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Light Effects (light + effects)
Selected AbstractsEffects of Light on the Growth and Clonal Reproduction of Ligularia virgaureaJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 8 2008Man-Tang Wang Abstract Ligularia virgaurea is a perennial herb that is widely distributed in the alpine meadow on the eastern Qinghai-Tibet plateau. We investigated the patterns of growth and reproduction of L. virgaurea under two contrasting levels of light conditions for two continuous growing seasons. Our results showed that the light effects on the maximum relative growth rate, the shoot weight ratio and the root weight ratio differed between the two growing seasons. L. virgaurea reproduced initially through rhizome in the second growing season, rather than sexual reproduction. The proportion of genets with clonal reproduction decreased under shaded conditions. A minimum genet size should be attained for clonal reproduction to begin under the shaded conditions. There was a positive linear relationship between clonal reproduction and genet size. Light level affected the allocation of total biomass to clonal structures, with less allocation under the full natural irradiance than under the shaded conditions. There seemed to be a trade-off between vegetative growth and clonal reproduction under the full natural irradiance, in terms of smaller relative growth rates of genets with clonal reproduction than those without clonal reproduction. L. virgaurea emphasized clonal reproduction under the full natural irradiance, while the plant emphasized vegetative growth under the shaded conditions. [source] Developmental and light effects on the accumulation of FtsH protease in Arabidopsis chloroplasts , implications for thylakoid formation and photosystem II maintenanceTHE PLANT JOURNAL, Issue 5 2005Adi Zaltsman Summary The chloroplast ATP-dependent metalloprotease FtsH is involved in the degradation of unassembled proteins, the repair of photosystem II (PSII) from photoinhibition, and, apparently, the formation of thylakoids. In Arabidopsis, it is encoded by a family of 12 genes. However, the products of only four of them, FtsH1, 2, 5 and 8, have been found in chloroplasts to date. Mutations in two of these, FtsH2 and 5, demonstrate a visible phenotype of variegated leaves, with the phenotype of the FtsH2 mutant being more pronounced. Moreover, the degree of variegation appears to be dependent on developmental stage and environmental factors, suggesting an intricate relationship between the different gene products. To explore this, developmental and light effects on the accumulation of FtsH protease were studied in wild-type (WT) and FtsH2-mutant plants. Whereas cotyledons of the mutant were indistinguishable from those of the WT, the first true leaves were almost completely white. Subsequent leaves contained increasing proportions of green sectors. Analysis of the mRNA of the four FtsH genes, in cotyledons, first and second leaves of WT and mutant plants, revealed that: (i) transcript level increases during development, and (ii) transcript level in the mutant is higher than in the WT. FtsH protein level in the mutant was ca. 50% of that found in the WT, whereas the levels of other thylakoid proteins were the same. In individual leaves, the level of FtsH protein increased during development as well. Exposure of seedlings to different light intensities did not affect the degree of variegation, suggesting that it is due to a defect in chloroplast development rather than photobleaching. Examination of FtsH protein during exposure to high light revealed a decrease in its level, concomitant with a decrease in PSII potential, suggesting that the kinetics of photoinhibition reflects not only photodamage to PSII and induction of protective mechanisms, but also a decrease in repair capacity due to a reduction in the level of FtsH protease. [source] HISTORY ILLUMINATED: WILLIAM HOLMAN HUNT'S LONDON BRIDGEART HISTORY, Issue 5 2006NANCY ROSE MARSHALL Grappling with the complex problem of how to represent history through the experience of ordinary people, William Holman Hunt's London Bridge of 1864 combined a modern urban crowd scene, a careful choice of depicted location, and an unusual deployment of light effects to create a painting about Victorian perceptions of time itself. By portraying a night-time scene lit by the gas illuminations on the bridge in honour of the wedding of the Prince and Princess of Wales, Hunt drew on the traditional aesthetic of the sublime to create a spectacle of an historic event , a royal marriage , that inspired both wonder and fear. Juxtaposing the flame-lit city with the moonlit Thames at the charged site of London Bridge allowed the artist to set in play the common Victorian framework one might term the ,moralizing sublime'. This pervasive mode of thought involved reading the mighty strivings of man and the modern industrial city as puny, transitory glimmers in comparison with the infinite onward rush of time; paradoxically, it also permitted the wilful overlooking of any negative yet ephemeral consequences of modernity. These ideas were underscored by the original exhibition of London Bridge with another work by Hunt in which light plays a key role in producing meaning: The Afterglow in Egypt. [source] Playing a violent television game affects heart rate variabilityACTA PAEDIATRICA, Issue 1 2009Malena Ivarsson Abstract Objective: To investigate how playing a violent/nonviolent television game during the evening affects sympathetic and parasympathetic reactions during and after playing as well as sleep quality during the night after playing. Subjects and Methods: In total, 19 boys, 12,15 years of age, played television games on two occasions in their homes and participated once without gaming. Heart rate, heart rate variability (HRV) and physical activity were measured during gaming/participating and the night to follow using a portable combined heart rate and movement sensor. A sleep diary and questionnaires about gaming experiences and session-specific experiences were filled in. Criteria for Selection of Games: Violent game involves/rewards direct physical violence (no handguns) against another person, and nonviolent game involves/rewards no violence; same game design (,third-person game'); conducted in the same manner; no differences concerning motor activity; similar sound and light effects; no sexual content, violence against women or racial overtones. Results: During violent (vs. nonviolent) gaming, there was significantly higher activity of the very low frequency component of the HRV and total power. During the night after playing, very low frequency, low frequency and high frequency components were significantly higher during the violent (vs. nonviolent) condition, just as total power. There were no significant differences between the three conditions (violent/nonviolent/no gaming) with respect to an index reflecting subjectively perceived sleep difficulties. Nor was there any difference between violent and nonviolent condition for any single sleep item. Conclusion: Violent gaming induces different autonomic responses in boys compared to nonviolent gaming , during playing and during the following night , suggesting different emotional responses. Subjectively perceived sleep quality is not influenced after a single gaming experience. Future studies should address the development of the autonomic balance after gaming over longer time than a night, physiological adaptation to frequent gaming and potential gender differences. [source] | ||||||||||