The effect of wavelength of light on stomatal opening

The effect of broad band green, blue and red light on stomatal opening of Vicia faba L. (broad bean) leaves was examined. In air, blue light caused greater stomatal opening than red light. In air with green light stomata were only slightly opened. In a nitrogen atmosphere red light caused greater opening than blue light, and green light caused only slight opening. Opening in air or nitrogen atmosphere in red or blue light was inhibited by the uncoupler CCCP, while the photosynthetic inhibitor DCMU inhibited opening in air but not in nitrogen atmosphere. We concluded that more than one light activated metabolic pathway can supply the energy needed to effect stomatal opening and that different pathways are operative under different conditions.     

Light elicited isolation of the complementary visual input systems in white-eye Drosophila.

Evidence is presented to show that the spectral sensitivity of the white-eye of Drosophila, indicated by the residual ERG following blue irradiation which renders the eye dark-depolarized, has a maximum around 460 nm, and represents the activity of R7 and possibly that of R8. Whereas the ERG of the repolarized dark-adapted white-eye, effected by orange irradiation, indicates a spectral sensitivity having a maximum around 490 to 500 nm, and represents the activity of R1 to 6 preferentially. Manipulation of these two visual input systems is achieved using various régimes of irradiation, the systems being switched at will. The critical flicker fusion frequency respectively for the two systems has been measured, that of R1 to 6 being twice as high as that of R7±8.Implications for the visual function of the eye are considered, in particular the significance of the wildtype red-eye colour. The ease of manipulation has considerable value to the experimentalist wishing to study the input systems in isolation and concomitantly.     

The sensitivity of opiate receptors and ligands to short wavelength ultraviolet light

The sensitivity of the opiate receptor, opiates and opioid ligands to ultraviolet light has been examined with the view of using this property to aid in characterizing the receptor. It is demonstrated that the opiate receptor is very sensitive to short wavelength ultraviolet light which causes rapid destruction of opiate binding activity. It is also shown that tritiated and cold opiate ligands are sensitive to light of this wavelength and when the receptor and opiate ligands are irradiated together, irreversible binding occurs. Along with the sensitivity of the receptor system to proteases and phospholipase the photosensitivity will aid in receptor isolation as well as in development of specific photoaffinity labels.     

The harmful effect of light on Drosophila is diet-dependent

Larvae and pupae of Drosophila melanogaster are light sensitive. Light increases mortality and retards development from egg to adulthood. This effect of light is diet dependent. High yeast concentrations protect larvae and pupae against the injurious effect of light. At low yeast concentrations the larvae and pupae become extremely light sensitive. Addition of vitamins to a low yeast medium also gave protection against light. A first analysis revealed that vitamin H (biotin) is involved in the protection. This is shown by the effect of avidin, an inhibitor of biotin dependent enzymes, on the development time. In all these aspects we recorded significant differences between two strains, a control strain C and a strain P. The latter had been adapted to a palmitic acid supplemented medium. In addition to the effect of vitamins on the survival, amino acids and sucrose supplements protect the control strain. These supplements have no effect on the survival of the P strain at high light intensities. At low light intensities they improve the survival of both strains. Palmitic acid supplements affect the survival of the control strain at both light intensities approximately to the same extent. The P strain is affected by palmitic acid only under the low light conditions.     

The effect of light wavelength on the susceptibility of plants to virus infection

Plants exposed for 24–72 h to light of different wavelengths differed in their subsequent susceptibility to virus infection. French bean leaves were less susceptible to infection by tobacco necrosis virus and Nicotiana glutinosa leaves were less susceptible to infection by tobacco mosaic virus when previously exposed to blue or red light than when exposed to green light. These differences were most pronounced at low energy levels. Leaves exposed to each kind of light were less susceptible than those kept in darkness.     

The response properties of retinula cells in the flyCalliphora erythrocephala as a function of the wavelength and polarization properties of visible and ultraviolet light

Detailed functional response properties of the class (1–6) retinula cells in the insectCalliphora erythrocephela have been determined as a function of the wavelength of monochromatic light and polarization conditions over a six log unit range of light adaptation levels. These stimuli were produced as a small parallel beam that could combine various wavelengths in both the ultraviolet and visible regions whose polarization planes could be individually controlled. The wild type and white-eyed mutant were studied and shown to have no significant differences in their response properties. It was shown that previous tests using transient stimuli, large compared to the adaptation levels produced responses of high orders of nonlinearity and rapidly changing transient properties. In contrast, the use of white-noise tests did not cause changes in the basic cell properties as established by a given light adaptation condition. These tests accurately model the visual conditions of a wide and representative range of normal behavioral conditions and the model response data thus obtained can be directly correlated to important physiological tests for the same stabilized adaptation conditions. The simultaneous application of both visible and ultraviolet monochromatic light revealed a complex response interaction which changed the self response contribution of the ultraviolet light from that due only to ultraviolet light but had no effect on the visible light response. It also produced a mutual interaction. This effect was found to be the same for all members of the (1–6) class of cells when the light was unpolarized but varied for different members of the class for polarized light depending upon the relative angles of theE-vectors for the two types of light which in turn vary for different members of the six cell classes.     

Angular sensitivity of light and dark adapted locust retinula cells

Summary Angular sensitivity functions for light and dark-adapted locust retinula cells have been measured. The angular sensitivity for light-adapted cells follows a Gaussian function but in the dark-adapted condition the measured function is broader than Gaussian at its base. Acceptance angles for light-adapted cells are 1.5°±0.2° (horizontal), 1.4°±0.1° (vertical) and for dark-adapted cells, 2.4°±0.5° (horizontal) and 2.5°±0.4° (vertical). These values are significantly smaller than those previously reported and show the locust eye to be closer to its theoretical limit of resolution than was previously indicated.The angular sensitivity of light-adapted cells agress well with the minimum resolvable stripe period reported by those authors refuting anomalous resolution.     

The role of retinula cell types in fixation behaviour of walkingDrosophila melanogaster

Summary Fixation behaviour of free walking wild typeDrosophila and various retinal mutants was tested in a circular arena. Optomotor response was also measured as a test of the function of R1-6.ora andsev,ora do not fixate a narrow stripe (10° or 20°, Fig. 1) but are able to orient towards broad stripes (110° or 180°, Fig. 1). The behaviour ofsev is not different from wild type. Fixation behaviour ofw rdgB is similar toora (Figs. 5, 6). The mutantora has a maximum optomotor response at low contrast frequencies (Fig. 2), but the threshold for this response is at least one log unit higher than in wild type orsev (Fig. 8). The light intensity threshold at 550 nm of fixation to a broad stripe (110°) is 1–2 log units higher inora than in wildtype, and 4 log units higher insev,ora and the structural brain mutantVam (Fig. 7).The conclusions are that retinula cells R1-6 mediate fixation to a narrow stripe at high and low ambient light intensities, and to a broad stripe at low ambient light levels. R8, possibly in conjunction with R1-6, contributes to orientation towards broad stripes at high light intensities. This hypothesis is supported by evidence that blue-adapted white-eyed flies are able to orient towards a broad stripe at high blue light intensities (Figs. 9 and 12). Blue adaptation totally eliminates the optomotor response (Figs. 10, 11) and so the optomotor response observed inora at low contrast frequencies (Figs. 2 and 8) is most likely due to the small remnants of the rhabdomeres of R1-6 that remain.Abbreviations PDA prolonged depolarising afterpotential - ERG electroretinogram     

The effect of light wavelength on the production and quality of eggs of the domestic hen

The effect of light color on egg-laying and on egg quality during the first 50 wk of egg production and during a second cycle of 19 wk following molting was examined. Hens were exposed to one of the following six sources of light: blue (B), green (G), red (R), tungsten (T), cool-white (C) fluorescent or simulated-sunlight (V) fluorescent tubes. Light intensity was equalized at photon output. Total egg production per hen was significantly influenced by the color of light with the most eggs being procuced in R light and the fewest in B light. Hens were more sensitive to light color in response to egg production during the second cycle than during the first cycle. Hens in C light produced significantly fewer eggs than those under V light in both laying cycles. Eggs laid under B or G light were consistently larger than those under R light. Egg weights of hens in V light were heavier than those for the C or T light groups. In the first cycle, shell quality was significantly better in G light than in B or R light. Percent of yolk increased and percent of albumen decreased with age during the first cycle in all treatments and the rate of change was directly related to light color (wavelength). In the second cycle, shell quality, percent of shell, yolk and albumen did not change significantly with age in any of the light treatments. It can be concluded that the wavelength of light may influence egg production, egg components and shell quality of the domestic laying hen.     

The effect of X chromosome heterozygosity on the structure of the ribosomal genes in Drosophila melanogaster.

Sucrose gradient analysis of DNA isolated from detergent-pronase lysates of adult flies has been used to look for ribosomal genes not integrated into the DNA of the chromosome in genotypes containing various combinations of inversions having breakpoints in the proximal heterochromatin of the X chromosome. Unintegrated genes are found in females heterozygous for inversions which have one breakpoint between the nucleolus organizer and the centromere. Homozygotes and males do not have unintegrated genes. The results suggest that unintegrated ribosomal genes result from an interaction between homologues having different arrangements of the proximal heterochromatin. In addition, data from a series of stocks carrying duplications of the X heterochromatin provide independent evidence for the size of the DNA on our gradients.     

The fine structure of the retinula of the compound eye of Astacus fluviatilis

Summary Intraventricular injections of moderate doses (25–75g) of 5,7-dihydroxytryptamine (5,7-DHT) into the left lateral ventricle of ether anaesthetized rats cause pronounced damage to CNS indoleamine axons, reflected by accumulations of large amounts of serotonin in distorted, heavily swollen axons, so called indoleamine droplet fibres. Larger doses (100, 150 or 300 g) provoke a piling up of catecholamines in drug affected preterminal catecholamine containing fibres besides extensive lesioning of indoleamine axons.5,7-DHT condenses with formaldehyde to form a light yellow fluorescent compound. Uptake and accumulation of 5,7-DHT into indoleamine terminals and axons—as revealed in short term experiments—provides a means of mapping of indoleamine neurons in the rat brain.Following the application of 5,7-DHT (25–150 g), rats develop characteristic behavioural disturbances, as e.g. increased sensitivity to sensory stimulation, and a failure to habituate to repeatedly applied sensory stimuli, and bizarre social behaviour, i.e. repeated fighting attacks in an unusual upright posture. These alterations resemble those observed after 5,6-DHT and may be indicative of a deprivation of the brain from functional serotonin.5,7-DHT is considered to be an important, additional tool for the investigation of serotonin neurons and problems of serotonin transmission in the mammalian brain.Dedicated to Prof. Dr. Dr. R. Janzen with the best wishes for his 65th birthday.Supported by the Deutsche Forschungsgemeinschaft.     

The effect of inversions on mitotic recombination in Drosophila melanogaster.

Summary The effect of inversions on mitotic recombination outside the inversion was studied in inversion-heterozygotes. Seven euchromatic inversions of the X-chromosome, with breakpoints within the interval between two cell markers, were chosen. The size of the inverted region and the distance from the proximal breakpoint to the proximal cell marker varied. Mitotic recombination was X-ray induced in larvae and clones scored in the tergites of emerged adults. The frequency of recombinants between both cell markers and the frequency of recombinants proximal to the proximal cell marker was used to estimate the effect of interference in pairing caused by the inversions. Such an effect only occurs in small chromosome intervals. This indicates that homologous sequences are tightly paired in the interphase nuclei of somatic cells. This conclusion is derived from data based on X-ray induced mitotic recombination. The possibility of extending this conclusion to non-irradiated cells is discussed.     

The effect of 313 nanometer light on initiation of replicons in mammalian cell DNA containing bromodeoxyuridine.

After unifilar substitution of thymine with bromouracil in either human HeLa or bovine cells, exposure to 313 nm light inhibits initiation of clusters of replicons. Since this treatment results in damage only to DNA and because the effect is the same as observed after 100-1000 rads of X-ray irradiation to the same cells, we infer that the effect of the later treatment is also mediated almost exclusively by DNA damage.