ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1985.tb01621.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1985.tb01622.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract—An examination has been made of the involvement of phytochrome in the circadian rhythm of flowering inPharbitis nilChois. The peak position of Pfrabsorption changes with time after a red light pulse. The shortest absorption wavelength of Pfroccurs at the same time as flowering is inhibited by red light in dark grown, red light pretreated plants. Pelletable and supernatant phytochrome show a similar trend with lowest values found at the time of flower inhibition. Neither phototransformation kinetics nor intermediates of phytochrome which accumulate in white light show such a relationship to the circadian rhythm found in flowering of dark grownP. ni

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1985.tb01623.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract—To probe the nature of primary photoprocess and the mechanism of the phototransformation of undegraded 124 kDa oat phytochrome, solvent deuterium isotope effects on the fluorescence and phototransformation of phytochrome have been investigated. The fluorescence intensity and lifetime of phytochrome (Prform) are greater in D20‐buffer than in H2O‐buffer, suggesting a possible involvement of proton transfer in the primary photoprocess of phytochrome. Although the photostationary equilibrium (Prto Pfrratio) was not altered by deuterium oxide, in contrast to degraded phytochrome, the rate constants of both transformations, Pr→ Pfrand Pfr→ Prwere enhanced by up to 24%. The Prto Pfrphototransformation of degraded phytochrome, however, was retarded by about the same percentage in D2O. These opposite effects of D2O with degraded and undegraded phytochromes underscore the fact that the Prform from the former reverts to the Prform in the dark, apparently catalyzed by deuterated general and/or conjugate acidic group(s). With the degraded phytochrome the deuterium oxide enhancement of the rate of dark reversion was approximately 2‐fold (Sarkar and Song, 1981).Both the fluorescence intensity and the rates of phototransformation of phytochrome were enhanced in D2O with successive photocyclings (Pr→ Pfr→ Pr→ Pfr→ Pretc.) with alternating red and far‐red irradiation. It has been proposed that successive photocycling of phytochrome in D2O results in proton‐deuteron exchange in the partially exposed Ptrchromophore and/or its surround

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1985.tb01624.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract—De‐etiolation of maize seedlings reduces their sensitivity for red light potentiation of rapid chlorophyll accumulation in white light. An earlier proposal (Raven and Spruit, 1973) attributes this to migration of the far‐red absorbing form of phytochrome (Pfr) to receptors essential for chlorophyll synthesis, thereby increasing the local Pfr/total phytochrome (Ptot)ratio. We have studied etioplasts as possible loci for such P(rreceptors.The level of spectrophotometric phytochrome in purified etioplasts isolated from red preirradiated maize seedlings was higher than that of dark grown plants. The difference was marginally significant, however. We argue that migration of a fraction of cytoplasmic Pfrto the etioplasts, too small to be spectrophotometically demonstrable, could still meet the requirements of the model.Dark destruction of bulk spectrophotometric Pfrfollowing saturating red irradiation of seedlings is not paralleled by a decrease of etioplast phytochrome. the latter remaining essentially constant over long periods. On the other hand, the potentiating effect of red light in intact seedlings is still partially reversible by far red light even after 24 h of darkness when destruction of bulk Pfris complete. Since this demonstrates persistent presence of Pfractive in potentiation, we propose that at least part of this Pfris associated with the etiop

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1985.tb01625.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract—The exact quantity of phytochrome in crude homogenates (2kS) prepared from embryonic axes ofPisum sativumduring imbibition at 25°C on 0,2% agar was estimated optically. The problem of the scattering factor was solved by using highly purified phytochrome as an internal standard. The content of phytochrome protein moiety in diluted samples of the crude homogenates of the axes was also determined by an enzyme‐linked immunosorbent assay (ELISA). Phytochrome was not detectable either spectropho‐tometrically or immunochemically in 2kS of dormant dry axes. Embryonic axes quickly absorbed water during the first1–2 h after the start of imbibition, after which the fresh weight stayed at a constant level for a further 10 h. The content of spectrophotometrically detectable phytochrome increased during imbibition in the dark, reaching about 0.2 μ.g/axis after 12 h. The amount of phytochrome in 2kS of axes in the light was so small that only about 0.05 μg/axis was detected after 12 h. The content of immunochemically detectable phytochrome greatly increased up toca.0.5 μg/axis after 12 h of dark incubation. In 2kS of the light‐grown axes the content of the phytochrome protein wasca.one fourth lower than in dark‐grown axes. We conclude that the appearance and increase of phytochrome in fragments of imbibed embryonic axes were caused byde novosynthesis and that the contents of both photometrically detectable phytochrome and its protein moiety in the light‐grown samples were lower than those in the dark throughout the early ge

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1985.tb01626.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract—Sensitization of the phytochrome‐mediated germination at 20°C of lettuce seeds (Lactuca sativa L. cv. Grand Rapids) by pretreatment at 4°C, 28°C, or on 1% ethanol, was studied. The 660 nm fiuence‐response characteristics were similarly biphasic for all sensitizing treatments and displayed responses at very low fluences (VLFR) as well as responses characteristic of non‐sensitized seeds at 10000‐fold higher, low fluences (LFR). Maximum VLFR increased with the duration of sensitizing treatments. However, the fluence ranges required for the two types of responses remained relatively constant. These and additonal responses of sensitized seeds to 730 nm fluences were compared to simulations of a mechanism involving a receptor,X, and based on the dimeric structure of phytochrome in which each monomer is independently phototransformed from the inactive (Pr) to the active (Pfr) form. The fluence requirements for phytochrome photoconversion in seeds were determined to be similar to those of purified Avena phytochrome in vitro, on which photochemical parameters for the simulations were based. The analyses suggest that Pr:Pfr‐Xand Pfr:Pfr‐Xare responsible, respectively, for the VLFR and the LFR, and that sensitization involves membrane influences on the activity ofPr:Pr‐X.They also suggest the concentration ofXto be about 0.001 that of total phytochrome di

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1985.tb01627.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract—Absorption spectra of the chromophore of C‐phycocyanin, in its free base form and as its zinc complex, were measured after denaturation with 8Murea and with a cationic detergent. An acidic and an alkaline form of the zinc complex are distinguished. The acidic form shows photoreversible photochrom‐ism, but only when it is embedded in detergent micelles. The photochromism is tentatively ascribed to a direct photoisomerization of the chromo

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1985.tb01628.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract—The CD spectra of a range of antenna complexes from several different species of purple photosynthetic bacteria were recorded in the wavelength range of 190 to 930 nm. Analysis of the far UV CD (190 to 250 nm) showed that in each case except for the B800‐850 fromChr. vinosumthe secondary structure of the light‐harvesting complexes contains a large amount of α‐helix (˜50%) and very little 0‐pleated sheet. This confirms the predictions of the group of Zuber of a high a‐helical content based upon consideration of the primary structures of several antenna apoproteins. The CD spectra from the carotenoids and the bacteriochlorophylls show considerable variations depending upon the type of antenna complex. The different amplitude ratios in the CD spectrum for the bacteriochlorophyll Qy, Qx and Soret bands indicate not only different degrees of exciton coupling, but also a strong and variable hyperchromism (Scherz and Pars

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1985.tb01629.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract—We have used specific, cloned cDNA hybridisation probes to measure the abundance of transcripts for the small subunit (SSU) of ribulose bisphosphate carboxylase‐oxygenase, and the major apoprotein (LHCP) of the light‐harvesting chlorophyllalbcomplex, in total RNA extracts ofPisum sativumshoots grown under different light qualities. The plants were grown in continuous white light of a constant fluence rate (50 p.mol m−2s−1;400–700 nm) supplemented with far‐red light to give different ratios of red: far‐red light, and hence differentin vivophytochrome photoequilibria. Variation of the red: far‐red ratio over the range 1.87 to 0.10, calculated to givein vivoPfr: Ptotalratios of 0.78 to 0.37, had no significant effect on leaf expansion but had a marked effect on internode extension rate. The abundances of the SSU and LHCP RNAs in RNA extracts from the terminal shoot were not significantly different in the four light quality treatments. The results are discussed in relation to the photoregulation of expression of these genes in l

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1985.tb01630.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY