Showing papers on "Light intensity published in 1969"
TL;DR: Moisture content of the lower litter layers and upper soil layer, where most of the northern understory herbs are rooted, is greatly influenced by variations in throughfall determined by canopy opening.
Abstract: Measurements of canopy opening, understory light, throughfall precipitation, and understory herb response in leaf surface area per square meter in pine forests on light—textured soils in northern Wisconsin show that the understory herb layer is more responsive to differences in throughfall precipitation determined by canopy opening than to difference in light. Canopy opening controls both the level of light reaching the herb layer and the proportion of total precipitation reaching the litter layer, but the light levels are apparently considerably above the minimum thresholds for these species. On the light—textured soil—moisture recharge in the surface layers, as influenced by canopy opening, exerts the major control over the total cover of herbaceous species. Moisture content of the lower litter layers and upper soil layer, where most of the northern understory herbs are rooted, is greatly influenced by variations in throughfall determined by canopy opening.
237 citations
TL;DR: Decomposition and effects of fire on microclimate and plant production of a Tall Grass Prairie were studied in east—central Illinois and total flowering was proportional to duration and degree of favourable microclimatic conditions from May to mid July.
Abstract: Decomposition and effects of fire on microclimate and plant production of a Tall Grass Prairie were studied in east—central Illinois After two years simulated litter samples in contact with soil lost 64% of their initial weight Burning caused a 2—3 fold increase in production and a ten fold increase in flowering Application of mulch, lowered flowering rate; response was proportional to thickness of mulch and length of time it was in place, Artificial shading of burned areas under green—house frames lowered flowering rate Burning or clear cutting vegetation increased percent N and P in May foliage A May application of N fertilizer increased flowering and dry matter production Nutrient release from ash had no effect on flowering or production Root production was similar on burned and Burn 3 areas; a turnover rate of 045 was calculated Calcium content of roots in May increased after fire and N content decreased Temperature from —5 to +50 cm and light intensity from 0 to +50 cm were higher on burned than Burn 3 areas Maximum soil surface temperatures occurred three months earlier on Burn 0 than Burn 3 areas Soil moisture was never severely limiting to plant growth Growing season microclimate measurements at 50 and 200 cm were combined into a microclimatic index, which allowed comparison of the microenvironment of three burning regimes Total flowering was proportional to duration and degree of favourable microclimatic conditions from May to mid July
226 citations
TL;DR: A well-developed subsurface chlorophyll maximum is present during summer in oceanic waters off the Oregon coast as mentioned in this paper, which appears to be formed at depth by a photosynthetically active phytoplankton community that is adapted to low light intensity.
Abstract: A well-developed subsurface chlorophyll maximum is present during summer in oceanic waters off the Oregon coast. It appears to be formed at depth by a photosynthetically active phytoplankton community that is adapted to low light intensity. It may be present and may affect the distributions and concentrations of primary production, oxygen, and nutrients over large areas of the North Pacific Ocean.
191 citations
TL;DR: In this paper, self-focusing of a laser beam in a plasma is treated in terms of the ponderomotive acceleration due to the gradient of the light intensity, and the focusing of radiation within the first minima of diffraction sets a lower limit to the laser power which is of the order of 1 MW for the usual lasers if cut-off density and a plasma temperature of about 10 eV are assumed.
Abstract: Self-focusing of a laser beam in a plasma is treated in terms of the ponderomotive acceleration due to the gradient of the light intensity The focusing of radiation within the first minima of diffraction sets a lower limit to the laser power which is of the order of 1 MW for the usual lasers if cut-off density and a plasma temperature of about 10 eV are assumed
178 citations
TL;DR: Results suggest that system I action causes D, and that P is due to reduction of Q (fluorescence quencher) and intersystem intermediates caused by development of a block in oxidation of XH (X being the primary electron acceptor of light reaction I).
177 citations
TL;DR: In this article, the authors derived quantum rate equations for semiconductor lasers (SL) in the high-temperature limit for pure and highly doped III-V compound semiconductors.
Abstract: Quantum-mechanical rate equations are derived for semiconductor lasers (SL). Fluctuation operators with shot-noise character describe the quantum nature of the transitions. These equations are treated in the high-temperature limit for pure and highly doped III-V compound semiconductors. Numerical calculations are carried out for GaAs. From the mean rate equations we determine (a) the temperature dependence of the threshold pump rate for pure bulk SL and the threshold current for SL junctions and (b) the temperature and pump dependences of the mean light intensity and of the mean quasi-Fermi-level. By linearizing the fluctuations around the mean values, the noise spectrum for the light intensity is obtained. The general form of the noise spectrum is the same as that obtained by McCumber for a four-level laser system. Above threshold a sharp resonance is found in the GHz region. The temperature and pump dependences of the spectrum and especially of the resonance frequency are calculated in detail. The results from the mean equations and from the noise calculations which are obtained for highly doped GaAs are compared with experimental results for junction lasers, and good agreement is found. For pure SL the present numerical results are in good agreement with former analytical results of Haug and Haken for the mean intensity and for the low-frequency part of the noise spectrum, which have been found for the regions below and above threshold. The results for pure bulk SL are applicable to experiments with optical or electron-beam excitation.
176 citations
TL;DR: Observations on the extinction of phototactic and light-dependent feeding behaviour, using both white and coloured light, enabled visual thresholds and spectral sensitivity to be determined and it was found that the larval cones have spectral properties similar to those of adult teleosts.
Abstract: 1. Plaice and sole larvae have a pure-cone retina and no retinomotor responses. 2. Observations on the extinction of phototactic and light-dependent feeding behaviour, using both white and coloured light, enabled visual thresholds and spectral sensitivity to be determined. 3. Visual threshold decreased (that is, sensitivity increased) with age. The values for extinction of negative phototaxis ranged from 10 -4 -10 -6 m.c. 4. Sole larvae could feed in the dark from the early post-hatching stage, plaice larvae only at metamorphosis. Thus light intensity thresholds for feeding were only determinable in younger plaice larvae. The values ranged from 10°-10 -2 m.c. 5. The spectral sensitivity curves were plateau-like and photopic in nature. Thus the larval cones have spectral properties similar to those of adult teleosts. The differences in threshold obtained by the two techniques are probably a measure of the extent of recruitment of high-threshold cones required for image formation in feeding. 6. No evidence of a dermal light sense was found.
118 citations
TL;DR: Salinity changes, similar to those occurring with change in tide in the inshore environment usually occupied by pink shrimp, were imposed on both postlarvae and juveniles in a constant-current apparatus.
Abstract: 1. The inshore movements of postlarval pink shrimp and the subsequent offshore movements of the juveniles are facilitated by flood and ebb tides, respectively. This investigation concerns the behavioral mechanisms involved in the selective use of one tide and the evasion of the other.2. Salinity changes, similar to those occurring with change in tide in the inshore environment usually occupied by pink shrimp, were imposed on both postlarvae and juveniles in a constant-current apparatus.3. Juvenile shrimp were almost invariably positively rheotactic. However, with a decrease in salinity the sign of the response was reversed, resulting in active downstream swimming. This often gave way to passive drifting.Under conditions of low light intensity postlarvae were active in the water column, and being unable to withstand even slow currents, were easily displaced. With a decrease in salinity they sank to the substrate or remained low in the water column where they were better able to maintain position.4. Respons...
114 citations
TL;DR: Growth did not occur at 16 C, but was excellent under certain combinations of light and salinity at 2, 7, and 12 C, being somewhat better at the 2 highest temperature levels.
Abstract: SUMMARY
The influence of 116 combinations of temperature (2, 7, 12, 16 C), salinity (5–35‰ at 5‰ intervals) and light (5 levels) on the mean daily cell division rate (K) of the Narragansett Bay clone of Detonula confervacea was examined following appropriate preconditioning. Growth did not occur at 16 C, but was excellent (K = 1.2–1.5) under certain combinations of light and salinity at 2, 7, and 12 C, being somewhat better at the 2 highest temperature levels. At 32%, and 1100–1200 ft-c, K increased approximately 2.5 fold from 0.6 to 1.5 between 2 and 12 C.
A light-temperature relationship was found which had the general trend of an increased optimal light intensity with increasing temperature. Within the optimal salinity range of 15–30‰, the optimal light intensity was 200–600 ft-c at 2 C, 600–1200 ft-c at 7 C, and 1200–1800 ft-c at 12 C. The light-temperature relationship was most pronounced at 2 and 12 C. At 2 C, K decreased with increasing light intensity, but was independent of this factor at higher temperatures. The optimal salinity range of 15–30‰ was independent of temperature negligible growth occurred at 5‰.
In situ and in vitro responses of Detonula confervacea to salinity were in general agreement but its pronounced cryophilic preference in nature (usually reaching maximum abundance below 1 C) contrasts with its excellent growth at 12 C in culture. The experiments suggest that termination of the bloom of Detonula confervacea in Narragansett Bay and elsewhere is not solely temperature-dependent. Temperature does not satisfactorily account for its apparent exclusion from waters contiguous to Narragansett Bay and from other more northerly portions of the northeastern coast of the U.S, or, together with light, for its equally surprising apparent unimportance in Norwegian coastal waters.
112 citations
110 citations
TL;DR: Effects of ferricyanide, dichlorophenyldimethylurea (DCMU), and uncouplers of phosphorylation on the prompt and delayed fluorescences from spinach chloroplasts are described.
TL;DR: Two types with regard to adaptation to different light intensities are described: tbe Chlorella type and the Cyclotella type, which is mostly found among the green algae, and which adapts to a new light intensity mainly by changing the pigment content.
Abstract: Two types with regard to adaptation to different light intensities are described: tbe Chlorella type and the Cyclotella type. The Chlorella type is mostly found among the green algae, the Cyclotella type among the diatoms. The Chlorella type adapts to a new light intensity mainly by changing the pigment content. Therefore the cells adapted to a high light intensity have a lower chlorophyll a content per cell than cells adapted to a low light intensity. Light saturation is mostly rather low for cells adapted to low light intensities. The light-saturated rate of photosynthesisist mostly lower for cells adapted to a high light intensity than for cells adapted to a low light intensity. The actual photosynthesis is not much higher at a high light intensity than at a low one. The actual photosynthesis is the photosynthesis at the light intensity where the cells are grown. - The Cyclotella type adapts only by changing the light-saturated rate. The chlorophyll content is the same in cells grown at low and high light intensities. Light saturation for cells grown at a low light intensity is rather high. The light-saturated rate is much higher in the case examined at the high light intensity than at the low one. The actual photosynthesis is considerably higher for cells grown at the high light intensities than for cells grown at low light intensities.- The two adaptation types are not sharply separated since transition types occur.
TL;DR: In this article, the primary production in Marion Lake is inversely related to the rate at which water enters the lake when light intensity is corrected to a standard level, thus seasonal variations in rainfall in southwestern British Columbia exert an appreciable influence on the annual productivity of the lake's phytoplankton.
Abstract: Primary production in Marion Lake is inversely related to the rate at which water enters the lake when light intensity is corrected to a standard level. Increased flushing rates reduce the phytoplankton standing crop thereby lowering the total primary productivity in the lake. Thus seasonal variations in rainfall in southwestern British Columbia exert an appreciable influence on the annual productivity pattern of the lake’s phytoplankton.
Lake water artificially enclosed within small areas of the lake produced algal blooms while phytoplankton standing crop in the rest of the lake remained low. Nannoplankton appear to have a selective advantage over larger, more slowly reproducing forms in Marion Lake. The production: biomass ratio for lake phytoplankton was used as an indication of the general type of limiting factor affecting the instantaneous rate of productivity in the lake.
TL;DR: Benzyladenine applied to primary leaves of intact bean plants delayed the senescence of both the leaves and the entire shoot, and the levels of incorporation of labelled precursors into protein and RNA were enhanced.
Abstract: Benzyladenine (BA) applied to primary leaves of intact bean plants delayed the senescence of both the leaves and the entire shoot. The retardation of senescence was manifested in higher levels of chlorophyll, protein, RNA and ribonuclease activity at all stages of development. Also, the levels of incorporation of labelled precursors into protein and RNA were enhanced. The effect of BA was largely independent of light intensity and the compound did not act merely as a nitrogen source.
TL;DR: Assays with Notemigonus crysoleucas and Bosmina longirostris indicate that the toxin from naturally occurring bloom populations, if released all at once, would be capable of killing certain species of fish and microcrustaceans.
Abstract: A toxic strain of Aphanizomenon flos-aquae was isolated and cultured in a defined medium (ASM-1). This strain fixes nitrogen, has a pH optimum of 7.5, and has maximum growth rates at 5000 lux and 26 °C. Phosphorus levels of 1.0 μM readily supported populations of 1 × 105 cells/ml with stimulation of growth evident at a concentration of 0.1 μM P. Tris is inhibitory to growth of this alga at concentrations above 2.5 mM.Toxin production is related to age of culture, temperature, and light intensity but not nitrogen source.Intraperitoneal injection of toxic extracts into Fundulus heteroclitus, Cyprinodon variegatus, and white mice gave a LD100 of 0.5 mg/kg, 0.5 mg/kg, and 8 mg/kg, respectively. Assays with Notemigonus crysoleucas and Bosmina longirostris indicate that the toxin from naturally occurring bloom populations (1 × 106 cells/ml), if released all at once, would be capable of killing certain species of fish and microcrustaceans. Daphnia catawba, however, was much more resistant to toxin (LD100 = 1.0 m...
TL;DR: In this paper, a theoretical analysis of acoustooptical pulse modulators is carried out that yield the intensity and rise time of the scattered light and the optimum relationship between the dimensions of the optical and acoustic beam is given.
Abstract: A theoretical analysis of acoustooptical pulse modulators is given Calculations are carried out that yield the intensity and rise time of the scattered light The optimum relationship between the dimensions of the optical and acoustic beam is given A fast high-efficiency modulator has been built based on the theoretical results The modulator is composed of a 350-MHz ZnO transducer sputtered on a quartz acoustic lens and an As 2 S 3 glass serving as the modulating material With 06 watt of electrical RF peak power driving the modulator, 70 percent of the light intensity (at 063μ) is deflected The rise time of the scattered light pulse is of the order of 6 ns
TL;DR: Experimental findings demonstrate the capacity of the rods to interact with the long-wave cones to produce color sensations, and shows that the rods can be as much a part of the human color-producing system as the cones.
Abstract: The duplicity theory states that cones produce photopic or color vision, whereas the rods produce scotopic or colorless night vision. This paper reports experimental findings which demonstrate the capacity of the rods to interact with the long-wave cones to produce color sensations. Radiances of 546 and 450 nm that excited only the rods, and radiances of 656 nm that excited only the long-wave cones were determined. When the rods and long-wave cones were selectively excited with the minimum radiance necessary to see form, the observers reported seeing a large variety of color sensations. These observers also reported the same variety of color sensations at greater radiances when the rods and long-wave cones were selectively excited. Color sensations produced by the excitation of rods and long-wave cones were independent of the wavelength used to excite the rods. Color sensations produced by rods and long-wave cones were identical, except for slight differences of brightness and sharpness, to the color sensations produced by 656 and 495±5 nm light when both were above cone threshold. Therefore, under the described conditions, the rods can be as much a part of the human color-producing system as the cones. All of the above results can be explained by Land’s retinex theory of color vision.
TL;DR: In this article, it was shown that the optical absorption coefficient varies inversely with light intensity, and that if a monochromatic light beam absorbed by a semiconductor generates enough carriers to fill band states up to and including those of the optical transition, then the absorption will be saturated and a condition of transparency should result.
Abstract: If a monochromatic light beam absorbed by a semiconductor generates enough carriers to fill band states up to and including those of the optical transition, the optical absorption will be saturated and a condition of transparency should result. Analysis shows that in this regime the absorption coefficient varies inversely with light intensity.
TL;DR: In this article, the rate of zinc uptake, the effects of carrier ions, temperature, light intensity and dinitrophenol (DNP) upon the uptake of zinc (using zinc-65 as tracer) by Fontinalis antipyretica were investigated.
Abstract: The rate of uptake, the effects of carrier ions, temperature, light intensity and dinitrophenol (DNP) upon the uptake of zinc (using zinc-65 as tracer) by Fontinalis antipyretica were investigated. The absorption medium contained 0.5 mW CaSO4 and the pH was kept constant using boric acid and sodium hydroxide as buffer.
About 50 per cent of the zinc absorbed at equilibrium was taken up in the first half hour, Analysis by semi-log plot procedures showed that, at least, three sections may be distinguished in the uptake curve, suggesting that three successive processes (stages) were involved. The first stage was very short, and not influenced by temperature, light intensity and DNP. The second stage, lasting no more than 90 minutes, mi very slightly affected by the same three factors. In this stage freshly killed plants absorb more zinc than living material. The third stage, lasting several days, was very slow and was light, temperature and DNP dependent.
Based on these findings, a mechanism for zinc uptake is proposed.
TL;DR: The effects of salinity, light intensity, temperature and pH on the amounts of nitrogen fixed and liberated extracellularly by the marine blue-green alga Calothrix scopulorum (Weber et Mohr) Ag. ex Bornet et Flahault have been investigated.
Abstract: The effects of salinity, light intensity, temperature and pH on the amounts of nitrogen fixed and liberated extracellularly by the marine blue-green alga Calothrix scopulorum (Weber et Mohr) Ag. ex Bornet et Flahault have been investigated.
TL;DR: In Glycine, Arachis, and Trifolium the intensity of the light coming from the moon to the upper surface of the leaf is reduced by circadian leaf movement to values between 5 and 20 per cent (or even less than 5 per cent) of full-moon light intensity, indicating that leaf movements have an adaptive value of the kind that Darwin sought to identify.
Abstract: Threshold values of photoperiodic time-measurements correspond approximately to moonlight intensities. Experiments with Glycine and Euglena reveal that this is also the threshold value for synchronization of the circadian cycle. Saturation of this reaction is reached with 10 lx in 12:12 hr light-dark cycles. Thus, moonlight might disturb time measurement.
In Glycine, Arachis, and Trifolium the intensity of the light coming from the moon to the upper surface of the leaf is reduced by circadian leaf movement to values between 5 and 20 per cent (or even less than 5 per cent) of full-moon light intensity. Such a reduction eliminates the disturbing effects of moonlight. This finding indicates that leaf movements have an adaptive value of the kind that Darwin sought to identify. It also indicates that the behavior of the upper leaf epidermis as a “sense organ for light”13 has an adaptive value.
In the short-day plants Perilla ocymoides and Chenopodium amaranticolor, a specific photoperiodic phenomenon was found that counteracts the disturbing effect of moonlight. Here light intensities similar to those of moonlight, introduced during the night, promote flowering instead of inhibiting it.
TL;DR: A ratio of pyruvate decarboxylation to nitrogen fixation of 3:1 has been established for A. cylindrica, indicating that light-generated ATP is required for nitrogen fixation in this alga, and agrees with the hypothesis that pyruVate acts as a hydrogen donor for nitrogen reduction.
Abstract: When carbon dioxide fixation was over 90% inhibited by CMU, nitrogen fixation remained unaffected in nitrogen-starved cells of Anabaena cylindrica. In normal cells under the same conditions nitrogen fixation was about 50% inhibited by CMU. These data suggest, first, that nitrogen fixation in this organism is independent of reducing potential generated by non-cyclic photo-electron transport and, secondly, that nitrogen fixation is stimulated by photosynthetically produced carbon skeletons to assimilate the fixed nitrogen. Although nitrogen fixation occurred to a limited extent in the dark, increasing light intensity stimulated nitrogen fixation both in the presence and absence of CMU. This suggests that light-generated ATP is required for nitrogen fixation in this alga. A ratio of pyruvate decarboxylation to nitrogen fixation of 3:1 has been established for A. cylindrica. This accords with the hypothesis that pyruvate acts as a hydrogen donor for nitrogen reduction and that provision of the required reductant is independent of photosynthesis in blue-green algae.
TL;DR: The techniques of small particle holography are extended in an elementary way to show that multiple exposure hologramy can be used to study the dynamic properties of particle fields.
Abstract: The techniques of small particle holography are extended in an elementary way to show that multiple exposure holography can be used to study the dynamic properties of particle fields. Experimental techniques for performing such a study are then described. Finally, as a typical example, a multiple exposure hologram of an aerosol is presented with a portion of the data extracted from it. The hologram exhibits a vast amount of information including the determination of the velocity and density field, size distribution, flow structure, and diffusion rate.
TL;DR: An attempt has been made to relate a quantitative assessment of the usnic acid content in C. subtenuis to the light incidence of the habitat, and a very yellow color of the podetia has been considered to indicate a high content of us Nic acid, a yellow lichen substance.
Abstract: Clinal variation in the usnic acid content of thalli of Cladonia subtenuis along determined light gradients was demonstrated spectrophotometrically. Integrated measurements of light incidence were made using ozalid paper light sensors. The percentage of usnic acid in the dry podetia is directly related to the percentage of full sunlight in the microhabitat of the plants. Extreme values ranged from 0.13% in plants from a site of low light intensity (3% full sunlight) to 2.82% in plants from a relatively open site (51% full sunlight). The yellowish color in the podetia of sun populations was not markedly altered by extraction of the usnic acid. Cladonia subtenuis (Abb.) Evans is a common lichen in the southeastern United 1 This research was supported in part by U.S. Public Health Research Grant GM-08345 from the Division of General Medical Sciences, National Institutes of Health, to Dr. Chicita F. Culberson. I thank Dr. Culberson for her help in this study. 2 Department of Botany, Duke University, Durham, North Carolina 27706. This content downloaded from 207.46.13.172 on Fri, 07 Oct 2016 06:14:56 UTC All use subject to http://about.jstor.org/terms 1969] RUNDEL: CLINAL VARIATION IN USNIC ACID PRODUCTION 41 States, occurring on soil in openings or at the edge of pine woods and on banks along old roadcuts. This species has long been known for great variation between sun and shade forms. This variation was noted by Evans (1944) when he raised the taxon to specific rank. Evans recognized four forms including f. cinerascens, a grayish-green shade form with little yellow color and little or no usnic acid, which he distinguished from the typical f. subtenuis or sun form, yellowish in color and containing usnic acid. These two forms have been separated solely on the basis of the degree of yellow coloring of the podetia which has been assumed to be related to the content of usnic acid, a yellow lichen substance. A very yellow color of the podetia has been considered to indicate a high content of usnic acid, a gray-green color to indicate little or no usnic acid. In the present study an attempt has been made to relate a quantitative assessment of the usnic acid content in C. subtenuis to the light incidence of the habitat. Usnic acid is one of the most widespread of lichen substances and a considerable body of literature concerning it exists. Few studies, however, have concerned themselves with quantitative determinations of the usnic acid content of lichens. Laaskso and Gustafsson (1952) used a ferric chloride reagent to make quantitative measurements of usnic acid sepctrophotometrically for Cladonia alpestris. Another spectrophotometric method was used by Ramaut et al. (1966) in a study of the chemotaxonomic significance of usnic acid in Cladonia tenuis, C. leucophaea, and C. impexa. In their study the height of the absorption curve at 380 my for a benzene extract of usnic acid from the lichens studied was used to measure usnic acid concentration. A more refined spectrophotometric analysis for usnic acid has been used in the present research. Usnic acid in benzene solution has a very strong ultraviolet absorption peak at 285 m/, and this peak provides a more satisfactory measurement of the usnic acid content than the absorption at 380 my where no peak occurs. MATERIALS AND METHODS Mats of Cladonia subtenuis were collected in Duke Forest (Durham County, North Carolina) from a range of ecological sites in which the percentage of full sunlight reaching the microhabitat of each mat had been measured. Light measurements at these sites were made with deciduous trees in full leaf. From each small mat of C. subtenuis studied, approximately 0.5 g of the terminal 5 mm of the podetia were collected and dried to constant weight in a desiccator over concentrated sulfuric acid. Material in obvious fruiting condition was not used. The dried sample was weighed and immediately extracted. The lichen was extracted in 15 ml of benzene for 10 minutes on a steam table. The filtered solutions from four successive extractions were pooled and diluted to 500 ml with benzene. Three ml of this solution were run on a Bausch & Lomb Spectronic 505 spectrophotometer against a benzene reference to give an absorption curve for the 280-330 my range (Fig. 1). The usnic acid content of the samples was determined from the absorption peak at 285 me. A calibration curve relating concentration of usnic acid in milligrams per 500 ml of benzene was obtained using solutions of known concentration of usnic acid. The relationship between peak height and usnic acid concentration is linear over the range measured. From the calibration chart the usnic acid concentration of each sample was determined; these data and the original dry weight of each sample enabled the calculation of the percentage of usnic acid by weight in each sample. Integrated measurements of light incidence on thallus mats in the field were made with ozalid paper light sensors (Friend, 1961). Packets of light-sensitive ozalid paper were exposed for 24 hours on the surface of the mats to be studied. The number of papers bleached by the sun at a given sample point was compared to that bleached in a totally This content downloaded from 207.46.13.172 on Fri, 07 Oct 2016 06:14:56 UTC All use subject to http://about.jstor.org/terms 42 THE BRYOLOGIST [Volume 72
TL;DR: It is shown that the red shift and decrease in amplitude of the CD extrema of particulate systems correlate with changes in the intensity of scattered light and with the extent of absorption flattening as measured, respectively, at wavelengths where significant absorption does not occur and at wavelengths corresponding to major absorption bands.
TL;DR: Results indicate that the intersystem electron transport pool A as well as the primary electron acceptor of pigment system II Q (fluorescence quencher) is normally being reduced at I, which restricts the Franck-Rosenberg model of photosynthesis, which is based on fluorescence yield doubling.
TL;DR: Monthly samples of larvae, pupae and imagines of Sericostoma personatum (Spence) were taken from Wilfin Beck, a small stony stream in the English Lake District and there was no evidence of an endogenous rhythm.
Abstract: Monthly samples of larvae, pupae and imagines of Sericostoma personatum (Spence) were taken from Wilfin Beck, a small stony stream in the English Lake District. There were six larval instars and eggs were laid underwater. First instars hatched from overwintering eggs in March and from newly laid eggs in June. Both groups of larvae grew rapidly through the summer and reached the sixth instar in October. The larvae overwintered in the sixth instar, started to pupate in April, and started to emerge in May. A third group of larvae hatched in late summer (August to October), overwintered in the second and third instars, started to pupate in July, and emerged until the end of August. Therefore there were at least three separate age groups. Imagines emerged and flew chiefly during the day, whereas the larvae were most active at night. The nocturnal periodicity in larval activity was controlled solely by changes in light intensity and there was no evidence of an endogenous rhythm. Feeding occurred chiefly at night and the diet consisted chiefly of algae, and the leaves of both terrestrial and aquatic macrophytes. Early instars were most abundant near the source and later instars were most abundant in the lower half of the stream. Larvae were neither drifting or crawling downstream under normal flow conditions, but some larvae were swept downstream in spates. The upstream flight of imagines before oviposition may compensate for this downstream movement of larvae from the upper reaches of the stream. Pe3IoMe
TL;DR: There is evidence that light intensity affected fruitfulness via effects on carbohydrate level, but the same could not be said for effects due to temperature; the mode of action of temperature is as yet unknown.
Abstract: Grapevines (Vitis vinifera L., c.v. Muscat Gordo Blanco, syn. Muscat of Alexandria) were grown in controlled-environment growth cabinets for 13 weeks after bud burst, and then buds which had developed on the shoot were dissected and examined for the presence of bunch primordia. Environmental variables examined were light intensity and temperature. Fruitfulness (number of bunch primordia per bud) increased with increasing light intensity over the range 900 ft-c-1,800 ft-c-3,600 ft-c (16-hr days at 25 C or 30 C). At 20 C buds were barren at 13 weeks, and fruitfulness was achieved above this temperature and increasingly so to a maximum between 30 C and 35 C. Temperature appeared to exert an effect on both rate of bud development and on actual number of bunch primordia differentiated. A temperature which promoted stem dry-weight accumulation (20 C) retarded differentiation and development of bunch primordia. There is evidence that light intensity affected fruitfulness via effects on carbohydrate level, but th...
TL;DR: The capacity for photosynthetic electron transport, phosphorylation, and CO(2) fixation in ac-31 is substantial, and it is concluded that these photosynthesis activities occur within the single membrane.
Abstract: A pale-green mutant strain of Chlamydomonas reinhardi, ac-31, is characterized by the absence of any stacking of its chloroplast membranes. The capacity for photosynthetic electron transport, phosphorylation, and CO(2) fixation in ac-31 is substantial, and it is concluded that these photosynthetic activities occur within the single membrane. The photosynthetic capacities of wild type and ac-31 as a function of increasing light intensity are compared. Saturation is attained at higher light intensities in ac-31, and the kinetics of the 2 sets of curves are distinctly different. The possibility that energy transfer is enhanced by membrane stacking is suggested by these results. The repeatedly-observed correlation between reduced stacking and disfunctional Photosystem II activities is discussed in view of the observation that ac-31 has no stacking but retains a functional Photosystem II.
TL;DR: Direct and indirect effects of light intensity produced significant changes in the levels of male light-brown apple moth responsiveness to the pheromone; light intensities greater than 3·5 lx suppressed the male response and, via the timing of a circadian rhythm, light/dark cycles established a set period of peak responsiveness within a diel cycle.