PHOTOCONTROL OF ANTHOCYANIN SYNTHESIS IN TOMATO SEEDLINGS: A GENETIC APPROACH*

The photocontrol of anthocyanin synthesis in dark-grown seedlings of tomato (Lycopersicon esculentum Mill.) has been studied in an aurea (au) mutant which is deficient in the labile type of phytochrome, a high pigment (hp) mutant which has the wild-type level of phytochrome and the double mutant au/hp , as well as the wild type. The hp mutant demonstrates phytochrome control of anthocyanin synthesis in response to a single red light (RL) pulse, whereas there is no measurable response in the wild type and au mutant. After pretreatment with 12 h blue light (BL) the phytochrome regulation of anthocyanin synthesis is 10-fold higher in the hp mutant than in the wild type, whilst no anthocyanin is detectable in the au mutant, thus suggesting that it is the labile pool of phytochrome which regulates anthocyanin synthesis. The au/hp double mutant exhibits a small (3% of that in the hp mutant) RL/far-red light (FR)-reversible regulation of anthocyanin synthesis following a BL pretreatment. It is proposed that the hp mutant is hypersensitive to the FR-absorbing form of phytochrome (P_fr) and that this (hypersensitivity) establishes response to the low level of P_fl. (below detection limits in phytochrome assays) in the au/hp double mutant.     

KINETICS OF Pfr APPEARANCE IN Amaranthus caudatus‡

Abstract— The kinetics of the far-red absorbing form of phytochrome (P_fr) appearance from intermediates in the pathway from the red absorbing form of phytochrome (P_r) to P_fr that accumulate under high fluence rate white light have been investigated in 3-day old dark grown Amaranthus caudatus seedlings. The appearance of P_(r after a 5 s white light pulse was measured over the temperature range -8 to 25^°C in samples flushed with O₂ or N₂. Over the whole temperature range under anaerobic conditions the kinetics of the slowest component of P_fr appearance are faster than in the presence of O₂. Arrhenius plots are linear over this temperature range and indicate the activation energy for the slowest component of P_fr appearance is 44.05 ± 1.97 kJ mol^?1 for O₂ and 53.69 ± 4.86 kJ mol^?1 for N₂.     

Scale size of magnetic turbulence in tokamaks probed with 30-MeV electrons

Measurements of synchrotron radiation emitted by 30-MeV runaway electrons in the TEXTOR-94 tokamak show that the runaway population decays after switching on neutral beam injection (NBI). The decay starts only with a significant delay, which decreases with increasing NBI heating power. This delay provides direct evidence of the energy dependence of runaway confinement, which is expected if magnetic modes govern the loss of runaways. Application of the theory by Mynick and Strachan [Phys. Fluids 24, 695 (1981)] yields estimates for the "mode width" (delta) of magnetic perturbations: delta<0.5 cm in Ohmic discharges, increasing to delta = 4.4 cm for 0. 6 MW NBI.     

Induced solvent chirality: A VCD study of camphor in CDCl3

It is shown how the presence of a chiral compound in solution induces chirality in the surrounding solvent molecules. Using Vibrational Circular Dichroism on camphor dissolved in deuterated chloroform, it is found that the C–D stretch in the latter indeed becomes VCD active. The experimental results agree with ab initio computed spectra for 1:1 associations between the solvent and solute.