Changes in Protein Content and in the Structure and Number of Chloroplasts during Leaf Senescence in Rice Seedlings

Two types of experiment were carried out to examine whetheror not the inactivation of photosynthesis is related to lossof chloroplasts during foliar senescence of rice seedlings.Levels of both soluble and insoluble leaf proteins decreasedduring senescence, the loss of the soluble proteins being fasterthan that of the insoluble ones. There was a good positive correlationbetween the rate of oxygen evolution and the level of solubleproteins. The inactivation of photosynthesis was also linearlyrelated to the loss of a major fraction of insoluble proteins.Thus, the loss of photosynthetic ability is ascribable to thedegradation of relevant proteins and enzymes during leaf senescence.Electron microscopy revealed that senescence caused the disorientationof the grana and stroma thylakoids, a decrease in the numberof starch granules, and an increase in the size and number ofplastoglobuli. Large grana consisting 20 to 30 thylakoids appearedin aged leaves. In addition to these changes in ultrastructure,there was a significant decrease in the size of chloroplasts.Furthermore, the number of chloroplasts in mesophyll cells wasalso notably reduced during senescence. Thus, the loss of leafproteins and inactivation of photosynthesis are both relatedto the decrease in the total mass of chloroplasts during senescenceof rice seedlings. ³Present address: Department of Botany, Faculty of Science,University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113 Japan. (Received January 4, 1989; Accepted April 19, 1989)     

Demonstration of light-induced potential change in Chara cells lacking tonoplast

Chara cells without tonoplasts, prepared by replacing the cellsap with EGTA-containing media, showed essentially the samepattern of light-induced changes in membrane potential and membraneresistance as normal cells although the concentrations of ionsand ATP in the cytoplasm decreased considerably (1/3–1/10)after loss of the tonoplast. Removal of the tonoplast reducedthe rate of photosynthetic O₂ evolution to about 50% of thatof normal cells but did not affect the magnitude of light-inducedpotential change. Not a full but a certain level of electronflow seems necessary to activate the putative electrogenic H⁺-pump. ¹ Present address: Department of Botany, Faculty of Science,University of Tokyo, Japan. ² Present address: Niigata College of Pharmacy, Niigata 950-21,Japan. (Received September 4, 1978; )     

Exposure of Leaves of Cucumis sativus L. to Low Temperatures in the Light Causes Uncoupling of Thylakoids I. Studies with Isolated Thylakoids

Chilling of leaves of cucumber (Cucumis sativus L.) at 5?C inmoderate light for 5 h caused almost complete suppression ofphotosynthetic oxygen evolution in the leaves. Comparison ofelectron transport activities determined in the presence andabsence of an uncoupler, methylamine, indicated that thylakoidsprepared from such treated leaves were uncoupled without anysignificant changes in the capacity for electron transport.Immunoblotting revealed that the amount of coupling factor 1(CF₁) associated with membranes was reduced by the chillingtreatment in the light. Thylakoids prepared from leaves thathad been chilled in moderate light for 5 h and then re-warmedfor 1 h were coupled and capable of synthesising ATP. However,the capacity of leaf photosynthesis was not restored by therewarming. These results indicate that the thylakoids are uncoupledby the dissociation of some CF₁ complexes from the thylakoidmembranes during the chilling treatment of leaves in the lightand that thylakoids are recoupled by reassociation of CF₁ duringthe subsequent rewarming of the treated leaves at 25?C. It alsoappears that chilling in the light causes irreversible damageto reaction(s) other than those involved in electron transportand photophosphorylation. ¹ Present address: Department of Biological Science, Facultyof Science, Himeji Institute of Technology, Kamigori, Ako-gun,Hyogo, 678-12 Japan (Received July 1, 1991; Accepted October 4, 1991)     

CHOICE OF BIOASSAY IN ASSESSING ACTIVITY OF ENDOGENOUS GROWTH SUBSTANCES

A chloroform extract of peelings and buds of ‘Red Pontiac’potato tubers yielded chromatographic eluates that exhibitedqualitatively and quantitatively different stimulating and inhibitingresponses on four bioassays. The essentiality of selecting asatisfactory array of bioassays, coupled with a thorough extractionprocedure, is emphasized. ¹This research was supported by United States Public HealthService Grant EF-61 ²Present address: Department of Botany, Hebrew University, Jerusalem,Israel ³Present address: Department of Agronomy, University of Tokyo,Bunkyo-ku, Tokyo     

Photoregulation of Respiratory Activity in the Cyanophyte Synechocystis PCC 6714: the Possibility of the Simultaneous Regulation of the Amount of PS I Complex and the Activity of Respiratory Terminal Oxidase in Thylakoids

Respiration of the cyanophyte Synechocystis PCC 6714 was studiedin relation to conditions for cell growth. Under our experimentalconditions, the KCN-sensitive O₂-uptake observed with intactcells was found to be limited at the step catalyzed by the terminaloxidase in thylakoids, indicating that the activity of O₂-uptakeby intact cells corresponds to that of the terminal oxidasein thylakoids. The activity was found to be variable dependingon the growth conditions; it was higher under conditions wherethe level of PS I, another terminal component of the thylakoidelectron transport system (ETS) was elevated, whereas it waslower under conditions where the level of PS I was reduced.Changes in the activity did not occur when protein synthesiswas suppressed by chloramphenicol. The results suggest that,similarly to the regulation of levels of PS I, the activityor the amount of terminal oxidase in thylakoids is regulatedin response to the redox steady-state of intermediate component(s)of ETS, in order to maintain a balance between the efflux ofelectrons from the ETS and the influx to the ETS. ¹Present address: P.G. Department of Botany, Utkal University,Bhubaneswar-751004, Orissa, Keonjhar, India (Received September 27, 1989; Accepted March 22, 1990)     

Effects of growth temperature on photosynthetic carbon metabolism in green plants III. Differences in structure, photosynthetic activities and activities of ribulose diphosphate carboxylase and glycolate oxidase in leaves of wheat grown under varied temperatures

The rate of ferricyanide photoreduction in broken chloroplastsisolated from leaves of wheat acclimatized to a low temperature(mean temperature, 5–7?C) was similar to that in chloroplastsfrom wheat acclimatized to a high temperature (20–25?C). There was no practical difference in glycolate oxidase activityin leaf extracts of wheat plants grown at low and high temperatures.In contrast, the ribulose diphosphate carboxylase activity ofchloroplasts from low temperature sample was less than halfthat for the high temperature sample. Chloroplasts having a high rate of photosynthetic CO₂-fixationwere obtained from wheat acclimatized to a low temperature,whereas the CO₂-fixation activity in chloroplasts isolated fromhigh temperature-acclimatized wheat was very low. Electron microscopy revealed that chloroplasts in high temperature-acclimatizedwheat were ellipsoidal, electron dense and contained starchgranules. Those in low temperature-acclimatized leaves wereround and did not contain starch granule. ²Present address: Department of Botany, Faculty of Science,University of Tokyo, Tokyo, Japan (Received August 7, 1973; )     

COMPARATIVE STUDIES ON GROWTH, RESPIRATION, PHOTOSYNTHESIS AND PIGMENT CONTENT IN RHODOPSEUDOMONAS PALUSTRIS

1. Comparative studies were performed on growth, photosyntheticand respiratory activities, and pigment content in Rhodopseudomonaspalustris.
2. The growth of the organism, as influenced by variousculturalconditions such as light, aerobiosis, anaerobiosisand nutritionalfactors was investigated.
3. The respiratoryactivity of the bacterium was found to be higherin dark-growncells than in cells grown in the light. The photosyntheticactivitydid not significantly depend on the growth conditionsof theculture. Cells of younger cultures were found to be moreactivethan those of older cultures, with respect both to respirationand photosynthesis.
4. The pigment content was found to be higherin the light-growncells than in the dark-grown ones. The ratiophotosyntheticactivity/bacteriochlorophyll was significantlyhigher in thelatter than in the former.
5. Light, as well asvarious nutritional factors, was found toexert a marked accelerationon pigment formation, although ithas not yet been possibleto culture cells completely lackingin photosynthetic pigmentsand accordingly in photosyntheticactivity.

¹ Present address: Division of Dermatology and Urology, TokyoMetropolitan Hiroo Hospital, Tokyo. ² Present address: Department of Biology, Saitama University,Urawa. ³ Present address: Department of Biochemistry, School of Medicine,Yokohama University, Yokohama. ⁴ Present address: Department of Biophysics and Biochemistry,Faculty of Science, University of Tokyo, Tokyo. (Received July 23, 1961; )     

Relationship between light-induced potential change and internal ATP concentration in tonoplast-free Chara cells

The effect of the intracellular concentration of ATP ([ATP]₁)on the light-induced potential change (LPC) in tonoplast-freeChara cells was studied. The LPC was hardly affected by loweringthe [ATP]₁ by about 1/10 or by raising it to about 10 timesthe normal cytoplasmic concentration (0.5–1.3 mM). Theinsensitivity of LPC to [ATP]₁ excludes the possibility thatan increase in [ATP]₁ due to photosynthesis may induce the LPC.However, extreme lowering of the [ATP]₁ to about 1–2 µMcompletely inhibited LPC, although photosynthetic O₂ evolutionwas not significantly inhibited. This fact supports the hypothesisthat light stimulates the putative H⁺pump fueled by ATP. Theuncoupling agents DNP and CCCP greatly depolarized the membrane,and inhibited LPC strongly, but they did not decrease [ATP]₁.Photosynthetic O₂ evolution was inhibited to some extent by2 µM CCCP and strongly inhibited by 0.1 mM DNP. Sincethe membrane resistance increased significantly, these chemicalsare believed to act on the membrane as an inhibitor of the electrogenicH⁺ pump not as an H⁺conductor. Introduction of 1 mM ATP intocells treated with uncouplers, to a large extent restored theirability to produce LPC although the membrane potential in darknesswas maintained at a low level. ¹Present address: Niigata College of Pharmacy, 5829 Kamishinei-cho,Niigata 950-21, Japan. ²Present address: Department of Agricultural Chemistry, Collegeof Agriculture, Kyoto University, Kyoto 606, Japan. ³Present address: Department of Botany, Faculty of Science,University of Tokyo, Hongo, Tokyo 113, Japan. (Received March 9, 1979; )     

Physiological evaluation of temperature effect on the growth processes of the mysid, Neomysis intermedia Czerniawsky

Ingestion, respiration, and molting loss rates were measuredover the 3 – 29°C range in Neomysis intermedia. Weightspecific rates of these physiological processes ranged from2 to 140% body C day^–1 for ingestion, from 2 to 15% bodyC day^–1 for respiration, and from 0.1 to 5% body C day^–1for molting loss. All weight-specific rates showed a logarithmicdecrease with a logarithmic increase in body weight, and a logarithmicincrease with a linear increase in temperature below 20 or 25°C.The effect of temperature, however, was different between thephysiological rates, with a large temperature dependency foringestion (Q₁₀ = 2.6 –3.9) and molting loss (Q¹⁰ = 2.9– 3.6) and a moderate temperature dependency for respiration(Q₁₀ = 1.9 – 2.1). Calculated assimilation efficiencychanged with body size, but was constant over the temperaturerange examined. Allocation of assimilated materials varied witha change in temperature, reflecting the different temperaturedependence between physiological processes. It was deduced thatthe strong temperature dependency of the growth rate in N. intermediaobserved in the previous studies resulted from the large temperatureeffect on ingestion and assimilation rates, superimposed bythe different allocation of assimilated materials. ¹Present address: Department of Botany, University of Tokyo,Hongo, Tokyo 113, Japan     

Action Spectrum in Ultraviolet and Blue Light Region for the Inhibition of Red-Light-Induced Spore Germination in Adiantum capillus-veneris L.

The action spectrum for the inhibition of red-light-inducedgermination of spores in the fern Adiantum capillus-veneriswas determined between 250 and 500 nm using the Okazaki largespectrograph. When monochromatic lights were given after red-lightirradiation, two prominent peaks for inhibition of spore germinationwere observed at 275 and 440 nm and a minor peak at ca. 390nm. ² Permanent address: Department of Botany, Faculty of Science,University of Tokyo, Hongo, Tokyo 113, Japan.     

Comparison of carbon dioxide fixation and the fine structure in various assimilatory tissues of Amaranthus retroflexus L

The pattern for primary products of CO₂-fixation and the chloroplaststructure of Amaranthus retrqflexus L., a species which incorporatescarbon dioxide into C₄ dicarboxylic acids as the primary productof photosynthesis, were compared in various chlorophyll containingtissues,i.e., foliage leaves, stems, cotyledons and pale-greencallus induced from stem pith. Despite some morphological differencesin these assimilatory tissues, malate and aspartate were identifiedas the major compounds labelled during a 10 sec fixation of¹⁴CO₂ in all tissues. Whereas, aspartate was the major componentin C₄-dicarboxylic acids formed in foliage leaves, malate predominatedas the primary product in stems, cotyledons and the pale-greencallus. The percentage of ¹⁴C-radioactivity incorporated intoPGA and sugar-P esters increased and ¹⁴C-sucrose was detectedin the prolonged fixation of ¹⁴CO₂ in the light, not only infoliage leaves, but also in stems and cotyledons. ¹ This work was supported by a Grant for Scientific ResearchNo. 58813, from the Ministry of Education, Japan. ² Present address: Institute of Applied Microbiology, Universityof Tokyo, Tokyo, Japan. ³ Present address: Department of Biochemistry, University ofGeorgia, Athens 30601. Georgia, U. S. A. (Received July 10, 1971; )     

Folylpolyglutamate Derivatives of Pisum sativum L. Determination of Polyglutamate Chain Lengths by High Performance Liquid Chromatography Following Conversion to p-aminobenzoylpolyglutamates

The folypolyglutamate derivatives of pea seedlings (Pisum sativumL. cv. Homesteader) were extracted in the presence of 2-mercaptoethanoland cleaved to p-aminobenzoylpolyglutamates by treatment withZn-HCl. Azo dyes were formed by reaction with naphthylethylenediamine and purified by polyacrylamide gel chromatography. p-Aminobenzoylpolyglutamateswere regenerated from these dyes by Zn treatment and then concentratedin vacuo. These derivatives were separated according to glutamylchain length by high performance liquid chromatography on WhatmanPartisil SAX columns. The folylpolyglutamates of 4 day old peacotyledons, pea leaves and isolated chloroplasts were mainlytetra- and pentaglutamates. These and folates of shorter chainlength were labelled when seeds and aerial shoots were incubatedwith p-aminobenzoate-[¹⁴C]. Labelling of the pentaglutamatewas reduced in seeds that were imbibed in the presence of 0.1mM methotrexate. Studies of cotyledon folylpolyglutamate synthetaseshowed that polyglutamate chain length was affected by incubationtime and the concentration of tetra-hydrofolate monoglutamatein the reaction system. ¹Present address: Department of Biology, University of Lethbridge,Alberta, Canada T1K 3M4 ²Present address: Department of Horticulture, Xiong-yue AgriculturalCollege, Xiong-yue, Liaoning Province, China (Received August 4, 1989; Accepted December 5, 1989)     

Effects of Deoxygibberellin C (DGC) and 16-Deoxo-DGC on Gibberellin 3{beta}-Hydroxylase and Plant Growth

Deoxygibberellin C (DGC), a C/D ring-rearranged isomer of GA₂₀,was shown to inhibit the conversion of [2,3-³H₂]GA₉ to [2-³H]GA₄by gibberellin 3ß-hydroxylase from immature seedsof Phaseolus vulgahs. Deoxygibberellin C inhibited the promotionof growth by exogenously applied GA₂₀ of rice (Oryza sativaL.) seedlings. Evidence is also presented that DGC is a competitiveinhibitor of the 3ß-hydroxylase from P. vulgaris.However, DGC only weakly inhibited the conversion catalyzedby the 3ß-hydroxylase from Cucurbita maxima at highconcentrations, and it did not inhibit the promotion of growthby exogenously applied GA₉ of cucumber (Cucumis sativus) seedlings.These results suggest that the 3ß-hydroxylases fromP. vulgaris and C. maxima have different structural requirementswith respect to their substrates. 16-Deoxo-DGC also inhibitedcatalysis of the same conversion by 3ß-hydroxylasefrom P. vulgaris, and it slightly inhibited the conversion catalyzedby the enzyme from C. maxima. Application of 16-deoxo-DGC causedthe promotion of the growth of seedlings of both rice and cucumber. ³ Present address: Genetic Engineering Center, Korea Instituteof Science and Technology, Daejeon 305–606, Korea ⁴ Present address: Department of Agricultural Chemistry, UtsunomiyaUniversity, Utsunomiya-shi, Tochigi, 321 Japan (Received September 25, 1990; Accepted December 17, 1990)     

Synergistic Function of rolB, rolC, ORF13 and ORF14 of TL-DNA of Agrobacterium rhizogenes in Hairy Root Induction in Nicotiana tabacum

Comparison of the frequency of rooting in the tobacco leaf segmentsinoculated with Agrobacterium tumefaciens harboring variouscombinations of rolB, rolC, ORF13 and ORF14 of TL-DNA of Riplasmid (pRiHRI) revealed that the genes differ in their functionto stimulate adventitious root induction. A single gene rolBinduced roots, while rolC, ORF13 and ORF14 independently promotedthe root induction by the rolB gene. The effects of these geneson the rolB-mediated rooting were in the order of ORF13>rolCORF14. Present address: Laboratory of Phylogenetic Botany, Departmentof Biology, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba,263-8522 Japan. ² Present address: Department of Chemical and Biological Sciences,Faculty of Science, Japan Women's University, 2-8-1 Mejirodai,Bunkyo-ku, Tokyo, 112-8681 Japan.     

Effects of growth temperature on photosynthetic carbon metabolism in green plants II. Photsoynthetic 14CO2-incorporation in plants acclimatized to varied temperatures

During photosynthetic ¹⁴CO₂-fixation, leaves of plants suchas wheat, the broad bean and spinach, which had been acclimatizedto high temperature (20–25?C), incorporated much moreradioactivity into sucrose, and less into glycine and serinein comparison with similar plants grown in the cold (mean temperature,5–7?C). Radioactivities incorporated into glycine and serine greatlydescreased on the addition of -hydroxyethylsulfonate or on theremoval of oxygen from the atmosphere, indicating that thesecompounds are synthesized through the glycolate pathway. In leaves of wheat grown under low temperatures, relativelyhigh radioactivity was detected in ribulose 1,5-diphosphateamong the photosynthetic ¹⁴CO₂-fixation products, whereas practicallyno radioactivity was detected in this compound in leaves ofwheat which had been acclimatized to high temperatures. We assumedthat the carboxylation reaction of ribulose 1,5-diphosphateis suppressed in plants acclimatized to low temperatures. It was further inferred that the C-2 and C-2 moiety of ribulose1,5-diphosphate accumulating as a result of suppression of carboxylationis converted to glycine and serine through the glycolate pathway. The possibility was also discussed that during photosyntheticCO₂-fixation in wheat leaves at least a part of the C₆-compoundformed by the carboxylation of ribulose 1,5-diphosphate is directlyconverted to sugar phosphate. ¹Part of this investigation was reported at the 2nd InternationalCongress on Photosynthesis Research at Stresa, Italy, June 1971.This paper is based on a dissertation submitted by S.S. to theFaculty of Science, the University of Tokyo, in partial fulfilmentof the requirements for a Ph.D. degree. ²Present address: Department of Botany, Faculty of Science,University of Tokyo, Tokyo, Japan. (Received July 20, 1973; )     

Effect of osmotic shock on auxin-induced cell extension, cell wall changes and acidification in Avena coleoptile segments

The effect of plasma membrane alteration caused by osmotic shockof different strengths on the auxin-induced responses of Avenacoleoptile cells was observed. Osmotic shock brought about by0.5–0.7 M mannitol solution for 10 or 30 min, followedby phosphate-buffer (1 mM, pH 6.0) treatment for 10 min at 4?Ccaused no significant inhibition of auxin-induced cell extension.The osmotic shock did not affect auxin-induced cell wall looseningrepresented by stress-relaxation time and a decrease in thenoncellulosic glucose level of the cell wall. The shock causedonly a temporary inhibition of transmembrane potential and noinhibition of oxygen consumption. However, it inhibited auxin-stimulatedH⁺ secretion which was reversed by 0.1 mM CaCl₂. We concludedthat the Osmotic shock may partly modify the plasma membranerelated to the hydrogen ion pump which interacts with auxin,but this modification which is reflected little by the transmembranepotential and cellular metabolism, is not closely related toauxin-induced cell wall loosening and thus cell extension inAvena coleoptiles. ³ Present address: Department of Botany, Faculty of Science,University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan (Received February 17, 1978; )     

Phase Transition Temperatures Determined for Chloroplast Thylakoid Membranes and for Liposomes Prepared from Charged Lipids Extracted from Thylakoid Membranes of Higher Plants

Lipid phase separation temperatures of intact thylakoid membranesfrom a number of chilling sensitive plants were measured usingchlorophyll a as the intrinsic fluorescent probe. The phospho-and sulfolipids were extracted from the thylakoid lamellae ofthese plants and purified by silicic acid column and thin layerchromatographies. These separated lipids were eluted and recombinedto give a total charged anionic thylakoid lipid fraction thatwas used to prepare liposomes containing purified chlorophylla as the fluorescent probe. The phase separation temperaturesof these liposomes were compared to phase separation temperaturesin intact thylakoid membranes isolated from the same plants. The chilling-sensitive plants—corn, pepper, tomato andwater hyacinth — showed phase separation temperaturesranging from 9 to 19°C for both the liposomes and the thylakoidmembranes. In addition, low temperature phase separations wereseen from –21 to –27°C. Mimulus, which is notas chilling sensitive as the former plants, had a phase separationtemperature near 0 to 2.5°C and at –27°C. In general,there was a good agreement between the phase separation temperaturesof intact thylakoids and the purified anionic lipid fractionextracted from these thylakoids. Similar results were obtained using either trans-parinaric acidor chlorophyll a as the fluorescent probe in liposomes madefrom anionic thylakoid lipids or in liposomes prepared frompure dimyristoyl phosphatidyl choline, distearoyl phosphatidylcholine, or mixtures of equal amounts of these phospholipids. ¹ CIW-DPB Publication # 728. ³ Present address: Laboratory of Experimental Physics, Departmentof Biophysics, State University of Utrecht, Princetonplein 5,Utrecht, The Netherlands. (Received January 18, 1981; Accepted July 2, 1981)     

A lack of correlation between the biological activity and rate of metabolism of ent-(3H)-17-kaurenoic acid by seedlings of dwarf rice cv. Tan-ginbozu

Significant leaf sheath elongation occurred within 24 hr afterapplication of 10 µg (0.67, µCi) of ent-(³H)-17-kaurenoicacid (KA) to individual seedlings of dwarf rice cv. Tan-ginbozu,but this growth was unaccompanied by production of significantlevels of radioactivity in more polar, acidic, ethyl acetate-solublemetabolites of (³H)-KA. However modest levels of radioactivityappeared in the highly water-soluble fraction by hour 24, subsequentto the most rapid phase of KA-induced growth. Growth continuedand by hour 48 was accompanied by the appearance of small amountsof radioactivity in polar, acidic products. It would appearthat KA per se, and not its metabolic products, may be responsiblefor the leaf sheath elongation noted at hour 24. On the speculation that it might be a metabolite of KA, gibberellinA₁₄ (GA₁₄) was applied simultaneously with (³H)-KA to individualrice seedlings. Several changes in the metabolism of ³H-KA inthe presence of GA₁₄ were noted, and GA₁₄ antagonized the KA-inducedsheath elongation. ¹Present address: Botany Department, Rhodes University, Grahamstown,6140, South Africa. ²Present address: Crop Science Department, University of Saskatchewan,Saskatoon, Sask. S7N OWO, Canada. (Received May 12, 1975; )     

Effects of Light on Degradation of Chlorophyll and Proteins during Senescence of Detached Rice Leaves

Regulatory effects of light on senescence of rice leaves wereinvestigated by measuring degradation of chlorophyll and proteinsin leaf segments which had been kept in the dark or under illuminationwith light of different intensities and colors. When leaveshad been left in total darkness for three days at 30°C,there was an initial long lag that lasted for one whole dayand then chlorophyll was rapidly degraded in the second andthird days. Breakdown of chlorophyll was strongly retarded bycontinuous illumination with white light of intensity as lowas 0.5 µmol photons m^–2 s^–1 but the effectof light decreased at intensities above 10 µmol photonsm^–2 s^–2. The initial lag and subsequent degradationof chlorophyll in the dark were little affected by illuminationwith red or far red light at the beginning of dark treatment.However, a brief illumination with red light at the end of thefirst and/or second day significantly suppressed degradationof chlorophyll during subsequent dark periods and the effectof red light was nullified by a short irradiation with far redlight. Thus, degradation of chlorophyll is regulated by phytochrome.Thylakoid membrane proteins and soluble proteins were also largelydegraded during three days in the dark. Degradation of membraneproteins such as the apoproteins of light-harvesting chlorophylla/b proteins of photosystem II and chlorophyll a-binding proteinsof reaction center complexes showed a long lag and was stronglysuppressed by illumination with weak white light. Thus, theloss of chlorophyll can be correlated with degradation of chlorophyll-carryingmembrane proteins. By contrast, light had only a weak protectingeffect on soluble proteins and ribulose-1,5-bisphosphate carboxylase/oxygenaserapidly disappeared under illumination with weak white light.Thus, breakdown of thylakoid membrane and soluble proteins aredifferently regulated by light. Artifacts which would be introducedby detachment of leaves were also discussed. ¹ Present address: Department of Applied Biology, Faculty ofScience and Technology, Science University of Tokyo, Yamazaki,Noda-shi, Chiba, 278 Japan. ² Present address: Department of Life Science, Faculty of Science,Himeji Institute of Technology, Harima Science Park City, Hyogo,678-12 Japan.     

Swelling of Etiolated Oat Protoplasts Induced by cAMP and Red Light

Etiolated oat protoplasts were treated with dibutyryl cAMP tostudy possible function of cAMP in the development by measuringthe protoplast swelling. The mean diameter of protoplasts inthe absence of any chemical treatment was 33.58±1.26(SE) µm, which increased to 36.96±0.86 µmin the presence of 100 µM dibutyryl cAMP. Prostacyclin,a potent activator of adenyl cyclase, also showed a significantswelling effect (diameter 38.01±0.98 µm). Red lightalso elicited the swelling of protoplasts (40.26±0.8µm). ¹Present address: Department of Biology, Pusan National University,Pusan 607, Korea. ²Present address: Department of Horticulture, Cheju NationalUniversity, Cheju 590, Korea. ³Present address: Department of Biological Sciences, Texas TechUniversity, Lubbock, TX 79409, U.S.A. (Received June 29, 1985; Accepted November 18, 1985)