Physiological Structure of the Critical Photoperiod of Lemna paucicostata 6746

The critical day length or the length of the critical photoperiodfor the short-day duckweed, Lemna paucicostata 6746 is about14 h (Oota 1983). With the min-SD method, I found that not thewhole critical photoperiod but only its initial and terminalbrief fractions, called respectively the LI- and L2-phases,need be illuminated for a given day to be a noninductive day.Inversely, the darkened LI- and/or L2-phase makes the day inductive.The rest of the day can be either darkened or illuminated withoutmodifying the inductive or noninductive property of the day. Thus, the physiological structure of the critical photoperiodfor L. paucicostata 6746 closely resembles that of the criticalphotoperiod for the long-day duckweed, L. gibba G3 (Oota 1981). (Received May 24, 1983; Accepted September 21, 1983)     

Floral Inhibition in Lemna paucicostata 6746 Due to Night Interruption

The floral response to various 24-h photoperiodic cycles ofthe short-day plant, Lemna paucicostata 6746 was investigated.No day that had a main photoperiod longer than about 14 h wasable to induce flowers, evidence that the critical day lengthwas ca.14 h. Flowering in the 12-, 9- or 6-h day was inhibitedcompletely by a light pulse inserted daily in the ‘inhibitionzone’ that ranged from about 14 h after the precedingdawn to about 14 h before the next dusk. In the 3- and 1-h days,only the pulse applied 14 h after the dawn completely inhibitedflowering. These results suggest that the daily night interruption prohibitedflowering only when it was linked to either the preceding orthe subsequent main photoperiod to form a skeleton photoperiodwhose length was equal to, or longer than, the critical daylength. Analysis of the floral response to skeleton schedules11:13 and 13:11 on Pittendrigh's model of the photoperiodicclock indicated that light-on circadian oscillation probablyis involved in the day length measurement. ¹ Dedicated to the memory of Dr. Joji Ashida. (Received July 13, 1982; Accepted January 17, 1983)     

Bimodal Floral Response of Lemna gibba G3 to Night Interruption: Photoperiodic Time Measurement

Lemna gibba G3 (M-1% sucrose medium, 26°C) showed a bimodalfloral response to a 2-hr light pulse scanning 21-, 18-, 15-and 12-hr nyctoperiods. With the simplified min-LD method, thelight pulse given early or late in these nyctoperiods was foundto signal false dusk or false dawn after two transient cycles.The magnitude of floral response to the light pulse dependedon the length of the asymmetric skeleton photoperiod comprisingeither the preceding main photoperiod and the false dusk orthe false dawn and the subsequent main photoperiod. No flowerwas induced by asymmetric skeleton photoperiods shorter thanthe critical daylength, 12 hr. In duckweed previously entrainedto an interrupted 15-hr nyctoperiod, false dawn or false duskwas physiologically equivalent to the light-requiring L1- orL2-phase of the critical photoperiod. Another light-requiringphase occurred 12 hr after or before the false dawn or falsedusk. These and relevant findings suggest that the timing ofthe L1- and L2-phases is under the control of the endogenouscircadian oscillator and that the skeleton as well as completephotoperiods are inductive only when both the L1- and L2-phases,whether they are shifted or not due to night interruption, areilluminated. (Received October 3, 1980; Accepted December 3, 1980)     

Some Characteristics of Protein Kinases in Lemna paucicostata

The three protein kinases of Lemna paucicostata that are separableby DEAE-Sephacel chromatography have been designated PI, PIIand PIII [Kato et al. (1983) Plant & Cell Physiol. 24: 841].The optimum pH for the PI and PII enzymes was 7.5 and for thePHI enzyme 7.0. The activities of these enzymes were stimulatedby divalent cations, the maximum stimulation being producedby 5 nw Mg^{2 $} for PI, by 3 mM Co^{2 $} for PII and by 1 mM Mn^2$ for PIII. The cytokinins; benzyladenine, kinetin and zeatin,inhibited the activity of the PIII enzyme. The molecular weightsof the PI and PII enzymes did not change after incubation withcAMP even though their activities were regulated by this compound. (Received October 17, 1983; )     

H+ tolerance of Chara Internodal Cells and Apparent Net Influx of H+ in Weakly Acidic Solutions: Implication of the Net Flux of H+ as a Minor Component among the Total Net Flux of Ions across the Intact Cell Membrane of Chara

Precise measurements of the net flux of protons in Chara internodalcells were made with a recently designed high-resolution pH-meter.Survival of intact Chara internodal cells in artificial pondwater (APW) that contained HC1 at various concentrations wasalso examined. The apparent net flux of H⁺ was inward and muchsmaller than that reported so far. In APW at pH 4.005, a valuehigher than the extracellular pH expected from the values ofH⁺ efflux reported to date, all of the intact Chara internodalcells died within a day. With reference to the data on the circadianflow of ions in the pulvinus of Phaseolus [Kiyosawa (1979) PlantCell Physiol. 20: 1621–1634, Hosokawa and Kiyosawa (1983)Plant Cell Physiol. 24: 1065–1072] and ionic regulationin Chara L-cells [Kiyosawa and Okihara (1988) Plant Cell Physiol.29: 9–19], a discussion is presented of the prossiblyminor contribution of the net flux of H⁺ in the generation ofthe electrical membrane potential. Regulation of the net fluxof H⁺ in weakly acidic APW is also discussed. (Received September 4, 1989; Accepted January 25, 1990)     

Effects of Net and Local Charges on the Interaction between Chemically-Modified Horse Heart Cytochrome c and P700 in Photosystem 1-Enriched Subchloroplast Particles

Effects of salt and pH on the re-reduction of P700 by chemically-modifiedhorse heart cytochrome c after a flash illumination were examinedin Triton-treated P700- enriched subchloroplast particles (TSF-1particles). At low salt concentrations net charges on the membrane surfaceand native, guanidinated or succinylated cytochrome c were majorfactors that determined the reaction rates, as in the reactionbetween plastocyanin and P700 [Tamura et al. (1981) Plant &Cell Physiol. 22: 603]. The reaction rates also depended onreactant-specific factors, particularly the localized distributionof charges on macromolecules and their interaction over shortdistances, as well as on long-range Coulombic interaction. Theeffect of this type became clearer at high salt concentrations. (Received October 7, 1982; Accepted December 20, 1982)     

Regulation of the Activity of Ribulose-1,5-Bisphosphate Carboxylase in Response to Changes in the Photosynthetic Source-Sink Balance in Intact Soybean Plants

Sink-limited conditions cause a reduction in the rate of photosyntheticfixation of CO₂ in single-rooted soybean leaves (Glycine max.Merr.). We suggested previously that this reduction is due tothe deactivation of ribulose-1,5-bisphosphate carboxylase (RuBPcase;EC 4.1.1.39 [EC] ) that is caused by a decrease in the level of freeP_i via a decrease in the rate of conversion of phosphorylatedintermediates to the end-product (sucrose) in sink-limited leaves[Sawada et al. (1989) Plant Cell Physiol. 30: 691, Sawada etal. (1990) Plant Cell Physiol. 31: 697, Sawada et al. (1992)Plant Cell Physiol. 33: 943]. In the present study, we investigatedwhether, in intact soybean plants, sink-limited conditions wouldalso cause a reduction in the rate of photosynthesis and whethersuch a reduction might be due to the deactivation of RuBPcasevia the same regulatory mechanism as that suggested from previousstudies with single-rooted leaves. Continuous removal of flowerbuds from intact plants brought a large decrease in ratio ofthe dry weight of sink organs (stem, roots, pods) to sourceorgan (leaves) as a result of the absence of pod formation.Pods are likely to function as the major sink at the reproductivestage. Upon continuous removal of flower buds, the treated (sink-limited)plants showed a large decrease in the rate of photosyntheticfixation of CO₂ as compared to control plants. RuBPcase in theleaves of treated plants was continuously inactivated with thedecrease in photosynthetic activity. However, the inactivatedenzyme was totally reactivated upon incubation in the presenceof 10 mM NaHCO₃ and 5 mM MgCl₂. The levels of sucrose and ribulose-1,5-bisphosphatein leaves of the treated plants increased significantly. Allthese results coincide exactly with those obtained in previousstudies of single-rooted leaves under the sink-limited conditions. (Received July 14, 1994; Accepted February 21, 1995)     

On the Relationship between Photocontrol of Phycoerythrin Formation and Photoreversible Pigment of Scheibe

Dose-response of photocontrolled phycobiliprotein formationwas studied with two types of Tolypothrix tenuis cells havingdifferent content of photoreversible pigment (PRP) of Scheibe[cf. Scheibe (1972) Science 176: 1037]. PRP was not detectablein cells grown in a medium rich in nitrogen source under weakred light (normal cells) while the content was much larger (morethan 10 times) in cells incubated in light under nitrogen-deficientconditions [nitrogen-deficient cells, cf. Ohki and Fujita (1979)Plant & Cell Physiol. 20: 1341]. Both cells were found toform phycoerythrin (PE) in the dark after a short green illumination,while red illumination suppressed its formation. The amount of PE formation depended on the dose of green orred preillumination. Despite a large difference in content ofPRP of Scheibe, the dose-response of PE formation induced bygreen light was almost the same in both types of cells. Suppressionby red light in normal cells required a dose larger than thatin nitrogen-deficient cells. The results indicate that PRP ofScheibe formed during the incubation under nitrogen-deficientconditions does not act as the photoreceptor in photocontrolof PE formation. (Received September 29, 1980; Accepted January 6, 1981)     

Inactivation of Ascorbate Peroxidase in Spinach Chloroplasts on Dark Addition of Hydrogen Peroxide: Its Protection by Ascorbate

Dark addition of hydrogen peroxide to intact spinach chloroplastsresulted in the inactivation of ascorbate peroxidase accompaniedby a decrease in ascorbate contents. This was also the casein reconstituted chloroplasts containing ascorbate, NADP⁺, NAD⁺and ferredoxin. The addition of hydrogen peroxide during light,however, showed little effect on ascorbate contents and ascorbateperoxidase activity in either the intact or reconstituted chloroplasts.In contrast to ascorbate peroxidase, the enzymes participatingin the regeneration of ascorbate in chloroplasts (monodehydroascorbatereductase, dehydroascorbate reductase and glutathione reductase)were not affected by the dark addition of hydrogen peroxide.Ascorbate contents increased again by illumination of the chloroplastsafter the dark addition of hydrogen peroxide. These resultsshow that the inactivation of the hydrogen peroxide scavengingsystem on dark addition of hydrogen peroxide [Anderson et al.(1983) Biochim. Biophys. Acta 724: 69, Asada and Badger (1984)Plant & Cell Physiol. 25: 1169] is caused by the loss ofascorbate peroxidase activity. Ascorbate peroxidase activitywas rapidly lost in ascorbate-depleted medium, and protectedby its electron donors, ascorbate, isoascorbate, guaiacol andpyrogallol, but not by GSH, NAD(P)H and ferredoxin. (Received June 14, 1984; Accepted August 15, 1984)     

Protein Kinase Inhibitors Inhibit Stimulation of Inositol Phospholipid Turnover and Induction of Phenylalanine Ammonia-Lyase in Fungal Elicitor-Treated Tobacco Suspension Culture Cells

Elicitor prepared from Phytophthora nicotianae stimulated inositolphospholipid turnover and induced phenylalanine ammonia-lyaseactivity in tobacco suspension culture cells [Kamada and Muto(1994) Plant Cell Physiol. 35: 397]. Protein kinase inhibitors,K252a and staurosporine inhibited both responses. These resultssuggest that inositol phospholipid turnover plays an importantrole in PAL induction through protein kinases. In addition,their mode of inhibition were different, proposing that severaltypes of protein kinases are involved in these elicitor-inducedresponses. ¹Present address: The Johns Hopkins University School of Hygieneand Public Health, 615 N. Wolfe St., Baltimore, Maryland 21205,U.S.A. ²Present address: Nagoya University BioScience Center and GraduateSchool of Agricultural Sciences, Nagoya University, Chikusa-ku,Nagoya, 464-01 Japan.     

Degradation of Endogenous Organic Acids Induced by Pi Uptake in Catharanthus roseus Cells: Involvement of the Biochemical pH-Stat

We have previously shown that inorganic orthophosphate (P_i)uptake by Catharanthus roseus cells proceeds by a proton/P_icotransport mechanism [Sakano (1990) Plant Physiol. 93: 479]that acidifies the cytoplasm [Sakano et al. (1992) Plant Physiol.99: 672]. In the present study, we analyzed changes in the contentof endogenous organic acids, carbon dioxide evolution, and oxygenconsumption upon P_i application. The results are consistentwith the operation of the biochemical pH-stat mechanism [Davies(1986) Physiol. Plant. 67: 702] during and after P_i uptake. (Received November 13, 1997; Accepted March 30, 1998)     

Accumulation of Demolybdo Nitrate Reductase during Induction and Its Separation from Active Nitrate Reductase in Chlorella

During induction of nitrate reductase in Chlorella vulgaris,synthesis of the precursor, demolybdo cytochrome c reductase,exceeds the synthesis of active enzyme. Evidence is also presentedwhich shows that the purification procedure of Funkhouser etal. [(1980) Plant Physiol. 65: 939] separates demolybdo cytochromec reductase from active nitrate reductase. ¹Supported in part by a grant to B. V. from the Deutsche Forschungsgemeinschaftand a contribution of the Texas Agricultural Experiment Station. (Received July 27, 1983; Accepted September 13, 1983)     

Separate Assays Specific for Ascorbate Peroxidase and Guaiacol Peroxidase and for the Chloroplastic and Cytosolic Isozymes of Ascorbate Peroxidase in Plants

Ascorbate (AsA) peroxidase can be inactivated both by p-chloromercuribenzoateand by the depletion of AsA but guaiacol peroxidases, such ashorseradish peroxidase, cannot. The cytosolic isozymes of AsAperoxidase are less sensitive to depletion of AsA than the chloroplasticisozymes, which include stromal [Chen and Asada (1989) PlantCell Physiol. 30: 987] and thyla-koid-bound [Miyake and Asada(1992) Plant Cell Physiol. 33: 541] enzymes. Exploring theseproperties, we established simple methods for separate assaysof AsA peroxidase and guaiacol peroxidase and of the three isozymesof AsA peroxidase in plant extracts. These methods were usedto characterize the guaiacol peroxidases and isozymes of AsAperoxidase in plants and algae. (Received October 20, 1993; Accepted February 7, 1994)     

Purification and Characterization of Rice Embryo BAPAase (Benzoyl-L-arginine p-nitroanilide Hydrolase)

Benzoyl-L-arginine p-nitroanilide hydrolase (BAPAase), whichhas both endopeptidase and carboxypeptidase activity towardthe Arg-X or Lys-X bond of small peptides [Shibata and Doi (1984)Plant & Cell Physiol. 25: 1421], was purified from riceembryos by ammonium sulfate and polymin fractionations and byion exchange, gel exclusion and hydrophobic chromatographies.The purified enzyme was homogeneous when analyzed by polyacrylamidegel electrophoresis. It was unstable in the absence of surface-activereagents such as Triton X-100. Maximum activity for benzoyl-Largininep-nitroanilide (L-BAPA) or carboxypeptidase activity towardbutoxycarbonyl-Gly-Lys-Leu was obtained at pH 9.0. L-BAPA athigh concentrations inhibited the enzyme's activity. Di-isopropylphosphofluoridate, N-tosyl-L-lysine chloromethyl ketone, leupeptinand antipain, which are specific inhibitors of trypsin, inhibitedBAPAase activity, but soybean and rice bran trypsin inhibitorhad no effect on it. Sulfhydryl reagents strongly inhibitedthe BAPAase activity. (Received May 26, 1984; Accepted August 29, 1984)     

In Vivo Treatment of Barley Roots with Vanadate Increases Vacuolar H+-Translocating ATPase Activity of the Tonoplast-Enriched Membrane Vesicles and the Level of Endogenous ABA

Evidence for an increase in the activity of the vacuolar H⁺-translocatingATPase of barley roots, accompanied by qualitative change, inresponse to exogenously applied abscisic acid (ABA) has beenreported previously [Kasai et al. (1993b) Plant Cell Physiol.34: 1107]. In the present study, such an increase in the H⁺-translocatingATPase activity was shown to occur upon treatment of barleyroots with vanadate. Furthermore, the level of endogenous ABAin the roots was shown to increase significantly as a resultof this treatment. The present observations provide furthersupport for the proposed physiological significance of cellularABA in the regulation of the vacuolar H⁺-translocating ATPaseactivity. (Received September 3, 1993; Accepted December 16, 1993)     

Response to nigh interruption in photoperiodic determination of wing form of the ground cricket Dianemobius fascipes

ABSTRACT. In the ground cricket Dianemobius fascipes (Walker), the occurrence of long- or short-winged form is determined by photoperiod during larval development. The pattern of this response is similar to that of diapause induction in other insects with a clearly defined critical nightlength (11.5 h). In symmetric skeleton regimes formed by a pair of 1 h light pulses, the critical nightlength is about 2 h longer than in the complete photoperiod. The long-night (short-wing) effect is eliminated by an interrupting light pulse. This response to night interruption shows only one peak in scotophases of various lengths and can be related to the critical nightlength before or after interruption. The light-reaction time required for the interruption effect changes during the night. In the early scotophase, 1 h of light is enough but 15 min fails to reverse the long-night effect, while a light pulse of only 1 min is effective about 1 h before the critical nightlength is reached. Several possible interpretations of this change are discussed.     

Effects of temperature on the cytokinin requirement of tobacco calluses

A cytokinin-nonrequiring strain (T22) was isolated from a cytokinin-requiringcallus strain T2 of tobacco (Nicotiana tabacum var. Bright Yellow). Strain T22 grew rapidly on the medium without added kinetinat 26?C. But its growth was completely suppressed at 16?C. Thisgrowth suppression at 16?C was partially recoverable by supplyingkinetin. Benzyladenine, geranylaminopurine and 2-methyl-8-benzylamino-s-triazolo[l,5-a]pyrazinewere also effective in removing growth suppression at 16?C.Adenine, which was unable to remove growth suppression of T22at 16?C, promoted the growth of T2 at 26?C, but not at 16?C.Physiological differences between cytokinin-requiring and -nonrequiringcalluses are discussed. ¹Part II in the series "Studies, on Plant Tissue Cultures";for Part I, See Plant & Cell Physiol. 9: 103–114 (1968). (Received May 29, 1970; )     

A cDNA Encoding the 57 kDa Subunit of a Cytokinin-Binding Protein Complex from Tobacco: the Subunit Has High Homology to S-Adenosyl-L-Homocysteine Hydrolase

130 kDa cytokinin-binding protein complex (CBP130) is a majorcytokinin binding entity in tobacco leaves (Nicotiana sylvestris)and contains two protein species of 57 and 36 kDa [CBP57 andCBP36, Mitsui and Sugiura (1993) Plant Cell Physiol. 34: 543].We have determined partial amino acid sequences of CBP57 andisolated cDNAs encoding the protein from a tobacco cDNA libraryusing an oligonucleotide probe. Sequence analysis revealed significanthomology between CBP57 and S-adenosyl-L-homocysteine hydrolasefrom other organisms, which catalyzes the reversible hydrolysisof S-adenosyl-L-homocysteine, a methyltransferase inhibitor.CBP57 contains an additional sequence of 41 amino acids whichis not present in animal and slime mold Sadenosyl-L-homocysteinehydrolases. This additional sequence is also found in the parsleyand Rhodobacter enzymes, suggesting that it is unique to photosyntheticorganisms. CBP57 is encoded by more than one nuclear genes intobacco. Northern and western blot analyses revealed that thelevel of expression of the genes is high in roots and low inleaves. They are also expressed in cultured tobacco cells. Wediscuss the possibility that at least some of the physiologicaleffects of cytokinin are mediated through the control of methylation/demethylationby regulating the intracellular concentration of S-adenosyl-L-homocysteinevia the hydrolase. (Received June 24, 1993; Accepted August 14, 1993)     

Properties of Alkaline Phosphatase in Cucumber Roots Induced by Calcium Starvation

Calcium deficiency caused an increase in alkaline phosphataseactivity in cucumber roots [Matsumoto and Yamaya (1981) Plant& Cell Physiol. 22: 1137]. The activities of other hydrolasesincluding acid phosphatase, nucleases and proteases, however,were much less affected by the removal of calcium. Nucleosidedi- and triphosphates and inorganic pyrophosphate were effectivelyhydrolyzed by the induced alkaline phosphatase, whereas nucleosidemonophosphate-hydrolyzing activity was basically equal in theroots grown with either complete medium or a medium lackingcalcium. The alkaline phosphatase in cucumber roots was foundin fractions pelleting at 3,000 x g and in the 100,000 x g supernatant.The calcium-starved roots increased their alkaline phosphataseactivity in both fractions. Four isozyme bands of the alkalinephosphatase in the soluble fraction were separated by polyacrylamidegel electrophoresis. One of the isozyme bands showed a prominentincrease with the calcium deficiency, but not in the presenceof cycloheximide. (Received June 24, 1981; Accepted September 3, 1981)