光强度对大草蛉成虫感光性和趋光性行为的影响

运用视网膜电位（electroretinogram, ERG）技术和行为学方法研究了大草蛉Chrysopa pallens Ramber成虫的光强度反应。结果显示: （1）白光（Log I= 4.5~0.0）可引发2 h暗适应的大草蛉复眼的电位反应。随光强增强其ERG值呈近线性增大, 最强时未出现高端平台, 表明该光强范围内其感光性基本一致, 且可感受更强的光; （2）一定光强度（Log I= 4.0）以上的白光可引发大草蛉较明显的趋光性行为, 该行为具有光强域值特征和较明显的光强度依赖性。弱光时（Log I=4.5）无趋光性行为, 随光强增大趋光性反应率增大, 光较弱（Log I= 4.5~1.5）时增大缓慢, 较强（Log I=1.5~0.0）时迅速增大, 至最强（Log I=0.0）时最大（37.1%）, 呈一近“J”型式样。避光行为无或很低, 且无规律, 最大值仅为4.5%。这些结果表明: 光强度是大草蛉感光性与趋光性行为的重要决定因素, 强光时感光性电位反应与趋光性行为反应基本一致, 弱光时则不同, 暗示了光强度信息在感光性和趋光性间作用的有条件性和复杂性。     

Inhibition of Phototaxis and Motility by UV-B Irradiation in Dictyostelium discoideum Slugs

The effect of monochromatic irradiation in and near the UV-Bregion (280–320 nm) on motility (speed of movement) andwhite light-induced phototactic orientation was studied in slugsof the cellular slime mold Dictyostelium discoideum (NC-4).Motility decreased to about 50% in UV-B fluences (about 100Jm^–2 at 280 nm) well below those required to inhibit slugand sorocarp development or to impair viability. At wavelengthsof 270–300 nm, the phototactic orientation was almosttotally eliminated by an exposure to U V (about 0.1 Wm^–2)for as short a time as half an hour when administered at thebeginning of the 24 h exposure to white light. (Received July 22, 1983; Accepted September 27, 1983)     

The Effects of Light Irradiation on the Orientation of Microtubules in Seedlings of Avena sativa L. and Pisum sativum L.

The effects of light irradiation on the arrangement of corticalmicrotubules (MTs) were examined in etiolated A vena mesocotylsand coleoptiles, and in Pisum epicotyls. Elongation of A venamesocotyls ceased as a result of irradiation with white lightwithin 1 h. The predominant orientation of MTs became more longitudinalwithin 1 h in epidermal cells and changed from transverse tooblique, after the elongation ceased, in parenchymal cells.Irradiation with red and with blue light also caused cessationof cell elongation and the same changes in the orientation ofMTs. Elongation of Avena coleoptiles ceased as a result of irradiationwith white light within 24 h. The predominant orientation ofMTs became more longitudinal in epidermal cells and changedfrom transverse to oblique in parenchymal cells. The changein orientation of MTs in epidermal cells preceded that in parenchymalcells. In Pisum epicotyls, elongation ceased as a result ofirradiation with white light within 1 h. Although the orientationsof MTs in epidermal cells did not show any remarkable change,those in parenchymal cells changed from transverse to obliqueafter cell elongation ceased. The change in orientation of MTs and the cessation of cell elongationof A vena mesocotyls induced by white-light irradiation wereboth significantly retarded by treatment with IAA. This resultsuggests that IAA is involved in maintaining the transverseorientation of MTs in Avena mesocotyls. (Received February 22, 1989; Accepted August 2, 1989)     

Spectral preferences of Lycorma delicatula (Hemiptera: Fulgoridae)

Many insects prefer lights with certain spectral properties, and such preferences may be associated with behavioral contexts such as mating, host finding or dispersal. Lycorma delicatula (Hemiptera: Fulgoridae) is a newly invasive species in Korea and is spreading rapidly. It is diurnal and may rely on visual cues for orientation. We conducted a series of three phototaxis experiments to understand spectral preferences in L. delicatula: light/dark choice, UV/white light choice, and color preference experiments. Nymphs of the third and final stages as well as adults were used for these experiments. In the light/dark choice, the orientation of L. delicatula was bimodal between the white light and darkness, for all stages and both sexes. In a choice of UV (395–410 nm wavelengths) vs. white light, L. delicatula of both sexes and all stages preferred the UV light. In the color preference experiment where insects had a choice of four colors in a circular arena, L. delicatula stayed significantly longer in the blue light than in white, yellow or green lights. Overall, nymphs and adults of L. delicatula oriented toward lights with shorter wavelengths, and this orientation was consistent throughout all stages, regardless of sex. It is necessary to investigate the behavioral contexts under which L. delicatula prefers the UV and blue lights.     

Phototaxis in the flagellates,Euglena gracilis and Ochromonas danica

Oriented movement with respect to laterally impinging white light of the flagellates Euglena gracilis and Ochromonas danica has been analyzed in an individual cell study with a microvideographic technique. Using the deviation of track segments (in given time intervals of 1 s) from the light direction as raw data allowed a computer based analysis of the direction distribution. A number of statistical methods employed to test the significance of the obtained results demonstrated an obvious phototactic orientation in Ochromonas which was positive (toward the light source) in low illuminance (1.25 lx=5.3×10^-3 Wm^-2) and negative in higher illuminance (>12.5 lx=5.3×10^-2 Wm^-2). Since in this flagellate the threshold for negative phototaxis is much lower than that for the step-up photophobic response, the hypothesis that negative phototaxis may be brought about by repetitive step-up phobic responses can be rejected for at least this organism. In Euglena positive phototaxis was observed in 50 lx (=0.21 Wm^-2), while an illuminance of 500 lx (=2.1 Wm^-2) caused a negative phototaxis.The experiments were carried out in this laboratory     

Studies on the Photoreceptors for the Promotion and Inhibition of Flowering in Dark-Grown Seedlings of Pharbitis nil Choisy

Three-day-old etiolated seedlings of Pharbitis nil were exposedto red light for 10 min and sprayed with N⁶-benzyladenine beforetransfer to a 48-h inductive dark period, after which they weregrown under continuous white light. A second red irradiationpromoted flowering when given at the 5 and 24th hour of theinductive dark period but inhibited flowering at the 10 and15th hour. Far-red light inhibited flowering when given at anytime during the first 24 h of the dark period. Red/far-red reversibilitywas clearly observed at the 0, 5, 10 and 24th hour, but notat the 15th hour when both red and far-red lights completelyinhibited flowering. The action spectrum for the inhibition of flowering at the 15thhour of the inductive dark period had a sharply defined peakat 660 nm and closely resembled the absorption spectrum of theP_R form of phytochrome. The photoreceptors involved in thesephotoreactions are discussed. (Received June 10, 1983; Accepted July 6, 1983)     

Light Environment within a Leaf I. Optical Properties of Paradermal Sections of Camellia Leaves with Special Reference to Differences in the Optical Properties of Palisade and Spongy Tissues

The attenuance (apparent absorbance), angular distribution oftransmitted light (scattering) and reflectance of paradermalsections of Camellia leaves were measured spectrophotometricallyand the data for the palisade and spongy tissues were compared. Attenuance in tissues could be expressed by Beer's law onlyfor wavelengths of strong absorption. At 680 nm, the apparentextinction coefficient of chlorophyll (e) for the spongy tissuewas about 1.4 times that for the palisade tissue. The largere for the spongy tissue is attributable mostly to the more effectiveincrease in the pathlength of light due to scattering at theinterfaces between the air space and cells because the differencebetween e for the two tissues was minimized by infiltrationof the air space in the tissues with a medium whose refractiveindex was similar to the index of the leaf cells. Scatteringwas larger for wavelengths of weak absorption, and the relativeincrease in attenuance caused by elongating the optical pathlengthwas even more prominent. Based on these data, we report an ecophysiological discussionof the internal light environment of a leaf and the meaningof the differentiation of mesophyll into the palisade and spongytissues. (Received May 18, 1983; Accepted September 21, 1983)     

Phototaxis inEuglena gracilis: Effect of sodium azide and triphenylmethyl phosphonium ion on the photosensory transduction chain

Phototaxis in the flagellateEuglena gracilis was studied by means of a microvideographic analysis, and the light-induced directional movement was determined by computer-based statistical treatments. Lateral white light with an illuminance of 25 lx (0.105 Wm^–2) caused the cells to preferentially swim toward the light source (positive phototaxis), while an illuminance of 1,000 lx (4.2 Wm^–2) induced negative phototaxis. The lipophilic membranepenetrating cation triphenylmethyl phosphonium ion (TPMP⁺) specifically inhibited positive phototaxis, while it hardly affected negative phototaxis. The uncoupler sodium azide, on the other hand, impaired negative phototaxis substantially.     

Gametic behavior in a marine green alga, Monostroma angicava: an effect of phototaxis on mating efficiency

The role of phototactic behavior of gametes was tested experimentally in the slightly anisogamous marine green alga Monostroma angicava Kjellman, and the effect of phototaxis on mating efficiency was discovered. Both male and female gametes showed positive phototaxis in response to a white light source. In contrast, they did not respond to a red light source. Their swimming velocity did not differ between these two illuminating light sources. It was, therefore, suggested that the search ability of the gamete itself might not vary between phototactic and non-phototactic conditions. The number of zygotes formed during the mating process may be expressed as the product of the number of encounters between male and female gametes and the fraction of encounters that result in sexual fusion. In this study, with high densities of male and female gametes mixed in test tubes, almost all minor (fewer in number) gametes fused sexually within 10 min. After dilution of the gamete suspensions by half, mating efficiency in test tubes illuminated by white light from above was higher than that in dark controls. This suggests that male and female gametes gathered at the water surface through their positive phototaxis, thus increasing the rate of encounters. Mating efficiency also decreased if the test tubes were illuminated from above by white light and also shaken. Since negative phototaxis is clearly shown in planozygotes, we suggest that positive phototaxis of male and female gametes in M. angicava is an adaptive trait for increasing the rate of gametic encounters rather than for the dispersal of zygotes as previously reported for zoospores of some marine algae. Received: 12 February 1999 / Revision accepted: 24 May 1999     

Effects of Far-red Light on the Labelling of Acyl Lipids during the Greening of Barley (Hordeum vulgare)

Etiolated Hordeum vulgare (barley) Plants were greened underwhite light or far-red (> 700 nm) light. Exposure to far-redlight inhibited chlorophyll synthesis (especially chlorophyllb) and the development of photosystem II which were seen whengreening took place under white light. Primary leaves were detachedand the labelling of their acyl lipids from [¹⁴C]acetate wasstudied under white light or far-red light illumination. Greeningwith far-red light caused a reduction in the radiolabellingof polyunsaturated fatty acids and diacylgalactosylglycerol.Total fatty acid labelling rates were unaffected. Phosphatidylethanolamine,which was normally poorly labelled, accounted for up to 15 percent of the total radioactivity in acyl moieties of lipids inleaves greened with far-red light. The results are discussedin connection with the role that acyl lipids may play in normalthylakoid structure and function. Hordeum vulgare, barley, acyl lipids, white light, far-red light, chloroplasts, thylakoids     

Mechanisms in the Shift of a Riparian Ground Beetle (Carabidae) Between Reproduction and Hibernation Habitat

Factors affecting the light response of the riparian species Bembidion petrosum (Coleoptera: Carabidae) were studied with various experimental designs in laboratory and in field. B. petrosum, which lives in open gravely/stony sites, oriented towards directed light at higher temperatures (above 15.0°C). This positive phototaxis was replaced by an orientation towards a dark silhouette (screen) at low temperatures. The orientation towards silhouettes is mainly a simple type of form vision, although a fraction of the individuals seems to exhibit a negative phototaxis. In experiments with a dark zone and a zone with directed light, individuals of B. petrosum mainly selected the dark zone. However, if two stones were placed in the light part of the arena, individuals tended to hide under them. This applied independent of light intensity and whether a tuft of grass was present or absent in the dark part of the arena. The experiments indicate that the shift of the species between the reproduction (spring/summer) and hibernation (autumn/winter) habitat involves a change from an orientation towards silhouettes at low temperatures in autumn to an orientation towards directed light at higher temperatures in spring. This is combined with a specialized low thigmokinesis (preference of heavy and rough objects) and lower moisture requirements of the species in autumn/winter than in spring/summer.     

Photoresponses of the copepod Mesocyclops edax

The predatory copepod Mesocyclops edax is an important componentof many zooplankton communities where it typically makes extensivedid vertical migrations. To describe the effect of light onadults we measured their photoresponses in the laboratory. Theresponse spectrum is characterized by a wide plateau of greatestsensitivity from about 480 – 580 nm. These animals areadapted to perceive light during the day since their regionof maximum sensitivity overlaps the spectral region of highestquantal intensity underwater (575 – 700 nm). The thresholdintensity for positive phototaxis by dark adapted animals wasabout 5 x 10^–1 Wm^–2 at 540 nm, and they were positivelyphototactic up to an intensity of 5 x 10^–1 Wm^–2.Above this intensity phototaxis is no longer observed. Light-adaptedanimals were less sensitive than dark-adapted, but their generalpattern of response to light intensity did not differ. Thereis no rhythm in phototaxis. Their photoresponses may providea mechanism for controlling vertical migration so as to minimizeexposure to planktivorous fish. ¹Contribution No. 1375-AEL from UM-CEES, Appalachian EnvironmentalLaboratory.     

Studies on the Cell Wall of Chlorella V. Comparison of the Cell Wall Chemical Compositions in Strains of Chlorella ellipsoidea

Cell walls of four strains of Chlorella ellipsoidea (IAM C-27,C-87, C-102 and C-183) were compared as to their chemical compositions.Many differences were found: (1) The sugar composition of alkali-soluble cell walls differedin quantity as well as quality with glucuronic acid being foundonly in C-27 and C-87. (2) In alkali-insoluble cell walls glucosamine was found onlyin C-27. The other three strains contained mainly glucose. (3) The amino acid compositions of the alkali-insoluble cellwalls markedly differed among the four strains. The cell wallof C-102 contained more amino acids than carbohydrates, butC-27 and C-87 contained extremely little amino acid. In addition to the variation in cell wall composition, the opticalanisotropy findings also differed for these cell walls of Chlorellastrains which had been grouped as the same species. (Received August 16, 1983; Accepted December 27, 1983)     

The role of two plant-derived volatiles in the foraging movement of 1st instar Helicoverpa armigera (Hübner): time to stop and smell the flowers

Positive phototaxis and negative geotaxis are behaviours that 1st instar Helicoverpa armigera use to direct their foraging movement upward towards nutritious new plant growth and reproductive structures. Odours emitted by fruits or seeds can attract larvae directly via chemotaxis. In this study we clarify the effect of leaf and flower odours on foraging 1st instar H. armigera. Using a Y-tube olfactometer we tested for chemotaxis towards two plant volatiles and found larvae were not attracted. Bioassays for phototaxis towards UV, blue, green and white light showed that a green leaf volatile ((Z)-3-hexenyl acetate) and a flower volatile (phenylacetaldehyde) reduced larval phototaxis towards blue light. Feeding on a host plant reduced phototaxis towards blue and green light. We concluded that the upward movement of 1st instars on plants is largely due to phototaxis towards the blue wavelengths of skylight. Plant attributes such as volatile chemicals affect the expression of phototaxis and therefore, indirectly influence larval movement to locate food resources. Handling Editor: Anna-Karin Borg-Karlson     

Phototactic Chloroplast Displacement in the Photosynthetic Mutant, Lemna paucicostata Strain 1073

The photosynthetic mutant, strain 1073, of Lemna paucicostataTorr. (L. perpusilla Hegelm.) which has a block in the electrontransport chain between plastoquinone and cytochrome f is capableof light-induced chloroplast displacement movements. At 8000–14000 lx, chloroplasts of the mutant move from their positionadjacent to the inner periclinal wall of the mesophyll cellsto the anticlinal walls, i.e. along those walls parallel tothe direction of the light. Light does not appear to enhancerespiration of the photosynthetic mutant or of the wild typestrain (6746). These and other results support the idea thatchloroplast displacement in light is not solely the result oflight effects on photosynthesis and respiration. Lemna paucicostata Torr., photosynthetic mutant, phototaxis, chloroplast displacement     

Radiation Interception, Partitioning and Use in Grass -Clover Mixtures

Mixed swards of perennial ryegrass /white clover were grownin competition under controlled environmental conditions, attwo temperatures and with different inorganic nitrogen supplies.The swards were studied after canopy closure, from 800 to 1200°C d cumulative temperatures. Clover contents did not varysignificantly during the period. A simulation model of lightinterception was used to calculate light partitioning coefficientsand radiation use efficiencies for both components of the mixturein this controlled environment experiment. Additionally, thissame radiative transfer model was applied to the field datafrom Woledge (1988) (Annals of Applied Biology112: 175 –186)and from Woledge, Davidson and Dennis (1992) (Grass and ForageScience47: 230 –238). The measured and simulated valuesof light transmission, at different depths in the mixed canopy,were highly correlated (P<0.001) with more than 80% of thetotal variance explained. The daily average of photosyntheticallyactive radiation (PAR) interception in a natural environmentwas estimated from simulations, for the field and controlledenvironment data. Under these conditions, white clover capturedsignificantly more light per unit leaf area than perennial ryegrassat low, but not at high, nitrogen supply. In the controlled environment experiment, the radiation useefficiency of the legume was lower than that of its companiongrass. For both species, radiation use efficiency was negativelycorrelated with the mean irradiance of the leaf. The role ofa compensation between light interception and light use forstabilizing the botanical composition of dense grass –cloverswards is discussed. Light interception; radiation transfer model; growth analysis; radiation use efficiency; white clover; perennial ryegrass; Trifolium repensL.; Lolium perenneL.; grassland     

Glycerolipid Synthesis in Avena Leaves during Greening of Etiolated Seedlings IV. Effect of Light on Fatty Acid Desaturation

Etiolated Avena sativa L. leaves were fed with [l-¹⁴C]acetatefor 20 h in the dark and labeled fatty acids in glycerolipidswere chased during 24 h in the light (greening condition) orin the dark, to determine the light effect on the fatty aciddesaturation. Oleate decrease in phosphatidylcholine was thesame in the light and in the dark, showing that oleate desaturationis independent of light (or greening). Linoleate desaturationin galactolipids, especially in monogalactosyl diacylglycerol,was enhanced by light and palmitate desaturation to hexadecenoatein phosphatidylglycerol was strictly light-dependent. (Received May 11, 1983; Accepted August 16, 1983)     

Haustoria of Cuscuta japonica, a Holoparasitic Flowering Plant, Are Induced by the Cooperative Effects of Far-Red Light and Tactile Stimuli

When seedlings of Cuscuta japonica were grown with Vigna radiata(the host plant) in a flower pot for 6 d under white light andthen irradiated with far-red or blue light (ca. 6 µmolphotons m^–2 s^–1), the seedlings parasitized V. radiata.However, no parasitism of the seedlings was observed under redor white light or in darkness. The parasitic behavior of seedlingsof C. japonica was observed even if an acrylic rod was usedas a substitute for the host plant. Upon incubation under far-redlight, the seedling twined tightly around the rod and developedhaustoria towards it. Haustoria also developed when apical andsubapical regions of seedlings were held between two glass platesthat were about 0.7 mm apart and were irradiated with far-redlight. However, no haustoria were induced by either the holdor irradiation alone. These results indicate that parasitismof Cuscuta japonica is controlled by the cooperative effectsof two physical signals, far-red light and appropriate tactilepressure. Our findings suggest that parasitism by the genusCuscuta involves a novel strategy. (Received April 10, 1996; Accepted August 21, 1996)     

Roles of cyclic AMP in regulation of phototaxis in <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis>

Chlamydomonas reinhardtii swims toward or away from light (phototaxis) in a graded way depending on various conditions. Activation of rhodopsin provides signals to control the steering of this unicellular organism relative to a light source and to up-regulate rhodopsin biosynthesis. Intracellular cAMP and cGMP concentrations were measured in positive (1117, swims toward light) and negative (806, swims away from light) phototactic strains with and without light stimulation or 3-isobutyl-1-methylxanthine (IBMX). In the dark, the levels of cAMP and cGMP were significantly higher in the strain with positive phototaxis than in the strain with negative phototaxis. To test whether either cyclic nucleotide influenced the direction, their pre-stimulus levels were pharmacologically manipulated. Higher pre-stimulus levels of cAMP biased the cells to swim toward green light and lower levels biased the cells to swim away. In addition, green-light activation of rhodopsin or addition of IBMX causes a sustained increase in cAMP in both strains. As a consequence of this increase in cAMP, carotenogenesis is induced, as shown by recovery of phototaxis in a carotenoid mutant. Thus, two functions for cAMP were identified: high pre-stimulus level biases swimming toward a light source and sustained elevation following rhodopsin activation increases rhodopsin biosynthesis.     

Involvement of Riboflavin in UV-A and White Light-induced Synthesis of Anthocyanin in Sorghum bicolor

Synthesis of anthocyanin in isolated mesocotyls of Sorghum bicolor(var. Vidisha 60–1) is promoted by the external feedingof riboflavin (FMN) under white and UV-A light. Potassium iodide,salicylhydroxamic acid and sodium azide, which are known tointerfere with the photoreactions of riboflavin, inhibit thesynthesis of anthocyanin induced by white and UV-A light. Thisinhibition is reversed by riboflavin and there is a direct interactionbetween the inhibitors and riboflavin. It is concluded thatriboflavin is the major photoreceptor for the induction of anthocyaninsynthesis in Sorghum bicolor by white and UV-A light. Key words: Sorghum, anthocyanin, riboflavin, UV-A