconcentrations, and it did not inhibit the promotion of growthby exogenously applied GA₉ of cucumber (Cucumis sativus) seedlings.These results suggest that the 3ß-hydroxylases fromP. vulgaris and C. maxima have different structural requirementswith respect to their substrates. 16-Deoxo-DGC also inhibitedcatalysis of the same conversion by 3ß-hydroxylasefrom P. vulgaris, and it slightly inhibited the conversion catalyzedby the enzyme from C. maxima. Application of 16-deoxo-DGC causedthe promotion of the growth of seedlings of both rice and cucumber. ³ Present address: Genetic Engineering Center, Korea Instituteof Science and Technology, Daejeon 305–606, Korea ⁴ Present address: Department of Agricultural Chemistry, UtsunomiyaUniversity, Utsunomiya-shi, Tochigi, 321 Japan (Received September 25, 1990; Accepted December 17, 1990)     

Effect of shade treatment on biosynthesis of catechins in tea plants

When tea plants were shaded with black lawn cloth for severaldays in the field, the accumulations of (—)-epicatechin,(—)-epicatechin-3-gallate, (—)-epigallocatechinand (—)-epigallocatechin-3-gallate decreased in newlydeveloping tea shoots. Radioactive tracer studies showed thatthe conversions of glucose-U-¹⁴C, shikimic acid-G-¹⁴C and phenylalanine-U-¹⁴Cinto (—)-epicatechin and (—)-epigallocatechin moietieswere depressed by the shade treatment for tea plants but theincorporation of trans-cinnamic acid-3-¹⁴C was not affected.The treatment was found to have no significant effect on theactivities of phospho-2-keto-3-deoxy-heptonate. aldolase (EC.4.1.2.15 [EC] ), 3-dehydroquinate synthase (EC. 4.6.1.3 [EC] ), 3-dehydroquinatedehydratase (EC. 4.2.1.10 [EC] ), shikimate dehydrogenase (EC. 1.1.1.25 [EC] )and trans-cinnamate 4-monooxygenase (EC. 1.14.13.11 [EC] ) in theshoots, whereas the activity of phenylalanine ammonia-lyase(EC. 4.3.1.5 [EC] ) clearly decreased. (Received March 17, 1980; )     

Recalling Taste Intensities in Sweetened and Salted Liquids

The effect of training on recalling taste intensities over 6weeks was studied using an ad libitum mixing procedure. Subjectstasted sweet and salty standards labeled as ‘weak’and ‘strong’ (3 and 8% sucrose in redcurrant juice;0.4 and 1.2% NaCl in beef broth). They subsequently mixed unsweetenedand sweetened juice, and unsalted and salted broth, to producetaste intensities that corresponded to the standards. A minimumtraining (MT) group (n = 13) produced comparison stimuli bytasting and directly comparing with standards in one sessiononly; an extensive training (ET) group (n = 13) did this insix sessions before producing comparison stimuli based on memoryonly at 1 h, 1 day, 1 week and 6 weeks. An upward bias (chemicallydetermined concentrations of comparison stimuli exceeding thoseof standards) occurred at 1 day or 1 week in MT subjects for‘weak’ and ‘strong’ sweetness, and for‘strong’ saltiness, and sustained thereafter. Theupward tendency was also observed in ET subjects but was significantonly for ‘strong’ sweetness. It is important torecognize memory effects such as the one described, as theyaffect food perceptions and can be a major source of bias insensory food research. Chem. Senses 21: 29–34, 1996. ³Current address: Psychonomics Department, Utrecht University,Heidelberglaan 2, 3584 CS Utrecht, The Netherlands     

The Sensitivity of Net Photosynthesis in Several Plant Species to Short-term Fumigation with Sulphur Dioxide

The effects of exposure of up to 2 h with sulphur dioxide ona range of plant species was observed by measuring changes inthe rate of net photosynthesis under closely controlled environmentalconditions. Ryegrass, Lolium perenne ‘S23’ was thespecies most sensitive to SO₂; significant inhibition was detectedat 200 nl l^–1. Fumigations at 300 nl l^–1 also inhibitedphotosynthesis in field bean (Vicia faba cv. ‘Three FoldWhite’ and ‘Blaze’) and in barley (Hordeumvulgare cv. ‘Sonja’). No effect was detected inwheat (Triticum aestivum cv. ‘Virtue’) at concentrationsup to 600 nl l^–1 SO₂, or in oil-seed rape (Brassica napuscv. ‘Rafal’) except at 800 nl l^–1 SO₂). Recoverycommenced immediately after the fumigation was terminated andwas complete within 2 h when inhibition had not exceeded 20%during the SO₂ treatment. Key words: Sulphur dioxide, short-term fumigation, photosynthesis     

Pyrimidine Nucleotide Biosynthesis in Vinca rosea Cells: Changes in the Activity of the de novo and Salvage Pathways during Growth in a Suspension Culture

Marked changes in the activity of the ‘de novo’and ‘salvage’ pathways of pyrimidine biosynthesisduring growth of Vinca rosea cells in a batch suspension culturewere observed. The activity of these pathways was investigated by determiningthe contribution of ¹⁴C of [2-¹⁴Cluracil, 12-¹⁴Cluridine. and[6-¹⁴Clorotate to the cell constituents and by measuring theactivity of the several enzymes of these pathways. During the lag phase of the culture, ‘uracil-’ and‘uridine-salvage’ pathways made the predominantcontribution to nucleotide biosynthesis, but, following theinitiation of cell division, the ‘de novo’ pathwayfor nucleotide biosynthesis operated appreciably. These results suggest that nucleotide synthesis during cellgrowth in a suspension culture can be divided into two stages:a ‘turnover stage’, during the lag phase of cellgrowth, and a ‘true biosynthetic stage’, which isinitiated in the cell division phase.     

The chloroplast envelope of Phaseolus vulgaris L. II. Enzymic characteristics

The isolated chloroplast envelope of Phaseolus vulgaris L. wasfound to synthesize galactolipids when supplied with exogenousUDP galactose. The rate of total galactose incorporation variedwithin the range 0.4-50 nmole g protein^–1 sec^–1with age of the tissues. The activities of NADH dehydrogenase,malate dehydrogenase and Mg²⁺-ATPase in the envelope fractionwere also investigated. The use of a positive "marker" activityfor the isolated chloroplast envelope is considered. ¹Present address: Boyce Thompson Institute, Tower Road, CornellUniversity, Ithaca, NY 14853, USA. (Received March 24, 1980; )     

Effect of Inorganic Phosphate on the Biosynthesis of Purine and Pyrimidine Nucleotides in Suspension-Cultured Cells of Catharanthus roseus

The levels of purine and pyrimidine nucleotides in suspensioncultures of Catharanthus roseus were determined 24 h after stationary-phasecells were transferred to fresh complete (‘+Pi’)or phosphate-deficient (‘–Pi’) Murashige-Skoogmedium. The levels of ATP, GTP, UTP and CTP were from approx.3 to 5-fold greater in the cells grown in ‘+Pi’medium than in the cells grown in ‘–Pi’ medium.The levels of almost all other nucleotides were slightly higherin the cells in ‘+Pi’ medium. The rates of de novoand salvage biosynthesis of purine and pyrimidine nucleotideswere estimated from the rates of incorporation of radioactivityfrom [¹⁴C]formate, [2–¹⁴C]glycine, NaH¹⁴CO₃, [6–¹⁴C]orotate,[8–¹⁴C]adenine, [8–¹⁴C]adenosine, [2–¹⁴C]uraciland [2–¹⁴C]uridine. The results indicated that the activityof both the de novo and the salvage pathway was higher in thecells in ‘+Pi’ medium than in the cells in ‘–Pi’medium. The rate of degradation estimated from the rate of releaseof ¹⁴CO₂ from labelled purines and pyrimidines indicated thatdegradation of uridine was significantly reduced in the cellsin ‘+Pi’ medium, but no significant difference wasfound in the degradation of adenine, adenosine and uracil. Thepossible role of Pi in the control of the biosynthesis of nucleotidesand in the degradation of uridine is discussed. Catharanthus roseus, Madagascar periwinkle, suspension culture, inorganic phosphate, nucleotides, purines, pyrimidines, biosynthesis, degradation     

Developmental rates of the copepods Calanus australisand Calanoides carinatus in the laboratory, with discussion of methods used for calculation of development time

The copepods Calanus australis and Calanoides carinatus developedfrom egg to adult in 20.3 and 18.3 days respectively at 15.5?Cand 16.0 and 12.0 days at 19.5?C. For both species the durationof the first two naupliar stages was short, <1 day. The thirdnaupliar stage was prolonged in C.australis but short in C.carinatus. Isochronal development was approximated from fourthnauplius through third copepodite; fourth and fifth copepoditestages were relatively long. Only female C.australis were produced;60% of the C.carinatus were female. Equiproportional developmentwas found for C.carinatus but not for C.australis. For bothspecies the variance in stage duration was established at thethird nauplius then remained unchanged through the older stages.In calculating developmental rates several commonly used methodswere compared. The method of ‘first appearance of an individualof a given stage’ and ‘mean time of appearance ofa stage’ both yielded estimates of development time thatwere 10–15% faster than the more commonly used methodof ‘median development time’. We suggest that allfuture work on developmental rates of copepods should use astandardized method for the calculation of stage-specific developmentalrates and that ‘median development time’ be themethod of choice. ³Present address: Marine Sciences Research Center, SUNY, StonyBrook, NY 11794-5000, USA