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Showing papers in "Planta in 1977"


Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: Quantum yield measurements of CO2 fixation confirm that hight-light conditions protect from heat-damage and it is suggested that chlorophyll acts as an intrinsic fluorescence probe of the thylakoid membrane and responds to the same changes which cause irreversible denaturation of photosynthetic enzymes.
Abstract: Methods were developed to measure chlorophyll fluorescence yield of intact leaf tissue during heat treatment under varying conditions of light intensity and photosynthetic activity. Fluorescence yield of a dark-adapted leaf increases by 2- to 3-fold with an increase of temperature into the region where heat-damage occurs. The temperatures of the fluorescence transition correlate well with the temperatures where quantum yield of CO2 fixation is irreversibly depressed. Fluorescence-temperature (F-T) curves allow ranking of different species according to their heat sensitivity. Within a single species acclimation to different growth temperatures is reflected by shifts of the transition temperatures in the F-T curves. When F-T curves are recorded in the steady light states at increasing light intensities, substantial shifts (up to 6°C) of transition temperatures to higher values are observed. Quantum yield measurements of CO2 fixation confirm that hight-light conditions protect from heat-damage. It is suggested that chlorophyll acts as an intrinsic fluorescence probe of the thylakoid membrane and responds to the same changes which cause irreversible denaturation of photosynthetic enzymes.

369 citations


Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: NADH was found to be oxidized by two different mechanisms, one involving Mn2+, monophenol, and the superoxide radical O2·- in a reaction that is not affected by superoxide dismutase, and another one depending on the presence of free O2 ·- and probably of an enzyme-NadH complex.
Abstract: Peroxidase associated with isolated horseradish cell walls catalyzes the formation of H2O2 in the presence of NADH The reaction is stimulated by various monophenols, especially of coniferyl alcohol NADH can be provided by a bound malate dehydrogenase This system is capable of polymerizing coniferyl alcohol yielding an insoluble dehydrogenation polymer NADH was found to be oxidized by two different mechanisms, one involving Mn2+, monophenol, and the superoxide radical O2·- in a reaction that is not affected by superoxide dismutase, and another one depending on the presence of free O2·- and probably of an enzyme-NADH complex A scheme of these reaction chains, which are thought to be involved in the lignification process, is presented

279 citations


Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: The effect of humidity on the gas exchange of leaves of the dicotyledons soybean, sunflower, jojoba, and saltbush and of whole, attached, single leaves showed that water use efficiency was highest in the C4 xerophytes and lowest in theC3 mesophytes.
Abstract: The effect of humidity on the gas exchange of leaves of the dicotyledons soybean (Glycine max (L.) Merrill), sunflower (Helianthus annuus L.), jojoba (Simmondsia chinensis (L.) Schneider), and saltbush (Atriplex halimus L.) and the monocotyledons wheat (Triticum aestivum L.), barley (Hordeum vulgare L.) sorghum (Sorghum bicolor (L.) Moench) and barnyard grass (Echinochloa crus-galli (L.) Beauv.) was examined under conditions of adequate soil moisture in a controlled environment. Photosynthesis and stomatal and internal diffusion resistances of whole, attached, single leaves were not affected by changes in humidity as the vapour pressure deficit between the leaf and atmosphere ranged from 8 to 27 mb. Transpiration increased linearly with increasing vapour pressure deficit. Whole plants of barley exhibited a different response. As humidity was increased, photosynthesis increased, transpiration expressed per unit of vapour pressure difference increased, and diffusion resistances became smaller. Reasons for the different behaviour of single leaves and whole plants are suggested. An index for water use efficiency, expressed per millibar of vapour pressure deficit, was calculated for single leaves of each species used in the experiments. This showed that water use efficiency was highest in the C4 xerophytes and lowest in the C3 mesophytes. The effect of environment on water use efficiency is examined using data from the literature.

251 citations


Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: The movement of photosynthetic intermediates between mesophyll and sheath cells is restricted largely or entirely to the plasmodesmata (symplastic pathway) and transpirational water movement to the cell walls (apoplastic pathway).
Abstract: In leaf blades of Zea mays L. plasmodesmata between mesophyll cells are aggregated in numerous thickened portions of the walls. The plasmodesmata are unbranched and all are characterized by the presence of electron-dense structures, called sphincters by us, near both ends of the plasmodesmatal canal. The sphincters surround the desmotubule and occlude the cytoplasmic annulus where they occur. Plasmodesmata between mesophyll and bundle-sheath cells are aggregated in primary pit-fields and are constricted by a wide suberin lamella on the sheath-cell side of the wall. Each plasmodesma contains a sphincter on the mesophyll-cell side of the wall. The outer tangential and radial walls of the sheath cells exhibit a continuous suberin lamella. However, on the inner tangential wall only the sites of plasmodesmatal aggregates are consistently suberized. Apparently the movement of photosynthetic intermediates between mesophyll and sheath cells is restricted largely or entirely to the plasmodesmata (symplastic pathway) and transpirational water movement to the cell walls (apoplastic pathway).

163 citations


Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: Removal of the dominant shoot apex rapidly restored the capacity of the subordinate shoot to transport apically-applied [14C]IAA, and at the same time led to rapid cambial development and secondary vascular differentiation in the previously inhibited shoot.
Abstract: Dwarf pea plants bearing two cotyledonary shoots were obtained by removing the epicotyl shortly after germination, and the patterns of distribution of (14)C in these plants was investigated following the application of [(14)C]IAA to the apex of one shoot. Basipetal transport to the root system occurred, but in none of the experiments was (14)C ever detected in the unlabelled shoot even after transport periods of up to 48 h. This was true both of plants with two equal growing shoots and of plants in which one shoot had become correlatively inhibited by the other, and in the latter case applied whether the dominant or subordinate shoot was labelled. In contrast, when [(14)C]IAA was applied to a mature foliage leaf of one shoot transfer of (14)C to the other shoot took place, although the amount transported was always low. Transport of (14)C from the apex of a subordinate shoot on plants bearing one growing and one inhibited shoot was severely restricted compared with the transport from the dominant shoot apex, and in some individual plants no transport at all was detected. Removal of the dominant shoot apex rapidly restored the capacity of the subordinate shoot to transport apically-applied [(14)C]IAA, and at the same time led to rapid cambial development and secondary vascular differentiation in the previously inhibited shoot. Applications of 1% unlabelled IAA in lanolin to the decapitated dominant shoot maintained the inhibition of cambial development in the subordinate shoot and its reduced capacity for auxin transport. These results are discussed in relation to the polarity of auxin transport in intact plants and the mechanism of correlative inhibition.

161 citations


Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: Cotyledons of Ricinus communis take up externally supplied sucrose at a rate of up to 150 μmol/h/g fresh weight, which is very high when compared with other sugar transport systems of higher plants, but the rate of uptake is subject to feedback inhibition by internal sucrose, and is regulated during growth of the seedlings.
Abstract: Cotyledons of Ricinus communis take up externally supplied sucrose at a rate of up to 150 μmol/h/g fresh weight, which is very high when compared with other sugar transport systems of higher plants. The uptake of sucrose is catalysed with a K m of 25 mmol l−1; at high sucrose concentrations a linear (diffusion) component becomes obvious. Other mono-, di-, or trisaccharides do not compete for sucrose uptake. Sucrose is accumulated by the cotyledons up to 100-fold, whereby most of the transported, externally supplied sucrose mixes with sucrose present in the tissue. At low sucrose concentrations, however; a small unexchangeable internal pool of sucrose becomes evident. Poisons of energy metabolism such as FCCP inhibit uptake and accumulation of sucrose. The transport of sucrose induces an increase of respiration, from which an energy requirement of 1.4 ATP/sucrose taken up can be calculated. Sucrose is taken up together with protons at an apparent stoichiometry of 0.3 protons/sucrose. Other sugars do not cause proton uptake. The K m for sucrose induced proton uptake is 5 mmol l−1; the discrepancy to the K m for sucrose uptake as well as the low proton: sucrose stoichiometry might possibly be caused by a large contribution of diffusion barriers. The estimated proton-motive potential difference would by sufficient to explain an electrogenic sucrose accumulation. The rate of uptake of sucrose is subject to feedback inhibition by internal sucrose. It is also regulated during growth of the seedlings since it develops rapidly during the first days of germination and declines again after the 4th day of germination, though no substantial increase of passive permeability resistance was observed.

147 citations


Journal ArticleDOI
S. T. C. Wright1
01 Jan 1977-Planta
TL;DR: In excised water-stressed leaves there was a sigmoid relationship between increasing ethylene and abscisic acid (ABA) levels and decreasing leaf water potential values and it seems unlikely that the stress-induced ethylene evolution in excised wheat leaves stimulated the accumulation of ABA.
Abstract: The amount of diffusible ethylene from excised wheat leaves (Triticum aestivum L. cv. Eclipse) increased when they were subjected to water stress. The quantity of ethylene produced was related to the severity of the stress, reaching a maximum at a leaf water potential ψleaf of approximately-12 bars. Irrespective of the severity of the stress, the maximum rate of ethylene production usually occurred between 135–270 min after applying the stress and then the rate declined. Part of the decline may have been due to an oxygen deficiency in the leaf chambers. In excised water-stressed leaves there was a sigmoid relationship between increasing ethylene and abscisic acid (ABA) levels and decreasing leaf water potential values. The two curves were displaced from each other by approximately 1 bar, with ethylene evolution leading that of ABA accumulation. The maximum rate of increase in ethylene occurred between-8 and-9 bars and for ABA between-9 and-10 bars. A significant increase in the levels of these two plant growth regulators was found when the ψleaf decreased outside the normal diurnal ψleaf range by 1 bar for ethylene and 2 bars for ABA. Because of the sigmoid nature of the curves there was no distinct threshold ψleaf value triggering-off an increase in ethylene or ABA, but with ABA the curve became very steep at a ψleaf value of-9.3 bars and this could be looked upon as a kind of “threshold” value.

139 citations


Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: Cell suspension cultures of Coleus blumei Benth have been found to accumulate 8–11% of their dry weight as rosmarinic acid (α-O-caffeoyl-3,4-dihydroxyphenyl-lactic acid) and this high rate of synthesis coincides with an increase in phenylalanine ammonia-lyase specific activity.
Abstract: Rosmarinic acid, or α-0-caffeoyl-3,4-dihydroxyphenyllactic acid (Fig. 1), is a representative of a major class of plant secondary metabolites, the ester- or amide-linked conjugates of hydroxycinnamic acids. These compounds, along with the flavonoid tannins, are believed to serve as the substrates for peroxidases and polyphenol oxidases during the browning of damaged plant tissues and the hypersensitive response to pathogen attack (Tomiyama et al. 1967). Auto-oxidation and enzymic oxidation convert the hydroxycinnamoyl moiety to various reactive species which can readily couple covalently with electron-deficient centers in proteins, nucleic acids and other metabolites (Pierpoint et al. 1977; Igarashi and Yasui 1985). Since this process can rapidly destroy the functional integrity of a cell, hydroxycinnamoyl conjugates in living cells must normally be sequestered in a cellular compartment which isolates them from oxidative enzyme catalysis. The limited evidence on this point indicates that the soluble conjugates are normally stored within the central vacuole (Chaprin and Ellis 1984). There is also a pool of insoluble conjugates associated with the cell wall (El-Basyouni et al. 1964), but their metabolic relationship to the soluble conjugates remains unknown.

138 citations


Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: It is concluded that the observed zein heterogeneity is partly based on in vivo deamidation of glutamine and asparagine and partly to spot mutations in some of the genes responsible for zein synthesis.
Abstract: The extensive charge heterogeneity of maize (Zea mays L.) zeins observed in isoelectric focusing (IEF) (about 15 bands with pI's in the pH range 6-9) has been found to be independent of extraction proce- dures or of endosperm development. Zeins do not stain for glycoproteins and exhibit only one lipo- protein component, with pI 3, representing 3-5% of the total protein. Zeins are very resistant to in vitro deamidation, at both acidic and alkaline pH, at high temperatures, and for rather prolonged times. On the basis of the zein content in acidic and basic amino acids, and of the respective pI's exhibited in IEF (mostly in the pH range 7-8) it has been calculated that at least 90% of the glutamic and aspartic acids ( ~ 52 residues out of a total of ~190) are present as asparagine and glutamine. Amino acid analysis of zein fractions isolated by preparative IEF has demonstrated changes in the composition of 18 amino acid residues. However, since these changes affect only neutral and hydropho- bic residues, it is concluded that the observed zein heterogeneity is partly based on in vivo deamidation of glutamine and asparagine and partly to spot muta- tions in some of the genes responsible for zein syn- thesis.

121 citations


Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: A convenient and reliable method for culturing cotton embryos is needed to obtain interspecific hybrids of this genus by developing a phytohormone-supplemented medium upon which the growth of ovules was similar that of in situ ovules.
Abstract: A convenient and reliable method for culturing cotton embryos is needed to obtain interspecific hybrids of this genus. C.A. Beasley and I.P. Ting (Amer. J. Bot. 60, 130, 1973) developed a phytohormone-supplemented medium (BTP) upon which the growth of ovules was similar that of in situ ovules. This medium was examined for in-ovulo embryo culture. Although good ovule growth occurred on BTP no embryos developed to maturity. However, when the medium was supplemented with NH4+, more than 50% of the ovules produced mature embryos, and many of these germinated precociously after 8–10 weeks of culture. After germination seedlings were established on a separate medium designed to give balanced root and shoot growth. Subsequently young plants could be transferred to pots for greenhouse culture.

117 citations


Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: The setting free of RER cisterns, which in the mature inactive pollen were aggregated in stacks, coinciding with polysome formation and resumption of protein synthesis, is in accord with the hypothesized role of R ER cistern stacks as a reserve of synthesizing machinery.
Abstract: Morphologic changes occurring during pollen grain activation and ultrastructural features of Lycopersicum peruvianum Mill. pollen tube during the first stages of growth in vitro have been studied. The more evident morphologic changes during activation, in comparison to those already described for mature inactive pollen, concern dictyosomes, rough endoplasmic reticulum (RER), and ribosomes. The dictyosomes are very abundant and produce “large” and “small” vesicles. Near the germinative pores both types of vesicles are present, while all along the remaining cell wall only the large type is observed. These latter react weakly to Thiery's test and probably contain a callose precursor necessary for the deposition of a callosic layer lining at first only the inner side of the functioning pore and occasionally the other two pores, and subsequently the entire inner surface of the cell wall. The small vesicles, highly positive to Thiery's test, are present only near the pores and could be involved in the formation of the pectocellulosic layer of the tube wall. The setting free of RER cisterns, which in the mature inactive pollen were aggregated in stacks, coinciding with polysome formation and resumption of protein synthesis, is in accord with the hypothesized role of RER cistern stacks as a reserve of synthesizing machinery. The pollen tube reaches a definitive spatial arrangement soon after the generative cell and vegetative nucleus have moved into it. At this stage four different zones that reflect a functional specialization are present. In the apical and subapical zone two types of dictysosome-originated vesicles, similar to those found in the activated pollen grain, are present. Their role in the formation of the callosic and pectocellulosic wall layers seems to be the same as in the activated pollen grain.

Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: The data are consistent with the hypothesis that ethylene forms a link between pollination of the style and petal wilting, but in the unpollinated flower the Style and petals can evolve a surge of ethylene independently of each other, about the time when the petals irreversibly wilt.
Abstract: Production of endogenous ethylene from the styles, ovary and petals of pollinated and unpollinated flowers of Dianthus caryophyllus L. was measured. The rate of ethylene production of cut, unpollinated flowers aged in water at 18°C was low until the onset of petal wilting, when a rapid surge of ethylene occurred in all tissues. The flower ethylene production was evolved mostly from the styles and petals. The bases of petals from unpollinated, senescing flowers evolved ethylene faster and sometimes earlier than the upper parts. Treatment of cut flowers with propylene, an ethylene analogue, accelerated wilting of flower petals and promoted endogenous ethylene production in all flower tissues. Pollination of intact flowers also promoted endogenous ethylene production and caused accelerated petal wilting within 2–3 days from pollination. Although the data are consistent with the hypothesis that ethylene forms a link between pollination of the style and petal wilting, in the unpollinated flower the style and petals can evolve a surge of ethylene independently of each other, about the time when the petals irreversibly wilt. The results are discussed in relation to the role of ethylene in flower senescence.

Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: Quantitative analyses of abscisic acid in different parts of maize root tips were performed by mass fragmentography using the hexadeuterated analog of ABA as internal standard, finding that the cap and the apex contained 36.1 μg and 66.5 μg ABA kg−1 fresh weight, respectively.
Abstract: Quantitative analyses of abscisic acid (ABA) in different parts of maize root tips (Zea mays L. cv. Kelvedon 33) were performed by mass fragmentography using the hexadeuterated analog of ABA as internal standard. It was found that the cap and the apex contained 36.1 μg and 66.5 μg ABA kg−1 fresh weight, respectively. The possibility that the growth regulator formed in the cap and inhibiting the elongation of the extending zone of the root is ABA is discussed.

Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: It is concluded that Anabaena has a hydrogenase whose natural function is to recycle the H2 lost by the action of nitrogenase.
Abstract: Nitrogen-fixingAnabaena cylindrica cells are found to evolve hydrogen in high quantities in the presence of CO plus C2H2. Studies with the inhibitors dichlorophenyldimethylurea (DCMU), disalicylidenepropanediamine (DSPD), dibromothymoquinone (DBMIB), undecylbenzimidazole (UDB) and chloro-carbonyl-cyanide-phenylhydrazone (CCCP) and also withAnabaena grown on nitrate- and ammonia-nitrogen show that the H2-formation is due to the ATP-dependent H3O+-reduction catalysed by nitrogenase. In control experiments CO plus C2H2 inhibited the activities of a cell-free hydrogenase fromClostridium pasteurianum. It is concluded that Anabaena has a hydrogenase whose natural function is to recycle the H2 lost by the action of nitrogenase.

Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: The extent of cooperation between the microsomal enzymes was proved to be influenced by treatment of the cotyledons with light and the extent of Cooperation in vitro was found to vary depending on the concentration of L-phenylalanine, which is known to enhance greatly the soluble phenylalanin ammonia-lyase activity in cell cultures.
Abstract: 1. Cooperation between phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) and cinnamic acid hydroxylases was investigated using microsomal fractions from cotyledons of cucumber (Cucumis sativus L.). The interpretations were based on experiments which demonstrate a limited exchange between the pool of cinnamic acid formed by the membrane-bound phenylalanine ammonia-lyase and the cinnamic acid pool external to the enzyme-membrane system. 2. The extent of cooperation between the microsomal enzymes was proved to be influenced by treatment of the cotyledons with light. On exposure to UV-light, which is known to enhance greatly the soluble phenylalanine ammonia-lyase activity in cell cultures, differential effects on the levels of microsomal and soluble phenylalanine ammonia-lyase, and of cinnamic acid hydroxylases, were observed. The time course of the enzyme activities and their cooperation in vitro after treatment of the cotyledons with light were studied. 3. The extent of cooperation in vitro was found to vary depending on the concentration of L-phenylalanine. 4. Homogenates obtained from etiolated cotyledons of Cucumis sativus in the absence of Mg(2+) were fractionated by sucrose density gradient centrifugation and examined for phenylalanine ammonia-lyase, cinnamic acid o-hydroxylase, cinnamic acid o-hydroxylase, and several marker enzymes. Ammonia-lyase activity was highest in fractions with 25% sucrose, in which primarily smooth endoplasmic reticulum is localized. Hydroxylase activities co-occur with phenylalanine ammonia-lyase in these fractions (density=1.100 g/cm(3)), and also in fractions at higher densities (d=1.12-1.13 and 1.15 g/cm(3)).

Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: It is concluded from the data that the major differences between the chloroplasts of the upper and lower leaf side reflect ionic and thylakoidmembrane conformational factors, rather than structural differences.
Abstract: In a variety of plants, the induction kinetics of chlorophyll fluorescence vary substantially depending on whether measured on the upper or lower side of the same leaf. The responses are comparable to those of plants grown under sun and shade conditions. Leaf morphology appears not to be the primary cause of the differences since inversion of the leaves can lead to reversed fluorescence responses. Fluorescence induction was analyzed in control and inverted leaves, and in one case, in chloroplasts from sun and shade leaves. It is concluded from the data that the major differences between the chloroplasts of the upper and lower leaf side reflect ionic and thylakoidmembrane conformational factors, rather than structural differences. Mg2+ flux probably plays a significant role in the adjustment of the thylakoid membrane to high or low light conditions.

Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: A specific radioimmunoassay for indole-3-acetic acid (IAA) in the 0.2 ng to 12 ng range is developed which, in principle, can be extended to other indole auxins as well.
Abstract: We have developed a specific radioimmunoassay [RIA] for indole-3-acetic acid (IAA) in the 0.2 ng to 12 ng range which, in principle, can be extended to other indole auxins as well. Methods are presented for obtaining suitable antibody, for the RIA procedure, and for measuring IAA in methanolic extracts of plant tissues. Antibody specific for IAA was obtained from rabbits immunized with IAA bound to bovine serum albumin by formaldehyde treatment. In assays with this antibody, 2,4-dichlorophenoxyacetic acid and indoles structurally related to IAA reacted from 300- to 3000-fold less than did IAA itself. However, α-and β-naphthaleneacetic acid reacted significantly and hence interfered with the assay. Extracts of tobacco (Nicotiana tabacum L.) tissue were immunoassayed after partial purification by buffer-ether partition. Crown-gall tumor tissue, which is auxin-autotrophic, and pith tissue depleted of auxin by the diffusion method contained, respectively, 26.7 ng and <0.5 ng extractable IAA per gram fresh weight.

Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: During the greening process, the activities of nitrate and nitrite reductase increased markedly, but glutamine synthetase, glutamate synthase and glutamate dehydrogenase changed little, so as to not affect the activity of these enzymes in mesophyll and bundle sheath cells of maize leaves.
Abstract: The activities of nitrate reductase (EC1.6.6.1), nitrite reductase (EC 1.6.6.4), glutamine synthetase (EC6.3.1.2), glutamate synthase (EC1.4.7.1) and NAD(P)H-dependent glutamate dehydrogenase (EC 1.4.1.3) were investigated in mesophyll and bundle sheath cells of maize leaves (Zea mays L.). Whereas nitrate and nitrite reductase appear to be restricted to the mesophyll and GDH to the bundle sheath, glutamine synthetase and glutamate synthase are active in both tissues. During the greening process, the activities of nitrate and nitrite reductase increased markedly, but glutamine synthetase, glutamate synthase and glutamate dehydrogenase changed little.

Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: Experiments on short-term photosynthesis in H14CO3- (2–5 s) using various species of different algal classes resulted in predominant 14C-labelling of phosphorylated compounds, consistent with data from enzyme analyses and with emphasis on the pathway of photosynthetic carbon assimilation in marine algae.
Abstract: Experiments on short-term photosynthesis in H14CO3 - (2–5 s) using various species of different algal classes resulted in predominant 14C-labelling (>90% of total 14C-incorporation) of phosphorylated compounds The percentage of malate and aspartate usually accounts for distinctly less than 10% of the total 14C-labelling These findings are consistent with data from enzymatic analyses, since 97–100% of the carboxylation capacity is due to ribulose-15-biphosphate carboxylase (EC 41139) in Rhodophyceae and Chlorophyceae Phaeophyceae are generally characterized by considerable activity of phosphoenolpyruvate carboxykinase (EC 41132): at least 10% of carboxylation is confined to this enzyme Similar ratios are obtained when rates of photosynthesis and of light-independent CO2-fixation are compared Activity of phosphoenolpyruvate carboxylase (EC 41131) could not be detected in the species investigated The results are discussed with emphasis on the pathway of photosynthetic carbon assimilation in marine algae

Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: It was concluded that stem length is a net response to two modes of phytochrome action: an inductive effect of Pfr inhibits a late stage in internode expansion, and a phy tochrome reaction which operates only in light (and may involve pigment cycling) promotes an early stage of internode development.
Abstract: Stems of the caulescent long-day plant, Fuchsia hybrida cv Lord Byron, showed 2 types of response to light. In one, internode length was increased by far-red irradiation given at the end of an 8 h photoperiod: the response was no greater with prolonged exposure and was less when the start of far-red was delayed. The effect of far-red was reversible by a subsequent exposure to red light. Internode length was inversely proportional to the Pfr/P ratio established before entry to darkness and there was no evidence for loss of Pfr during a 16 h dark period. The inhibitory effect of Pfr acted at a relatively late stage of internode growth. With the development of successive internodes a second response appeared in which stems lengthened following prolonged daily exposures to red or far-red light, or mixtures of the two, or to brief breaks with red or white light. In these later internodes, a short exposure to far-red near the middle of the night was not reversible by red because red alone promoted elongation at this time. Internode length increased with increase in the daily duration of light and, when light was given throughout an otherwise dark period of 16 h, with increase in illuminance to a saturation value of 200 lx from tungsten lamps. Elongation increased as a linear function of decrease in photostationary state of phytochrome down to Pfr/P≃0.3; however, internodes were shorter in far-red light than in 25% red/red+far-red. It was concluded that stem length is a net response to two modes of phytochrome action. An inductive effect of Pfr inhibits a late stage in internode expansion, and a phytochrome reaction which operates only in light (and may involve pigment cycling) promotes an early stage of internode development. Stem elongation is thus a function both of the daily duration of light and its red/red+far-red content. The outgrowth of axillary buds was controlled by the first type of phytochrome action only.

Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: A model is proposed for a proton co-transport of sugars from the free space driven by a linked proton efflux/potassium influx pump in a hollow petiole of Ricinus communis L.
Abstract: Loading of 14C-labelled sugars from the hollow petiole of Ricinus communis L. was stimulated by potassium and by low pH in that both the 14C-activity and the sugar concentration of phloem sap collected from a nearby incision increased. A pH drop was observed in the solution perfusing a hollow petiole. This pH drop was greater in the presence of potassium and less in the presence of sugars, while the uncoupler CCCP induced a pH rise in the perfusing solution. Sugars were detected in the perfusing solution when it was buffered at pH>9. A model is proposed for a proton co-transport of sugars from the free space driven by a linked proton efflux/potassium influx pump.

Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: The major cytokinin in these leaves was identified by Sephadex LH 20 chromatography, sensitivity to β-glucosidase and permanganate oxidation, and by combined gas chromatography-mass spectrometry as 6-(4-O-β-D- glucosyl-3-methylbutylamino) purine, (dihydrozeatin-O’β- D-Glucoside).
Abstract: Phaseolus vulgaris plants decapitated above the primary leaves accumulate high cytokinin activity. The major cytokinin in these leaves was identified by Sephadex LH 20 chromatography, sensitivity to β-glucosidase and permanganate oxidation, and by combined gas chromatography-mass spectrometry as 6-(4-O-β-D-glucosyl-3-methylbutylamino) purine, (dihydrozeatin-O-β-D-glucoside). A possible reason for the persistance of this compound in the primary leaves is discussed.

Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: It is shown that nitrogen fixation by the plants nodulated by parent or mutant strains was depressed by similar amounts in the presence of nitrate, and it is unlikely that nitrite produced from nitrate by the rhizobia, plays a significant role in the inhibition of nodulation by nitrate.
Abstract: The effect of nitrate on the symbiotic properties of nitrate-reductase-deficient mutants of a strain of cowpea rhizobia (32H1), and of a strain of Rhizobium trifolii (TA1), were examined; the host species were Macroptilium atropurpureum (DC.) Urb. and Trifolium subterraneum L. Nitrate retarded initial nodulation by the mutant strains to an extent similar to that found with the parent strains. It is therefore unlikely that nitrite produced from nitrate by the rhizobia, plays a significant role in the inhibition of nodulation by nitrate. Nitrite is an inhibitor of nitrogenase, and its possible production in the nodule tissue by the action of nitrate reductase could be responsible for the observed inhibition of nitrogen fixation when nodulated plants are exposed to nitrate. However, the results of this investigation show that nitrogen fixation by the plants nodulated by parent or mutant strains was depressed by similar amounts in the presence of nitrate. No nitrite was detected in the nodules. Nodule growth, and to a lesser extent, the nitrogenase specific activity of the nodules (μmol C2H4g(-1) nodule fr. wt. h(-1)), were both affected by the added nitrate.

Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: A study was made of the structure and function of senescent chloroplasts from a non-yellowing (NY) mutant of Festuca pratensis, suggesting that the stroma matrix was destroyed but that thylakoid membranes persisted in a loose, unstacked condition.
Abstract: A study was made of the structure and function of senescent chloroplasts from a non-yellowing (NY) mutant of Festuca pratensis. Electron microscopy suggested that the stroma matrix was destroyed but that thylakoid membranes persisted in a loose, unstacked condition. By contrast, chloroplasts from the normal (Y) genotype lost both stroma and recognizable thylakoid systems. Fraction 1, the major protein of the stroma, disappeared from Y and NY at similar rates during senescence. The activities of photosystems I and II from NY also declined at a similar rate to Y photosystems. Polypeptides of chloroplast membranes were separated by SDS gel electrophoresis into at least 30 components. There was considerable heterogeneity in rates of breakdown of the different protein species of the membranes. Of the five major polypeptide components, two had kinetics of breakdown similar to those of stroma proteins and were lost from NY and Y at about the same rate, whereas the remaining three (one of which was tentatively identified as the apoprotein of the light-harvesting chlorophyll-protein complex) were more stable in NY than in Y. These results are discussed in relation to the mechanism and function of chloroplast disintegration during leaf senescence.

Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: The results indicate that phytochrome and Ca2+ are involved in the light-induced depolarization of the membrane, consistent with the hypothesis that phYtochrome may act by triggering a Ca2-influx at the plasma membrane.
Abstract: Isolated internodes of Nitella (N. opaca, N. flexilis) and Nitellopsis spec. were punctured with single microelectrodes and their membrane potentials were recorded continuously during various light treatments. In red light the initial response was always a depolarization. This depolarization began with a lag-time of 0.4-3.5s and reached a steady state within 1–2 min of continuous illumination. Repolarization began within several seconds after turning off the light. The magnitude of the red-light-induced depolarization increased with the Ca2+-concentration of the medium. The largest depolarizations were recorded in 5 m mol l-1 Ca2+. Ca2+ could not be replaced in this function by Na+, Mg2+, La3+ or mannitol. Far-red light alone had no effect on the resting membrane potential. Far-red light applied immediately after red light accelerated the repolarization of the membrane potential. Far-red light applied simultaneously with red light reduced the amount of depolarization and increased the rate of repolarization. The results indicate that phytochrome and Ca2+ are involved in the light-induced depolarization of the membrane. They are consistent with the hypothesis that phytochrome may act by triggering a Ca2+-influx at the plasma membrane.

Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: The results give evidence that the phosphate translocator of the inner envelope membrane of chloroplasts is also involved in sulfite and sulfate transport — at least in part.
Abstract: The permeability of the inner envelope membranes of spinach (Spinacia oleracea) chloroplasts to sulfite and sulfate was investigated in vitro, using the technique of silicone oil centrifugal filtration. The results show that there is a permeability towards both ions, resulting in rates of uptake of about 1.0 (SO32-) and 0.7 (SO42-) μmol mg chlorophyll-1 h-1 respectively (external concentration 2 mmol l-1). The rates depend on the external concentration of the anions. Anion exchange experiments with 35S-preloaded chloroplasts indicate that sulfite and sulfate are exchanged for inorganic phosphate, phosphoglyceric acid, and dihydroxyacetone phosphate with rates up to 14 nmol mg chlorophyll-1 min-1. There is no exchange for glucose-6-phosphate and malate. Because of the similarities to the transport of inorganic phosphate and triose phosphates the results give evidence that the phosphate translocator of the inner envelope membrane of chloroplasts is also involved in sulfite and sulfate transport — at least in part.

Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: Intact maize ovaries were excised from unpollinated ears (pistillate inflorescences of field-grown plants and placed on defined, agar-based media in Petri dishes and the extent of subsequent kernel (caryopsis) development varied.
Abstract: Intact maize (Zea mays L.) ovaries were excised from unpollinated ears (pistillate inflorescences of field-grown plants and placed on defined, agar-based media in Petri dishes. Application of pollen to the end of silks (styles) positioned outside the Petri dish resulted in fertilization of 46% of the ovaries. The extent of subsequent kernel (caryopsis) development varied. After 40 days some kernels had only embryo development while others had embryo and variable endosperm development. About 5% of the initial ovaries developed into normal kernels; 60% of the kernels with some endosperm germinated under laboratory conditions, and 70% of the embryos excised from the embryo-only kernels germinated on culture media.

Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: Wilting-rate following pollination is faster in young plants as compared with wilting in old plants and the role of flower-wilting as a means of communication to the environment with regard to pollination of the style is discussed.
Abstract: Differences in rate of wilting in cross-, self-and unpollinated flowers of self-incompatiblePetunia hybrida L. clone W166H appeared to be significant. Wilting rate was fastest following cross-pollination and slowest in unpollinated flowers. The difference between wilting behaviour of cross- and self-pollinated flowers was not caused by rate of pollen tube growth and not by the incompatibility (recognition or rejection) reaction either. It is assumed, that, following pollination, the wilting reaction is only retarded after penetration of pollen tubes of the same genetic composition as the style (complete self-pollination). The number of viable pollen grains necessary to initiate a maximal wilting-rate of flowers following cross- and self-pollination is about 800, which means that a fifth of the stigmatic surface must be covered with living pollen grains. It is suggested that pollen tube penetration and injury of the style have a similar influence on the initiation of wilting. Wilting-rate following pollination is faster in young plants as compared with wilting in old plants. The wilting process of unpollinated and self-pollinated flowers started in the early morning and lasted till afternoon. Cross-pollinated flowers wilted independently of the hour of the day. The role of flower-wilting as a means of communication to the environment with regard to pollination of the style is discussed.

Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: During stomatal closing guard cells can dispose of malate by release, gluconeogenesis, and consumption in the tricarboxylic-acid cycle, which indicates that gluc oneogenesis can occur in epidermal tissue, involving the decarboxylation of malates.
Abstract: Epidermal strips with closed stomata were exposed to malic acid labelled with (14)C either uniformly or in 4-C only. During incubation with [U-(14)C]malate, radioactivity appeared in products of the tricarboxylic-acid cycle and in transamination products within 10 min, in sugars after 2 h. Hardly any radioactivity was found in sugars if [4-(14)C]malate had been offered. This difference in the degree of labelling of sugars indicates that gluconeogenesis can occur in epidermal tissue, involving the decarboxylation of malate. Epidermis incubated with labelled malate was hydrolyzed after extraction with aqueous ethanol. The hydrolysate contained glucose as the only radioactive product, indicating that starch had been formed from malate. Microautoradiograms were black above stomatal complexes, showing that the latter were sites of starch formation. In order to follow the fate of malate during stomatal closure, malate was labelled in guard cells by exposing epidermes with open stomata to (14)CO2 and then initiating stomatal closure. Of the radioactive fixation products of CO2 only malate was released into the water on which the epidermal samples floated; the epidermal strips retained some of the malate and all of its metabolites. In the case of rapid stomatal closure initiated by abscisic acid and completed within 5 min, 63% of the radioactivity was in the malate released, 22% in the malate retained, the remainder in aspartate, glutamate, and citrate. We conclude that during stomatal closing guard cells can dispose of malate by release, gluconeogenesis, and consumption in the tricarboxylic-acid cycle.

Journal ArticleDOI
01 Jan 1977-Planta
TL;DR: It is stated that guard cells continuously take up CO2 if present, and are thus able to recognize the presence of CO2 in their environment at all times.
Abstract: Isolated epidermes of Tulipa gesneriana L and Commelian communis L were exposed to 14CO2 in the light and in darkness, when stomata were either closed or open The labelling patterns did not differ: the main products of CO2 fixation were malate and aspartate Small amounts of radioactivity appeared also in acids of the tricarboxylic-acid cycle and their transamination products Since the capacity of epidermis to assimilate CO2 is known to reside in the guard cells, we can state that guard cells continuously take up CO2 if present, and are thus able to recognize the presence of CO2 in their environment at all times Epidermal samples exposed to 14CO2 in the light contained only small amounts of radioactive 3-phosphoglyceric acid (3-PGA) and sugar phosphates, or none at all Epidermal samples from Commelina communis did not contain labelled 3-PGA if all adhering mesophyll cells had been removed before exposure to 14CO2 Homogenates of clean epidermal strips of Commelina communis were able to convert exogenous ribulose diphosphate to 3-PGA at a low rate, but could not catalyze the conversion of exogenous ribulose-5-phosphate to ribulose diphosphate Guard cells of Commelina communis, and probably also those of Tulipa gesneriana, appear not to possess the reductive pentosephosphate pathway, despite the presence of chloroplasts In such species, the guard cells will have to rely on import in order to maintain their carbon balance Earlier findings of photosynthetic reduction of CO2 by epidermal tissues were probably obtained with samples that were contaminated with mesophyll cells