Biosynthetic events required for lag elimination in chlorophyll synthesis in EuglenaSchwartzbach, Steven; Schiff, Jerome; Klein, Shimon
doi: 10.1007/BF00387337pmid: 24424687
Levulinic acid, a competitive inhibitor of δ aminolevulinic acid dehydratase, cycloheximide, an inhibitor of translation on 89s cytoplasmic ribosomes, and chloramphenicol, an inhibitor of translation on 68s chloroplast ribosomes, are reversible inhibitors of light induced chlorophyll synthesis in resting Euglena gracilis Klebs. When dark grown resting cells are preilluminated for 2 h followed by darkness for 12 h prior to exposure to continuous light, the usual lag period in chlorophyll formation is eliminated. If cycloheximide, chloramphenicol, or levulinic acid are present during either the preillumination period or the subsequent dark period, the lag is reestablished. Only the very beginning of the dark period is sensitive to cycloheximide but the dark period is less sensitive to levulinic acid than is the light period. Exposure of preilluminated cells to cycloheximide or levulinic acid at the time of exposure to continuous illumination completely inhibits chlorophyll synthesis indicating that the potential for rapid chlorophyll synthesis generated by preillumination and a dark period does not result simply from the accumulation of porphyrin precursors. Preillumination has little effect on the development of the capacity to fix CO2 photosynthetically. These results indicate that the control of chlorophyll formation is more complex than in higher plants and a model based on the formation of certain crucial enzymes in the porphyrin pathway, rather than simply upon the accumulation of δ aminolevulinic acid is presented to explain the experimental findings.
Die Lokalisation der Peroxidase-Isoenzymgruppe GI in der Zellwand von Tabak-GewebenMäder, Michael
doi: 10.1007/BF00387338pmid: 24424688
By vacuum infiltration of intercellular spaces of tobacco tissues it is possible to extract substances from cell walls which move freely in the walls. The peroxidases (E.C. 1.11.1.7) contained in these extracts are predominantly isoenzymes of GI (fast migrating anodic group) as was shown by discelektrophoresis of the extracts. As has been demonstrated previously GI is not present in the protoplast; therefore GI is the typical cell wall fraction of tobacco peroxidases. Different tissues of tobacco always differ in the isoenzyme pattern of GI. This pattern also changes during tissue development. We can therefore say that there exists an enzymatic differentiation of plant cell walls during development. As GI is not bound to the walls, it always appears in high amounts in crude extracts of plant material. Therefore GI is always called the soluble cytoplasmic fraction, but our investigations clearly demonstrate that GI is localized in cell walls only. Beside GI there are much smaller amounts of GIII (slow migrating cathodic group) and if present in the tissue GII (slow migrating anodic group) detectable in the infiltration fluids of intracellular spaces. GIII and GII are localized mainly in the protoplast. But they are also bound to the walls, ionically in the case of GIII and covalently in the case of GII.
Movement of labelled metabolites from mitochondria to plastids during developmentWellburn, A.; Hampp, R.
doi: 10.1007/BF00387339pmid: 24424689
The exchange of metabolites from isolated mitochondria of Avena sativa L. to isolated etioplasts or 1–24 h etio-chloroplasts, from the same laminae, has been investigated. The results confirm the synchronised changes in the permeabilities of the inner membranes of each during plastid development. They also indicated the possibility of directed transport of certain metabolites from mitochondria to plastids especially during the early stages of chloroplast maturation. Over 80% of labelled succinate and oxaloacetate previously associated with mitochondria was found to be associated with 1 and 2 h etio-chloroplasts after in vitro incubation, with their respective mitochondria, for only 1 min at 0°C. Other metabolites showed variable but lower rates of transfer and that of aminolevulinic acid was at a much reduced level throughout development.
Changes in the permeability of the inner mitochondrial membrane associated with plastid developmentHampp, R.; Wellburn, A.
doi: 10.1007/BF00387340pmid: 24424690
Mitochondria isolated from greening etiolated laminae of Avena sativa L. show changes in the permeability of their inner membranes during chloroplast development similar to those described earlier for plastids. Oxalo-acetate, succinate and α-keto-glutarate permeate most readily inner membranes of mitochondria isolated from laminae given 2 h illumination whilst glutamate and glycine show later and more general penetration into the matrix spaces of mitochondria from greening tissue. Aminolevulinic acid (ALA) by contrast does not readily enter Avena mitochondria especially those isolated from laminae illuminated for longer than 2 h.
Phytochrome-induced changes of β-fructosidase activity in radish cotyledonsZouaghi, M.
doi: 10.1007/BF00387341pmid: 24424691
β-fructofuranosidase (E.C.3.2.1.26) activity can hardly be detected in cotyledons from dark-grown radish (Raphanus sativus) seedlings. Under continuous far-red light two waves of β-fructofuranosidase activity can be observed. The first one concerns an acidic invertase which progressively disappears. This wave is followed by the appearance of a neutral invertase. Some characteristics of these two enzymes are given. Their regulation by light via phytochrome is discussed.
The estimation of phenylalanine ammonia-lyase (PAL)-activity in intact cells of higher plant tissueAmrhein, Nikolaus; Gödeke, Karl-Heinz
doi: 10.1007/BF00387343pmid: 24424693
Fluctuations in the activity of phenylalanine ammonia-lyase (PAL) in tissues of buckwheat seedlings were monitored by an intact cell assay and compared with results obtained with the conventional in vitro assay. Good correlation between measurements with the different assays was found for PAL activity changes during 1) growth of seedlings in the dark, 2) illumination of seedlings, and 3) incubation of hypocotyl segments. When leaf disks of buckwheat, strawberry, or sunflower were allowed to float on either water or a sugar solution, PAL activities determined with the intact cell assay increased irrespective of the presence of sugar, while PAL activities determined in cell homogenates increased only in disks floating on a sugar solution. Possible explanations for these discrepancies are discussed.
Dark fixation of CO2 by flowers of cut rosesSchnabl, Heide; Mayer, Irmtraud
doi: 10.1007/BF00387345pmid: 24424695
Complete flower heads of cut roses (cv. Baccara) were exposed to 14CO2 for 1–4 h. The flower tissue was able to fix CO2 via PEP carboxylase (E.C. 4.1.1.31) in the dark; various TCA products were identified in petals, ovary and anthers, including malate, aspartate, citrate, serine/glycine, glutamate and asparagine. The concentrations of these labelled products were similar in the petals and anthers, but lower in the ovary. After removal of the petals the amounts of these components were reduced in the anthers to a relatively high extent (to 1/6), whereas the amounts in the ovary increased slightly. It is suggested that the petals are necessary for supplying the anthers with the described components.
The movement of 2,4-dichlorophenoxy acetic acid in root segments of Pisum sativum L.Wilkins, Henry; Wilkins, Malcolm
doi: 10.1007/BF00387346pmid: 24424696
An acropetal polarisation of the movement of 2,4-dichlorophenoxy acetic acid (2,4-D) through subapical segments of Pisum seedling primary roots has been monitored throughout a 60 h transport period in darkness at 25° C using [1-14C]2,4-D and [2-14C]2,4-D. Uptake of 2,4-D does not proceed at a constant rate; periods in which the amount of 14C in the root segments and receiver blocks increases rapidly are followed by periods in which the amount of radioactivity remains relatively constant or declines slightly. These oscillations do not appear to be related to the time of day at which the experiments are begun or ended. Immobilisation and degradation of 2,4-D during transport in the segments seems to be low. Replacement of [1-14C]2,4-D donor blocks after 25 h by blocks containing unlabelled 2,4-D results in continued transport of the compound into receiver blocks, with only small amounts of 14C remaining in the root tissues. Radioactivity is also exported from the segments into the blocks used to replace the donor blocks, with larger amounts being exported into the blocks applied to the apical ends than into those applied to the basal ends of the segments. This radioactivity may be taken-up again by the segments but more 14C is exported into these blocks towards the end of the experiments. The possibility of regular oscillations in uptake and movement of 2,4-D in Pisum root segments is discussed.