Mean development rates under cycling temperature regimes (both alternating and sinusoidal regimes) have been found to be either accelerated, decelerated or unaffected when compared to development at constant temperature regimes with equivalent means. It is generally accepted that this phenomenon is a consequence of the non-linearity inherent in the temperature-rate relationship of insect development and is known as the rate summation, or Kaufmann, effect. Some researchers invoke an additional physiological mechanism or specific adaptation to cycling temperatures resulting in a genuine alteration of development rate. Differences in development rates at constant and cycling temperatures may have important implications for degree-day (linear) population models, which are used in bath pest management and ecological studies.
Larvae of Aglais urticae L. (small tortoiseshell), Inachis io L. (peacock), Polygonia c-album L. (comma) and Vanessa atalanta L. (red admiral) (Lepidoptera: Nymphalidae) were reared at constant (10, 15, 20, 25, 30°C) and alternating (20/10, 25/15, 30/10, 30/20°C) regimes. Development rates under the alternating regimes used were found to differ from those under equivalent constant temperatures in a pattern suggestive of the Kaufmann effect: in all species development at 20/10°C was faster than at 15°C, and for three species development at 30/20°C was slower than at 25°C. The exception was A. urticae. A similar pattern was found for growth rate and pupal weight. The results are discussed with respect to cycling temperature theory and degree-day modelling., Simon R. Bryant, Jeffrey S. Bale, Chris D. Thomas, and Lit
In this study, effects of yellow (Y), purple (P), red (R), blue (B), green (G), and white (W) light on growth and development of tobacco plants were evaluated. We showed that monochromatic light reduced the growth, net photosynthetic rate (PN), stomatal conductance, intercellular CO2, and transpiration rate of tobacco. Such a reduction in PN occurred probably due to the stomatal limitation contrary to plants grown under W. Photochemical quenching coefficient (qP), maximal fluorescence of dark-adapted state, effective quantum yield of PSII photochemistry (ΦPSII), and maximal quantum yield of PSII photochemistry (Fv/Fm) of plants decreased under all monochromatic illuminations. The decline in ΦPSII occurred mostly due to the reduction in qP. The increase in minimal fluorescence of dark-adapted state and the decrease in Fv/Fm indicated the damage or inactivation of the reaction center of PSII under monochromatic light. Plants under Y and G showed the maximal nonphotochemical quenching with minimum PN compared with the W plants. Morphogenesis of plants was also affected by light quality. Under B light, plants exhibited smaller angles between stem and petiole, and the whole plants showed a compact type, while the angles increased under Y, P, R, and G and the plants were of an unconsolidated style. The total soluble sugar content increased significantly under B. The reducing sugar content increased under B but decreased significantly under R and G compared with W. In conclusion, different monochromatic light quality inhibited plants growth by reducing the activity of photosynthetic apparatus in plants. R and B light were more effective to drive photosynthesis and promote the plant growth, while Y and G light showed an suppression effect on plants growth. LEDs could be used as optimal light resources for plant cultivation in a greenhouse., L. Y. Yang, L. T. Wang, J. H. Ma, E. D. Ma, J. Y. Li, M. Gong., and Obsahuje bibliografii
Atmospheric CO2 concentration continues to rise and is predicted to reach approximately 700 ppm by 2100. Some predictions suggest that the dry season in West Africa could be extended with climate change. This study examined the effects of elevated CO2 concentration and water deficit on growth and photosynthesis of juvenile cacao. Light-saturated photosynthesis (Pmax), quantum efficiency, and intrinsic water-use efficiency increased significantly in response to elevated CO2, as did a range of growth and development responses (e.g. leaf area and leaf number), but the magnitude of the increase was dependent on the water treatment. Stomatal index was significantly greater in the elevated CO2 treatment; an atypical response which may be a reflection of the environment in which cacao evolved. This study shows a positive effect of elevated CO2 on juvenile cacao which may help to alleviate some of the negative impacts of water deficit stress., F. Lahive, P. Hadley, A. J. Daymond., and Obsahuje bibliografii
The present study was carried out to assess the role of zinc oxide nanoparticles (ZnO-NPs) in tomato plants on growth, photosynthetic efficiency, and antioxidant system. At 20-d stage of growth, roots of tomato plants were dipped into 0, 2, 4, 8, or 16 mg(ZnO-NPs) L-1 for 15, 30, and 45 min and then seedlings were transplanted in their respective cups and allowed to grow under natural environmental conditions. At 45-d stage of growth, the
ZnO-NPs treatments significantly increased growth, photosynthetic efficiency together with activities of carbonic anhydrase and antioxidant systems in a concentration- and duration-dependent manner. Moreover, the treatment by 8 mg(ZnO-NPs) L-1 for 30 min proved to be the most effective and resulted in maximum activities of antioxidant enzymes, proline accumulation and the photosynthetic rate. We concluded that presence of ZnO-NPs improved the antioxidant systems and speeded up proline accumulation that could provide stability to plants and improved photosynthetic efficiency., M. Faizan, A. Faraz, M. Yusuf, S. T. Khan, S. Hayat., and Obsahuje bibliografii