Effects of continuous illumination on the rhizome of Caulerpa prolifera

Caulerpa plants were grown under a 12-hr light and 12-hr dark(12L-12D) regime for 8 days followed by 8 days of continuouslight (24L-0D). Under both light regimes the elongation of therhizome was by means of "tip growth". However, the rate of rhizomeelongation in 24L-0D regime (10.9 mm/day) was higher than thatof 12L-12D regime (7.9 mm/day). Jn the region of 1.5 mm fromthe tip, the RERE (relative elemental rate of elongation) under24L-0D and 12L-12D regimes were respectively 4% and 3% elongationper hr. Under 12L-12D photoperiod the subapical part of therhizome exhibited distinctive oscillation: bending upward duringthe light period or at the time of rhizoid cluster initiation,and in the dark becoming relatively straight except at the timeof cluster initiation. No such distinctive oscillation was observedin continuous light. ¹ Report of work supported by research grant GB-7885 from theNational Science Foundation, and in part by Research Councilof Rutgers University. (Received June 8, 1971; )     

THE INITIATION AND ELONGATION OF RHIZOID CLUSTERS IN CAULERPA PROLIFERA

Under improved environmental conditions the average rate of elongation of the rhizoid cluster was 5.2 mm/day in the first 3 days. The rate decreases thereafter and is close to zero around 5–6 days after initiation. The elongation, like that of the rhizome, is chiefly by means of “tip-growth.” The presumptive site of the initiation is 1.3–1.7 mm from the rhizome tip. Under present experimental environment, the presumptive time of the initiation was mainly at 1 to 3 hr after the beginning of the light period. Initiation in the dark period was less frequent, and little or no initiation in the middle and later parts of the light period was observed. The average plastochron of the cluster was 0.91 day. The rate of elongation of the rhizoid cluster was less variable than that of the rhizome. Hence, the slope of calculated regression line from the plot, the cluster length vs. its distance from the rhizome tip, is steeper when the rhizome grows slower (4.9–5.8 mm/day) and less steep when the rhizome grows faster (7.3–8.9 mm/day). In spite of some variation in the slope of the regression line, the intersection between the line and X-axis remains about the same. The application of information on the presumptive site and presumptive time of the rhizoid cluster initiation to a developmental study of micro-events taking place prior to the morphological differentiation is proposed.     

Light dependency of the mating process in Closterium acerosum

Sexual cell division and activation of gametangial cells forconjugation in Closterium acerosum were induced by light. L₂₀₀cells conjugated at maximum level under the following conditions;(i) a light intensity higher than 1,000 lux in a 16-hr lightand 8-hr dark regime and (ii) an illumination time longer than12 hr at 3,000 lux. L₂₀₀ cells also conjugated under continuousillumination at 3,000 lux. The action spectrum for the activation of gametangial cellshad peaks around 450, 611 and 665 nm. 3-(4'-Chlorophenyl)-l,l-dimethylurea (CMU) inhibited the accumulationof carbohydrates and sexual cell division at 10^–5 M andthe activation of gametangial cells for conjugation at 10^–4M. (Received August 15, 1977; )     

QUANTITATIVE STUDY OF DEVELOPMENT OF THE GIANT COENOCYTE,CAULERPA PROLIFERA

The lengths of rhizomes, rhizoid clusters, and leaves of many plants of Caulerpa prolifera cultured under controlled conditions were measured daily. Their rates and patterns of growth were analyzed mathematically with the aid of an electronic computer. All organs elongated at the rate of ca. 4.4 mm per day. Rhizomes elongated linearly for more than 2 weeks, and curvilinear regression usually did not improve the fit significantly. Rhizome elongation is apical. Every 1.18 days, on the average, a rhizoid cluster developed on the lower surface of each rhizome. The length of the younger rhizoid clusters shows a linear relationship to their distance from the rhizome tip. Little or no significant improvement of fit resulted from fitting polynomials of the 2nd through 4th degree. Accordingly, by extrapolating the straight line to zero rhizoid length, we calculated the presumptive site of rhizoid initiation to be 0.84 mm from the rhizome tip. The rate and distribution of growth were compared to those of other coenocytes and of multicellular plants.     

A Short Day Photoperiodic Response in Constantinea subulifera

SYNOPSIS. Constantinea subulifera, a perennial red alga witha bushy type growth, uses a short day (long night) photoperiodicresponse to initiate a new blade at the tips of several stipesin September to October. These blades complete the lag phaseof their growth during the winter via a food transfer from theold blade. Under a 9L–15D photoperiod it requires 21–28 daysto initiate a new blade. The critical photoperiod is 11–12hr. This is a phytochrome-mediated response which can be negatedby a low quantum dose light break of red or blue light in themiddle of a 16-hr dark period. Blades will initiate and growin complete darkness. The initiation of new blades in the fall and their slow growththroughout the winter (lag phase) gives Constantinea subuliferaan advantage in capture of habitat space.     

Morphological and physiological characterization of IAA-less-sensitive and IAA-sensitive phases in rooting of Azukia cuttings

In disbudded epicotyl cuttings taken from light grown 5-dayold Azukia angularis Phaseolus angularis) seedlings, all adventitiousrootlets appeared on the second day of incubation. No root primordiawere observed within the first 24 hr and no increase in thenumber of roots occurred after 48 hr. Puromycin (5.5?10^–5M), p-fluorophenylalanine (1?10^–3M),2-thiouracil (2.3?10^–4M) and 2,6-diaminopurine (2?10^–5M)inhibited rooting when applied to cuttings on the second day,but showed no inhibition when applied on the first day. Unlike these inhibitors, pyrithiamine (7.2?10^–5M) inhibitedrooting when it was applied to cuttings on the first day. A rooting promoting effect was observed with actinomycin D (2.4?10^–6M),2,4-dinitrophenol (3?10^–5M) and p-fluorophenylalanine(1?10^–4M) applied to the cuttings on the first day, whereasindoleacetic acid (1.7?10^–4M) showed its promoting effectmost effectively on the second day. ¹Contribution No. 17 from the Botanical Gardens, Faculty ofScience, University of Tokyo, Tokyo, Japan. (Received June 4, 1969; )     

Phototropism in a red alga, Griffithsia pacifica

In the red alga, Griffithsia pacifica, shoot portions of a plantare positively phototropic and rhizoids are negatively phototropic.We have studied the phototropic response of rhizoids which elongateby tip growth. For 45 min after the beginning of unilateralillumination a rhizoid grows straight, then phototropic curvaturebegins and continues rapidly until the rhizoid is growing awayfrom the light. Curvature is 70–80% complete after 3 hr.If the unilateral stimulus is given for a short time (15 min),curvature again begins at 45 min. However, within an additional30–45 min the rhizoid stops growing away from the lightand wanders back towards its original direction of growth. Phototropismis elicited by light of wavelengths from 350 nm to 500 nm; inlight of wavelengths above 550 nm, little, if any, responseoccurs. ¹Present address: Division of Natural Sciences, University ofCalifornia, Santa Cruz, California 95064, U.S.A. (Received December 10, 1976; )     

Diurnal change in temperature sensitivity gibba G3 induced by acetylcholine in continuous light

When Lemna gibba G3 was in contact with 10^–5 M Ach oreserine, floral response to chilling changed diurnally under[24(0)], as was the case for control cultures exposed to [16(8)].On the other hand, with a rise in temperature, the min-[24(0)]decreased discontinuously in 24-hr units in Ach cultures subjectedto [24(0)], as did the min-[16(8)] in control cultures. Thusin the presence of Ach or eserine, this long-day plant tookthe continuous light regime, i.e. [24(0)], for another typeof long-day regime consisting of a long light period and a shortdark period, e.g. [16(8)]. In Ach cultures, the lower limitof the min-[24(0)] (72 hr) was attained at 22.5?C and remainedunaltered at the higher temperatures examined. The min-[16(8)]for control cultures, however, known to reach its lower limit(48 hr) at 26?C. Sodium lauryl sulphate (10^–5 M) and ouabain(10^–6 M) also caused a similar diurnal change in temperaturesensitivity of 24(0)] cultures. We surmised that exogenous Ach or inserted dark period modifiesthe relative rates chemical and physical component reactionsinvolved in the floral evocation processes, resulting in therhythmical floral response to chilling. (Received August 1, 1974; )     

Phototropism in Vaucheria geminata I. The action spectrum

A xanthophycean coenocytic alga Vaucheria geminata exhibitedtypical tip-growth. The growth pattern was closely related tothe external L-D regime. Under a 12 L-12 D regime, the algastarted to grow at the beginning of the dark period and ceasedto grow at the end of the light period; while under a 24 L-0D, it grew at a constant rate ranging from 100 to 200 µm/hr.The algaa lso exhibited positive phototropism. Using the half-side-illuminationmethod the bending process was analyzed. The process followedWeber-Fechner's law and Bunsen-Roscoe's law. The action spectrumfor the phototropism was determined, and results indicated thatonly blue light was effective. The hyaline cap, which was foundonly at the growing tip, shifted to the illuminated side ofthe tip prior to bending. (Received December 20, 1974; )     

Spectral Dependence of Night-break Effect on Photoperiodic Floral Induction in Lemna paucicostata 441

A single dark period of longer than 8 hr induced flowering inLemna paucicostata 441 cultured in E medium. Monochromatic lightsof 450, 550, 650 and 750 nm with a half-power bandwidth of 9nm given for 10 min at the 8th hour of a 14-hr dark period inhibitedflowering. The fluence rates required for 50% inhibition were10, 0.5, 0.1 and 3 µmol m^–2. sec^–1, respectively.When applied between the 4th and the 10th hour of the dark period,lights of 450, 550 and 650 nm were inhibitory showing a maximumeffect at the 8th hour. But 750-nm light completely inhibitedflowering when applied at any time during the first 8 hr ofthe dark period. The inhibitory effect of 750-nm light givenat the beginning of the dark period was totally reversed bya subsequent exposure to 650-nm light, and the fluence-responsecurves for the effect of 750-nm light given at the 0, 4th and8th hour were essentially the same. This suggests that the presenceof P_FR is crucial for the floral initiation throughout the first8 hr of the inductive dark period. The role of phytochrome inthe photoperiodic flower induction of L. paucicostata is discussed. (Received January 4, 1982; Accepted March 19, 1982)     

Induction of DNA synthesis and callus formation from tuber tissue of Jerusalem artichoke by 2,4-dichlorophenoxyacetic acid

Cellus induction was observed from Jerusalem artichoke tubertissue on a synthetic medium containing 2,4-D at 10^–6,10^–5 (optimum conc.) and 10^–4 M. The first DNA synthesis(thymidine incorporation) was observed only at 2,4-D concentrationsof 10^–5 to 10^–4M. In 10^–5 M 2,4-D treatedtissue, DNA synthesis increased after a 20 hr lag and reacheda maximum at 36 hr, after which it decreased. Actinomycin Dand 8-aza-guanine; inhibitors of RNA synthesis, inhibited DNAsynthesis completely. 2,4-D caused the characteristic changesin RNA and protein syntheses. In comparison with the control,RNA and protein syntheses were first repressed then inducedbefore the peak of DNA synthesis. Treatment with cycloheximide(10^–4M) for one hour before inoculation inhibited proteinsynthesis completely for 12 hr; consequently DNA synthesis wasalso delayed. The results suggest that RNA and protein synthesesneeded for callus induction are regulated by 2,4-D in the firstDNA synthesis. (Received July 19, 1973; )     

Removal by chemicals of photoperiodic light requirements of Lemna gibba G3

Both the initial and the terminal 1 hr portions of the subjectiveday fraction, namely the L1- arid L2-phases, of a 24 hr daymust be illuminated in order for the day to be perceived asa long day in the min-LD determination by the long-day plant,Lemna gibba G3 (9). The light requirement of the L1-phase wassatisfied by a 10 min red light pulse given at the beginningof the phase. The red light effect was erased by a subsequent10 min far-red light, indicating phytochrome-mediated processesoccurring in the L1-phase. The light requirement of the L2-phasewas satisfied by blue or far-red light given during the terminal10 min period of the phase; there was no indication of phytochromeinvolvement. The light action on the L1-phase was replaced by10^–5 M of cyclic AMP or 10^–7 M of DL-isoproterenol.The isoproterenol action was antagonized by 10^–7 M ofDL-propranolol. Cyclic AMP (10^–5 M) combined with salicylicacid (10^–6 M), which can remove the light requirementof the L2-phase (10), rendered a completely dark day physiologicallyequivalent to a long day. Acetylcholine (10^–5 M) exertednyctomimetic action on the L1-phase of the second light day.The action of acetylcholine was antagonized by cyclic AMP (10^–5M). The L2-phase required no light in the presence of 10^–7M of DL-propranolol, and this propranolol action was not affectedby isoproterenol. These findings suggest changes in membranepermeability caused by the light given during the L1- and L2-phases. (Received July 7, 1976; )     

Environmental and hormonal control of turion formation in Myriophyllum verticillatum

The turions of Myriophyllum verticillatum, an aquatic vascularplant, develop in the fall and function in propagation and dispersalas well as in over-wintering. Experiments with controlled evnironmentsindicate that both temperature and photoperiod regulate turionformation. Turions can be induced at 15°C or lower, butnot at 20°C. At 15°C, turions form in both 8- and 12-hrdays, but not in 16-hr days. Plants collected in early springdo not form turions readily in response to short days unlesspreviously exposed to long days; thus, turion formation is along-day-short-day response. This combination of photoperiodand temperature requirements probably prevents turion developmentin early spring when the temperature and photoperiod are similarto those in the fall. Treatment of plants with ABA (10^–5M) enhances turion development under marginally inductive conditions(12-hr days at 15°C) but cannot induce it under long days.On the other hand, the cytokinin benzyladenine (10^–5 M)blocks turion formation. GA3 (10^–5 M) and AMO-1618 (10^–5M) exert only small qualitative effects on turion development,while IAA (10^–5 M) retards it. During turion development,the level of ABAlike activity and of one or two unidentifiedinhibitors increases. Cytokinin activity decreases at the startof turion formation, increases during development, then decreasesat abscission. Thus two lines of evidence suggest that a decreasein cytokinin activity and an increase in acidic inhibitor activityplay important roles in turion induction. ¹Present address: Biological Station, University of Michigan,Ann Arbor, Michigan 48109, U. S. A. (Received December 1, 1975; )     

Population structure and swarm formation of the cyclopoid copepod Dioithona oculata near mangrove cays

The cyclopoid copepod Dioithona oculata forms swarms in water>30 on deep among prop roots of red mangroves (Rhizophoramangle) which fringe protected areas of two lagoonal cays, TwinCays, Belize. During 7 of 8 months surveyed by in situ observation,swarms were present but differed in size from small cylindricalswarms (5–10 cm diameter) to bands extending up to 1200m Swarms were never observed at night Swarms formed at dawnwhen light intensities reached an average value of 13.82 (logioquanta cm^–Abstract. s^–1) and dispersed at dusk atsimilar intensities Swarms observed in June formed earlier anddispersed later in the day than swarms observed in January,their swarming behavior followed seasonal changes in light intensityMean dioithonan density in swarms (10 ml^–1) was much higherthan the mean density (0 15 ml^–1) of non-swarming dioithonansaround mangrove prop roots. In open water 3–5 m away fromthe mangroves, mean dioithonan density was 7 9 x 10^–5ml¹ during the day, and 2 68 x10^–3 ml^–1 at nightSwarms were composed predominantly of adults and copepodid stagesIV and V, although younger copepodid stages could be presentNauplii were never present. The ‘average copepodid stage’for all 95 swarms sampled was 5 3, where 6 0 represents a swarmwith only adults In open water 3–5 m away from the mangroves,the youngest copepodids (stage one) dominated the dioithonanpopulation during the day. At night when swarms dispersed toopen waters, average copepodid stage was higher (3 5) comparedwith the day value (1.2) in open waters. Although densitiesin swarms were higher in June than January, average copepodidstage in June was higher (5 6) than that in January (4.9). Ahigher percentage of adults were females during June than January.Therefore higher densities did not result from increases ofsmaller stages in swarms, but perhaps changes in behavior orpopulation structure.     

Light, temperature and nitrogen as interacting factors affecting diel vertical migrations of dinoflagellates in culture

Diel vertical migrations of the marine dinoflagellates Gonyaulaxpolyedra Stein and Ceratium furca (Ehr.) Clap, et Lachm. werefollowed in a laboratory tube (2.02 m x 0.25 m) under a 12:12hlight:dark cycle. The effects of temperature stratification,two levels of surface irradiance and nitrogen depletion on patternsof vertical migrations were examined. At temperatures between22–26°C with small temperature gradients, both speciesmigrated at a rate of 0.7 –1.0 m h^–1. Steeper thermoclines(ca. 0.8°C 0.1 m^–1) with temperatures below ca. 20°Ccaused a marked decrease in swimming speed which resulted inaccumulations of cells in these thermocline regions. Under conditionsof nutrient sufficiency both algae migrated into the surfacelayers at irradiance values of over 1000 µE m^–2s^–1. Increasing nitrogen depletion caused the downwardmigration of both algae to commence progressively earlier inthe day and before the end of the light period. The earlierdownward migrations enabled a more complete descent throughthe thermocline. Nitrogen depleted cells of Gonyaulax continuedto undertake vertical migrations but avoided high irradiancesthus forming subsurface maxima at irradiance levels close to150 µE m^–2 s^–1. Ceratium cells which exhaustedboth inorganic nitrogen and phosphorus ceased to migrate accompaniedby a large change in cellular fluorescence.     

Studies on CN--insensitive respiration in plant roots III. Induction of CN--insensitive respiration with low concentrations of respiratory inhibitors

Induction of CN^–-insensitive respiration with low concentrationsof respiratory inhibitors was studied. If roots were treatedwith 10^–3 M CN^– for 96 hr, the plants died, whilethose treated with 10^–4 M CN^– showed healthy growth. O₂ uptake in untreated rice and wheat roots showed a negativeresponse to 10^–2 M CN^– to a considerable extent.On the other hand, pretreatment with 10^–4 M CN^–for more than 6 hr did not greatly affect respiratory rate,but made respiration insensitive to 10^–2 M CN^–.A similar induction of CN^–-insensitivity was also broughtabout with 10^–4 and 10^–3 M H₂S and 10^–4 MNaN₃. (Received July 6, 1971; )     

The vitamin B requirement of Phaeocystis globosa (Prymnesiophyceae)

In batch cultures of flagellates and non-flagellate cells ofPhaeocystis globosa, the biomass yield was significantly enhancedby the addition of a mixture of the vitamins thiamine (B1),cyanocobalamin (B12) and biotin (H). A bioassay with B1 andB12 using the non-flagellate cells of P.globosa showed thatthis prymnesiophyte is a B1 auxotroph. The bioassay also indicateda significant difference in growth rate between culture mediumwith 10 nmol l^–1 B1 (µ = 0.80 day^–1) and culturemedium with 10 nmol l^–1 B12 (µ = 0.52 day^–1).These findings are discussed in relation to the hypothesis thatcentric diatoms, through vitamin B1 excretion or B12 depletion,initiate Phaeocystis blooms. It is concluded, however, thatan alternative hypothesis, that diatoms provide a solid substratefor colony initiation, has more experimental support.     

Growth Analysis of Sweet Pepper (Capsicum annuum L.): 2. Interacting Effects of Irradiance, Temperature and Plant Age in Controlled Conditions

A growth analysis was carried out with sweet pepper plants grownin a phytotron. Irradiance conditions were: 0.84 or 3.25 MJm^–2 in 8 h, 1.67 MJ m^–2 in 16 h and 2.51 MJ m^–2in 24 h. Temperatures applied were 25 or 21 °C during thephotoperiod in combination with 25, 21 and 17 or 21, 17 and13 °C respectively during the nyctoperiod. Highest values for leaf area and total dry weight were foundwhen applying 1.67 MJ m^–2 in 16 h, followed by 3.25 MJm^–2 in 8 h, irrespective of the temperature regime. Continuousirradiance ultimately resulted in leaf drop. A reduction inthe day temperature decreased leaf area and total dry weight.At a day temperature of 25 °C the dry weight increased withdecreasing night temperature when applying 3.25 MJ m^–2in 8 h. At a day temperature of 21 °C leaf area and dryweight were reduced when 17 or 13 °C were applied duringa 16 h nyctoperiod. Values for relative growth rate, net assimilation rate, leafarea ratio and leaf weight ratio strongly decreased with advancingplant age. The effects of irradiance treatment on RGR and NARwere analogous to those on total dry weight while the reversepattern was observed for the LAR. A decrease in day temperaturedecreased the RGR. The effects of night temperature exhibitedstrong interactions with day temperature and photoperiod. Theinfluence of temperature on RGR was largely mediated throughchanges in the LAR. The latter parameter was highly correlatedwith the specific leaf weight. Capsicum annuum L., sweet pepper, growth analysis, irradiance, temperature, plant age     

The Influence of Seedling Size and Carbohydrate Status and of Photon Flux Density During Vernalization on Inflorescence Initiation in Onion (AIlium cepa L.)

Experiments were done in controlled conditions to investigatethe relationship of plant weight, leaf number and raising conditionsto inflorescence initiation in onion seedlings. Above a shootdry weight of 0.06 g the spring-sown cv. Rijnsburger could initiateinflorescences, whereas the autumn-sown cv. Senshyu semi-globeYellow needed to be heavier than 0.45 g. Plants raised at aphoton flux density of 200 µmol m^–2S^–1 anda temperature of 25 C required longer to initiate inflorescencesthan plants raised at 600 µmol m^–2S^–1 and17 C which had higher reserve carbohydrate content. The minimumleaf number for inflorescence initiation was larger for plantswith low reserve carbohydrate content. Photon flux densitiesof 50, 100, 200 and 400 µmol m^–2S^–1 duringvernalization at 9 C caused no differences in inflorescenceinitiation in plants previously raised at l7 C and 600 µmolm^–2S^–1 but the lowest photon flux density duringvernalization reduced initiation in plants previously raisedat 25 C and 200 µmol m^–2S^–1.     

Intercellular Transport and Cytoplasmic Streaming in Chara hispida

The correlation between the velocities of cytoplasmic streamingand of translocation of ¹⁴C-photosynthate and ³²P-phosphateassociated radioactivity has been investigated in whole plantsof the green freshwater alga Chara hispida L. Tracer was suppliedto the plant's rhizoid system in a split-chamber. The velocityof cytoplasmic streaming of 52±3.3 µm s^–1compares with 57±10 µm s^–1 found for ¹⁴C-transportand 32±20 µm s^–1 found for ³²P-transport.There was no indication of intercellular translocation at avelocity faster than visible streaming. Cytochalasin B inhibitedthe translocation of ³²P and cytoplasmic streaming. CytochalasinB becomes fully effective in inhibiting streaming and transportafter an incubation time of at least 5 h. Key words: Chara hispida, Cytoplasmic streaming, Intercellular transport