A METHOD FOR MEASURING PHYTOCHROME IN PLANTS GROWN IN WHITE LIGHT

Abstract— Quantitative spectrophotometric measurement of phytochrome in plants grown for relatively long periods of time in white light is not possible due to the presence of chlorophyll. A method is described that prevents the accumulation of chlorophyll permitting such direct spectrophotometric measurement in light-grown tissue. Oat seedlings grown in the presence of the herbicide San 9789† (Norflurazon) for 6 days in constant light have considerably less chlorophyll than etiolated seedlings exposed to 1 min of light. Phytochrome concentrations measured in vivo and in vitro in these herbicide-treated plants were found to be about 2% of the level in etiolated tissue.     

STIMULATION OF THE SHIBATA SHIFT BY PHOTOCHROME IN THE COTYLEDONS OF THE MUSTARD SEEDLING SINAPIS ALBA L.

Abstract— In the cotyledons of the mustard seedling Sinapis alba L. the duration of the Shibata shift can be greatly shortened by a pretreatment with light pulses prior to the protochlorophyllide– chloro-phyllide a photoconversion. It was shown that the light pulses act through photochrome (P _fr ). Since reversibility of a red light pulse induction by a far-red light pulse is rapidly lost (within 2 min) it is concluded that at least the initial action of P_fr occurs rapidly in this response. On the other hand, the effect of a red light pulse on the rate of protochlorophyll regeneration in the mustard seedling cotyledons is fully reversible by a far-red light pulse for more than 5 min. It is concluded that control of protochlorophyll regeneration and control of the Shibata shift by phytochrome cannot be consequences of the same initial action of P_fr Apparently P_fr controls both phenomena independently.     

STUDIES ON PHYTOCHROME PHOTOCONVERSIONS IN VITRO WITH LASER-INDUCED OPTOACOUSTIC SPECTROSCOPY*

After excitation at room temperature with a 15 ns dye laser pulse, phytochrome (60 kDalton) from etiolated oat seedlings was studied by optoacoustic spectroscopy, which records the heat emission caused by non-radiative deactivation processes of the photoexcited molecule. The action spectrum for the heat emitted by P_r deviates from the absorption spectrum around 610 and 695 nm, indicating the build-up of photoproduct(s) within 15 ns after excitation. It is proposed that the 695 nm product is identical with I₇₀₀ and lumi-R known to be the first intermediate on the P_r× P_fr pathway, and that the photochemical back reaction of I₇₀₀ to P_r occurs on the same time scale. About 90% of the absorbed light energy was lost by radiationless deactivation. Values for the rate constants of excited state deactivation of P_r and for the internal energy content difference of the primary photoproducts are calculated.     

Multi-orbital Anderson models and the Kondo effect: a NCA study enhanced by vertex corrections

The low energy region of certain transition metal compounds reveals dramatic correlation effects between electrons, which can be studied by photoelectron spectroscopy. Theoretical investigations are often based on multi-orbital impurity models, which exhibit modified versions of the Kondo effect. We present a systematic study of a multi-orbital Anderson-like model, based on a new semi-analytical impurity solver which goes beyond simple modifications of the well known NCA. We discuss one-particle excitation spectra and in particular the role of level positions and Coulomb-matrix elements. It is shown that the low-energy region as well as the overall features of spectra critically depend on the model parameters and on the quality of the approximations used. Recent photoelectron experiments and corresponding existing calculations are put into perspective. An interesting crossover scenario between different regimes of ground states with characteristically different local correlations is uncovered.     

PHOTOPHYSICAL PARAMETERS OF CHLOROPHYLLS a AND b·FLUORESCENCE AND LASER-INDUCED OPTOACOUSTIC MEASUREMENTS

Abstract— The quantum yields of internal conversion (energy loss) of the photoexcited chlorophylls a and b in ethanol at 24°C have been determined by measuring the quantum yields of the competing radiative (fluorescence) and non-radiative (intersystem crossing) deactivation processes (which lead to energy storing species) by means of emission and laser-induced optoacoustic spectroscopy, respectively. The values for internal conversion of chlorophyll a are 10% and 14% in the presence and absence of molecular oxygen, respectively. The corresponding yields for chlorophyll b are negligibly small. The internal conversion in chlorophyll a is attributed to vibronic coupling with the substituents of the porphin system, since internal conversion was found to be substantially reduced for unsubstituted Mg-porphin in ethanol and for chlorophyll a when dissolved in a viscous medium.     

Strukturuntersuchungen an Copolymeren aus Methylmethacrylat und Methylenmalons?uredimethylester durch kernmagnetische Resonanz

Zusammenfassung Aus zwei oder mehreren Monomerbausteinen aufgebaute Copolymere sind nicht nur durch ihre Bruttozusammensetzung, sondern auch durch die Häufigkeiten der in ihnen enthaltenen — chemisch und konfigurativ unterschiedlichen — Sequenzen charakterisiert. Die entsprechende chemische Mikrostruktur läßt sich grundsätzlich aus der Kinetik der Copolymerisation vorausberechnen, was am Beispiel der radikalisch initiierten Copolymeren aus Methylmethacrylat (MMA) und Methylenmalonsäuredimethylester (MME) in dieser Arbeit erfolgt. Unabhängig davon wurde die chemische Mikrostruktur durch hochauflösende protonenmagnetische Resonanz bei 220 MHz ermittelt; zusätzlich wurde hierdurch auch die konfigurative Mikrostruktur der Copolymeren aufgeklärt.Der Anteil der beiden Monomerbausteine wurde in einer Reihe von Copolymeren aus den Spektren ermittelt und daraus die Copolymerisationsreaktivitätsverhältnisse zu r _A =0,43±0,02 und r _B =0,35±0,05 berechnet. Der Resonanzbereich der -CH₃-Protonen wurde als in 6 Peaks aufgespalten gefunden, verursacht durch den unterschiedlichen chemischen und konfigurativen Aufbau von Triaden aufeinanderfolgender Monomerbausteine. Die Zuordnung der 6 Peaks zu den 6 möglichen durch KMR unterscheidbaren Triaden wurde durchgeführt. Das für die Berechnung der Reaktivitätsverhältnisse und die Ermittlung der Zuordnung vorausgesetzte Copolymerisationsmodell sowie der für die Zuordnung ebenfalls benötigte und aus den KMR-Spektren von Polymethylmethacrylat abgeleitete Taktizitätsparameter _AA , wurden mit Hilfe der Flächen der -CH₃-Peaks auf ihre Gültigkeit hin überprüft. Die bedingten Wahrscheinlichkeiten der Mikrostruktur wurden sowohl aus den Reaktivitätsverhältnissen als auch unabhängig davon aus den relativen Mächen der -CH₃-Resonanzpeaks ermittelt und verwendet, um die Häufigkeiten von Sequenzen chemischer und konfigurativer Art an einigen typischen Beispielen zu berechnen.

---

Investigations of structure of copolymers of methyl methacrylate and methylene malonic acid dimethylester by nuclear magnetic resonance

Copolymers consisting of two or more monomer units are characterized not only by their gross composition, but also by the frequencies of occurrence of their different chemical and configurational sequences. The corresponding chemical micro structure may in principle always be pre-calculated from the kinetics of copolymerization. This calculation has been carried out for radial initiated copolymers of methyl methacrylate (MMA) and methylene malonic acid dimethylester (MME). Independently, the chemical micro structure has been determined by high resolution proton magnetic resonance at 220 MHz. In addition, the configurational micro structure has been elucidated by this means.In a series of copolymers the fraction of the monomer units has been determined from the spectra, and the copolymerization reactivity ratios r _A =0.43±0.02 and r _B =0.35±0.05 have been calculated therefrom. The resonance region of the -CH₃ protons has been found to be split into 6 individual peaks which are overlapped to a different degree. The splitting is caused by different chemical and configurational structures in triads of consecutive monomer units. The assignment of the 6 individual peaks to the 6 possible triads, which latter are distinguishable by NMR, has been carried out. The copolymerization model on which the calculation of the reactivity ratios and the elucidation of the assignment has been based, as well as the tacticity parameter _AA which was also necessary for securing the assignment and which was derived from the NMR spectra of polymethyl methacrylate, have been checked for their validity by means of the areas of the -CH₃ resonance peaks. The conditional probabilities of micro structure as derived from the reactivity ratios and also, independently, from the areas of the -CH₃ peaks have been employed for calculating the frequencies of occurrence for some typical chemical and configurational sequence of monomer units.

---

---

Vortrag anläßlich der Tagung der GDCh-Fachgruppe Analytische Chemie vom 9.–11. April 1969 in Freiburg i. Br.     

DEPENDENCE OF Pfr/Ptot-RATIOS ON LIGHT QUALITY and LIGHT QUANTITY

Abstract— Not only the spectral distribution of the light source determines the relative proportion of phytochrome in the P_fr(P_r) form, the P_fr/P_tot-ratio also depends strongly on the fluence rate of the irradiation. This dependence has been observed in the cotyledons of etiolated mustard seedlings for blue light of fluence rates below 20 Wm_-2. It has also been observed for white light and seems to be a characteristic of the phytochrome system resulting from the involvement of phytochrome thermal reactions as well as P_r P_fr photoconversions. The fluence rate dependence of P_fr/P_tot-ratios can be used to analyze the characteristic transformations of the phytochrome system. Phototransformations together with a fast thermal transformation (τ_½⋍ 3min) are consistent with the results obtained for blue and white light.     

PHYTOCHROME-STIMULATED REGENERATION OF PROTOCHLOROPHYLL IN COTYLEDONS OF THE MUSTARD SEEDLING

Abstract —It has been shown [Kasemir, H., U. Oberdorfer and H. Mohr, Photochem. Photobiol. (1973) 18 , 481–486] that elimination of the lag phase of chlorophyll a (Chl) accumulation in continuous white light is due exclusively to the action of phytochrome (P_fr). In the present paper we show that the action of P_fr on the lag phase of Chl accumulation can be understood quantitatively as a consequence of the action of P_fr on the initial rate of protochlorophyll (PChl) regeneration. Disappearance of PChl (or formation of Chl) can be excluded as a control signal for the light-mediated changes in rate of PChl regeneration. The P_fr control of PChl regeneration does not discriminate between PChl 650 and PChl 637. The action of P_fr on the PChl regeneration is a relatively fast process (time lag < 3 h). On the other hand, the effect remains stable over long periods (at least 24 h) in darkness.     

PHYTOCHROME DESTRUCTION IN DARK - AND LIGHT-GROWN AMARANTHUS CAUDATUS SEEDLINGS

Abstract— Slow destruction of the far-red-absorbing form of phytochrome (P_fr), which has been observed in light-grown oat and maize, occurs in light- and dark-grown Amaranthus, Pharbitis , and Brassica seedlings as well. Destruction of P_fr in these seedlings shows two phases: if a high level of P_fr is produced in dark-grown seedlings, the destruction is fast in the beginning and then slows after a low P_fr level has been reached. Slow P_fr destruction is predominant in light-grown tissue.