Light quality influences indigo precursors production and seed germination in Isatis tinctoria L. and Isatis indigotica Fort

Isatis tinctoria L. and Isatis indigotica Fort. are biennial herbaceous plants belonging to the family of Cruciferae that are used as a source of natural indigo and show several morphological and genetic differences. Production of indigo (indigotin) precursors, indican (indoxyl beta-D glucoside) and isatan B (indoxyl ketogluconate), together with seed germination ability were compared in Isatis tinctoria and Isatis indigotica grown under six different light conditions (darkness, white, red, far red, blue, yellow light) at 25 degrees C. Light quality influenced both germination and production of indigo precursors in the two Isatis species. Different responsiveness to far red and blue light was observed. Indeed, a detrimental effect on germination by blue and far red light was found in I. tinctoria only. Different amounts of isatan B were produced under red and far red light in the two Isatis species. In I. tinctoria, the level of main indigo precursor isatan B was maximal under red light and minimal under far red light. Whereas in I. indigotica far red light promoted a large accumulation of isatan B. The photon fluence rate dependency for white and yellow light responses showed that the accumulation of indigo precursors was differently influenced in the two Isatis species. In particular, both white and yellow light enhanced above 40 micromol m(-2) s(-1) the production of isatan B in I. indigotica while only white light showed a photon fluence dependency in I. tinctoria. These results suggest a different role played by the labile and stable phytochrome species (phyA and phyB) in the isatan B production in I. tinctoria and I. indigotica. I. indigotica, whose germination percentage was not influenced by light quality, demonstrated higher germination capability compared with I. tinctoria. In fact, I. tinctoria showed high frequency of germination in darkness and under light sources that establish high phytochrome photoequilibrium (red, white and yellow light). Germination in I. tinctoria was negatively affected by far red and blue light. I. indigotica seeds appear to be indifferent to canopy-like light (far red). Our results provide further insights on the distinct behaviour of I. tinctoria and I. indigotica that belong to two different genetic clusters and different original environments.     

A comparison between plane wave and Gaussian-type orbital basis sets for hydrogen bonded systems: formic acid as a test case

The formic acid molecule, its dimers, and its molecular crystal are adopted as test systems to compare results obtained with plane wave (PW) basis sets and norm-conserving pseudopotentials to all-electron Gaussian-type orbital (GTO) calculations. The CPMD and CRYSTAL06 codes, respectively, are applied with the PBE, PW91, and BLYP density functionals. Hydrogen bonding is the leading interaction in the dimers and the crystal. In the latter, dispersive and weak C-H...O interactions are also relevant. Irrespective of the adopted functional, for all considered structures PW and GTO results converge smoothly as a function of the quality of the adopted basis sets to the same values for structures, energies of interaction, and harmonic vibrational features. To achieve a high level of mutual agreement the use of GTO basis sets of at least of triple-zeta quality including one set of polarization functions and PW basis sets with a kinetic energy cutoff higher than 110 Ry is recommended. Pros and cons of both approaches for studying molecular crystals are also discussed.     

Analytical calculation of the solvent-accessible surface area and its nuclear gradients by stereographic projection: A general approach for molecules,polymers, nanotubes,helices, and surfaces

In this article, we explore an alternative to the analytical Gauss–Bonnet approach for computing the solvent-accessible surface area (SASA) and its nuclear gradients. These two key quantities are required to evaluate the nonelectrostatic contribution to the solvation energy and its nuclear gradients in implicit solvation models. We extend a previously proposed analytical approach for finite systems based on the stereographic projection technique to infinite periodic systems such as polymers, nanotubes, helices, or surfaces and detail its implementation in the Crystal code. We provide the full derivation of the SASA nuclear gradients, and introduce an iterative perturbation scheme of the atomic coordinates to stabilize the gradients calculation for certain difficult symmetric systems. An excellent agreement of computed SASA with reference analytical values is found for finite systems, while the SASA size-extensivity is verified for infinite periodic systems. In addition, correctness of the analytical gradients is confirmed by the excellent agreement obtained with numerical gradients and by the translational invariance achieved, both for finite and infinite periodic systems. Overall therefore, the stereographic projection approach appears as a general, simple, and efficient technique to compute the key quantities required for the calculation of the nonelectrostatic contribution to the solvation energy and its nuclear gradients in implicit solvation models applicable to both finite and infinite periodic systems.     

Space charge limited avalanche growth in multigap resistive plate chambers

The European Physical Journal C - The ALICE TOF array will be built using the Multigap Resistive Plate Chamber(MRPC) configured as a double stack. Each stack contains 5 gas gaps with width of...     

Copolymerization of Propene and Buta‐1,3‐diene in the Presence of Highly Hindered C2‐Symmetric Zirconocene‐Based Catalyst

Summary: Copolymerizations of propene and buta‐1,3‐diene performed in the presence of rac‐[CH₂(3‐tert‐butyl‐1‐indenyl)₂]ZrCl₂ and methylaluminoxane (MAO) have been investigated. Buta‐1,3‐diene gives prevailingly primary coordination to the metal, producing overall 1,2 units. Cyclopropane and cyclopentane rings, although in low amounts, are also obtained. The presence of butadiene would be responsible for some regioirregular 2,1‐inserted propene units, which at high temperatures give rearrangement to 3,1 units.

     

Accelerated oxidative ageing of polypropylene fibers in aqueous medium under high oxygen pressure as studied by thermal analysis

Stabilised polypropylene fibres of 28 μm diameter have been exposed at 80 °C under 5 MPa oxygen pressure, in dry conditions, in pure water and in alkaline medium. Their residual stability is determined from the temperature T_ox of the onset of the oxidation exotherm, measured by differential scanning calorimetry at 10 K min⁻¹ scanning rate. The time t_ex to reach the characteristics of unstabilised samples (T_ox=175 °C) is of the order of 220 (dry conditions), 160 h (water) and 80 h (alkaline medium), whereas it is of the order of 750 h at 110 °C in classical tests made at atmospheric pressure. This increase of ageing rate is discussed in terms of kinetic effect of O₂ pressure and efficiency of the liquid medium to extract stabilisers.     

The Use of UV Radiation to Control the Architecture of Salvia splendens Plants. II. Relationships between PAR Levels and UV Radiation in the Photoregulation of Stem Elongation

The effects of UV irradiation on stem elongation of Salvia splendens plants preadapted to two and grown under four different irradiances of visible light, were studied using linear voltage differential transducers. The levels of radiant energy during the experimental phase showed a temporary and opposite effect during the day-time and the night-time: increasing levels of photosynthetically active radiation (PAR)? reduced stem growth during the day and enhanced elongation growth during the night. It appears, therefore, that similar final stem elongation in plants grown under very different PAR levels is the result of the algebraic sum of different and sometimes opposite effects of PAR on stem growth. Except for the controls, the plants received one UV treatment from Philips TL 12 40 W fluorescent tubes either in the middle of the light period or at the beginning of the dark period. The results show that the preadapting PAR conditions changed the sensitivity of the plants to both UV and to the following PAR conditions. The sensitivity of S. splendens to UV radiation is inversely correlated to the PAR levels before and during the UV treatments. Furthermore the presence of active photosynthetic and photomorphogenic systems, i. e. the presence of visible light during the UV treatment, decreases the sensitivity of the plants to UV radiation. Depending on PAR levels, the UV treatments given during the night induced a temporary inhibition of growth followed by a promotion of stem elongation.     

Kinetics of Stem Elongation in Light-Grown Tomato Plants. Responses to Different Photosynthetically Active Radiation Levels by Wild-Type and aurea Mutant Plants

Abstract— In this research, we measured the short- and long-term, stem elongation responses of wild-type and aurea(au) mutant tomato plants to different photosynthetically active radiation (PAR) levels by using linear voltage transducers. Stem elongation was continuously measured in green tomato plants over 2.75 days, under 12 h light/12 h dark photoperiods or in darkness after a 6 h irradiation period. There is no significant difference in stem elongation between wild-type plants pregrown at either LOO or 400 μmol m^?2 s^?1 and then exposed to 12 h photoperiods. However, in the au mutant there is a very large difference between plants pregrown under 100 or 400 umol m ^?2 s^?1 and then exposed either to 12 h photoperiods or to continuous darkness. Total stem elongation of the wild type appears to be maximal at 100 umol m^?2 s^?1, while that of the au mutant appears to be maximal with PAR 400 umol m^?2 s^?1. Wild-type plants displayed PAR-dependent (in the range 100-800 umol m^?2 s^?1) inhibition of growth both during the day and during the night. In contrast, the au mutant showed a fluence-rate-dependent promotion of growth during the dark periods in the range of 10-400 umol m^?2 s^?1. Large, fast and opposite changes in stem elongation rate at the light/dark and dark/light transitions were present in both genotypes. Internode elongation rate in the first half of the night was always modest in wild-type tomato, whereas it increased rapidly in the au mutant. Stem elongation rate of wild type starts to increase after about 6 h in darkness, showing the typical time course of escape from Pfr-mediated inhibition of elongation by an end-of-day response. The role of phytochrome level and type in sensing light quantity is discussed.