Mesembryanthemum crystallinum is an annual succulent plant that is being used as an emerging healthy leafy vegetable. To investigate the growth and physiological response of M. crystallinum to artificial lighting, five different light treatments were applied at 150 µmol(photon) m-2 s-1, which were white (W), different rations of red/blue (B) (15, 40, and 70%B), and blue (100%B), respectively. Our results showed that plants could gain as much as edible leaf area and dry mass with a certain ratio of blue (40%) in comparison with W. Plants grown under 100%B resulted in reduced photosynthetic rate, leaf area, and fresh mass compared with W. Adding blue fraction in the light regime enhanced the photosynthetic performance by influencing the amount of chlorophyll (Chl), Chl a/b, and specific leaf area. Under red/blue treatments, the electron transport rate and effective quantum yield of both PSII and PSI increased, while the nitrate content was reduced and flavonoids and total antioxidant capacity were unaffected.
This study was designed to test the hypothesis that the spectral composition of incident radiation, as defined by the relative proportions of blue (B; λmax = 455 nm) and red (R; λmax = 625 nm) photons, can affect photosynthetic induction, since B photons stimulate stomatal opening and are more effectively absorbed by leaves than R photons. Different stages of photosynthetic induction, primarily determined by the photo-modulation of Rubisco activity and stomata opening, were investigated in dark-adapted leaves of Fagus sylvatica transferred to saturating irradiance [800µmol(photon) m-2 s-1] at B/R ratios of 1/3, 1/1, or 3/1.
In agreement with our hypothesis, photosynthesis was induced faster by irradiance with a high B/R ratio (3/1); as demontrated by a higher IS60 (induction state 60 s after leaf illumination) and lower T 90 (the time period required to reach 90 % of maximum steady-state photosynthesis). However, there were no differences in induction between leaves receiving equal (1/1) and low (1/3) B/R ratios. Electron transport was highly sensitive to radiation quality, exhibiting faster induction kinetics with increasing B/R ratio. Such stimulation of carbon-assimilatory processes corresponds with faster activation of Rubisco and lower non-photochemical quenching (NPQ) as the proportion of B photons is increased. In contrast, the kinetics of stomatal opening was independent of the spectral composition of incoming radiation. Since slightly higher absorption efficiency of high B/R radiation does not fully explain the changes in induction kinetics, the other possible mechanisms contributing to the stimulation of electron transport and Rubisco activity are discussed. and M. Košvancová-Zitová ... [et al.].
This article provides a critical edition and exposition of several phrases from scholastic poems (or from two or four combined poems) with the incipit Ex fideli veterum scriptura cognovi (Walther, Initia No. 5984), whose authorship is ascribed to the protonotary of Václav IV., Vlachník of Weitmile († 1399), inspired by the intellectual atmosphere of the Prague Court.
This article provides a critical edition and exposition of several phrases from scholastic poems (or from two or four combined poems) with the incipit Ex fideli veterum scriptura cognovi (Walther, Initia No. 5984), whose authorship is ascribed to the protonotary of Václav IV., Vlachník of Weitmile († 1399), inspired by the intellectual atmosphere of the Prague Court.