Internode length in Pisum sativum L. The kinetics of growth and [3H]gibberellin A20 metabolism in genotype na Le

The relationship between shoot growth and [³H]gibberellin A₂₀ (GA₂₀) metabolism was investigated in the GA-deficient genotype of peas, na Le. [17-¹³C, ³H₂]gibberellin A₂₀ was applied to the shoot apex and its metabolic fate examined by gas chromatographic-mass spectrometric analysis of extracts of the shoot and root tissues. As reported before, [¹³C, ³H₂]GA₁, [¹³C, ³H₂]GA₈ and [¹³C, ³H₂]GA₂₉ constituted the major metabolites of [¹³C, ³H₂]GA₂₀ present in the shoot. None of these GAs showed any dilution by endogenous ¹²C-material. [¹³C, ³H₂]GA₂₉-catabolite was also a prominent metabolite in the shoot tissue but showed pronounced isotope dilution probably due to carry-over of endogenous [¹²C]GA₂₉-catabolite from the mature seed. In marked contrast to the shoot tissue, the two major metabolites present in the roots were identified as [¹³C, ³H₂]GA₈-catabolite and [¹³C, ³H₂]GA₂₉-catabolite. Both of these compounds showed strong dilution by endogenous ¹²C-material. Only low levels of [¹³C, ³H₂]GA₁, [¹³C, ³H₂]GA₈, [¹³C, ³H₂]GA₂₀ and [¹³C, ³H₂]GA₂₉ accumulated in the roots. It is suggested that compartmentation of GA-catabolism may occur in the root tissue in an analogous manner to that shown in the testa of developing seeds. Changes in the levels of [1,3-³H₂]GA₂₀ metabolites over 10 d following application of the substrate to the shoot apex of genotype na Le confirmed the accumulation of [³H]GA-catabolites in the root tissues. No evidence was obtained for catabolic loss of [³H]GA₂₀ by complete oxidation or conversion to a methanol-inextractable form. The results indicate that the root system may play an important role in the regulation of biologically active GA levels in the developing shoot of Na genotypes of peas.Abbreviations GA_n gibberellin A_n - GC-MS gas chromatography-mass spectrometry - HPLC high-pressure liquid chromatography     

The quantitative relationship between gibberellin A1 and internode growth in Pisum sativum L.

The metabolism and growth-promoting activity of gibberellin A₂₀ (GA₂₀) were compared in the internode-length genotypes of pea, na le and na Le. Gibberellin A₂₉ and GA₂₉-catabolite were the major metabolites of GA₂₀ in the genotype na le. However, low levels of GA₁, GA₈ and GA₈-catabolite were also identified as metabolites in this genotype, confirming that the le allele is a leaky mutation. Gibberellin A₂₀ was approximately 20 to 30 times as active in promoting internode growth of genotype na Le as of genotype na le. However, the levels of the 3-hydroxylated metabolite of GA₂₀, GA₈ (2-hydroxy GA₁), were similar for a given growth response in both genotypes. In each case a close linear relationship was observed between internode growth and the logarithm of GA₈ levels. A similar relationship was found on comparing GA₂₀ metabolism in the three genotypes le ^d, le and Le. The former mutation results in a more severe dwarf phenotype than the le allele (which has previously been shown to reduce the 3-hydroxylation of GA₂₀ to GA₁). These results indicate that GA₂₀ has negligible intrinsic activity and support the contention that GA₁ is the only GA active per se in promoting stem growth in pea.Abbreviations GA_n gibberellin A_n - GC-MS gas chromatography-mass spectrometry - HPLC high-pressure liquid chromatography     

Identification,quantitation and distribution of gibberellins in fruits of Pisum sativum L. cv. Alaska during pod development

In addition to the previously-reported gibberellins: GA₁; GA₈, GA₂₀ and GA₂₉ (García-Martínez et al., 1987, Planta 170, 130–137), GA₃ and GA₁₉ were identified by combined gas chromatography-mass spectrometry in pods and ovules of 4-d-old pollinated pea (Pisum sativum cv. Alaska) ovaries. Pods contained additionally GA₁₇, GA₈₁ (2-hydroxy GA₂₀) and GA₂₉-catabolite. The concentrations of GA₁, GA₃, GA₈, GA₁₉, GA₂₀ and GA₂₉ were higher in the ovules than in the pod, although, with the exception of GA₃, the total content of these GAs in the pod exceeded that in the seeds. About 80% of the GA₃ content of the ovary was present in the seeds. The concentrations of GA₁₉ and GA₂₀ in pollinated ovaries remained fairly constant for the first 12 ds after an thesis, after which they increased sharply. In contrast, GA₁ and GA₃ concentrations were maximal at 7 d and 4–6 d, respectively, after anthesis, at about the time of maximum pod growth rate, and declined thereafter. Emasculated ovaries at anthesis contained GA₈, GA₁₉ and GA₂₀ at concentrations comparable with pollinated fruit, but they decreased rapidly. Gibberellins a₁ and A₃ were present in only trace amounts in emasculated ovaries at any stage. Parthenocarpic fruit, produced by decapitating plants immediately above an emasculated flower, or by treating such flowers with 2,4-dichlorophenoxyacetic acid or GA₇, contained GA₁₉ and GA₂₀ at similar concentrations to seeded fruit, but very low amounts of GA₁ and GA₃ Thus, it appears that the presence of fertilised ovules is necessary for the synthesis of these last two GAs. Mature leaves and leaf diffusates contained GA₁, GA₈, GA₁₉ and GA₂₀ as determined by combined gas chromatography-mass spectrometry using selected ion monitoring. This provides further evidence that vegetative tissues are a possible alternative source of GAs for fruit-set, particularly in decapitated plants.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - FW fresh weight - GA_n gibberellin A_n - GC-MS combined gas chromatography-mass spectrometry - HPLC high-performance liquid chromatography - KRI Kovats retention index - m/z mass to charge ratio We thank Mr M.J. Lewis for qualitative GC-MS analyses and Ms M.V. Cuthbert (LARS), R. Martinez Pardo and T. Sabater (IATA) for technical assistance. We are also grateful to Professor B.O. Phinney, University of California, Los Angeles, for gifts of [17-¹³C]GA₈ and -GA₂₉ and to Mr Paul Gaskin, University of Bristol, for the mass spectrum of GA₂₉-catabolite and for a sample of GA₈₁ The work in Spain was supported by Dirección General de Investigación Cientifica y Técnica (grant PB87-0402 to J.L.G.-M.). We also acknowledge the British Council and Ministerio de Educacion y Ciencia for travel grants through Accion Integrada Hispano-Britanica 56/142 (J.L.G.-M. and P.H.).     

Gibberellins in developing fruits of Pisum sativum cv. Alaska: Studies on their role in pod growth and seed development

Gibberellins A₁, A₈, A₂₀ and A₂₉ were identified by capillary gas chromatography-mass spectrometry in the pods and seeds from 5-d-old pollinated ovaries of pea (Pisum sativum cv. Alaska). These gibberellins were also identified in 4-d-old non-developing, parthenocarpic and pollinated ovaries. The level of gibberellin A₁ within these ovary types was correlated with pod size. Gibberellin A₁, applied to emasculated ovaries cultured in vitro, was three to five times more active than gibberellin A₂₀. Using pollinated ovary explants cultured in vitro, the effects of inhibitors of gibberellin biosynthesis on pod growth and seed development were examined. The inhibitors retarded pod growth during the first 7 d after anthesis, and this inhibition was reversed by simultaneous application of gibberellin A₃. In contrast, the inhibitors, when supplied to 4-d-old pollinated ovaries for 16 d, had little effect on seed fresh weight although they reduced the levels of endogenous gibberellins A₂₀ and A₂₉ in the enlarging seeds to almost zero. Paclobutrazol, which was one of the inhibitors used, is xylem-mobile and it efficiently reduced the level of seed gibberellins without being taken up into the seed. In intact fruits the pod may therefore be a source of precursors for gibberellin biosynthesis in the seed. Overall, the results indicate that gibberellin A₁, present in parthenocarpic and pollinated fruits early in development, regulates pod growth. In contrast the high levels of gibberellins A₂₀ and A₂₉, which accumulate during seed enlargement, appear to be unnecessary for normal seed development or for subsequent germination.Abbreviations GA_(a) gibberellin A_n - GC-MS combined gas chromatography-mass spectrometry - HPLC high-performance liquid chromatography - PFK perfluorokerosene - PVP polyvinylpyrrolidone     

Ethylene metabolism in Pisum sativum L.

The possible role of C₂H₄ metabolism in mediating the responses of plants to C₂H₄ is re-examined. It is demonstrated that (i) the effects of inhibitors upon C₂H₄ action do not correspond with their effects on metabolism, (ii) elicitors of C₂H₄ effects do not have appropriate effects on C₂H₄ metabolism, (iii) inhibitors of C₂H₄ metabolism do not affect the response of plants to C₂H₄. It is concluded that metabolism of C₂H₄ is not linked to the mode of action of the growth regulator.Abbreviations DTC sodium diethyldithiocarbamate - FW fresh weight     

Metabolism of gibberellin A29 in seeds of Pisum sativum cv. Progress No. 9; Use of [2H] and [3H]GAs,and the identification of a new GA catabolite

The metabolism of GA₂₉ in maturing seeds of Pisum sativum cv. Progress No. 9 was further investigated, and the utility of ²H-labelled GAs in conjuction with GC-MS is illustrated. Using [2-²H₁]GA₂₉ as an internal standard, endogenous GA₂₉ was shown to reach a maximal level (ca. 10 g/seed) 27 days from anthesis, and to decline to ca. 1.6 g/seed in mature seeds. In a time-course feed the metabolism of [2-²H₁] [2-³H₁]GA₂₉ applied to 27 day old seeds, and of endogenous GA₂₉, was compared from the ¹H:²H ratios in the recovered GA₂₉. Although both [2-²H₁] [2-³H₁]GA₂₉ and endogenous GA₂₉ were metabolised to the same limited extent to a putative conjugate, in the main metabolic process endogenous GA₂₉ was preferentially converted to an untraceable (i.e. unlabelled) metabolite. In contrast, endogenous GA₂₉ and [1,3-²H₂] [1,3-³H₂]GA₂₉, derived from [1,3-²H₂] [1,3-³H₂]GA₂₀ in a time-course feed, were metabolised in an identical manner. In the latter case isotope loss precluded identification of the metabolite. The structure (8) has been assigned to a GA catabolite present in maturing seeds and seedlings of pea. The isotope data are consistent with this compound being the hitherto untraced metabolite of GA₂₉ in pea.Abbreviations GA_n gibberellin A_n - GC gas chromatography - GC-MS combined gas chromatography-mass spectrometry - GC-RC combined gas chromatography-radio counting - M⁺ molecular ion - Me methyl ester - R_T retention time - SICM selected ion current monitoring - TLC thin layer chromatography - TMS trimethylsilyl ether     

Metabolism of gibberellins by immature barley grain

Gibberellins A₁, A₄, A₉, A₁₂-aldehyde, A₂₀ and A₅₁, each labelled with both a radioactive and stable isotope were fed to immature barley grain by injection into the endosperm. After 7 d, extensive metabolism of all substrates had occurred, and metabolites were identified by combined capillary gas chromatography-mass spectrometry. A proposed scheme of gibberellin metabolism in immature barley grain is presented.Abbreviations GA_n gibberellin A_n - GC-MS combined gas chromatography-mass spectrometry - HPLC high-performance liquid chromatography     

Gibberellin translocation in Pisum sativum L.

The physiological and biochemical consequences of treating Le (tall) and le (dwarf) pea seedlings with varying quantities of the gibberellins [³H]GA₂₀ and GA₁ have been investigated. Although the percentage uptake of these compounds from the site of application on the 3 stipules was low and most of the applied GA remained unmetabolised in situ, the quantitative relationship between GA translocation and GA dosage was found to be linear for GA₁ but saturating for GA₂₀. The movement of the GAs and their subsequently produced metabolites was mainly acropetal. They accumulated in greatest quantity in the apical extremities of the shoot. Overall, the extent to which GA₂₀ was metabolished in le seedlings was considerably less than in Le pea seedlings. Although all le tissues contained significantly less [³H]GA₁ than their Le counterparts, phenotypic effects of the le mutation were apparent only on internode and tendril development. Increased tissue growth, consequent upon GA treatment, was also apparent only in the internodes and tendrils of le plants. For internodes, GA₁ content determined the mid-logarithmic-phase growth rate and, consequently, final length. For tendrils, GA₂₀ rather than GA₁ may be the primary stimulatory agent.Abbreviations GA gibberellin - HPLC high-performance liquid chromatography - 1–6 consecutive developmental numbering system for plant tissues/organs as shown in Fig. 1 The author gratefully acknowledges financial support from Imperial Chemical Industries, Plant Protection, Jealott's Hill, Bracknell, Berks., UK and the Science and Engineering Research Council.     

Endomitosis and the effect of gibberellic acid in different Pisum sativum L. cultivars

The evolution of the total amount of DNA in epicotyls and of the amount of DNA per cell nucleus in epicotyl cortex cells during germination was followed in two closely related pea varieties, Pisum sativum cv. Finale and Pisum sativum cv. Rondo. Under etiolating conditions, growth of the cv. Rondo occurs only by cell elongation which is preceded by endomitotic DNA synthesis, while in the cv. Finale growth is the result of cell elongation accompanied by endomitotic DNA synthesis and cell division. The maximum C-level attained in both cultivars under etiolating conditions is 8 C (C=haploid amount of DNA in a gamete cell). Both the maximum C-level reached and the percentage of cells reaching this C-level seem to be under strict genetic control. In both cultivars, light inhibits the endomitotic DNA replication.Neither gibberellic acid (GA₃), nor AMO 1618 alter the maximum C-level or the percentage distribution of the C-classes. Both growth regulators are effective, although in an opposite way, only in tissues where cell division occurs or where endomitotic DNA synthesis is blocked, as in light-grown pea epicotyls.     

Carnitine acyltransferases in chloroplasts of Pisum sativum L.

Carnitine-acetyltransferase (EC 2.3.1.7) and carnitine-palmitoyltransferase (EC 2.3.1.21) activities were shown to be present in chloroplasts of green pea leaves and possibly to occur in leaf mitochondrial and peroxisomal fractions. A role for the enzymes in the transfer of acyl groups across membranes is suggested.     

The partial purification and characterization of a gibberellin C-20 hydroxylase from immature Pisum sativum L. seeds

A gibberellin (GA) C-20 hydroxylase that catalyses the conversion of GA₅₃ to GA₄₄ was purified from developing pea embryos by ammonium-sulfate precipitation, gel filtration and anion-exchange column chromatography. The purification was about 270-fold and 15% of the enzymic activity was recovered. The relative molecular mass was 44000 by Sephadex G-200 gel filtration. The apparent Michaelis constant was 0.7 M and the isoelectric point was 5.6–5.9. The enzymic activity was optimal at pH 7.0 2-Oxoglutarate and ascorbate were required for activity. Low concentrations of Fe²⁺ stimulated the reaction, but externally added Fe²⁺ was not essential, even in the most purified preparation. Catalase and bovine serum albumin also stimulated. Dithiothreitol preserved the activity during purification but was not needed during incubation. In fact, the simultaneous presence of dithiothreitol and Fe²⁺ in the incubation mixture was inhibitory to the purified enzyme. The cofactor requirements are typical for those of 2-oxoglutarate-dependent dioxygenases.When the incubation time was long enough, GA₅₃ was converted to both GA₄₄ and GA₁₉. The proportions of these two products remained constant throughout the purification, but this does not necessarily mean that their formations is catalysed by a single enzyme. Sodium dodecyl sulfatepolyacrylamide gel electrophoresis showed that the final preparation contained several proteins. Although the most prominent protein band was located within the range expected for the enzyme on the grounds of its molecular weight, this band did not represent the enzyme, since it separated from the GA C-20 hydroxylase activity on ultrathin-layer isoeletric focusing.Abbreviation BSA bovine serum albumin - DEAE diethylaminoethyl - DTT dithiothreitol - EDTA ethylenediamine-tetraacetic acid - GA_n gibberellin A_n - HPLC high-performance liquid chromatography - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis - Tris 2-amino-2-(hydroxymethyl)-1,3-propanediol     

Metabolism of gibberellins in a cell-free system from immature seeds of Phaseolus vulgaris L.

The biosynthetic steps from gibberellin A₁₂-aldehyde (GA₁₂-aldehyde) to C₁₉-GAs were studied by means of a cell-free system from the embryos of immature Phaseolus vulgaris seeds. Stable-isotope-labeled GAs were used as substrates and the products were identified by gas chromatography-mass spectrometry. Gibberellin A₁₂-aldehyde was converted to GA₄ via non-hydroxylated intermediates and to GA₁ via 13-hydroxylated intermediates. 13-Hydroxylation took place at the beginning of the pathway by the conversion of GA₁₂-aldehyde to GA₅₃-aldehyde. The conversion of GA₂₀ to GA₅ and GA₆ was also shown but no 2-hydroxylating activity was found. Endogenous GAs from embryos and testas of 17-dold seeds were re-examined by gas chromatography-selected ion monitoring using stable-isotopelabeled GAs as internal standards. Gibberellins A₉, A₁₂, A₁₅, A₁₉, A₂₃, A₂₄, and A₅₃ were identified for the first time in P. vulgaris, in addition to GA₁, GA₄, GA₅, GA₆, GA₈, GA₁₇, GA₂₀, GA₂₉, GA₃₇, GA₃₈ and GA₄₄, which were previously known to occur in this species. The levels of all GAs, except the 2-hydroxylated ones, were greater in the embryos than in the testas. Conversely, the contents of GA₈ and GA₂₉, both 2-hydroxylated, were much higher in the testas than in the embryos.Abbreviations GA_n gibberellin A_n - GC-MS gas chromatography-mass spectrometry - GC-SIM gas chromatography-selected ion monitoring - HPLC high-performance liquid chromatography - TLC thin-layer chromatography - m/z ion of mass     

Quantitation of gibberellins A1, A3, A4, A9 and an A9-conjugate in good- and poor-flowering clones of Sitka spruce (Picea sitchensis) during the period of flower-bud differentiation

The levels of endogenous gibberellin A₁ (GA₁), GA₃, GA₄, GA₉ and a cellulase-hydrolysable GA₉-conjugate in needles and shoot stems of Sitka spruce [Picea sitchensis (Bong.) Carr.] grafts with different coning or flowering histories were estimated by combined gas chromatography-mass spectrometry selected ion monitoring using deuterated GA₃, GA₄ and GA₉ as internal standards. The samples were taken at the approximate time of the start of flower-bud differentiation, i.e. when the shoots had elongated approx. 95% of the final length. The needles of the good-flowering clones contained 11–12 ng per g fresh weight (FW) and 15–28 ng· (g FW) ^–1 of GA₉-conjugate and GA₉, respectively. The shoot stems of the same material contained no detectable amounts of GA₉-conjugate and 11–15 ng-(g FW)^–1 of GA₉. The amounts of GA₉-conjugate and GA₉ were apparently lower in the poor-flowering clones, the needles containing 4–9 ng-(g FW)^–1 and 7–17 ng·(g FW)^–1, respectively. Also in this material the shoot stems contained no detectable amounts of GA₉-conjugate. The amounts of GA₄ were very small in both materials, ranging from 1–1.6 ng-(g FW)^–1. The good-flowering clones contained no detectable amounts of the more polar gibberellins, GA₁ and GA₃. The poor-flowering clones, on the other hand, contained high levels of GA₁₅ 17–19ng·(gFW)^–1 in the needles and 10–13 ng·(g FW) ^–1 in the shoot stems, and also smaller amounts of GA₃, 2–3 ng·(g FW)^–1 in the needles and approx. 1 ng·(g FW)^–1 in the shoot stems. The results demonstrate differences in GA-metabolism between the poor- and the good-flowering clones. The higher amounts of GA₉-conjugate and GA₉ might indicate a higher capacity for synthesizing GA₄ in the good-flowering material. This synthesis does not, however, result in a build-up of the GA₄-pool, maybe because of a high rate of turnover. Gibberellin A₄ was apparently neither hydroxylated to GA₁ nor converted to GA₃ in the goodflowering material, as was the case in the poor-flowering material. This might indicate that gibberellin metabolism in the poor-flowering material is directed towards GA₁ and GA₃, GAs preferentially used in vegetative growth.Abbreviations FW fresh weight - GA_n gibberellin A_n - HPLC high-performance liquid chromatography     

The endogenous gibberellins of vegetative and reproductive tissue of G2 peas

The gibberellins (GAs) of both vegetative (leaves and stems) and reproductive (pods and seeds) tissue of the G2 strain of peas Pisum sativum L. were characterized in purified extracts by a combination of sequential silicic-acid partition column chromatography, and gas chromatography-mass spectrometry. Gibberellins A₁₉, A₂₀, A₂₉ and an A₂₉ catabolite were identified in both types of tissue. Gibberellins A₉, A₁₇ and A₄₄ were also found in pods and seeds.Abbreviations FID Ilame ionization detector - GA(s) gibberellin(s) - GC gas chromatograph(y) - HPLC high performance liquid chromatograph(y) - LD long day - MS mass spectrum(a) or mass spectrometer(ry) - SD short day     

Paraquat-resistant lines in Pisum sativum cv. Alaska: biochemical and phenotypic characterization

In plants, the oxygen generated by photosynthesis can be excited to form reactive oxygen species (ROS) under excessive sunlight. Excess ROS including singlet oxygen (¹O₂) inhibit the growth, development and photosynthesis of plants. To isolate ROS-resistant crop plants, we used paraquat (PQ), a generator of O₂ ^·− as a source of screening and mutagen, and obtained two PQ-resistant lines in Pisum sativum, namely R3-1 and R3-2. Both lines showed greater resistance to PQ than their wild type (WT) siblings with respect to germination, root growth, and shoot growth. Biochemical analysis showed differences in these lines, in which ROS-scavenging enzymes undergo changes with a distinguishable increase in Mn-SOD. We further observed that the cytosolic catalases (CATs) in leaves in both lines were shifted in a native-PAGE analysis compared with that of the WT, indicating that the release of bound ¹O₂ was enhanced. Phenotypic analysis revealed distinguishable differences in leaf development, and in flowering time and position. In addition, R3-1 and R3-2 showed shorter individual internode lengths, dwarf plant height, and stronger branching compared with the WT. These results suggested that PQ-induced ROS-resistant Pisum have the potential pleiotropic effects on flowering time and stem branching, and that ROS including ¹O₂ plays not only important roles in plant growth and development as a signal transducer, but also appears as a strong inhibitor for crop yield. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Immunochromatographic purification of gibberellins from vegetative tissues of Cucumis sativus L: Separation and identification of 13-hydroxy and 13-deoxy gibberellins

Immunological methods are described for the separation and purification of 13-hydroxy and 13-deoxy-gibberellins of Cucumis sativus. Qualitative and quantitative data show that 13-deoxygibberellins predominate over 13-hydroxygibberellins in stems and leaves of this species.Abbreviations FCS foetal calf serum - FW fresh weight - GA_n gibberellin A_n - GC-MS combined gas chromatography-mass spectrometry - IAC immunoaffinity chromatography David Marshall is thanked for help with the preparation of the extracts. The authors also thank ICI Plant Protection, Jealotts Hill, Bracknell, Berks., UK, the Science and Engineering Research Council, the Agricultural and Food Research Council, and also the National Science Foundation (grant DCB 8718540 to V.M. Sponsel) for financial support.     

The source of gibberellins in the parthenocarpic development of ovaries on topped pea plants

The role and source of gibberellins (GAs) involved in the development of parthenocarpic fruits of Pisum sativum L. has been investigated. Gibberellins applied to the leaf adjacent to an emasculated ovary induced parthenocarpic fruit development on intact plants. The application of gibberellic acid (GA₃) had to be done within 1 d of anthesis to be fully effective and the response was concentration-dependent. Gibberellin A₁ and GA₃ worked equally well and GA₂₀ was less efficient. [³H]Gibberellin A₁ applied to the leaf accumulated in the ovary and the accumulation was related to the growth response. These experiments show that GA applied to the leaf in high enough concentration is translocated to the ovary. Emasculated ovaries on decapitated pea plants develop without application of growth hormones. When [³H] GA₁ was applied to the leaf adjacent to the ovary a substantial amount of radioactivity accumulated in the growing shoot of intact plants. In decapitated plants, however, this radioactivity was mainly found in the ovary. There it caused growth proportional to the accumulation of CA₁. Application of LAB 150978, an inhibitor of GA biosynthesis, to decapitated plants inhibited parthenocarpic fruit development and this inhibition was counteracted by the application of GA₃ (either to the fruit, or the leaf adjacent to the ovary, or through the lower cut end of the stem). All evidence taken together supports the view that parthenocarpic pea fruit development on topped plants depends on the import of gibberellins or their precursors, probably from the vegetative aerial parts of the plant.Abbreviations FW flesh weight - GA_n gibberellin A_n - HPLC high-performance liquid chromatography     

Ultrastructural organization of chloroplast membranes in mutants of Pisum sativum L. with impaired activity in the photosystems

The ultrastructural organization and the photosynthesis reactions of chloroplast membranes were studied in three lethal mutants of Pisum sativum, Chl-1, Chl-19 and Chl-5, all lacking the capacity to evolve oxygen. The rates of 2,6-dichloroindophenol reduction, delayed fluorescence and electron-spin-resonance signal 1 indicate that Chl-1 and Chl-19 have an impaired activity in photosystem II (PS II), while in Chl-5 the electron transport is blocked between PS I and the reactions of CO₂ fixation. Ultrathin sectioning demonstrates the presence of giant grana in the chloroplasts of Chl-1 and Chl-19, while the chloroplast structure of the Chl-5 is very similar to that of the wild-type. The grana of the Chl-19 mutant contain large multilamellar regions of tightly packed membranes. When the chloroplast membranes were studied by freeze-fracture, the exoplasmic and protoplasmic fracture faces (EF and PF, respectively) in both stacked and unstacked membranes were found to show large differences in particle concentrations and relative population area (per m²), and also in particle size distribution, between all mutant chloroplast membranes and the wild-type. A close correlation between increasing k_mt (ratio of particle concentrations on PF/EF) and PS II activity was observed. The differences in particle concentrations on both fracture faces in different regions of the intact chloroplast membranes of the wild-type are the consequence of a rearrangement of existing membrane components by lateral particle movements since quantitative measurements demonstrate almost complete conservation of intramembrane particles in number and size during the stacking of stroma thylakoid membranes. The results indicating particle movements strongly support the concept that the chloroplast membranes have a highly dynamic structure.Abbreviations DPIP 2,6-dichloroindophenol - EF and PF exoplasmic and protoplasmic fracture faces, respectively - PS I and PS II photosystems I and II, respectively     

Oleate metabolism in microsomes from developing leaves ofPisum sativum L.

Microsomes from young leaves of pea,Pisum sativum L., metabolized oleate principally by the reactions mediated by oleoyl-CoA synthetase, oleoyl-CoA thioesterase, oleoyl-CoA: phosphatidylcholine acyltransferase and oleoyl phosphatidylcholine desaturase. Hydrogen peroxide specifically inhibited oleate desaturation and the evidence presented argues for a specific inhibition of the terminal enzyme of the desaturase system, i.e. oleoyl phosphatidylcholine desaturase. Catalase, ascorbic acid, or ascorbate peroxidase, in conjunction with ascorbic acid, stimulated oleate desaturation, possibly by the removal of hydrogen peroxide. Lysophosphatidylcholine was found to be the preferred acceptor for acyl transfer from oleoyl-CoA, which indicates that the transfer of oleoyl moieties was catalyzed predominantly by oleoyl-CoA:lysophosphatidylcholine acyltransferase. Acyl exchange between oleoyl-CoA and phosphatidylcholine, with a possible involvement of phospholipases, was also detected but at much lower rates than acyl transfer. When intact or broken chloroplasts were added to microsomes, which had been preincubated with oleoyl-CoA, some stimulation of the reactions catalyzed by oleoyl-CoA:phosphatidylcholine acyltransferase and oleoyl phosphatidylcholine desaturase was observed. However, only minor amounts of microsomal linoleoyl phosphatidylcholine were converted to galactolipids containing linolenoyl moieties.Abbreviations FA unesterified fatty acid (s) - PC phosphatidylcholines - 18:1 oleoyl moieties - 18:2 lmoleoyl moieties Dedicated to Professor Helmut K. Mangold, Bundesanstalt für Fettforschung, Münster, on his 60th birthday