Resistance to Oxidative Injury in Submerged Rice Seedlings after Exposure to Air

Rice (Oryza sativa L.) seedlings were germinated under waterin darkness for 5 or 6 days (submerged seedlings) and then inair for 1 day. Control seedlings were germinated in air, indarkness, for 5 or 6 days (aerobic seedlings). Changes in levelsof antioxidants and in the extent of oxidative damage afterexposure of submerged seedlings to air were studied. -Tocopherol,which inhibits lipid peroxidation, was present in submergedseedlings at about 3 times the level found in aerobically growncontrols, and higher levels than in controls were maintainedfor 24 h after transfer of the seedlings to air. Products oflipid peroxidation were present at a one-third of the levelsfound in aerobic controls, and their levels increased aftertransfer to air. However, these levels remained lower than thosein aerobic controls even after 24 h of contact with air. Carotenoids,which are considered to protect chlorophyllous compounds againstphotooxidation, were not found in submerged seedlings, but theirlevels increased after exposure of the seedlings to air. Lightat an intensity that did not cause photooxidative damage tochlorophyllous compounds in aerobic controls induced photobleachingof these compounds in submerged seedlings during the early stagesof adaptation to air. However, the extent of photobleachingdiminished as adaptation to air proceeded, and photobleachingwas no longer detected after 24 h of adaptation to air. Thus,the system for protection of cellular membranes from lipid peroxidationin the post-hypoxic phase appeared already to exist in submergedseedlings. However, the system for protection of pigments fromphotobleaching was poorly developed in submerged seedlings andwas fully active only after 24 h of adaptation to air. ¹Present address: Department of Biology, Faculty of Science,Shizuoka University Shizuoka, 422 Japan ²Present address: Research Institute for Bioresources, OkayamaUniversity, Kurashiki, 710 Japan     

Regulation of Protochlorophyll(ide) Levels in Dark-Grown Non-Dividing Euglena 3. Proplastid Structure during Loss and Regeneration of Protochlorophyll(ide)

Cells of Euglena gracilis Klebs var. bacillaris Cori growingin darkness on a complete medium have small undifferentiatedproplastids. On transfer to an incomplete (resting) medium indarkness, the cells cease division within 72 h. During thistime the proplastid expands and several prothylakoids and prolamellarbodies develop even though phototransformable protochlorophyll(ide)[PT-Pchl(ide)] is decreasing. As PT-Pchl(ide) decreases furtherand reaches a stable plateau after 4–5 more days in darkness,the proplastid structure becomes highly reduced. Forty minutesof light plus a one h dark period, or addition of glutamateor malate for 7 h does not change the proplastid structure significantlyeven though PT-Pchl(ide) returns to the level found in growingcells. Upon prolonged incubation in darkness after light treatment(72 h) an expanded proplastid containing prothylakoids, prolamellarbodies and membrane whorls with mitochondria in close associationis seen; most of the cellular paramylum is lost during thisperiod leaving cavities in the cytoplasm. Without light, prolongedincubation in darkness (72 h) with malate leads to accumulationof cellular paramylum but no change in proplastid structurewhile prolonged treatment with glutamate (72 h) allows the formationof a few prothylakoids but no prolamellar bodies. ¹Supported by Grants GM 14595 from the National Institutes ofHealth. ²Permanent address: Department of Microbiology, Tokyo MedicalCollege, 6-1-1 Shinjuku, Tokyo 160, Japan. ³Abraham and Etta Goodman Professor of Biology. (Received July 23, 1983; Accepted September 22, 1983)     

Protochlorophyll(ide) in a Blue-Green Alga

During growth under far-red (>650 nm) light, Anacystis nidulans accumulates protochlorophyllide to concentrations about one-tenth of the chlorophyll. From whole cell fluorescence spectra, protochlorophyll(ide) was identified also in another blue-green, and in a red, alga grown in far-red light.     

A Reversible Conversion of Phototransformable Protochlorophyll(ide)(656) to Photoinactive Protochlorophyll(ide)(656) by Hydrogen Sulfide in Etiolated Bean Leaves

The relationship of phototransformable protochlorophyll-(ide) to photoinactive protochlorophyll(ide) has been studied in the primary leaves of 7- to 9-day-old dark-grown bean (Phaseolus vulgaris L. var. Red Kidney) seedlings. Subjecting the leaves to an atmosphere of H₂S causes an immediate loss of phototransformable protochlorophyll(ide)₆₅₀ and a simultaneous increase in photoinactive protochlorophyll(ide)₆₃₃. When such leaves are returned to air or N₂, the absorbance at 650 nm increases, whereas the absorbance at 633 nm decreases and photoactivity is restored. The reversion of protochlorophyll-(ide)₆₃₃ to protochlorophyll(ide)₆₅₀ is one-half complete in 3 minutes at 22 C in 8-day-old leaves. Ninety-five per cent recovery of protochlorophyll(ide)₆₅₀ is obtained when exposure to H₂S is less than 3 minutes in duration; longer periods reduce the reversion capacity proportionately. The leaves are relatively undamaged by brief exposures to H₂S, as judged by electron microscopy and by their ability to synthesize chlorophyll under continuous illumination. Hydrogen sulfide has no immediate effect upon the absorption properties of a partially purified preparation of the protochlorophyll(ide) holochrome, an etioplast suspension, or leaves subjected to freezing and thawing. Compounds such as HCN and HN₃ cause an irreversible conversion of protochlorophyll(ide)₆₅₀ to protochlorophyll(ide)₆₃₃ with total loss of photoactivity. Sulfhydryl agents, such as β-mercaptoethanol and cysteine, cause a slow, irreversible transformation of the photoactive pigment to the photoinactive form and inhibit the ability of the leaves to synthesize chlorophyll under continuous illumination. The results obtained suggest that H₂S may alter the interaction between the source of hydrogens on the protein moiety of the holochrome and the chromophore in vivo by reducing a disulfide bond in the protein, thereby causing a reversible conformational change in the complex.     

The Capacity of Various Detergents to Solubilize and Stabilize Protochlorophyll(ide) Holochrome

Earlier work has shown that protochlorophyll(ide) holochrome is associated with the prolamellar body membranes in etioplasts of barley (Hordeum vulgare L.), and that this pigment-protein complex can be extracted in a stable, photoactive form by the use of saponin. For future work it would be advantageous if saponin, a detergent mixture, could be replaced by a single, well-characterized substance. The spectral characteristics of holochrome extracted with 10 ionic and nonionic detergents were compared to those of the holochrome extracted with saponin. Mulgofen BC-840 and digitonin extracted significant amounts of photoactive protochlorophyll(ide) holochrome, but this activity was highly labile, and no adequate substitute for saponin was found. Thus the stabilizing and solubilizing function of saponin is not simply related to the general properties of detergents.     

Protochlorophyll(ide) forms in hypocotyls of dark-grown bean (Phaseolus vulgaris)

The protochlorophyll(ide) forms and plastid ultrastructure were investigated in hypocotyls of dark-grown seedlings of kidney bean ( Phaseolus vulgaris L. cv. Brede zonder draad). By deconvolution of the fluorescence emission spectra into Gaussian components three protochlorophyll(ide) forms were found with maxima at 633, 642 and 657 nm, respectively. The ratio of protochlorophyll(ide) emitting at 657 nm to protochlorophyll(ide) emitting at 633 nm decreased downwards the hypocotyl. The gradient was established already after 4 days in dark-grown Phaseolus and was also seen in hypocotyls of 7-day-old dark-grown plants of 8 other species. Ultrastructural observations revealed a plastid developmental sequence along the hypocotyl. Plastids in the upper parts of the hypocotyl contained prolamellar bodies typical of etiolated leaves while those in the lower parts contained only stroma lamellae. Immunological detection of NADPH-protochlorophyllide oxidoreductase (EC 1.3.1.33) on nitrocellulose membranes after sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDSPAGE) indicated the occurrence of the enzyme in upper, middle and lower sections of hypocotyls and in the root tips.     

Development of the Formula-Detoxification System during Adaptation to Air of Submerged Rice Seedlings

Changes in activities of enzymes and levels of antioxidant substratesinvolved in the -detoxification system in seedlings of rice (Oryza sativa L. cv. Yamabiko) inresponse to variations in the oxygen environment were studied.Activities of superoxide dismutase, ascorbate peroxidase, monodehydroascorbatereductase, dehydroascorbate reductase, glutathione reductaseand catalase, expressed either on the basis of fresh weightof shoots or relative to levels of soluble protein were muchlower in seedlings germinated under water for 6 days than inthose germinated in air for the same period of time. When submergedseedlings were exposed to air, the activities of these six enzymesincreased to or exceeded the levels in aerobically grown controlsduring 24 h of adaptation to air. Ascorbate and glutathione,which act as antioxidant substrates in the -detoxification system, were present in submergedseedlings at nearly the same levels as those found in aerobicallygrown controls. On exposure of submerged seedlings to air, thelevel of ascorbate in creased slightly, but the level of glutathioneshowed a rapid increase, reaching 7 times that in aerobicallygrown controls within 12 h of adaptation to air. Levels of allsix antioxidative enzymes and of two substrates involved inthe detoxification of the superoxide radical increased withincreases in oxygen tension in the environment. Moreover, thedevelopment of this system consisted of two steps, namely, arapid increase in the level of glutathione and a subsequentslow increase in the activities of antioxidative enzymes. ¹ Present address: Research Institute for Bioresources, OkayamaUniversity, Kurashiki, 710 Japan.     

Separation of Protochlorophyll(ide)-Binding Proteins by Size-Exclusion, High-Performance Liquid Chromatography

Three protochlorophyll(ide)-binding proteins were separatedfrom an SDS-solubilized extract of etiolated leaves of kidneybean (Phaseolus vulgaris) by size-exclusion, high-performanceliquid chromatography. The molecular masses of these pigmentproteins were determined to be 84, 38 and 25 kDa. In the illuminatedsample, the peak areas of the 84 and 38 kDa proteins decreased,indicating phototransformation of the pigments in these proteins. (Received December 17, 1984; Accepted February 12, 1985)     

Photosynthetic Development of Anaerobically Grown Rice (Oryza sativa) after Exposure to Air

During anaerobic germination, rice produces a coleoptile devoid of carotenoid and chlorophyll. Further development and greening of the shoot occur upon exposure of the seedlings to air. In this study, a comparison was made between anaerobically (N₂) germinated rice, greened upon exposure to air, and air/dark (A/D) germinated seedlings, greened upon exposure to light. After exposure to air, N₂-grown seedlings had a 76-hour lag before net oxygen evolution occurred compared to a 6-hour lag for A/D-grown seedlings. After 98 h of greening, N₂-grown seedlings reached a rate of oxygen evolution equivalent to that of A/D-grown seedlings after 24 hours. Chlorophyll and carotenoid content showed a similar lag, but did not reach the level found in A/D-grown seedlings even after 124 hours of exposure to air. RuBPcase activity also lagged in N₂-grown seedlings, ultimately reaching greater values than in the `greened' A/D-grown seedlings. Phosphoenolpyruvate carboxylase activity was constant and low in all treatments except for a transient increase after 24 hours of greening of the N₂-grown seedlings.     

Changes in the Pools of Carotenoids and Protochlorophyll(ide) in Etiolated Cucumber (Cucumis Sativus) Cotyledons Treated with Norflurazon and KC 6361

Changes in the pools of carotenoids and protochlorophyll(ide) were investigated in etiolated cucumber cotyledons treated with norflurazon (NF) and an experimental herbicide KC 6361 (KC). Both the NF- and the KC-treated tissues considerably accumulated the colourless carotenes phytoene and phytofluene with a concomitant depletion of the coloured carotenoids lutein and β-carotene in darkness. However, the profiles of changes in chlorophylls (Chls) and carotenoids were different for the two herbicides. The plants were also influenced by the photosynthetic photon flux densities (PPFD's), with a more pronounced decline of Chl under high PPFD than under low PPFD. The ratios of protochlorophyll (PChl)/protochlorophyllide (PChlide) were greatly altered due to a decrease and an increase of PChl in the NF- and the KC-treated etiolated tissues, respectively, whereas the PChlide content was not significantly influenced by the inhibitors. Large increase of PChls in the KC-treated tissues seems to derive from the binding of accumulated geranylgeraniol (GG) equivalents, through carotenogenic inhibition, to PChlide. Therefore, the alterations of PChl and PChlide occurring under disturbed carotenogenesis may suggest an interaction between the biosynthetic pathways of Chls and carotenoids. In addition, the great proportion of PChl GG and PChl dihydro-GG in the KC-treated tissues implies that PChl formation is regulated at the level of hydrogenation. This revised version was published online in June 2006 with corrections to the Cover Date.     

The Effect of Phytohormones on Chlorophyll(ide), Protochlorophyll(ide) and Carotenoid Formation in Greening Dark Grown Wheat Leaves

The influence of phytohormones on chlorophyll and carotenoid formation during the greening of irradiated dark grown wheat leaves (Triticum aestivum L. cv. Starke II Weibull) was studied. Leaves were floated on solutions of abscisic acid, gibberellic acid and kinetin for 24 h. The chlorophyll and carotenoid contents were determined during a subsequent period of 48 h of continuous irradiation. Leaves treated with abscisic acid showed a longer lag phase and a lower rate of accumulation of chlorophyll as compared to the control than did leaves treated with gibberellic acid and kinetin. The carotenoid content was low both in leaves treated with abscisic acid and in those treated with gibberellic acid. Treatment with abscisic acid lowered the protochlorophyllide regeneration after a saturating light flash while gibberellic acid as well as kinetin had no effect. The influence of ABA was partly dependent on an increase of the wounded part of the cut leaf segments. The accumulation of protochlorophyllide in leaves treated with δ-aminolevulinic acid was not affected by the different hormonal treatments. These results suggest that the main effect of abscisic acid is probably outside the chloroplast, i.e. on the formation or transport of δ-aminolevulinic acid.     

The Absence of Protochlorophyll(ide) Accumulation in Algae with Inhibited Chlorophyll Synthesis

Golenkinia, Chlorella protothecoides, and mutant C-2A′ of Scenedesmus were grown in darkness and on media in which chlorophyll synthesis is reduced significantly. The pigments were analyzed by spectrophotometry or by paper chromatography and compared with similar extracts from light-grown algae and dark-grown beans. No protochlorophyll(ide) was present in the dark-grown algae indicating that chlorophyll synthesis is blocked by a mechanism other than feedback regulation of aminolevulinic acid synthesis by protochlorophyll(ide) which has been proposed for flowering plants.     

Divinyl Chlorophyll(ide) a Can Be Converted to Monovinyl Chlorophyll(ide) a by a Divinyl Reductase in Rice

3,8-Divinyl (proto)chlorophyll(ide) a 8-vinyl reductase (DVR) catalyzes the reduction of 8-vinyl group on the tetrapyrrole to an ethyl group, which is indispensable for monovinyl chlorophyll (Chl) synthesis. So far, three 8-vinyl reductase genes (DVR, bciA, and slr1923) have been characterized from Arabidopsis (Arabidopsis thaliana), Chlorobium tepidum, and Synechocystis sp. PCC6803. However, no 8-vinyl reductase gene has yet been identified in monocotyledonous plants. In this study, we isolated a spontaneous mutant, 824ys, in rice (Oryza sativa). The mutant exhibited a yellow-green leaf phenotype, reduced Chl level, arrested chloroplast development, and retarded growth rate. The phenotype of the 824ys mutant was caused by a recessive mutation in a nuclear gene on the short arm of rice chromosome 3. Map-based cloning of this mutant resulted in the identification of a gene (Os03g22780) showing sequence similarity with the Arabidopsis DVR gene (AT5G18660). In the 824ys mutant, nine nucleotides were deleted at residues 952 to 960 in the open reading frame, resulting in a deletion of three amino acid residues in the encoded product. High-performance liquid chromatography analysis of Chls indicated the mutant accumulates only divinyl Chl a and b. A recombinant protein encoded by Os03g22780 was expressed in Escherichia coli and found to catalyze the conversion of divinyl chlorophyll(ide) a to monovinyl chlorophyll(ide) a. Therefore, it has been confirmed that Os03g22780, renamed as OsDVR, encodes a functional DVR in rice. Based upon these results, we succeeded to identify an 8-vinyl reductase gene in monocotyledonous plants and, more importantly, confirmed the DVR activity to convert divinyl Chl a to monovinyl Chl a.Chlorophyll (Chl) is the main component of the photosynthetic pigments. Chl molecules universally exist in photosynthetic organisms and perform essential processes of harvesting light energy in the antenna systems and by driving electron transfer in the reaction centers (Fromme et al., 2003). In higher plants, there are two Chl species, Chl a and Chl b. The photosynthetic reaction centers contain only Chl a, and the peripheral light-harvesting antenna complexes contain Chl a and Chl b (Grossman et al., 1995). Chl a is synthesized from glutamyl-tRNA, and Chl b is synthesized from Chl a at the last step of Chl biosynthesis (Beale, 1999). So far, genes for all 15 steps in the Chl biosynthetic pathway have been identified in higher plants, at least in angiosperms represented by Arabidopsis (Arabidopsis thaliana; Beale, 2005; Nagata et al., 2005). Analysis of the complete genome of Arabidopsis showed that it has 15 enzymes encoded by 27 genes for Chl biosynthesis from glutamyl-tRNA to Chl b (Nagata et al., 2005). However, only six genes encoding three enzymes involved in Chl biosynthesis have been identified in rice (Oryza sativa). Magnesium chelatase comprises three subunits (ChlH, ChlD, and ChlI) and catalyzes the insertion of Mg²⁺ into protoporphyrin IX, the last common intermediate precursor in both Chl and heme biosyntheses. Jung et al. (2003) characterized OsCHLH gene for the OsChlH subunit of magnesium chelatase, and Zhang et al. (2006) cloned Chl1 and Chl9 genes encoding the OsChlD and OsChlI subunits of magnesium chelatase. Chl synthase catalyzes esterification of chlorophyllide (Chlide), resulting in the formation of Chl a. Wu et al. (2007) identified the YGL1 gene encoding the Chl synthase. Chl b is synthesized from Chl a by Chl a oxygenase; Lee et al. (2005) identified OsCAO1 and OsCAO2 genes for Chl a oxygenase.According to the number of vinyl side chains, Chls of oxygenic photosynthetic organisms are classified into two groups: 3,8-divinyl Chl (DV-Chl) and 3-vinyl Chl (monovinyl Chl [MV-Chl]). Almost all of the oxygenic photosynthetic organisms contain MV-Chls, regardless of the variation in their indigenous environments (Porra, 1997). The exceptions are species of Prochlorococcus marinus, marine picophytoplanktons that contain DV-Chls as their photosynthetic pigments (Chisholm et al., 1992).Chl biosynthetic heterogeneity is assumed to originate mainly in parallel DV- and MV-Chl biosynthetic routes interconnected by 8-vinyl reductases that convert DV-tetrapyrroles to MV-tetrapyrroles by conversion of the vinyl group at position 8 of ring B to the ethyl group (Parham and Rebeiz, 1995; Rebeiz et al., 2003). Most of Chls carry an ethyl group or, less frequently, a vinyl group. For example, Chl a and b occur as the MV-derivatives in green plants, but Chl precursors sometimes accumulate as DV-intermediates, and the ratio between the two forms can vary depending on the species, tissue, and growth conditions (Shioi and Takamiya, 1992; Kim and Rebeiz, 1996). So far, five 8-vinyl reductase activities have been detected at the levels of DV Mg-protoporphyrin IX (Kim and Rebeiz, 1996), Mg-protomonomethyl ester (Kolossov et al., 2006), protochlorophyllide (Pchlide) a (Tripathy and Rebeiz, 1988), Chlide a (Kolossov and Rebeiz, 2001; Nagata et al., 2005), and Chl a (Adra and Rebeiz, 1998). What is not clear at this stage is whether the various 8-vinyl reductase activities are catalyzed by one enzyme of broad specificity or by a family of enzymes of narrow specificity encoded by one gene or multiple genes, as is the case for NADPH Pchlide oxidoreductases (Rebeiz et al., 2003). The issue could be settled by purification of the various putative reductases and comparison of their properties.Nagata et al. (2005) and Nakanishi et al. (2005) independently identified the AT5G18660 gene of Arabidopsis as a divinyl reductase (DVR) that has sequence similarity to isoflavone reductase. Chew and Bryant (2007) demonstrated that BciA (CT1063), which is an ortholog of the Arabidopsis gene, encodes a DVR of the green sulfur bacterium Chlorobium tepidum TLS. They also considered that BchJ, which had been reported to be a vinyl reductase (Suzuki and Bauer, 1995), is not the enzyme, but it may play an important role in substrate channeling and/or regulation of bacteriochlorophyll biosynthesis. Islam et al. (2008) and Ito et al. (2008) independently identified a novel 8-vinyl reductase gene (Slr1923) in DVR-less cyanobacterium Synechocystis sp. PCC6803. However, no DVR gene has yet been identified in monocotyledonous plants.In this study, we isolated a spontaneous mutant, 824ys, from indica rice cv 824B. The mutant exhibited a yellow-green leaf phenotype throughout the growth stage, reduced level of Chls, arrested development of chloroplasts, and retarded growth rate. Map-based cloning of the mutant resulted in the identification of the OsDVR gene, showing sequence similarity to the DVR gene of Arabidopsis. In the 824ys mutant, nine nucleotides were deleted at residues 952 to 960 in the open reading frame (ORF), resulting in three amino acid deletion in the encoded protein. HPLC analysis of Chls indicated the mutant accumulates only DV-Chls. Enzymatic analysis demonstrated that the recombinant protein expressed in Escherichia coli is able to catalyze the conversion of DV-Chl(ide) a to MV-Chl(ide) a. Therefore, this study has confirmed that the OsDVR gene encodes a functional DVR in rice.     

Chlorophyll Synthesis from Protochlorophyll(ide) in Chill-Stressed Maize (Zea mays L.)

Illumination of aetiolated maize at temperatures lower than20 °C results in negligible accumulation of chlorophyll.Illumination of leaf tissue, previously incubated in 10 molm^–3 ALA in darkness, shows only a slight conversion ofprotochlorophyll(ide) to chlorophyll a and b at temperaturesless than 20 °C. A refined procedure for measuring photosynthesisby photo-acoustic spectroscopy in leaves that differ in chlorophyllcontent is presented. Studies of photosynthesis in aetiolatedseedlings illuminated at different temperatures by photo-acousticspectroscopy suggests that impairment of the chlorophyll pathwayis paralleled by an aberrant development of the thylakoid membrane. Key words: Protochlorophyll(ide), temperature, photo-acoustic spectroscopy, membrane biogenesis     

Comparison of Light-dependent Oxygen Uptake, Protochlorophyll(ide)-650 Photoconversion, and Chlorophyll Disappearance in Wheat Etioplasts

Red light exposures given to dark-grown wheat seedlings (Triticum aestivum L.) prior to etioplast isolation reduced the ability of these organelles to consume O₂. The same preharvest red light exposures also decreased protochlorophyll(ide) content of etioplasts. In addition, regeneration of both O₂ uptake rates as well as protochlorophyll(ide) levels followed a parallel time course. These similarities suggested that photoconversion of protochlorophyll(ide)-650 to chlorophyll(ide) may mediate some process with O₂ as the electron acceptor. This process appears to involve photooxidation of nonphotoconvertible protochlorophyll(ide) as well as of newly formed chlorophyll(ide). This hypothesis is further supported by the observations that: (a) the in vitro light induced O₂ uptake phenomenon was observed in solubilized protochlorophyll(ide) holochrome preparations; and (b) photoinduced O₂ uptake was reduced to zero rate by light exposure time equivalent to that required for chlorophyll(ide) and nonphotoconvertible protochlorophyll(ide) destruction.     

Changes in Levels of Cytokinins in Etiolated Squash Seedlings after Illumination

When etiolated seedlings of squash (Cucurbita maxima Duch. cv.Houkou-aokawaamaguri) were exposed to light, their cotyledonsbegan to accumulate chlorophyll at a low rate for the firsthour but at a high rate therafter. After 0, 1 and 2 h of illumination,cytokinin levels in cotyledons, hypocotyls and roots were analyzedby ELISA (enzyme-linked immunosorbent assay) and GC-SIM (gaschromatography-selected ion monitoring). Cytokinin levels measuredby ELISA were about 10 times higher than those measured by GC-SIM,suggesting that ELISA was not suitable for the measurementsof cytokinin levels in the extracts from these tissues. Cytokininsfound by GC-SIM were t-RZ (t-ribosyl zeatin), c-RZ, t-Z (t-zeatin),c-Z, RiP (ribosyl isopentenyladenine) and iP (isopoentenyladenine).Levels of biologically active cytokinins (t-RZ and t-Z) didnot show marked changes after illumination. Levels of c-RZ andc-Z did, however, decrease in cotyledons and increase in hypocotylsafter illumination. Promotion of the accumulation of the chlorophyllin detached squash cotyledons by exogenously applied t-Z waspartially inhibited by the addition of c-Z, suggesting thatthe decrease in the endogenous level of c-Z in cotyledons ofintact seedlings after illumination permits the light-inducedformation of chlorophyll. (Received August 8, 1990; Accepted April 4, 1991)     

Developmental Physiology of Bean Leaf Plastids III. Tube Transformation and Protochlorophyll (ide) Photoconversion by a Flash Irradiation

A light flash of about 1 millisecond duration elicits tube transformation in paracrystalline prolamellar bodies as well as maximal protochlorophyll(ide) photoconversion in etiolated bean leaves (Phaseolus vulgaris L.). These findings support a more detailed hypothesis on the linkage between tube transformation and protochlorophyll(ide) photoconversion than has been offered previously.     

The Correlated Appearance of Prolamellar Bodies, Protochlorophyll(ide) Species, and the Shibata Shift during Development of Bean Etioplasts in the Dark

The structure and physiology of the etioplast was investigated in developing primary leaves of 3- to 9-day-old dark-grown bean (Phaseolus vulgaris L. var. Red Kidney) seedlings. Increase in total protochlorophyll(ide) content followed that of leaf fresh weight. In 3- to 4-day-old bean leaves more than 50% of the protochlorophyll(ide) is in the form of protochlorophyll(ide) 628, which is nontransformable by light. Most of the transformable pigment is protochlorophyll(ide) 635, with smaller amounts of protochlorophyll(ide) 650. During leaf development from the 3rd to the 7th day phototransformable protochlorophyll(ide) with an absorbance maximum at 650 nm accumulates faster than nontransformable protochlorophyll(ide) or protochlorophyll(ide) 635. This increase in protochlorophyll(ide) 650 is correlated with the formation and enlargement of prolamellar bodies.