The Photostability of Different Chlorophyll Forms in Dark Grown Leaves of Wheat

The stability against high intensity irradiation (red light, 700 W m²) was investigated for the chlorophyll(ide) pigments formed after photoreduction of the protochlorophyllide in dark grown leaves of wheat. Connections were found between changes in absorption spectrum in vivo (the Shibata shift and the late red-shift) and changes in photostability both in young (five-day) and old (12-day) leaves. The photostability of both the 684-form and the 673-form as well as the rate of the changes in photostability (the Shibata shift and the late red-shift) decreased with the age of the dark grown plants. It was concluded that the more pronounced decrease in the chlorophyll(ide) contents found at irradiation of older dark grown leaves mostly depended on the lower rate of the changes in the photostability of the pigment in old leaves. No resynthesis of protochlorophyllide occurred before the onset of the late red-shift. The results and their connection with the lag in chlorophyll formation are discussed. This lag is more pronounced in older dark grown wheat.     

The Photostability of Different Chlorophyll Forms in Dark Grown Leaves of Wheat

The stability against high intensity irradiation (red light, 700 W m^?2) was investigated for the chlorophyll(ide) pigments formed after the primary photoreduction of the protochlorophyll(ide) in dark grown leaves of wheat. After photoreduction, most of the chlorophyll(ide) exists in a form with an absorption maximum at 684 nm. This form is gradually transformed into a form with an absorption maximum at 673 nm (the Shibata shift). It was possible to ascribe a specific photostability to each of the pigment forms. This photostability was higher for the 673-form than for the 684-form. A red-shift in the absorption maximum following upon the Shibata shift, reflects the successive transformation of the 673-form into other pigment forms, which were quite photostable at the intensity used.     

The Photostability of Different Chlorophyll Forms in Dark Grown Leaves of Wheat

The effect of denaturing treatments on the stability against high intensity irradiation (red light, 700 W m^?2) was investigated in vivo for various chlorophyll forms in wheat. Three pigment forms were investigated: the 650-form (protochlorophyllide) present in dark grown leaves; the 684-form (chlorophyllide) formed within 5 s after photoreduction of the 650-form; and the 673-form (chlorophyll), into which the 684-form has been transformed 25 min after photoreduction of the 650-form. (The pigment forms are denoted by their absorption maxima in the red region before denaturation.) Two denaturing treatments were used: heat treatment (water of 55°C for 2 min) and freezing and thawing (freezing in liquid nitrogen followed by thawing in water of 25°C). Heat treatment as well as freezing and thawing caused a shift in the absorption peak of the two nonesterified pigment forms. The peak of of the chlorophyllide 684-form shifted to 673 nm and that of the protochlorophyllide 650-form to 636 nm. The absorption maximum of the chlorophyll 673-form was not affected by the above treatments. Heat treatment as well as freezing and thawing had profound effects on the structural organization of the plastid pigments, as shown by a decrease in the photostability. For the 684-form, heat treatment reduced the photostability by a factor of about 14 (half-life in strong light changed from 170 s to 12 s). Freezing and thawing also reduced the photostability, although the effect was less pronounced (c. 3–4 times decrease in half-life). Upon transformation of the chlorophyllide 684-form into the chlorophyll 673-form (the Shibata-shift) the pigments became less sensitive to light, and were no longer “aggregated” by heat treatment. The “aggregating” effect of freezing and thawing was still present after the Shibata shift. The results thus verify a clear difference in structural organization of the 684-form and the 673-form, since the two pigment forms were differently affected by heat treatment. The 650-form behaved similarly to the 684-form, although it appeared to be slightly less aggregated by heat treatment. — The decrease in photostability, caused by heat treatment of the 684-form, changed the kinetics for the photodecomposition from a first towards a second order reaction.     

The Long Wave Length Forms of Chlorophyll a

When Euglena gracilis is cultured with light of low intensity (ca. 250 ft-c), an absorption band at 695 mμ is formed in an amount equal to about 20 per cent of the total chlorophyll absorption in this red region. An equally large proportion of C_a695 is observed in Ochromonas danica, irrespective of light intensity. Other algae tested appear to contain approximately 3 to 5 per cent of their chlorophyll as C_a695; this proportion does not increase as strikingly with lowering of the light intensity as it does in Euglena. C_a695 bleaches more readily than the other chlorophyll forms both reversibly, in whole cells, and irreversibly, in homogenates. Cells containing a large proportion of C_a695 have a fluorescence maximum at 708 mμ, as contrasted to the 687 mμ maximum in other algae. Occasionally, old cultures of Euglena contain cells with an absorption band at approximately 710 mμ. This absorption band is quite stable in aqueous extracts; when the pigment is transferred to ether an equivalent amount of pheophytin a is found to be present. Conditions leading to the formation of the 710 mμ absorption band are not yet known.     

Stacking Capacity and Chlorophyll Forms of Thylakoids in Normal and Mutant Maize Chloroplasts of Different Granum Content

Stacking of chloroplast lamellae, isolated from normal and carotenoid mutant chloroplasts of maize (Zea mays L.), was determined after a high-salt treatment. Stacking of isolated lamellae under favourable ionic conditions was almost identical with that occurring in intact chloroplasts; thus, differences in granum content could be attributed to the architectural properties of lamellae. Gaussian analyses, performed on the red band of room temperature absorption spectra, have shown that chloroplasts with lamellae of high stacking capacity contain relatively more Chl a₆₆₂ than chloroplasts containing lamellae of low stacking capacity. The presence of Chl a_705–708 was characteristic of preparations containing considerable amounts of stroma lamellae.     

The Spectral Response of Light Dependent Chlorophyll b Formation

Dark grown seedlings of barley will obtain a high ratio chlorophyll a/chlorophyll b when exposed to intermittent light (1 min of incandescent light or one electronic flash every hour). Such material has been exposed to monochromatic light of different wavelengths for 1 h. The ratio a/b gets a minimum in light of 670 nm, indicating the highest rate of chlorophyll b formation at this wavelength. The possibility is discussed that the light absorber (and also precursor) could be a short-lived chlorophyll a form, existing prior to the forms in the Shibata-shift. Chlorophyll b formation in darkness is discussed from the findings that the rate of formation of chlorophyll b is higher in intermittent light than it should be, calculated from the rate in continuous light, where the saturation intensity is rather low.     

不同光强对加拿大一枝黄花生长和叶绿素荧光的影响

以外来入侵种加拿大一枝黄花(Solidago canadensis)为研究对象,在4种光照强度处理下,对其光合色素含量、叶绿素荧光特性、比叶重、植株的生长特征和生物量分配等指标进行了测定分析.结果表明:(1)随着光照强度的减弱,加拿大一枝黄花叶片的Chla、Chlb和Chl(a b)均上升,Chla/Chlb下降,4种光强处理下叶片的初始荧光(Fo)、光系统Ⅱ实际光化学效率(ФPSⅡ)、光系统Ⅱ最大光能转化效率(Fv/Fm)日变化曲线相似,高光强下的Fo、ФPSⅡ和Fv/Fm均小于中、低和弱光强下的,这说明加拿大一枝黄花能适应较大的光强幅度,同时对低、弱光强有一定的抗逆性.(2)生长在高(RI为100%)、中(RI为60%)光强下的加拿大一枝黄花植株正常生长,生长于低(RI为20%)弱(RI为5%)光强下的植株生长不良,表现为植株矮小,茎秆细弱.中度的遮荫对它的生长没有明显影响,但在严重遮阴下生长受抑.(3)生长在高、中光强下的总生物量、地下部分生物量明显增多,低、弱光强处理下的叶生物量比显著增加.结果表明,加拿大一枝黄花在高、中光强下对生长最有利,能够适应较大幅度的光照变化,但在严重遮阴下生长明显受抑,说明该入侵植物不易入侵到密林等光照强度比较弱的生境.     

披针叶茴香叶绿素荧光参数对不同光环境的响应

以天目山披针叶茴香(Illicium lanceolatum)4年生栽培幼苗为对象,经不同光环境(自然全光照,50%光照和20%光照)处理后,采用雅欣理1611植物效率仪测试,并进行光系统Ⅱ(PSⅡ)快速叶绿素荧光诱导动力学分析(JIP-test),以探讨其光适应机制,为高莽草酸含量植株高效栽培技术提供理论依据。结果显示:(1)随着遮光程度增加,披针叶茴香叶片叶绿素a(Chl a)、叶绿素b(Chl b)和总叶绿素含量(Chl(a+b))呈上升趋势,均与全光照存在显著差异;Chl a/Chl b值分别降低了22.92%和31.56%,均与全光照差异极显著。(2)随遮光程度增强,PSⅡ最大光能转换效率(Fv/Fm)降低,50%和20%光照处理的Fv/Fm值分别比全光照下降了1.34%和2.79%,且20%光照处理与全光照差异显著。(3)随遮光程度增强,50%光照和20%光照处理叶片单位面积光合机构含有的反应中心数目(RC/CSo)分别比全光照减少了2.94%和13.63%,单位反应中心以热能形式耗散的能量(DIo/RC)分别增加了2.2%和62.9%。研究表明,50%光照处理下披针叶茴香叶片用于光合电子传递的能量占吸收光能的比例变化不显著,而在20%光照处理则显著降低,即50%遮光环境有利于披针叶茴香提高光能利用效率,促进其生长和增加生物量积累。     

不同光环境和发育阶段美国山核桃叶的荧光性状研究

研究美国山核桃同一枝条不同叶位、苗木不同部位、不同方位叶片的叶绿素荧光特性,探讨不同光环境和发育阶段叶片的光合效率,旨在为其高效栽培提供科学依据.以湖南省永州市冷水滩采穗圃中的美国山核桃为试材,系统田间测定了两个品种同一枝条不同叶位、同株苗木不同部位、不同方位叶片叶绿素荧光参数(F0-初始荧光、Fm-最大荧光、Fv/Fm-PSⅡ原初光能转化效率、Fv/F0-PSⅡ潜在活性、Yield-光合量子产额、qp-光化学猝灭系数、qN-非光化学猝灭系数),并测定了苗木不同部位叶片基本性状.结果表明,同一枝条不同叶位、同株苗木不同方位叶片荧光参数末达显著差异,但仍表现一定的规律性;同株苗木不同部位叶片性状与荧光参数Yield、qN均存在显著或极显著差异.相关分析表明,苗木不同部位叶片的Yield、qN与部分叶片性状均呈显著或极显著相关.     

不同光照条件下东北红豆杉幼苗叶绿素荧光特性日变化

为了解东北红豆杉的光适应特性达到高效培育的目的,以5年生东北红豆杉幼苗为研究对象,研究了3种光照条件下（全光照FL、60%全光照F1和30%全光照F2）幼苗荧光参数的日变化规律。结果显示：7:00~17:00时,FL和F1条件下幼苗的F_o分别升高了23.0%和14.0%,F2略有下降。3组幼苗的F_m和F_v/F_m在降到最低点后都有所回升,FL、F1和F2幼苗的F_m最多下降了38.0%,28.0%和23.0%,F_v/F_m下降了14.0%,6.4%和4.2%。F2幼苗的Φ_PSⅡ最高,变化趋势与光照强度相近;FL和F1幼苗的Φ_PSⅡ变化趋势相似,在9:00时达到高点后逐渐下降,至15:00时达最低点,只是FL幼苗的更低。3组幼苗ETR变化的明显差异体现在一天中的高光温时段（11:00~15:00时）,F2幼苗的ETR呈现峰值,F1幼苗保持平稳,FL幼苗呈现谷值。F2幼苗的qP最高,变化趋势与光照强度一致;FL和F1条件下幼苗的qP在13:00时和15:00时现谷值。F2幼苗的NPQ全天平缓下降;FL和F1幼苗的NPQ在9:00时和13:00时（15:00时）呈现峰值。综合以上荧光参数变化,F2幼苗全天以光化学反应为主,以热辐射形式耗散掉的光能较少。FL和F1幼苗在高光温时段出现光抑制,此时幼苗通过增加热耗散的方式进行了自我保护,且其光合机构未受到破坏。     

Oligomeric Forms of Glycolytic Enzymes in Chlorella Grown in Different Light Qualities*

Fast protein liquid chromatography on Superose 6 of crude extracts from the green alga Chlorella kessleri cultivated autotrophically in white light reveals several peaks with phosphofructokinase (PFK, EC 2.7.1.11) or pyruvate kinase (PK, EC 2.7.1.40) activity with molecular weights larger than the usually reported ones of 320–380 and 240 kDa, respectively. All other glycolytic enzymes are eluted as one peak each with a molecular weight corresponding to data from the literature. Indirect evidence indicates that the various forms of PFK and presumably PK are oligomers. The occurrence of different PFK species depends markedly on growth conditions such as wavelength of light: Red light leads to only one rather large PFK (1,580 kDa), blue light to two smaller species (760 and 360 kDa). All species are probably present in white light-grown cells (1,500, 1,050, 930, 700 and 440 kDa). The various light qualities do not significantly affect all other glycolytic enzymes. PK constantly exhibits four forms with molecular weights of 830, 680, 480, 305 kDa. Experiments with the chlorophyll-free mutant no. 20 of Chlorella kessleri support the assumption that oligomerization of enzymes is characteristic of regulatory enzymes, thereby providing the cell with an additional regulatory means.     

Properties of Oligomeric Forms of Phosphofructokinase from Chlorella kessleri Grown under Different Light Conditions

Fast protein liquid chromatography on Superose 6 of crude extracts from Chlorella kessleri, Fott et Novákóva, grown autotrophically in blue or in red light yields three different oligomeric forms of phosphofructokinase (PFK, EC 2.7.1.11). Their substrate affinities and responses to homotropic and heterotropic effectors are different. In vitro, the degree of oligomerization of the enzyme can be influenced by specific intermediates or cofactors. Its substrate, MgATP (10 mM/5 mM), and the negative effector, phosphoenolpyruvate (5 mM), both lead to some dissociation, while the second substrate, fructose-6-phosphate (5 mM), and the positive effector, inorganic phosphate (50 mM), have no effect. It is discussed whether formation or dissociation of oligomeric PFK forms in vivo result from alterations in the levels or in the intracellular distribution of effector molecules and whether such processes are involved in the different regulation of cell metabolism in blue or in red light.     

Temperature-Induced Change of Chlorophyll a Forms in Phosphatidylcholine Liposomes

Absorption spectra of chlorophyll a in phosphatidylcholine liposomesat different temperatures were analyzed by a curve fitting method.The absorption spectrum was found to be composed of one majorband with a peak at 670–671 nm and minor bands with peaksat 650–652, 662–663 and 684–686 nm. Upon coolingbelow the phase transition temperature of the lipid, the componentabsorbing at 670–671 nm increased significantly at theexpense of the component absorbing at 662–663 nm. No changein the extents of other bands was observed. ¹ CIW-DPB Publication No. 795. ²On leave from the Department of Biology, Faculty of Science,Kanazawa University, Marunouchi, Kanazawa 920, Japan. (Received December 20, 1982; Accepted April 27, 1983)     

Urease Activity and Urea Gene Sequencing of Coccoid Forms of H. pylori Induced by Different Factors

Helicobacter pylori exists in two morphologic forms: spiral shaped and coccoid. The nonculturable coccoid forms were believed to be the morphologic manifestations of cell death for a long time. However, recent studies indicate the viability of such forms. This form of H. pylori is now suspected to play a role in the transmission of the bacteria and is partly responsible for relapse of infection after antimicrobial treatment. Urease activity of H. pylori is an important maintenance factor. Determination of urease activity and possible mutations in the DNA sequences of coccoid bacteria will hence contribute to the understanding of pathogenesis of infections, which these forms might be responsible for. In this study, our aim was to analyze the urease activity and investigate the urease gene sequences of coccoid H. pylori forms induced by different factors with respect to the spiral form. For this purpose, the urease activities of H. pylori NCTC 11637 standard strain and two clinical isolates were examined before and after transformation of the cells to coccoid forms by different methods such as exposure to amoxicillin, aerobiosis, cold starvation, and aging. The effects of these conditions on the urease gene were examined by the amplification of 411-bp ureA gene and 115-bp ureB gene regions by PCR technique and sequencing of the ureA gene. The urease activities of coccoid cells were found to be lower than those of the spiral form. ureA and ureB gene regions were amplified in all coccoid cells by PCR. Inducing the change to coccoid form by different methods was found to have no effect on the nucleotide sequence of the ureA gene. These results show that the urease gene region of coccoid H. pylori is highly protected under various mild environmental conditions.     

Light Gradients and the Transverse Distribution of Chlorophyll Fluorescence in Mangrove andCamelliaLeaves

The light gradient and transverse distribution of chlorophyllfluorescence in mangrove andCamellialeaves, which have differentmorphological characteristics, were examined using a micro-fluorescenceimaging system reported previously (Takahashiet al., Plant,Cell and Environment17: 105–110, 1994). Epidermal cellsscattered light strongly, resulting in an increase in the fluencerate in epidermal cells. For theCamellialeaf, a light gradientwas formed by absorption of light by photosynthetic pigmentsassociated with the induction of chlorophyll fluorescence. Forthe mangrove leaf, a light gradient was formed by backward scatteredlight within a thick layer of non-assimilatory cells. Lightwith a low absorption coefficient (515 nm) penetrated deeperthan that with a higher absorption coefficient (477 nm and 488nm) in theCamellialeaf, while light of both wavelengths showedsimilar profiles in the mangrove leaf. In the mangrove leaves,scattered light declined significantly in the non-assimilatorycell layer which is in front of the assimilatory cells. Light,the intensity of which was reduced to approx. 10% of the maximum,was well scattered and induced a considerable amount of chlorophyllfluorescence in the assimilatory cells, which appear to be wellorganized to capture weak light.Copyright 1998 Annals of BotanyCompany fluorescence, intact leaf, light gradient, mangrove (Rhizophora mucronataLamk.),Camellia japonicaL.     

Effect of Different Carbon Sources on the Ammonium Induction of Different Forms of NADP-Specific Glutamate Dehydrogenase in Chlorella sorokiniana Cells Cultured in the Light and Dark

The ammonium induction of the chloroplast-localized NADP-specific glutamate dehydrogenase (NADP-GDH) was shown not to be a light-dependent process per se in Chlorella sorokiniana. In the dark without exogenous organic substrates, the cells synthesized low levels of fully active NADP-GDH, provided endogenous starch reserves had not been depleted. When cells were supplied with exogenous acetate, the rate of induction of NADP-GDH activity per milliliter of culture in the dark was equal to or slightly greater than the rate observed under photosynthetic conditions without an organic carbon source. Glucose supported only a low rate of induction of NADP-GDH activity in the dark. Both acetate and glucose inhibited induction of enzyme activity in the light. The NADP-GDH holoenzyme had at least 7 different electrophoretic forms. These forms differed in net charge and/or molecular weight. Their difference in molecular weight was due to the presence of 2 subunits with similar antigenic properties but different molecular weights (M_r = 55,500 and 53,000; α-and β-subunits, respectively). Depending upon the cultural conditions and length of the induction period, a wide variation was observed in the α:β subunit ratio and in the numbers and sizes of the NADP-GDH holoenzymes.