THE LIFE-CYCLE AND REPRODUCTIVE ACTIVITY OF ACHATINA FULICA (BOWDICH) IN LABORATORY CULTURE

The life-cycle, growth characteristics and reproductive activityof Achatina fulica were studied in laboratory culture. Six generationshave been completed. Sexual maturity is reached as early as5 months of age, with a peak in egg production between 210–270days. Egg clutches contain 100–200 eggs which hatch synchronouslywithin a 24-hour period. The incubation period (days betweenoviposition and hatching) was determined exactly. The rangeof incubation times was 1–25 days, due to a variable degreeof ovoviviparity exhibited by the snail. The success of laboratoryculture provides a basis for experimental studies in developmentalneurobiology utilizing Achatina fulica. ^*Present address and to whom correspondence should be addressed:Jerry Lewis Neuromuscular Research Center, UCLA School of Medicine,Los Angeles, California 90025 U.S.A. (Received 14 February 1983;     

The effect of salinity and temperature on the larval development of Mithrax caribbaeus Rathbun, 1920 (Brachyura: Majidae) reared in the laboratory

Larvae of Mithrax caribbaeus were reared in the laboratoryin a factorial experiment employing three temperatures (22,25 and 28°C) and three salinities (32, 35 and 38). Survivaland duration of larval stages were recorded. Ovigerous femalesof M.caribbaeus were collected from the south-eastern coastof Margarita Island, Venezuela, and maintained in individualaquaria until hatching. Eggs from three of the females hatchedin the laboratory. Larvae from each hatching were subdividedinto groups of 10 and reared in plastic bowls containing 200ml filtered and UV-irradiated sea water at different temperature–salinitycombinations. Larvae were transferred daily to clean bowls withnewly hatched Artemia nauplii, and the number of molts and mortalitywithin each bowl was recorded. Complete larval development ofM.caribbaeus occurred under all experimental conditions. Salinityhad the greatest effect on percentage survival of each larvalstage and complete development up to the first crab stage. Thefirst zoeal stage exhibited the highest survival rate. Maximumsurvival for this stage occurred at 25°C, 32–35. Survivalin the second zoeal stage and the megalopa was affected onlyby salinity. Effects of temperature and salinity on survivaldecreased with advance in development. The duration of the twozoeal stages, the megalopa, and development to the first crabstage showed a gradual reduction with increasing temperature.Salinity showed an effect on the duration of zoeal stages butnot on the megalopal stage. Development from hatching to thefirst crab stage required 8–18 days, depending on thetemperature–salinity combination, and was inversely relatedto temperature, averaging 14.3 days at 22°C, 11.8 days at25°C and 9.2 days at 28°C.     

GROWTH AND REPRODUCTION OF THE MINUTE LAND SNAIL PUNCTUM PYGMAEUM (DRAPARNAUD)

Reproductive characters and growth of Punctum pygmaeum wereinvestigated under laboratory conditions. Eggs were laid singlyat intervals of 2–8 days. Egg size averaged 0.41 by 0.50mm. Due to a variable period of egg retention, newly depositedeggs contained differently developed embryos resulting in anincubation period varying from 1 to 34 days. Each snail on averagelaid 6.0 eggs (range 1–16 eggs) during its life. Egg productionrate and hatching success in individuals kept in isolation werethe same as in individuals kept in pairs. Hatchlings measured0.49 mm in shell breadth. Snails grew throughout their life,but the growth rate declined significantly at a shell breadthof 1.3–1.4 mm, the point at which the onset of sexualmaturity occurred. Comparison of reproductive characters ofsnails living in leaf litter revealed that very small-sizedspecies produce few, but in relation to their shell size largeeggs, which they oviposit singly. ^*Present address: Zoological Institute, University of Basel,Rhein-sprung 9. CH-4051 Basel, Switzertand (Received 23 May 1988; accepted 11 July 1988)     

Regeneration from Rhizome Fragments of Agropyron repens (L.) Beauv. III. Effects of Nitrogen and Temperature on the Development of Dominance Amongst Shoots on Multi-node Fragments

Not all buds developed equally when 7-node rhizome fragmentsof Agropyron repens (L.) Beauv. were incubated in the dark at23 °C. Instead, after an initial flush of several shoots,buds were inhibited in a highly ordered sequence to leave onlyone dominant shoot growing. Applying an exogenous supply ofnitrogen KNO₃) early during this sequence increased the meanshoot lengths and delayed the onset of dominance. Additionally,the application of nitrogen after eight days incubation alteredthe sequence of shoot growth such that, in some instances, smallrapidly-growing basal shoots ‘dominated’ largerand more slowly-growing apical ones. Dominance (correlativeinhibition) was maintained in untreated fragments for up to383 days Numbers of active budsand shoot extensionrate weremaximal intherange 13°to 23 °C where dominance was establishedwithin 30 days. Incontrast only 6 per cent of rhizome fragmentskept at 33 °C had dominant shoots after 65 days. At 3 °Cshoot growth was so slow that dominance was not permanentlyestablished within 150 days. Numbers ofactive budsand shoot extensionrate weremaximal intherange 13° to 23°C where dominance was establishedwithin 30 days. Incontrast only 6 per cent of rhizome fragmentskept at 33 °C had dominant shoots after 65 days. At 3 °Cshoot growth was so slow that dominance was not permanentlyestablished within 150 days It is suggested that the effects of nitrogenand temperatureon dominance in multi-noderhizome fragments can be interpretedin terms of competition for nutrients between shoots, and theantagonistic effects of nitrogen on an auxin-mediated inhibitionby the dominant shoot.     

Effect of temperature and food concentration on post-embryonic development, egg production and adult body size of calanoid copepod Eurytemora affinis

Post-embryonic development time, egg production rate and adultbody size of calanoid copepod Eurytemora affinis from Lake Ohnuma,Japan, were determined under six temperature-food conditions(10³,5 x 10³, 10⁴ and 5 x 10⁴ cells ml^–1 at 15°C,5 x 10⁴ cells ml^–1 at 10and20°C) in the laboratory.The measured parameters varied with both temperature and foodconcentration. Development time from hatching to adult femalewas 9.2, 11.4 and 22.8 days at 20, 15 and 10°C respectively,at the highest food concentration. The males developed to adultat one to two days earlier than the females. An effect of foodshortage on development time occurred at the lowest food concentration.This development time was 24.8 days even at 15°C, beingtwice as long as that at the highest food concentration. Prosomelength of these food-limited females was approximately 75% ofwell-fed ones, which reduced by only 10% with increasing temperaturefrom 10 to 20°C. Clutch size (C, eggs clutch^–1) ofwell-fed individuals depended on prosome length of the adultfemale (L, mm), and was expressed as an equation: C = 65.2 L³⁸³. Clutch size of individuals reared at less than 10⁴ cellsml^–1, however, mostly laid below the estimated curve,especially at the lowest food concentration being only 10% ofthat at the highest food concentration. These results suggestthat food availability is a more important factor affectingpopulation growth of E.affinis in Lake Ohnuma than variationof temperature.     

OBSERVATIONS ON THE GROWTH, REPRODUCTION AND FEEDING OF THE NUDIBRANCH ARMINA TIGRINA

One specimen of the sand-burrowing nudibranch Armina tigrinaRafinesque was collected from South Carolina in June. The specimendeposited a single egg mass of approximately 6500 white eggswhich developed into lecithotrophic veligers in 8 days at 23°C.Of the veligers which metamorphosed, 9 lived 4–5.5 months(i.e. the life cycle was subannual). Eight individuals reachedsexual maturity in about 80 days. Copulation began at a bodylength of 24 mm and oviposition at 28 mm. During the 1.5 monthegg-laying period, each individual laid 2–4 wavy egg masseswith 2000–7000 eggs per mass. Death followed oviposition.Average growth rate of fed and starved pre-ovipositional nudibranchswas 3.4% and 0.9% per day respectively. Growth rate of ovipositingspecimens was 0.6% or less per day. Based on average feedingrates, each nudibranch consumed approximately 1.6 g damp weightof Renilla reniformis (one small colony) between metamorphosisand egg laying and 6.1 g damp weight (about two average colonies)from egg laying to death. Feeding efficiency is presumably increasedby interlocking and abutting radular teeth. Egg diameters reportedfor Armina tigrina from South Carolina and Florida were 199µm and 82 µm respectively. This difference suggeststhe existence of two species of Armina or ne species with twogeographically separated developmental types. Current address: Marine Science Institute, Northeastern University,Nahant, Massachusetts 01908. U.S.A. (Received 10 April 1980;     

Embryonic, early larval development time, hatching mechanism and interbrood period of the sac-spawning euphausiid Nyctiphanes simplex Hansen

Females of the sac-spawning euphausiid Nyctiphanes simplex Hansenwere incubated under shipboard laboratory conditions to observethe embryonic and larval development time and hatching mechanism.Females ready to spawn have a pale pink ovary that extends fromthe back of the stomach to the first abdominal segment, fillingmost of the haemocoel. This species usually behaves as a totalspawner (produces one batch of oöcytes per cycle of theovary) leaving an ‘empty’ space in the cephalothoraxwhere the spent ovary is located. After spawning, the youngoöcytes mature and turn pale pink. The eggs do not havea measurable perivitelline space (PVS) in any of the embryonicstages (6.6 x magnification). The embryos hatch as nauplius(80–91 h after spawning, 16°C ± 1°C). Theyfurther develop into pseudometanauplii (PMN, 90–105 hafter spawning) and metanauplii (MN, 92–140 h after spawning)inside the ovigerous sac. The nauplius breaks the thin and fragilechorion by increasing the volume of the body and by using thefirst and second antennae. We call this an ‘expansion’hatching mechanism, the fifth distinct hatching mechanism observedso far among euphausiids. N. simplex larvae escape from theovigerous sac late in the MN stage (5 days after spawning),just a few hours before molting into calyptopis 1 (C1) (0.5–4h). This delayed release extends protection by the female, likelydecreasing the risk of predation or early cannibalism. Additionally,this may save energy by not swimming independently increasingthe time of not return if the calyptopis does not find favorablefeeding conditions. Females are not ready to spawn again untilat least two days after the previous batch of embryos leavesthe ovigerous sac. The interbrood period (IBP) observed rangedbetween 7 and 15 days at 16–18°C. This IBP is aboutone-fourth to half than was previously assumed for this speciessuggesting a significant underestimation of the fecundity ofthis species. N. simplex hatching success usually was 100%,except for a few females with all of their embryos dying duringembryonic development. Other females either molted before releasingthe embryos, or the oöcytes were spawned unfertilized (0%hatching success), particularly during winter conditions. Efficienthatching and late free-swimming strategy may partially explainwhy this species is the most abundant neritic euphausiid inthe southern part of the California Current System (CCS) andin the Gulf of California.     

Growth and development of Neocalanus flemingeri/plumchrus in the northern Gulf of Alaska: validation of the artificial-cohort method in cold waters

In situ growth and development of Neocalanus flemingeri/plumchrusstage C1–C4 copepodites were estimated by both the artificial-cohortand the single-stage incubation methods in March, April andMay of 2001–2005 at 5–6°C. Results from thesetwo methods were comparable and consistent. In the field, C1–C4stage durations ranged from 7 to >100 days, dependent ontemperature and chlorophyll a (Chl a) concentration. Averagestage durations were 12.4–14.1 days, yielding an averageof 56 days to reach C5, but under optimal conditions stage durationswere closer to 10 days, shortening the time to reach C5 (fromC1) to 46 days. Generally, growth rates decreased with increasingstage, ranging from 0.28 day^–1 to close to zero but weretypically between 0.20 and 0.05 day^–1, averaging 0.110± 0.006 day^–1 (mean ± SE) for single-stageand 0.107 ± 0.005 day^–1 (mean ± SE) forartificial-cohort methods. Growth was well described by equationsof Michaelis–Menten form, with maximum growth rates (G_max)of 0.17–0.18 day^–1 and half saturation Chl a concentrations(K_chl) of 0.45–0.46 mg m^–3 for combined C1–3,while G_max dropped to 0.08–0.09 day^–1 but K_chl remainedat 0.38–0.93 mg m^–3 for C4. In this study, in situgrowth of N. flemingeri/plumchrus was frequently food limitedto some degree, particularly during March. A comparison withglobal models of copepod growth rates suggests that these modelsstill require considerable refinement. We suggest that the artificial-cohortmethod is the most practical approach to generating the multispeciesdata required to address these deficiencies.     

The Freezing Response of an Arctic Cushion Plant, Saxifraga caespitosa L.: Acclimation, Freezing Tolerance and Ice Nucleation

Cold hardiness in actively growing plants of Saxifraga caespitosaL., an arctic and subarctic cushion plant, was examined. Plantscollected from subarctic and arctic sites were cultivated ina phytotron at temperatures of 3, 9, 12 and 21 °C undera 24-h photoperiod, and examined for freezing tolerance usingcontrolled freezing at a cooling rate of 3–4 °C eitherin air or in moist sand. Post-freezing injury was assessed byvisual inspection and with chlorophyll fluorescence, which appearedto be well suited for the evaluation of injury in Saxifragaleaves. Freezing of excised leaves in moist sand distinguishedwell among the various treatments, but the differences werepartly masked by significant supercooling when the tissue wasfrozen in air. Excised leaves, meristems, stem tissue and flowerssupercooled to –9 to –15 °C, but in rosettesand in intact plants ice nucleation was initiated at –4to –7 °C. The arctic plants tended to be more coldhardy than the subarctic plants, but in plants from both locationscold hardiness increased significantly with decreasing growthtemperature. Plants grown at 12 °C or less developed resistanceto freezing, and excised leaves of arctic Saxifraga grown at3 °C survived temperatures down to about –20 °C.Exposure to –3 °C temperature for up to 5 d did notsignificantly enhance the hardiness obtained at 3 °C. Whenwhole plants of arctic Saxifraga were frozen, with roots protectedfrom freezing, they survived –15 °C and –25°C when cultivated at 12 and 3 °C, respectively, althougha high percentage of the leaves were killed. The basal levelof freezing tolerance maintained in these plants throughoutperiods of active growth may have adaptive significance in subarcticand arctic environments. Saxifraga caespitosa L., arctic, chlorophyll fluorescence, cold acclimation, cushion plant, freezing stress, freezing tolerance, ice nucleation, supercooling     

NATURAL HISTORY OBSERVATIONS ON THE BUSYCONINE WHELKS BUSYCON CONTRARIUM (CONRAD) AND BUSYCOTYPUS SPIRATUM (LAMARCK)

Several aspects of the natural history of the sympatric busyconinewhelks Busycon contrarium and Busycotypus spiratum were examinedalong the northwest Gulf coast of Florida. Field and laboratoryobservations were made on feeding rate, crawling speed, sizedistributions, growth rate and reproduction. The two specieswere similar in several respects. Both were slow-growing withgrowth occurring only above 20°C. Modal sizes for both specieshave markedly declined over the past two decades. Feeding ratesand crawling speeds were affected by seasonal temperature changes,being highest at intermediate temperatures. Both species copulatein late autumn to early winter, lay egg capsules in early spring,with hatching beginning in May. One major interspecific difference was observed; the crawlingspeed of B. spiratum was twice that of B. contrarium. This differencewas correlated with the larger foot of B. spiratum. (Received 20 January 1982;     

Effects of temperature and temperature acclimation on survival of zebra mussels (Dreissena polymorpha) and Asian clams (Corbicula fluminea) under extreme hypoxia

Following acclimation to 5°, 15° or 25°C for 14days, samples of 30 Dreissena polymorpha (zebra mussels) andCorbicula fluminea (Asian clams) were held in either aerated(control) or extremely hypoxic N₂ gassed water (PO2 < 3%of full air saturation). Mortality was negligible in all aeratedcontrols. Mean hypoxia tolerance in D. polymorpha ranged from3–4 days at 25°C to 38–42 days at 5°C. Hypoxiatolerance time of zebra mussels increased significantly withdeclining test temperature (P < 0.001) and increasing acclimationtemperature (P < 0.001). Larger zebra mussels were more tolerantthan smaller individuals. Asian clams were 2–7 times moretolerant of hypoxia than zebra mussels, surviving a mean of11.8 and 35.1 days at 25°C and 15°C, respectively, andwithout mortality for 84 days at 5°C, and were not influencedby temperature acclimation. At 25°C, larger specimens ofAsian clams were less tolerant of hypoxia than smaller individuals.Both species are amongst the least hypoxia tolerant freshwaterbivalve molluscs, reflecting their prevalence in well-oxygenatedshallow water habitats. Prolonged exposure to extreme hypoxiamay provide an efficacious control strategy, particularly forD. polymorpha (Received 12 January 1998; accepted 30 September 1998)     

VARIABILITY OF EGG CANNIBALISM IN THE LAND SNAIL HELIX ASPERSA IN RELATION TO THE NUMBER OF EGGS AVAILABLE AND THE PRESENCE OF SOIL

Egg cannibalism by hatchlings has been demonstrated in somepulmonate land snails; this behaviour is promoted by a highhatching asynchrony within the egg-batch. Under laboratory conditions,the percentage of new-born snails Helix aspersa having cannibalisedunhatched eggs was not influenced by the soil factor: about70% of them ingested one egg within their first four days oflife whether soil was present or not. The propensity to eggcannibalism in hatchlings of H. aspersa increased with egg density.However, most of the new-born hatchlings consumed a single eggduring the four days following hatching, and only exceptionallytwo. The consumption of one egg increased the snails wet weightby 38.7% within four days. A weak ingestion of soil componentsalso occurred, but it induced a growth that was three-timesless than that due to the consumption of an egg. In addition,the survival of newly hatched snails maintained under non-dehydratingthermohygrometric conditions was high, even when they were submittedto four days food-deprivation. (Received 22 July 1999; accepted 24 November 1999)     

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.     

Summer reproduction of the planktonic copepod Calanus sinicus in the Yellow Sea: influences of high surface temperature and cold bottom water

We have observed that Calanus sinicus retreated from neriticareas in the Yellow Sea and concentrated in the Yellow Sea ColdBottom Water (YSCBW) area in summer. To investigate the summerreproductive strategy of C. sinicus in this situation, effectsof high temperature on reproduction and hatching, as well asgeographical variation of in situ egg production rate, werestudied by onboard incubation in August 2001. Diel verticalmigration (DVM) of females was investigated within and outsidethe YSCBW, respectively. Onboard incubation at 27°C (i.e.surface temperature) resulted in lower fecundities than thatat 9.8 and 12°C (i.e. bottom temperature inside and outsidethe YSCBW) together with decreased hatching rates and increasednaupliar malformation. Egg production was more active at stationsoutside the YSCBW than inside, where chlorophyll-a concentrationwas also relatively low. Females inside the YSCBW underwentDVM although they rarely entered the surface layer, but DVMwas not observed outside the YSCBW. We conclude that surfacetemperature in summer has deleterious effects on C. sinicusegg production and hatching, and that it cannot reproduce successfullyover the whole area. Inside the YSCBW, egg production is depressedby low food availability, while females outside suffer fromhigh temperatures because of strong vertical mixing.     

Development, growth and egg production of Centropages abdominalis in the eastern subarctic Pacific

Centropages abdominalis is a neritic, omnivorous, temporallyabundant copepod present throughout the subarctic Pacific andits marginal seas. The two main objectives of this study wereto determine how temperature influences the development of C.abdominalis and whether growth rates of in situ populationsmay be limited by available food. At 6.9°C, median developmenttime from eggs laid to 50% adults was 42 days and the averageweight-specific somatic growth rate was 0.17 day^–1. At4.6°C, median development time to adult was 59 days (projected)and growth rate averaged 0.08 day^–1, suggesting that 4.6°Cmay be approaching the lower temperature for development andgrowth in this species. The functional relationship betweendevelopment time and temperature was established over the temperaturerange in which this species occurs. The in situ adult growthrates between 10 and 13°C averaged 0.14 day^–1 andwere generally lower than the laboratory-reared juvenile growthrates, which may indicate that adult C. abdominalis are foodlimited in the field during summer and autumn.     

Comparative Thermal Physiological Ecology of Syntopic Populations of Cacama valvata and Tibicen bifidus (Homoptera: Cicadidae): Modeling Fitness Consequences of Temperature Variation

SYNOPSIS. This paper develops a model based on egg-laying ratesand female oviposition temperature preferences in two speciesof cicada, Cacama valvata and Tibicen bifidus, from a centralNew Mexico desert grassland habitat. Output from the model indicatesthat C. valvata achieves maximal daily egg production (eggsfemale^–1 day^–1) on days when maximum shade ambienttemperatures reach 41°C; the corresponding value for T.bifidus is 33°C. These differences correlate with the thermalregime experienced by each species in its respective typicalhabitat. Simulations of the effects of variation in mean habitatambient temperature on egg production demonstrated that knowndistributional limits for T. bifidus correspond to thermal conditionsthat reduce daily egg production by only about 5–10% relativeto long-term means at the study site. The same is true for C.valvata only in lower-ambient temperature habitats. In higher-temperaturehabitats, C. valvata exhibits an unusual plasticity in the timingof adult activity and reproduction that allows it to occupya much wider geographic range than T. bifidus. Contrary to expectations,frequency distributions of predicted daily egg production rateswere negatively skewed in each species' respective ‘typicalhabitat’, and Gaussian only in thermally marginal habitats.The findings are discussed in the context of attempts to modelpopulation- and community-level effects of climatic change.     

STUDIES ON THE CONDITIONS FOR GIBBERELLIN ASSAY USING RICE SEEDLING

Of many varieties of rice plant tested, a dwarf mutant "Tamanishiki"was the most suitable material for gibberellin assay. It respondsto neither kinetin nor indoleacetic acid in the concentrationrange from 0.01 to 10 µg/l. Seeds were sterilized withsodium hypochiorite solution (chlorine content, one per cent)for one hour and soaked in water for 2 days. Germinating seedsselected for uniformity were then placed in test tubes containing1–3 ml of test solution, and the length of the 2nd leafsheath of the seedlings was measured after 7 days of incubation.The best conditions for the incubation were: pH of the testsolution, 4; temperature, 30°; continuous illumination ofintensity stronger than 50 lux. Under the best conditions statistically significant growth promotionwas found with 7 seedlings grown in one ml of the test solutionwhich contained 0.001 µg gibberellin A_s In double logarithmicplot, the growth promotion over control increased linearly withincreasing gibberellin concentration up to 1 µg in oneml test solution. (Received March 7, 1963; )     

Endosulfan-enhanced crest induction in Daphnia longicephala: evidence for cholinergic innervation of kairomone receptors

Daphnia iongicephala were reared from early embryogenesis inthe presence or absence of crest-inducing kairomones releasedby Anisops gratus (Notonectidae) and from birth in one of fiveconcentrations of the organochiorine pesticide, endosulfan (0,0.1, 1.0, 10 or 100 g 1^–1 The morphologyof the daphnidswas measured 3 days after birth and on production of the firstbrood of eggs. The reproductive parameters, first brood size,age at first reproduction, mean egg volume and total egg volume,were also measured. Endosulfan significantly induced crest developmentin 3-day-old daphnids at 0.1, 1.0 and 10 g ^1– in thepresence and absence of Anisops kairomone, although crest sizein the absence of kairomone was only marginally greater thancontrols. A concentration of 10 pg 1^–1 endosulfan significantlyenhanced crest growth of kairomone-exposed daphnids at maturity.The Anisops kairomone alone induced a large crest in D.iongicephola,reduced first brood size, mean egg volume and total egg volume,and increased age at maturity. The coefficient of variationof mean egg volume was significantly reduced by Anisops kairomone.It is hypothesized that endosulfan enhances crest developmentbyinhibition of .     

Environmental Control of Flowering in some Northern Carex Species

The environmental control of flowering in some arctic-alpineCarexspecies has been studied in controlled environments.Carex nigra,C. brunnescens, C. atrata, C. norwegica andC. serotina all hada dual induction requirement for flowering. In all exceptC.nigra either low temperature (12 °C or lower) or short days(SD) over a wider range of temperatures were needed for primaryfloral induction and inflorescence formation. InC. nigra primaryfloral induction took place in SD only (9–21 °C),8–10 weeks of exposure being required for a full response.In all these species long days (LD) were required for, or stronglypromoted, culm elongation and inflorescence development (secondaryinduction). Quantitative ecotype differences in both primaryand secondary induction were demonstrated. Unlike the otherspecies,C. bicolor proved to be a regular LD plant which requiredLD only for inflorescence initiation and development. In allspecies leaf growth was strongly promoted by LD, especiallyin the higher temperature range (15–21 °C). In SDand temperatures below 15 °C the leaves became senescentand the plants entered a semi-dormant condition which was immediatelyreversed by LD. The results are discussed in relation to growthform and life history of shoots. Carex ; dual induction; ecotypic diversity; flowering; growth; photoperiod; sedges; temperature     

Effect of growth temperature on reserve mobilization and hydrolytic enzyme activities in Vigna mungo cotyledons

Seeds of Vigna mungo were allowed to germinate at 27, 18 and15°C, and time-course changes of hydrolytic enzyme activitiesand the mobilization rate of reserve components in cotyledonswere studied. The seeds germinated at 27 and 18°C grew normally,whereas the growth at 15°C was markedly retarded. In cotyledonsof seedlings grown at 27 and 18°C, amylolytic and proteolyticenzyme activities increased at early stages of growth and therates of starch and protein mobilization changed correspondingto the hydrolytic enzyme activities. At 15°C the enzymeactivities increased gradually during the experimental periodof 16 days, but the reserves in cotyledons remained almost unchangeduntil the end of the experimental period. Changes of zymogram patterns of amylolytic and proteolytic activitiesin cotyledons of seedlings grownat 27, 18 and 15°C wereexamined using polyacrylamide gel electrophoresis. The intensitiesof a main band of a-amylase and at least two bands of protease(gelatin-hydrolyzing activity) increased concurrently with invitro activities of amylolytic and proteolytic enzymes. At leastthree bands of starch phosphorylase were present in cotyledonsat early stages of germination and their intensities decreasedduring the growth of seedlings at 27, 18 and 15°C. (Received June 4, 1980; )