Autolysis Promotes the Extension Capacity of Zea mays Coleoptile Cell Walls in Response to Acid pH Solutions

The relationship between autolytic degradation of ß(1–3),(1–4)-D-glucanand acid pH-induced extension of isolated Zea mays cell wallshas been investigated using a constant-load extension technique.Acidic buffer (4.5) was able to induce an additional extension(E_a) on cell walls already extended at pH 6.8 buffer under a20 g-mass load, indicating that the additional extension (E_a)was the parameter that better represented the effect of thedifferent treatments on the mechanical properties of maize coleoptilecell walls. The additional extension in response to acidic pHwas higher when cell walls had been previously autolysed for24 h at pH 5.5. Furthermore, the acid-pH effect was dependenton the presence during the constant load extension of some thermo-labilefactors, suggesting the participation of expansins. Acid pHincreased E_a of native cell walls through an increase in theplastic extension (E_p) in agreement with a one step mechanismleading directly to irreversible (plastic) wall extension assuggested by Cosgrove (1977). The autolytic degradation of ß(1–3),(1–4)-D-glucan was also able to modify the mechanicalproperties of maize coleoptile cell walls increasing its elasticextension (E_e) in response to pH 4.5 buffer but that modificationonly leads to an increase in wall extension when expansins areactive, suggesting a cooperation between ß-glucanturnover and expansin action. (Received August 5, 1998; Accepted March 16, 1999)     

Behavioural discrimination of oilseed rape volatiles by the honeybee Apis mellifera L.

This study investigated the ability of the honeybee to discriminatebetween six compounds previously identified as oilseed rapefloral volatiles: linalool, 2-phenylethanol, methyl salicylate,benzyl alcohol, (E)-2-hexenal and 1-octen-3-ol. These componentswere tested individually or in a synthetic mixture for theirability to elicit the conditioned proboscis extension response.Three experiments were done: conditioning to the mixture atone concentration (1.0, 0.1 or 0.01 µg per component)and testing to the individual components either at the conditioningor at the other concentrations; conditioning to individual componentsand testing to the mixture (1.0 µg); conditioning andtesting to the individual components (1.0 µg). The resultsfrom the proboscis extension assay were then compared to thoseobtained from free-flying bees in a flight room. From the conditionedproboscis extension assay, a conditioning threshold level wasfound (0.1 µg for the mixture studied) below which a reliableconditioning could not be achieved. Recognition thresholds wereobserved: bees responded to concentrations ten-fold higher orlower than that used for conditioning. Responses to lower concentrationswere weaker, whilst responses were increased at concentrationshigher than the conditioning one. A hierarchy within the compoundstested was found, with linalool, 2-phenylethanol and methylsalicylate cueing mixture recognition more effectively thanthe other components. The ranking order of the six componentswas similar in both the conditioned proboscis extension andthe conditioned foraging behaviour in flight room. When conditionedand tested to the individual components, bees discriminateda learned odour from a number of others. However, the specificitylevel for the recognition of the learned odour varied accordingto the component, the most clearly discriminated being the compoundswhich were used by the bee in mixture recognition.     

赤松毛虫性信息素次要组分的鉴定——组分、电生理和田间效果

用带有极性和非极性毛细柱的气相色谱(GC)分析赤松毛虫Dendrolimus spectabilis性信息素腺体提取物,发现腺体中除含有已鉴定的性信息素(顺,反)-5,7-十二碳二烯醇(Z5,E7-12∶OH)外,还有微量的(顺,反)-5,7-十二碳二烯醛(Z5,E7-12∶Ald)和(顺,反)-5,7-十二碳二烯乙酸酯(Z5,E7-12∶Oac),三种成分以100∶5-6±5-4∶3-2±1-8的比例存在。使用气相色谱-质谱选择性离子检测法（GC-MS-SIM）分析赤松毛虫腺体提取物,发现腺体中确实含有微量的Z5,E7-12∶Oac和痕量的Z5,E7-12∶Opr。赤松毛虫腺体提取物的气相色谱和触角电位检测联用（GC-EAD）分析发现只有Z5,E7-12∶OH能激起EAD反应,然而使用较高剂量的标准化合物进行GC-EAD分析发现Z5,E7-12∶OH、Z5,E7 12∶Oac和(顺,反)-5,7-十二碳二烯丙酸酯(Z5,E7-12∶Opr)均能刺激起EAD反应,而Z5,E7-12∶Ald则不能。触角电位（EAG）剂量-反应关系研究表明,当剂量变化范围在0.01～1 μg时,雄虫触角对Z5,E7-12∶OH最敏感,对Z5,E7-12∶Oac和Z5,E7-12∶Opr次之。田间试验表明,由Z5,E7-12∶OH, Z5,E7-12∶Oac和Z5,E7-12∶Opr配制的三组分诱芯,其诱蛾量显著高于由Z5,E7-12∶OH组成的单组分或是它与其乙酸酯或丙酸酯组成的两组分诱芯,当Z5,E7-12∶OH,Z5,E7-12∶Oac和Z5,E7-12∶Opr的比例为100∶3∶25时,诱蛾效果最佳。在上述三组分混合物中加入一定量的Z5,E7-12∶Ald,则对诱蛾有明显的抑制作用。上述事实表明,Z5,E7-12∶Oac和Z5,E7-12∶Opr是赤松毛虫性信息素的两种次要组分,而Z5,E7-12∶Ald则是信息素的抑制剂。     

Foraging Behaviour of Wild Bees at Hot Pepper Flowers (Capsicum annuum) and its Possible Influence on Cross Pollination

Native bees are effective pollinators of hot pepper plants,Capsicum annuum. In four gardens in south-central Brazil (Patosde Minas and Brasília) flowers of three cultivars receivedvisits from 16 species of bees in eight genera: Hylaeus(Colletidae),Dialictus, Halictus, Augochlora,Augochloropsis and Ceratalictus(Halictidae),Exomalopsis andBombus (Apidae). No other insects were observedto visit the flowers. Some species of bee occurred in more thanone garden. Individual bees gathered a full pollen load from18 to 47 flowers and visited one to eight plants on a singleforaging trip. In 76 shifts between plants, the bees made nineswitches between cultivars. It is suggested that small nativespecies of bees pollinate the flowers effectively and that theirsmall foraging areas are important in keeping the cultivarsof both hot and sweet peppers genetically distinct where severalcultivars are grown close together. Copyright 2000 Annals ofBotany Company Capsicum annuum, hot pepper, native bees, fruit set, Brazil     

Flower Morphology and Pollination Mechanism in Three Sympatric Goodyerinae Orchids from Southeastern Brazil

The pollination biology of Aspidogyne argentea, Aspidogyne longicornuandErythrodes arietina was studied in south-eastern Brazil.The three species are self-compatible but are pollinator-dependent.These three orchid species offer nectar as a reward to pollinatorsand flower visitors. The twoAspidogyne spp. have a dorsally-adhesiveviscidium, a feature which precludes pollinators other thanbees. Erythrodes arietina flowers are protandrous and show aventrally-adhesive viscidium. Aspidogyne argentea is visitedby halictid bees (here ranked as probable pollinators) and Hesperiidaebutterflies. Aspidogyne longicornu is pollinated by femalesof Euglossa(Euglossini) and visited by the hummingbird Phaethornisruber and by the euglossine bees Eulaema seabrai(females) andEulaema cingulata(males). The pollinarium adheres to the ventralsurface of the bee labrum, a very difficult place for bees toclean. The dorsally adhesive viscidium in Aspidogyne parallelsthat of the Spiranthinae genera of the so-called ‘Pelexiaalliance’. This condition seems to be particularly adaptativeunder conditions of low-frequency pollinator visits. Erythrodesarietina is pollinated by bees of the genera Paratetrapediaand Osiris which carry the pollinarium on the dorsal surfaceof their proboscis. Occasionally, these bees remove pollinariafrom their mouthparts using their forelegs. In general, in thespecies studied, a combination of both pollinator behaviourand morphological peculiarities promotes cross-pollination.Copyright 2001 Annals of Botany Company Orchids, Goodyerinae, Aspidogyne, Erythrodes, pollination, bees, hummingbirds, butterflies, morphology, viscidium, protandry     

黄斑卷蛾雄蛾对性信息素的行为反应

分别在风洞中和田间观察了黄斑卷蛾Acleris fimbriana Thunberg et Becklin雄蛾对合成性信息素三种成分（E11,13-14∶Ald, E11,13-14∶Ac和E11-14∶Ac）及其不同组合的行为反应。在风洞中,主要活性成分E11,13-14∶Ald能引起雄蛾完成从兴奋到搜索释放源的行为反应,但雄蛾对单个组分E11,13-14∶Ac 或 E11-14∶Ac不呈现任何行为反应。当释放源为双组分 E11,13-14∶Ald＋E11,13-14∶Ac （6∶4）或三组分E11,13-14∶Ald＋E11,13-14∶Ac＋E11-14∶Ac（6∶4∶1）时,可以明显增加雄蛾定向飞行和到达释放源的数量。三组分 E11,13-14∶Ald＋E11,13-14∶Ac＋E11-14∶Ac的比例为6∶4∶1时,500 μg剂量效果最好。田间试验结果表明,E11,13-14∶Ald单独使用表现出良好的诱蛾活性,其诱蛾量为活雌蛾的1.9倍,而E11,13-14∶Ac和E11-14∶Ac则不具有诱蛾活性。E11,13-14∶Ac对E11,13-14∶Ald有明显的增效作用,三组分E11,13-14∶Ald＋E11,13-14∶Ac＋E11-14∶Ac（6∶4∶1）诱芯的诱蛾效果最好。     

Variations with Age in Net Assimilation Rate and other Growth Attributes of Sugar-beet, Potato, and Barley in a Controlled Environment: With two Figures in the Text

Sugar-beet, potato, and barley plants were grown in a controlledenvironment, for periods of up to 10 weeks from sowing, witha light intensity of 1,8oo f.c. (4·9 cal./cm.²/hr.) anda temperature of 20° C. during the 18-hour photoperiod and15° C. during the dark period, to test whether net assimilationrate varied with age and differed between the three species. Net assimilation rate of all species based on leaf area (E_A)fell approximately linearly with time. During 5 weeks E_A ofsugar-beet decreased by only about 20 per cent. and E_A of potatodecreased by 50 per cent. E_A of barley remained approximatelyconstant for 4 weeks after sowing and was halved during thesubsequent 4 weeks. The average value of E_A for all times wasgreatest for sugarbeet and least for barley. Net assimilation rates based on leaf weight (E_W) and leaf N(E_N) decreased at about 15 per cent. of the initial value perweek for all species; this was similar to the mean rate of decreaseof E_A of potato and barley, but greater than that of E_A of sugar-beet.Mean values of E_W or E_N for potato and barley were similar andless than for sugar-beet. Relative growth rate (R_W), relative leaf growth-rate (R_A), andleaf-area ratio (F) fell with time at similar rates for allspecies. Average values of R_W decreased and of F increased inthe order sugar-beet, potato, barley. R_A was greatest for potatoand least for barley.     

Production of the Water-Extractable Flower-Inducing Substance(s) in Lemna

Crude water extract of Lemna paucicostata Hegelm., strain 441,had high flower-inducing activity. This activity was heat-stable,but water extract of this plant after heat treatment had verylow activity. The water extract heated immediately after homogenizationalso had low activity, and this activity increased rapidly duringincubation of the plant homogenate before heating even at 0?C.The increase in activity did not occur during separate incubationof the supernatant and pellet obtained by centrifugation ofthe homogenate; some reaction between the components of thesupernatant and pellet may be necessary for production of theheat-stable flower-inducing substance(s). Oxygen deprivation(incubation in nitrogen gas) or presence of ascorbate duringincubation of the plant homogenate markedly lowered the generationof the flower-inducing activity. These results suggest thatthe active substance(s) is produced by an oxidative reaction.No significant difference could be found between photoperiodicallyinduced and non-induced plants in the activity of the waterextract after heat treatment. (Received April 9, 1990; Accepted July 5, 1990)     

Variation in Photosynthesis and Enzyme Activity in Cenchrus ciliaris L.

Populations of Cenchrus ciliaris differ significantly in relativegrowth-rate (R), net assimilation rate (E), and leaf-area ratio(F). Differences in R were related to differences in E ratherthan in F. The populations also differed in the rate of apparentphotosynthesis of individual leaves as measured by infra-redgas analysis. Warburg and ^l4CO₂ techniques. Temperature andlight-response measurements revealed optimum temperature forphotosynthesis of 35 °C and the rate in most populationscontinued to increase up to the highest levels of irradianceemployed (200 W m²). The relative order of the populations wassimilar in all methods of analysis, but there was no relationshipevident between leaf photosynthesis and E derived from growthanalysis. The activity of the enzyme PEP carboxylase, expressedin terms of unit leaf area, was correlated with photosyntheticrate of the leaf. Activities of PEP carboxylase and of proteinsynthesis in vitro expressed on a basis of soluble protein contentwere correlated with E, but no such relationship was found forthe enzymes acid phosphatase and alanine--ketoglutarate aminotransferase.     

Stretch-induced nitric oxide modulates mechanical properties of skeletal muscle cells

In this study, we examined the hypothesis that stretch-induced (nitric oxide) NO modulates the mechanical properties of skeletal muscles by increasing accumulation of protein levels of talin and vinculin and by inhibiting calpain-induced proteolysis, thereby stabilizing the focal contacts and the cytoskeleton. Differentiating C₂C₁₂ myotubes were subjected to a single 10% step stretch for 0–4 days. The apparent elastic modulus of the cells, E_app, was subsequently determined by atomic force microscopy. Static stretch led to significant increases (P < 0.01) in E_app beginning at 2 days. These increases were correlated with increases in NO activity and neuronal NO synthase (nNOS) protein expression. Expression of talin was upregulated throughout, whereas expression of vinculin was significantly increased only on days 3 and 4. Addition of the NO donor L-arginine onto stretched cells further enhanced E_app, NOS activity, and nNOS expression, whereas the presence of the NO inhibitor N-nitro-L-arginine methyl ester (L-NAME) reversed the effects of mechanical stimulation and of L-arginine. Overall, viscous dissipation, as determined by the value of hysteresis, was not significantly altered. For assessment of the role of vinculin and talin stability, cells treated with L-NAME showed a significant decrease in E_app, whereas addition of a calpain inhibitor abolished the effect. Thus our results show that NO inhibition of calpain-initiated cleavage of cytoskeleton proteins was correlated with the changes in E_app. Together, our data suggest that NO modulates the mechanical behavior of skeletal muscle cells through the combined action of increased talin and vinculin levels and a decrease in calpain-mediated talin proteolysis. mechanical stimulation; apparent elastic modulus; skeletal muscle cells; nitric oxide; stretch     

Dihydrokaempferol Glucoside from Cotyledons Promotes Flowering in Pharbitis nil

An extract of cotyledons of Pharbitis nil, which had been exposedto short-day conditions, was tested for flower-promoting activityin a shoot-tip assay system in vitro. The crude extract hadno flower-promoting activity, however, after partitioning ofthe crude extract with dichloromethane, the resulting aqueousfraction had flower-promoting activity. This activity was separatedinto two fractions by column chromatography on Toyopearl HW-40.One active fraction was identified as dihydrokaempferol-7-O-rß-D-glucoside(DHK-glc). This compound exhibited flower-promoting activityat the extremely low concentration of 4.4x10^-9. (Received April 25, 1995; Accepted August 11, 1995)     

Cessation of cell elongation in rye coleoptiles is accompanied by a loss of cell-wall plasticity

The mechanism by which endogenous cessation of coleoptile elongationafter emergence of the primary leaf is brought about was investigatedin rye seedlings (Secale cereale L.) that were either grownin darkness or irradiated with continuous white light. In 3-d-oldetiolated (growing) coleoptiles a turgor pressure of 0.59 MPawas measured. In 6-d-old coleoptiles, which had ceased to elongate,cell turgor was 0.51 MPa and thus only 13% lower than in therapidly growing organ. Hence, the driving force for growth (turgor)is largely maintained. Cell-wall plasticity (E_pl) and elasticity(E_Ql were determined with a constant load extensiometer bothin vivo (turgid coleoptile segments) and in vitro (frozen-thawedsamples). Cessation of coleoptile elongation was correlatedwith a 95% reduction in E_pl9 whereas E_Ql was only slightly affected.Extension kinetics were measured with living and frozen-thawedsegments cut from growing and non-growing coleoptiles. The correspondingstress-strain (load-extension) curves indicate that the cellwall of the growing coleoptile behaves like an elastic-plasticmaterial whereas that of the non-growing organ shows the behaviourof an elastic solid. These data demonstate that E_pl representsa true plastic (irreversible) deformation of the cell wall.It is concluded that cessation of coleoptile growth after emergenceof the primary leaf is attributable to a loss of cell-wall plasticity.Hence, a mechanical stiffening of the cell wall and not a lossof turgor pressure may be responsible for the deceleration ofcell elongation in the rye coleoptile. Key words: Extension growth, rye coleoptile, cell-wall extensibility, turgor pressure     

Effects of Root Temperature and Form of Nitrogen Nutrition on Nitrate Reductase Activity in Oilseed Rape (Brassica napus L.)

The effect of root temperature and form of inorganic nitrogensupply on in vitro nitrate reductase activity (NRA) was studiedin oilseed rape (Brassica napus L. cv. bien venu). Plants weregrown initially in flowing nutrient solution containing 10 µMNH₄NO₃ and then supplied with either nitrate or ammonium for15 d at root temperatures of 3, 7, 11 or 17 °C. Shoot temperatureregime was similar for all plants; 20/15 °C, day/night.Root NRA was highest when roots were grown at 3 and 7 °C.In laminae and petioles NRA was highest when roots were 11 or17 °C. The plants supplied with ammonium had much lowerlevels of NRA in roots after 5 d than the plants supplied onlywith nitrate. NRA in the laminae of plants supplied with ammoniumwas low relative to that in plants supplied with nitrate onlywhen root temperature was 11 or 17 °C. Values of the apparent activation energy (E_a) of NR, calculatedfrom the Arrhenius equation, in laminae and petioles were differentfrom roots suggesting difference in enzyme conformation. Evidencethat the temperature at which roots were growing affected E_awas equivocal. Oilseed rape, Brassica napus L., activation energy, ammonium, Arrhenius equation, nitrate, root temperature, nitrate reductase     

An electrophysiological study of the membrane in aplanospore-like cell of Boergesenia forbesii

Membrane potential and resistance, each of which was the sumof those of the plasmalemma and tonoplast, measured in the coenocyticthallus of Boergesenia forbesii were 6.7 mv inside positiveand 2.8 k.cm², respectively. Protoplasm squeezed from the thallus into artificial sea water(ASW) formed numerous spherical bodies, which are termed aplanospore-likecells (simply "spores"). The following electrical propertiesof the "spores" 20–40 hr after squeezing were obtained:potential difference (p.d.) across plasmalemma (E_co) was –66mv (– means inside negative), plasmalemma resistance 665cm², p.d. across the tonoplast (E_vc) +73 mv, and tonoplast resistance2.6 k.cm². Tenfold increase in external [K⁺] caused +45 mv changein E_co and +17 mv in E_vc. The plasmalemma was entirely depolarizedin Ca⁺⁺-free ASW or ASW containing Triton X-100. When the "spore" was immersed in potassium-rich (277 mil) ASW,E_co was almost zero and the tonoplast showed two states (I andII, E_ve about +70 mv and +20 mv, respectively). E_vc went backand forth between the two states spontaneously or when a smallcurrent was applied. In most cases oscillatory changes in E^vcoccurred after the lapse of a long time in the K+-rich sea water.Membrane resistances in states I and II were 5 and 9 k.cm²,respectively. (Received July 11, 1977; )     

Cytokinins and the Growth Responses of Seedlings of Betula pendula Roth. and Acer pseudoplatanus L. to Nitrogen and Phosphorus Deficiency

Deficiencies in the supply of nitrogen and phosphorus broughtabout the cessation of shoot extension and the formation ofterminal resting buds in seedlings of Acer pseudoplatanus maintainedunder long days, whereas seedlings of Betula pendula maintainedunder the same conditions continued extension growth of themain axis over a long period, although they showed symptomsof nitrogen deficiency, including a reduced chlorophyll content.The endogenous cytokinin levels of the base/nucleoside fractionin leaves of B. pendula were significantly lower in the nitrogen-deficientplants than in the controls only 3 d after transfer to deficientconditions. Similar, though less marked, changes were observedin response to phosphorus deficiency. Changes in the levelsof cytokinin activity in the nucleotide fraction in responseto nitrogen deficiency were much less marked. No significantchanges in cytokinin levels of the base/nucleoside or nucleotidefractions could be detected in leaf material from seedlingsof A. pseudoplatanus, even after a nitrogen or phosphorus deficiencytreatment of 4 weeks. Application of exogenous benzyladenineto seedlings of B. pendula subjected to nitrogen deficiencyresulted in a rapid regreening and to outgrowth of inhibitedlateral buds after only 2 d.     

Relationship between Coleoptile Elongation and Alcoholic Fermentation in Rice Exposed to Anoxia. I. Importance of Treatment Conditions and Different Tissues

The relationship between coleoptile elongation and alcoholicfermentation of rice under anoxia is examined using seeds either:(a) N₂ flushed during submergence, (b) incubated in stagnantdeoxygenated agar at 0·1% w/v to simulate the stagnantconditions of waterlogged soil, or (c) incubated in waterloggedsoil. Coleoptile elongation growth was greater for N₂ flushing> stagnant agar > soil; seed survival was also greatestin this order over 1-5 d. Ethanol concentrations in coleoptiles and intact seeds (cv.IR42) were approximately 300 and 100 mol m^-3 respectively whenseeds were grown 3 d in stagnant agar, however 92% of the ethanolin seeds diffused into the external medium when solutions weremixed for 5-10 s. Coleoptile growth under anoxia was relatedto rates of ethanol synthesis (R_E) in different treatments;there was greater coleoptile growth and R_E for seeds in N₂ flushedsolutions than in stagnant deoxygenated agar. Coleoptile growthof individual seeds was also related to the R_E of each seedat 2-3 d after anoxia (r² = 0·46). Analysis of different tissues was important in evaluating growthand metabolism of coleoptiles. Although the coleoptile onlyaccounted for 0·7% of seed dry weight at 3 d after anoxia,it contained 21% of the ethanol produced by rice seeds. Therewere also three-fold higher rates of R_E on a fresh weight basisin expanding tissues in the base of the coleoptile relativeto the elongated tissues at the apex. Results are discussedin terms of the importance of environmental conditions usedto impose anoxia, quantification of R_E in specific tissues andthe possibility that under stagnant conditions high ethanolconcentrations in tissues may limit R_E and coleoptile growth.Copyright1994, 1999 Academic Press Anoxia, ethanol, alcoholic fermentation, Oryza sativa L., rice, submergence     

Physiological Growth Attributes of Saccharum Clones and their Progenies

Characters obtained by growth analysis techniques were studiedin seven sugar-cane clones and their seedling progenies froma ratton crop 139 days after virgin harvest. Significant differences in progeny means for R_wand E_Awere mainlyaccounted for by differences in L. Four select clones had amean R_w and mean E_A which, when adjusted to allow for theirsuperior L, were significantly greater than average (P< 0.05).This illustrated that for selection to be effective from theprogenies, segregants with improved L and better leaf-area dependencemust be isolated. The estimates obtained of both L and E_A wereeffective in predicting final weight of cane. Variance componentsindicated especially large ‘male X female’ interactionin progeny means. Some evidence was obtained to suggest thatleaf-area ration is a character which could be used in selectingsmall plots for weight.     

Growth rates of dominant planktonic ciliates in two freshwater bodies of different trophic degree

The in situ growth rates of dominant ciliate species were studiedduring and shortly after phytoplankton peaks in two water bodies:the eutrophic Rímov Reservoir (South Bohemia, Czech Republic)and the oligo-mesotrophic Piburger See (Tyrol, Austria). Growthrate estimates based on changes in ciliate abundances in incubatedpre-screened samples (E_N) were compared with those derived fromthe ciliate cell volume and ambient temperatures (E_T). The valuesof E_N were always rather lower than those of E_T. During thestudies, the food supply limited the ciliate growth dependingon the ciliate feeding mode. An ecological grouping into filterfeeding versus raptorial feeding (‘hunting’) species,on the one hand, and attached/crawling (browsing) versus freeswimming species, on the other hand, clearly affected experimentalestimation. Both fine filter feeders (namely attached) and browsersexhibited a calculated E_N closer to the theoretical (maximum)E_T than did hunters and coarse filter feeders. It was apparent,for example, comparing E_N and E_T (day^–1) of the followingspecies: filter feeders Halteria grandinella (E_N = 0.42; E_T>1.4), Strobilidium hexakinetum (0.34;>1.9), Pelagohalteriaviridis (0.27;>0.9), Vorticella aquadulcis complex (0.75;>1.0);raptorial Balanion planctonicum (0.65;>1.5), Urotricha furcata(in Rímov Reservoir 0.65;>2.1; in Piburger See 0.20;>1.5),Rhabdoaskenasia minima (0.22;>1.0), Askenasia acrostomia(0.12;>0.6); opportunistic Cyrtolophosis mucicola (0.42;>1.6)and Cinetochilum margaritaceum (0.86;>1.4). Predation byrotifers apparently affected measurements in several samplescontaining {small tilde}400 rotifers l^–1 however, it seemedto be of little importance in the water column.     

Flower-Inducing Activity of Water Extracts of Various Plant Species, in Particular Pharbitis nil

The crude water extracts of leaves of many plant species belongingto Spermatophyta and some belonging to Bryophyta induced floweringof Lemna paucicostata 151 (PI51) under continuous light, atthe concentrations equivalent to 0.1 to 10 mg fr wt leaf per10 ml culture medium (mg fr wt/10 ml). The extract of Salvinia(Pterydophyta) added together with the extract of Lemna at aconcentration lower than that necessary to cause flowering alsoinduced flowering. The activity of the water extracts of someplants varied considerably from experiment to experiment dueto unknown factors, but the extracts of Pharbitis nil strainViolet, a sensitive short-day plant, always showed a high activity,as did the extracts of Lemna paucicostata reported previously. The extract of Pharbitis cotyledons induced flowering of P151even at 0.3 mg fr wt/10 ml, and significantly promoted floweringof L. paucicostata 441 and 6746 at 1–3 mg fr wt/10 ml.Ex-udate from the cuttings of the seedlings was also active.However, neither the activity of the water extract nor thatof the exudate could be correlated with photoperiodic floralinduction. On the other hand, the extract of leaves or cotyledonshad higher activity (on a fr wt basis) than that of other organs,and the activity of the extract of cotyledons changed with theirage roughly in parallel with their photoperiodic sensitivity. (Received April 17, 1989; Accepted August 10, 1989)     

Characterization of the Photoperiodic Response of Post-flowering Development in Maturity Isolines of Soyabean [Glycine max(L.) Merrill] 'Clark'

Plants of all eight isolines of three maturity genes (all combinationsof two alleles at the three lociE₁/e₁,E₂/e₂,E₃/e₃) of soyabean[Glycine max(L.) Merrill] were grown in four different photoperiods(12, 13, 14 or 15 h d^-1) at 30/24 °C from first flower openingto harvest maturity. Photoperiod, isoline, and their interaction,affected significantly (P<0.01) the duration between firstand last flowering, and reproductive duration. The interactionsbetween genotype and photoperiod were sufficiently strong thatconsiderable differences in these durations were detected amongisolines in the least-inductive environment (15 h d^-1) whereasdifferences were negligible in the most-inductive regime (12h d^-1). There was a negative linear relation between photoperiodand both rate of progress from the appearance of the first tothe last flower, and rate of progress from first flowering toharvest maturity; sensitivity to photoperiod varied (P<0.05)six- and five-fold, respectively, among the extreme isolines(e₁e₂e₃andE₁E₂E₃). The three dominant allelesE₁,E₂andE₃, singly,had comparatively little effect on post-flowering traits, butconsiderable epistasis (particularly betweenE₁andE₂) was detectedfor sensitivity to photoperiod in respect of rates of progressfrom the appearance of the first to the last flower, and fromfirst flower to harvest maturity. Thus the large variationsdetected for these traits are the consequence of genexgene (xgene)xenvironmentinteractions.Copyright 1998 Annals of Botany Company. Glycine max(L.) Merrill, soyabean, maturity genes, flowering, photoperiod.