bluuebunny/crossref_metadata_2025 huggingface dataset:
The role of the leaves in the regulation of internode elongation in Phaseolus vulgaris
Authors: KIGEL JAIME
Published: April 2006

Time‐course patterns of leaf and internode elongation were studied in bean plants. Each leaf started its main elongation period when the leaf below reached half of its final length. The onset of leaf unfolding was nearly synchronous with the initiation of the elongation of the subjacent internode. Excision of young leaves increased the rate of stem elongation as a result of an earlier unfolding of the next upper leaves and the concomitant advancement in the elongation of their subjacent internodes. IAA or NAA (1% in lanolin) suppressed the enhancement effects of leaf excision on leaf and internode elongation. The excision of a young leaf increased the final length of internodes located below it, and at the same time decreased the final length of the internodes located above the excised leaf. The reduction was greater the younger the internode. Differences in internode elongation after leaf excision were related to changes during internode ontogenesis in their relative response to the availability of assimilates on the one hand, and on the other hand to hormonal factors transported acropetally from the young leaves to the growing internodes.
The occurrence of free and bound cytokinins in clubroots and Plasmodiophora brassicae infected turnip tissue cultures
Authors: DEKHUIJZEN H. M.
Published: April 2006

This paper deals with the quantitative determination of free and bound cytokinins in clubroot tissue and in Plasmodiophora brassicae Woron, infected Brassica campestris L. callus tissue. The fractions were separated in a butanol soluble fraction containing the free cytokinins such as zeatin and zeatin riboside and a water soluble fraction containing the bound cytokinins.

The butanol fraction was extensively purified and analysed by high pressure liquid chromatography (HPLC). The butanol fraction contained cytokinins which cochromatographed with zeatin and zeatin riboside and not with dihydrozeatin. Zeatin and zeatin riboside were quantitatively determined by HPLC. Recovery of the cytokinins varied between 30–50%. Clubs contained 50–160 ng zeatin and 210–300 ng zeatin riboside per g dry weight. Callus tissue contained 133 ng zeatin and 169 ng zeatin riboside per g dry weight.

Clubs, callus as well as healthy tissue contain large amounts of bound cytokinins. Upon treatment of the water soluble fraction first with alkaline phosphatase and then with β‐glucosidase biologically active fractions were found which coeluted with zeatin and zeatin riboside on Sephadex LH20 in 20% ethanol. Evidence is presented for a novel cytokinin in the water soluble fraction which yields free zeatin and glucose‐6‐phosphate after treatment with β‐glucosidase.
Effect of some heterocyclic herbicides on CO2 assimilation by spinach chloroplasts
Authors: DÍAZ MARÍA A. , CHUECA ANA , GORGÉ JULIO L.
Published: April 2006

We have studied the inhibitory effect of heterocyclic herbicides simazine, paraquat, pyrazon and amitrole on photosynthetic CO2 fixation and on the level of intermediates of the CO2 assimilation cycle in isolated spinach (Spinacia oleracea) chloroplasts, as well as their in vitro activities on ribulose‐1,5‐bisphosphate carboxylase and fructose‐1,6‐bisphosphatase. The half inhibitory concentrations (I50) of CO2 assimilation were about 1 μM for simazine and paraquat, and 10 μM for pyrazon. Amitrole, with an I50 100 μM, gave only a weak inhibition. In the presence of simazine or pyrazon the triose‐phosphates/phosphoglycerate ratio diminished because of a decrease of the triose‐phosphates percentage from 47% to 19%, which means an inhibition of the phosphoglycerate reduction step by a low NADPH synthesis. However, there was not a parallel increase of phosphoglycerate, because of collateral pathways leading to phospho‐enolpyruvate, amino acids and other non‐identified compounds. Paraquat did not give such a decreased ratio, which could be explained as an inhibition of some step of the Calvin cycle later than triose‐phosphates by the H2O2 formed in a Mehler reaction. Amitrole did not show any effect on the pattern of intermediates. Simazine and pyrazon at 10 μM concentration promote a 20–30% activation of ribulose‐1,5‐bisphosphate carboxylase activity, whereas paraquat, pyrazon and simazine showed an I50 about 100 μM for the inhibition of the photosynthetic fructose‐1,6‐bisphosphatase.
Cytokinin production by Asparagus shoot apex cultured in vitro
Authors: KODA YASUNORI , OKAZAWA YOZO
Published: April 2006

The cytokinin producing capacity of asparagus (Asparagus officinalis L.) shoot apex was examined by means of shoot apex culture in vitro, where adventitious roots were never formed. The cultured shoot apices continued to diffuse a small but constant amount of cytokinin into the medium throughout five passages of subculture. The cytokinin content in the apices at the end of the subculture was not different from that at the beginning of the subculture. These results indicate a production of cytokinin by the apices.

However, the finding is not in conflict with the hypothesis that the root tip is the major source of cytokinin supply, because the root tip of asparagus produced more cytokinin than the shoot apex and the decline of shoot growth observed during the subculture was partially restored by an application of zeatin into the medium.
The influence of water stress preconditioning on dark respiration
Authors: BROWN K. W. , THOMAS J. C.
Published: April 2006

The respiration rate of individual leaves of cotton (Gossypium hirsutum L. cv. Stoneville 213), beans (Phaseolus vulgaris L. cv. Bush Blue Lake), and sorghum (Sorghum vulgare Pers.) which had been fully expanded prior to a series of severe water stresses was compared with those of unstressed leaves of similar age. Measurements were made over a range of leaf temperatures. The respiration rate per unit area of the leaves of all rewatered plants were significantly lower than those of the plants which had not undergone water stress. During the stress periods, the leaves of all species suffered dry matter loss. The respiration rates per unit dry matter for cotton and beans were the same for the plants which had undergone stress as they were for the plants which had not undergone stress, thus for these two C3 plants the decrease in dark respiration due to water stress may be explained entirely by the loss of dry matter. Respiration rates of the water stressed sorghum leaves expressed on a per unit weight basis were significantly lower than those which had not undergone water stress preconditioning. The lower respiration rates of the stressed leaves when expressed on both a per unit area basis and a per unit weight basis for the C4 species indicate that water stress adaptation of C4 plants may include alterations in the respiratory mechanism or on the amount of residual respirable substrate. The light compensation points of all the species were not altered by the water stress preconditioning. This indicates that the mechanisms controlling the net photosynthetic exchange per unit leaf area underwent adaptations as a result of repeated water stress which decreased its efficiency.
Light induced transpiration in a chlorophyll deficient mutant of Hordeum vulgare
Authors: SKAAR H. , JOHNSSON A.
Published: April 2006

A chlorophyll deficient mutant of Hordeum vulgare L. was investigated with respect to its transpiration response to light pulses. Broad band blue light. 380–500 nm, caused a significant transpiration response, while broad band red light did not. The transpiration response to changes in the ambient CO2‐concentration was the same in the chlorophyll deficient mutant as in green plants. The absence of a transpiration response to red light in the mutant was therefore not the result of a defective CO2‐response. It is concluded that the specific blue light response is not mediated via photosynthetic CO2‐fixation. The nature of the blue light response is discussed.
Nutrient utilization and requirement under photoheterotrophic growth of Marchantia polymorpha: Improvement of the culture medium
Authors: KATOH KENJI , ISHIKAWA MOMOYO , MIYAKE KEIKO , OHTA YOSHIMOTO , HIROSE YOSHIO , IWAMURA TATSUICHI
Published: April 2006

Previously we reported on a suspension culture of chlorophyllous cells of a liverwort, Marchantia polymorpha L., under photoheterotrophic conditions. The chemically defined medium was a modified Murashige and Skoog's medium, which contained, besides glucose, inorganic salts, a growth regulator (2,4‐D), and twenty‐four organic compounds as micro constituents. Because of this complexity, we undertook a simplification of the medium. Having examined the utilization of the major nutrients and the requirements for the micro constituents, we have succeeded in improving the medium. The new medium contains phosphate at 3.13 mM and only eight out of the twenty‐four original micro organic constituents. In this new medium, the cells grow under a well‐balanced nutritional condition, with richer chlorophyll and at a higher rate during the exponential phase than in the original medium.
Influence de quelques acides aminés libres de l'ovule sur la croissance et le développement cellulaire in vitro du tube pollinique chez Juniperus communis (Cupressaceae)
Authors: DUHOUX EMILE , THI ANH THU PHAM
Published: April 2006

Influence of some free amino acids of the ovule on growth and cellular development of the pollen tube of Juniperus communis L. in vitro.

The extraction and analysis of free amino acids show that a partial complementary relationship exists between the amino acids of the pollen and those of the ovule of Juniperus communis. The main free amino acids of the pollen are threonine, proline, arginine and γ‐aminobutyric acid; those of the ovule are threonine, serine, alanine, citrulline and glycine. The addition of the main amino acids of the ovule in the pollen culture media increased the growth and the cell development of pollen tubes cultured in vitro. This indicates the nature of the correlations which exist between the male and female gametophyte of Juniperus communis.
Effects of light on terpene hydrocarbon synthesis in Pinus pinaster
Authors: GLEIZES MICHEL , PAULY G. , BERNARD‐DAGAN C. , JACQUES R.
Published: April 2006

The biosynthesis of terpene hydrocarbons has been investigated in maritime pine (Pinus pinaster Ait.) seedling primary leaves under light and darkness and with different precursors. Impossible in darkness, the synthesis of monoterpenes (mainly α‐ and β‐pinene) is strongly activated by light. Only 14C‐carbonate and 14C‐acetate can be incorporated into monoterpenes. Activation by light is comparatively much more effective for seedling leaves previously cultivated under short days than in leaves from seedlings given long days. The spectral bands which are efficient for the synthesis of monoterpenes are located around 480 and 685 nm with 14C‐carbonate and 480 and 630 nm with l‐14C‐acetate. Furthermore, this light activation does not occur if leaf pieces instead of whole leaves are used for the incorporation experiments. When 2‐14C‐mevalonic acid and 1‐14C‐isopentenyl pyrosphosphate are applied as precursors, no radioactivity is recorded in monoterpene hydrocarbons even after light exposures. In contrast, sesquiterpene hydrocarbons (caryophyllene and humulene) are easily synthesized under light or darkness in intact or fragmented leaves from the different precursors of photosynthetic or exogenous origin. From these results the compartmentalization in the synthesis of C10 and C15 hydrocarbons appears clear. There is a metabolic cooperation between the photosynthetic tissues and the specific site of elaboration of C10 hydrocarbons, which site is located in the parts where the epithelial cells of resin ducts are functional. The synthesis of sesquiterpene hydrocarbons takes place in the whole leaf without activation by light.
Thigmomorphogenesis: Evidence for a translocatable thigmomorphogenetic factor induced by mechanical perturbation of beans (Phaseolus vulgaris)
Authors: ERNER Y. , BIRO R. , JAFFE M. J.
Published: April 2006

Mechanical perturbation of bean (Phaseolus vulgaris L.) internodes results in reduced elongation and increased diameter of the internodes (thigmomorphogenesis). Perturbation of a single lower internode results in thigmorphogenesis in that internode and all of those internodes above it, the degree of which depends on the age (size) of the internodes and the frequency of perturbation. Application of ethephon to the internodes mimics mechanical perturbation. Early removal of the shoot tip or the cotyledons does not effect thigmomorphogenesis, indicating that those organs do not exert control over the response. Mechanical perturbation of one plant of a pair grafted together at the first internodes results in thigmomorphogenesis in both plants. This indicates the transport of some factor from the mechanically perturbed donor to the non‐treated receiver. Evidence is presented to support the contention that ethylene is not this transportable factor.
Effect of some disaccharides, hexoses and pentoses on nitrate reductase, glutamine synthetase and glutamate dehydrogenase in excised pea roots
Authors: SAHULKA JOSEF , LISÁ LUDMILA
Published: April 2006

The effects of exogenous sucrose, lactose, d‐glucose, d(‐)fructose, d‐galactose, d‐mannose, l‐sorbose, l‐arabinose and d‐xylose on nitrate reductase (NR), glutamine synthetase (GS) and glutamate dehydrogenase (GDH) levels, on anaerobic nitrite production and on respiratory O2 consumption were studied in excised roots of pea (Pisum sativum L. cv. Raman). Sucrose, glucose and fructose increase NR and GS levels and decrease GDH level (when compared with roots cultures without any sugar) at all concentrations used, but the extent of this effect varies. NR induction is enhanced by all sugars within the concentration range studied. Precultivation of roots with mannose and galactose results in an increase in anaerobic nitrite production in a medium consisting of phosphate buffer and KNO3. GS reaches its maximum at lower sugar concentrations, this fact being especially clear‐cut with galactose. The decrease in GS level observed in roots cultured without sucrose is enhanced by higher sorbose concentrations. The increase in GDH level occurring in roots cultured without sucrose is depressed by low galactose and mannose concentrations but enhanced by high galactose, mannose, xylose and a wide range of sorbose concentrations. Lactose exerts only slight influence on the enzymes. The effects of sugars are in no case consistent with their effect on respiratory O2 consumption which is most pronounced with NR.

The above results show that the effects of sugars on NR, GS and GDH are not mediated by one universal mechanism.
Sequential extraction of chlorophyll from chlorophyll‐protein complexes in lyophilized pea thylakoids with solvents of different polarity
Authors: ÖQUIST GUNNAR , SAMUELSSON GÖRAN
Published: April 2006

Lyophilized chloroplasts of Pisum sativum (pea) have been extracted with petroleum ether of different polarity (obtained by adding varying amounts of ethanol to the petroleum ether). Extracted thylakoids have then been solubilized by sodium dodecyl sulphate (SDS) and chlorophyll‐protein complexes have been isolated by polyacrylamide gel electrophoresis (PAGE). Absorption‐ and low temperature fluorescence emission spectro‐scopy have been used to characterize thylakoids and purified chlorophyll‐protein complexes.

Weakly polar solvents extracted mainly chlorophyll a. SDS‐PAGE scan profiles of similarly extracted thylakoids contained no photosystem II chlorophyll a reaction center antennae (CP‐an) and the amount of photosystem I chlorophyll a reaction center antennae (CP‐a1) was reduced as compared with an unextracted control. This was due partly to the extraction of chlorophyll a prior to SDS‐PAGE, and partly to the increased solubilization of chlorophyll a by SDS as a result of β‐carotene extraction. By increasing the polarity of the solvent CP‐a1 also disappeared in the scan profile, leaving only the light‐harvesting chlorophyll a/b‐protein complex (CP‐a/b) and SDS complexed chlorophyll.

From these results we conclude that the chlorophyll molecules in the reaction center antennae are relatively more hydrophobically associated than the molecules in the light‐harvesting CP‐a/b complex. The chlorophyll a of CP‐au and the far red absorbing chlorophyll a fraction of CP‐a1 appear to be the most hydrophobically associated chlorophyll molecules.
On the role of ß‐carotene in the reaction center chlorophyll a antennae of photosystem I
Authors: OQUIST By GUNNAR , SAMUELSSON GÖRAN , BISHOP NORMAN I.
Published: April 2006

Absorption and low temperature fluorescence emission spectra were measured on chloroplast thylakoids and on purified reaction center chlorophyll a‐protein complexes of photosystem I, CP‐a1. A clear association between the presence of ß‐carotene and the occurrence of far red absorbing and emitting chlorophyll a components of the reaction center antennae of photosystem I was demonstrated. For this study chloroplasts and CP‐a1 were obtained from normal and carotenoid deficient plant material of various sources. The experimental material included 1) lyophilized pea chloroplasts extracted with petroleum ether, 2) the carotenoid deficient mutant C‐6E of Scenedesmus obliquus and 3) wheat chloroplasts derived from normal and SAN‐9789 treated plants. Removal of carotenoids, most likely principally ß‐carotene, caused a loss of long wavelength absorbing chlorophylls in chloroplasts and purified CP‐a1, and the loss or diminution of the long wavelength peak seen in the low temperature fluorescence emission spectrum. This association between ß‐carotene and special chlorophyll a forms may explain both the photoprotective and antenna functions ascribed to ß‐carotene. In the absence of carotenoids in wheat and in the Scenedesmus mutant, the chlorophyll a antenna of photosystem I was extremely photosensitive. A triplet‐triplet resonance energy transfer from chlorophyll a to ß‐carotene and a singlet‐singlet energy transfer from excited ß‐carotene to chlorophyll would explain the photoprotective and antenna functions, respectively. The role of this association in determining some of the fluorescence properties of photosystem I is also discussed.
Growth of corn in saline waters
Authors: SIEGEL S. M. , SIEGEL B. Z. , MASSEY JANE , LAHNE PAMELA , CHEN JUNG
Published: April 2006

Eight cultivars of Zea mays plus the wild species Zea diploperennis were screened for seedling saline tolerance up to 3.2% NaCl. The best performances were given by the cultivars Mo 17 and commercial Hawaiian Super Sweet Hybrid. These two were then field grown on coral‐cinder beds using drip irrigation with fresh of half‐strength sea water (1.5–1.7% dissolved solids). Growth and chemical data for Mo 17 at 12 weeks show reduced growth but the same percentage dry matter. Ash, protein and total sulfur were higher in saline plants, silica and total phosphorus lower. Na, K. Mg, and Cl were elevated and Ca reduced slightly. Fe was also increased in saline plants. Both Mo 17 and Super Sweet Hybrid corn flowered and produced seed which retained essentially normal viability both in fresh and salt water.
The effect of fluoride on the growth and fatty acid composition of Sphagnum fimbriatum at two temperatures
Authors: SIMOLA LIISA KAARINA , KOSKIMIES‐SOININEN KRISTIINA
Published: April 2006

The fatly acid composition of different lipid fractions (neutral, glyco‐ and phospholipids) was studied in Sphagnum fimbriatum Wils, gametophytes grown in aseptic cultures at two temperatures (15°C and 25°C). The effect of a growth‐retarding concentration (0.1 mM) of KF was also investigated.

Fifteen‐day treatment with KF affected the fatty acid composition more strongly at the higher than at the lower temperature. The proportion of palmitic acid (16:0) increased but the proportion of linoleic (18:2) decreased in all the lipid fractions, and that of linolenic (18:3) acid decreased in the fractions containing glyco‐ and neutral lipids. This indicates that the fluoride ions inhibit lengthening of the fatty acid chain.

Compared with gametophytes grown at 25°C, material cultivated at 15°C had a much higher proportion of a highly unsaturated fatty acid, linolenic acid (18:3), in all the lipid fractions, but a lower proportion of oleic acid (18:1) in the neutral and phospholipids, and a lower proportion of linoleic (18:2) acid in all three fractions.
Physiological studies on pea tendrils
Authors: JAFFE M. J. , SHOTWELL M.
Published: April 2006

When tendrils which have been dark adapted for 3 days are mechanically stimulated, they will only coil appreciably if they are irradiated with light. A spectral response curve suggests that this is a blue light effect. Red or far red light do not modulate this response, but a high intensity flash of blue white light given before the actinic blue light blocks coiling for 30 min. The dark‐adapted tendril, which has not been previously rubbed, has the ability to store the tactile sensory information for about 60 min, but loses it if it is not irradiated within 120 min after mechanical perturbation.
On simultaneous transport of water and solute through plant cell membranes: Evidence for the absence of solvent drag effect and insensitivity of the reflection coefficient
Authors: PALTA JIWAN P. , STADELMANN EDUARD J.
Published: April 2006

The simultaneous efflux of tritiated water and 14C labelled ethanol from inner epidermal cells of the bulb scale of Allium cepa was measured with a specially designed efflux chamber. It was found that water and ethanol moved essentially independently. Rates of efflux of tritiated water and 14C ethanol were essentially the same in the presence or absence of a simultaneous influx of water.

Using the same technique the efflux of tritiated water from the epidermal cells was measured during a simultaneous flow of nonlabelled ethanol. When tritiated water and ethanol moved in opposite directions, the water permeability values became slightly reduced depending upon the concentration of ethanol. When ethanol and tritiated water moved in the same direction, however, no effect on water permeability values could be detected. These results are best explained by the molecular theory of diffusion across lipid bilayer membranes, and are consistent with the above findings of lack of interaction between water and ethanol as they are transported across the cell membrane.

In another study, the solute permeability coefficients (Ks) for non‐electrolytes such as urea and methyl urea were measured by plasmolyzing the epidermal cells and transferring them to equimolal solutions of urea and methyl urea. This method was also used to measure the reflection coefficient (σ) for these nonelectrolytes. The Ks values for methyl urea were 16 times greater than the ones for urea. The values of σ for both of these solutes, however, were very close to 1.

Using the Ks data available in the literature for the subepidermal cells of the Pisum sativum stem basis, the σ values were calculated for malonamide, glycerol, methyl urea, ethyl urea, dimethyl urea, and formamide. Again the Ks values for these nonelectrolytes varied by several orders of magnitude, whereas all σ values were found to be close to 1.

These findings point out that σ is an insensitive parameter and that Ks, the solute permeability constant, has to be used for characterizing solute transport through the membrane. The present study shows that fast (e.g. ethanol, formamide) as well as slowly permeating molecules do not interact with water as they are transported across the cell membrane. Aqueous pores for the simultaneous transport of water and solutes, therefore, are absent in the plant cell membranes investigated here.
Hormonal regulation of secondary abscission in pear pedicels in vitro
Authors: PIERIK R. L. M.
Published: April 2006

In vitro cultivated pear, Pyrus communis L. cv. Beurré Hardy, pedicels cut above their primary abscission layer can form a secondary abscission layer, especially under the influence of auxins or cytokinins in the culture medium. The maximum percentage of abscission reached by auxin application was always higher than that by cytokinin. The presence of the flower was of no consequence to the abscission. Characteristic differences in abscission were observed between pear and apple pedicels. In contrast to apple (1) secondary abscission in pear could also be induced by cytokinins, and (2) the site of abscission in pear was dependent on the auxin concentration. At lower auxin concentrations abscission was induced in the basal parts of the pedicels inserted in the medium, whereas at higher auxin concentrations the abscission layer was formed in the terminal parts of the pedicels above the culture medium. A clear effect of gibberellins, ABA and CEPA could not be detected.
Effects of various buffers, 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU) and NaN3 on menadione mediated photophosphorylation in isolated chloroplasts
Authors: DURAINI M. USAMAH , HAMLIN LEIF , TILLBERG JAN‐ERIC
Published: April 2006

The effects of DCMU and NaN3 were studied on menadione‐mediated photophosphorylation in broken spinach chloroplasts kept in low oxygen tension in Tricine or HEPES buffers at either high or reduced irradiances. – (A) At high irradiance (131 W. m−2) and absence of NaN3 the ATP formation was inhibited by DCMU regardless of the type of buffer used. – (B) At high irradiance and presence of NaN3 some concentrations of DCMU stimulated, whilst others inhibited the ATP formation in a HEPES buffer. The ATP formation was predominantly inhibited by DCMU in a Tricine buffer. – (C) At reduced irradiance (57 W. m−2) the chloroplasts in a HEPES buffer were almost insensitive towards DCMU both in the presence and absence of NaN3. – (D) Chloroplasts in a Tricine buffer were slightly stimulated in their ATP formation by DCMU at reduced irradiance either with or without the presence of NaN3 in the experimental medium. When menadione acts as a terminal electron acceptor, oxygen is consumed on its reoxidation. The results indicate that this process may occur with oxygen released by the splitting of water as the main oxidant. – The data also demonstrate the importance of caution when selecting buffering substances as well as when choosing light intensities for experiments on photophosphorylation in chloroplasts.
Redistribution of potassium, boron, iron, magnesium and calcium in apple trees determined by an indirect method
Authors: Van GOOR BEREND J. , Van LUNE PIET
Published: April 2006

The intensity of the process of redistribution of the elements potassium, boron, iron, magnesium and calcium was determined by following the rate of accumulation of these elements into the fruits of apple (Malus domestica Borkh.) trees. The determination is based on the assumption that the process of primary distribution via the xylem becomes relatively unimportant with respect to supply along the phloem during the period of fruit growth. Thus a decreasing rate of accumulation for a phloem‐immobile and xylem‐mobile element will be seen during this period of growth, while an element which is mobile in both pathways will give a linear rate of accumulation when the supply by the root does not alter too much.

In addition, the ratios of the contents in fruits and leaves were used as an indicator of the relative mobility in redistribution.

In these experiments with apple, potassium and boron showed a high mobility. Magnesium and especially calcium showed a much lower mobility in redistribution than in the primary rate of supply. Iron was intermediary. The results, especially for boron and magnesium, are in contradiction to some of the data in the literature. Further studies are needed before these contrasting results can be explained.
Inhibition of photosynthetic electron transport and formation of inactive chlorophyll in winter stressed Pinus silvestris
Authors: ÖQUIST GUNNAR , MARTIN BJÖRN
Published: April 2006

Kinetics of fluorescence at room temperature, electron transport and photooxidation of P700 and cytochrome f have been studied in chloroplasts isolated from active and winter stressed Pinus silvestris. The winter stress induced block in the electron transport chain between the two photosystems is close to the site of plastoquinone, since winter stress and DCMU caused the same type of inhibition of the reoxidation of the primary electron acceptor Q of photosystem II. No winter inhibition of the electron transport between cytochrome f and P700 was observed.

Time course studies of P700 photooxidation in chloroplasts of active and winter stressed pine have shown that the photosynthetic unit size must be about equal in the two types of chloroplasts. An apparent increase of the photosynthetic unit size was induced by winter stress, as revealed by the high chlorophyll/P700 ratio of winter stressed pine. The phenomenon is explained by the formation of photosynthetically inactive chlorophyll.

Low‐temperature fluorescence emission spectra were recorded when either chlorophyll a (433 nm) or chlorophyll b (477 nm) were preferentially excited. Winter stress induced the formation of a chlorophyll a fraction emitting at 673 nm. This chlorophyll is most likely derived from the chlorophyll a antennae of the two photosystems, and it probably contributes to the photosynthetically inactive pool of chlorophyll in winter stressed pine. The light harvesting chlorophyll a/b complex is relatively resistant to winter stress.
Structural and functional relationships in developing Pinus silvestris chloroplasts
Authors: LEWANDOWSKA MARY , ÖQUIST GUNNAR
Published: April 2006

The light dependent chloroplast development of dark grown seedlings of Pinus silvestris L. was followed by analyses of chlorophyll content, chlorophyll a/b ratios, chlorophyll/P700 ratios, chlorophyll‐protein complexes and structural changes.

Low‐temperature fluorescence emission spectra of isolated chloroplasts and separation of sodium dodecyl sulphate solubilized chlorophyll‐protein complexes by gel electrophoresis showed that the chlorophyll‐protein complexes of photosystem 1 (P700‐CPa), photosystem II (PS II‐CPa) and the light‐harvesting complex LH–CPa/b were present in dark grown seedlings. The low‐temperature fuoorescence emission maxima of isolated P700–CPa and PS II–CPa shifted towards longer wavelengths during greening in light, indicating a light induced change of the chlorophyll organisation in the two photosystems. Illumination caused LH–CPa/b to increase relative to P700–CPa, whereas the ratio between LH–CPa/b and PS II–CPa remained essentially constant. Analyses of low‐temperature fluorescence spectra with or without 0.01 M Mg2+ showed that the Mg2+ controlled distribution of excitation energy into PS I was activated upon illumination of the seedlings.

The photosynthetic unit size, as defined by the chlorophyll/P700 ratio, did not change over a 96 h illumination period, although the chlorophyll content increased about 6–fold during that time. This result and the constant electron transport rate per unit chlorophyll and time during chlorophyll accumulation provided evidence for a sequential development of the photosynthetic units when illuminating dark grown pine cotyledons. Electron micrographs showed that exposure of dark grown seedlings to light for 2 h caused the prolamellar body to disappear and grana to form. These changes occurred prior to substantial accumulation of chlorophyll or change in the ratio between LH–CPa/b and P700–CPa. However, both the water‐splitting system of photosystem II and the Mg2+ controlled redistribution of excitation energy was activated during this period.
Kinetic studies of a (Na++ K++ Mg2+)ATPase in sugar beet roots. III. A proposed model for the (Na++ K+) activation and its significance for field properties
Authors: LINDBERG SYLVIA
Published: April 2006

A microsomal (Na++ K++ Mg2+)ATPase preparation from sugar beet roots was used. The activation by simultaneous addition of Na+ and K+ at different levels was examined in terms of steady state kinetics. The observed data can be summarized in the following way:

1. The apparent affinity between the enzyme and the substrate MgATP depends on the ratio between Na+ and K+. At low Na+ concentration (below 5 mM), the apparent Km decreases with increasing concentrations of K+ (1–20 mM). At 5 mM Na+, the K+ level does not change the apparent Km, while at Na+ levels above 10 mM, the apparent Km between enzyme and substrate increases with increasing concentration of K+.

2. When the MgATP concentration is kept constant, homotropic cooperativity (concerning one type of ligand) and heterotropic cooperativity (concerning different types of ligands) exist in the activation by Na+ and K+. The Na+ binding is cooperative with different Km values and Hill coefficients (n) in the presence of low and high concentration of K+. At low Na+ level (< 5 mM). a negative cooperativity exists for Na+ (nNa < 1) which is more pronounced in the presence of high [K+]. When the concentration of Na+ is raised the negative cooperativity disappears and turns into a positive one (nNa > 1).

Only K+ binding in the presence of low [Na+] shows cooperativity with a Hill coefficient that reflects changes from negative to positive homotropic cooperativity with increasing concentrations of K+ (nK < 1 → nK > 1). In the presence of [Na+] > 10 mM, the changes in nk are insignificant.

3. A model is proposed in which one or two different K sites and one or two Na sites control the catalytic activity, with multiple interactions between Na+, K+ and MgATP.

4. In the presence of Na+ (< 10 mM), K+ is probably bound to two K sites, one of which translocates K+ through the membrane by an antiport Na+/K+ mechanism. This could be connected with an elevated K+ uptake in the presence of Na+ and could therefore explain some field properties of sugar beets.
Interaction of light and auxin in regulation of rooting in pea stem cuttings
Authors: ELIASSON LENNART
Published: April 2006

Irradiation of the base internode of stem cuttings of Pisum sativum L. with white light during the rooting period resulted in the formation of fewer roots. IBA applied to the rooting solution for 4 days counteracted this inhibition even at low concentrations. IBA stimulated rooting, also, in cuttings grown under low irradiance where availability of photosynthetic products is probably the limiting factor for rooting. IAA, however, did not reverse the inhibition of rooting, resulting from unfavourable light conditions, at concentrations lower than 10−5M, but 10−4M IAA had a similar action to IBA. Under light conditions giving good root formation IAA over a concentration range from 10−7M to 10−5M decreased the number of roots formed.

It is hypothesized that light prevents the action of endogenous auxin, or low exogenous concentrations of IAA, in the root‐forming process while the synthetic auxin IBA is fully active in irradiated tissues.
Photoactivation of the latent O2‐evolving center in chloroplasts isolated from dark‐grown spruce seedlings
Authors: OKU TATSUO , TOMITA GIITI
Published: April 2006

The latent O2‐evolving center in chloroplasts isolated from spruce [Picea abies (L.) Karst.] seedlings grown in the dark was readily activated by pre‐illuminating the chloroplast suspension with weak white light. The photoactivation depended on pH with the optimum at pH 7–8, and was strongly stimulated by ascorbic acid. The optimal stimulation was also obtained at pH 7–8. The temperature dependence of the photoactivation suggested the involvement of some dark reaction in the activation process.
Comparison of acetylene‐reduction and nitrogen‐15 techniques for the determination of nitrogen fixation by field bean (Vicia faba) nodules
Authors: HUDD G. A. , LLOYD‐JONES C. P. , HILL‐COTTINGHAM D. G.
Published: April 2006

Field bean (Vicia faba L.) cv. Maris Bead seeds were inoculated with Rhizobium Catalogue No. 1001, supplied by Rothamsted Experimental Station, and grown in sand culture supplied with a complete nutrient solution which included nitrate at either 1.5 or 6.0 mM. Nodules were detached from the roots at intervals during plant development and their rates of nitrogen fixation estimated by both acetylene reduction and 15N gas technique.

There was a constant relationship, independent of nitrate supply, between the results obtained by these two methods at all samplings. The amounts of acetylene reduced divided by a factor of 5.75 gave the amount of true nitrogen fixation; this factor is about twice the theoretical value. It is suggested that this discrepancy arose because, with acetylene, all the electrons available to the nitrogenase were used to form ethylene, whereas during normal fixation only about half the electron supply was used to fix nitrogen, the remainder having been consumed in the production of hydrogen gas.
The influence of nitrate supply on nitrogen fixation during growth of the field bean Vicia faba in sand
Authors: HILL‐COTTINGHAM D. G. , LLOYD‐JONES C. P.
Published: April 2006

Field bean (Vicia faba L.) cv. Maris Bead seeds were inoculated with Rhizobium Catalogue No. 1001, supplied by Rothamsted Experimental Station and grown in sand culture supplied with 15N‐labelled nitrate at two concentrations. Plants were sampled at intervals throughout their growth for 15N and total N analysis. The rate of nitrate uptake was almost uniform up to pod‐fill and was proportional to the nitrate concentration. Nodule weight was slightly depressed by the larger nitrate concentration at all samplings, and there was a corresponding reduction in the amount of atmospheric nitrogen fixed. However, at harvest the bean seeds from plants given most nitrate contained slightly more total N, as the enhanced nitrate uptake outweighed the reduction in fixation.
Effect of kinetin and abscisic acid on the distribution of 2‐amino (1‐14C) isobutyric acid in leaves of Zea mays
Authors: FENNER RUDOLF , DÖRFFLING KARL
Published: April 2006

2‐Amino (1‐14C) isobutyric acid (AIB) was applied to the leaf tips of thirteen‐day‐old primary leaves of Zea mays L. cv. Goldprinz. Simultaneously, the leaves were treated in the basal region with solutions of kinetin (KN), abscisic acid (ABA) and mixtures of both hormones. The distribution of the radioactive material was determined after 72 h. Treatment with KN caused an accumulation of radioactive material at the point of application (KN spot). In comparison to controls, the leaf zones between the KN spot and the leaf tip contained lower amounts of radioactive material. Treatment with ABA caused a pattern of distribution opposite to that induced by KN. The ABA point of application (ABA spot) was depleted of radioactive material, whereas the leaf area between the ABA spot and the leaf tip showed enhanched levels of radioactive AIB. The effect of ABA was reduced by application of ABA and KN in equimolar amounts. The results are discussed in relation to the possible role of ABA in hormone‐directed transport processes.
Development of photosynthetic electron transport in Pinus silvestris
Authors: LEWANDOWSKA MARY , ÖQUIST GUNNAR
Published: April 2006

Photosynthetic electron transport activity has been measured in chloroplasts isolated from dark‐grown seedlings of Pinus silvestris L. and in chloroplasts isolated from seedlings subjected to illumination for periods of up to 48 h. Activities of photosystem 2, photosystem 1 and photosystem 2 plus 1 have been measured. Chloroplasts isolated from dark‐grown seedlings showed significant electron transport activity through both photosystems and through the entire electron transport chain from water to NADP. Illumination of the seedlings for only 5 min markedly promoted photosystem 2 activity. The artificial electron donor, diphenylcarbazide. promoted activity in chloroplasts from dark‐grown seedlings and in chloroplasts from seedlings illuminated for up to 30 min. In comparison to photosystem 2 and overall electron transport from water to NADP, photosystem 1 activity increased only slightly during illumination. Measurements of electron transport and fluorescence kinetics have confirmed that photosynthetic electron transport capacity is limited on the water splitting side of photosystem 2 in dark‐grown seedlings, whereas the primary and secondary electron acceptors of photosystem 2 are fully synthesized and functioning in darkness.

Polyethylene glycol must be used as a protective agent when isolating photoactive chloroplasts from secondary needles of conifers. However, the presence of polyethylene glycol, when isolating chloroplasts from dark‐grown pine cotyledons, caused a total inhibition of the activity of photosystem 2. The failure of others to show a substantial electron transport activity in chloroplasts from dark‐grown Pinus silvestris might depend on their use of polyethylene glycol in the preparation medium and/or on their use of suboptimal reaction conditions for the electron transport measurements.
Starch and prolamin level in single and double high‐lysine barley mutants
Authors: KREIS MARTIN , DOLL HANS
Published: April 2006

At maturity the high‐lysine barley (Hordeum vulgare L.) Ris0 mutants 1508, 527 and 29 kernels contained about 20% less starch and twice as much free sugars as the parent varieties Bomi and Carlsberg II. An enhanched effect on starch reduction and free sugar accumulation was observed during kernel development when the single mutants 527 and 29 are combined with the mutant 1508. At maturity, kernels of the double mutants 527/1508 and 29/1508 contained, respectively, 68 and 43% less starch than Bomi.

The double mutant 29/1508 kernel had a slightly lower prolamin content than mutant 1508 which is the most prolamin‐deficient single mutant. In the double mutant 527/1508, however, an almost complete suppression of prolamin synthesis was observed during kernel development. The percentage of lysine in the seed proteins of the double mutants was about the same as in the most extreme single mutant 1508.

Based on the additive effect of the individual high‐lysine genes in the double mutants, it is concluded that the influences of these genes on prolamin and starch synthesis are independent.
Water stress and root formation in pea cuttings
Authors: RAJAGOPAL VELAMOOR , ANDERSEN A. SKYTT
Published: April 2006

The stock plants of pea (Pistum sativium L. cv. Alaska) grown for 11 days at 16 W m−2 38 W m−2 were subjected to different degrees of moisture stress, simulated with polyethyleneglycol (PEG, 6000) for different periods. The cuttings were made at the end of stress treatments, planted in perlite and allowed to root in a mist propagation chamber.

The number of adventitious roots formed on the cuttings from non‐stressed plants was significantly higher under low (16 W m−2) than under high (38 W m−2) irradiance. However, under the influence of short duration stress the number of roots increased significantly under high but not under low irradiance. There was significantly poor rooting after prolonged stress under both irradiances.

The leaf osmotic potential ψπ showed a greater reduction with increasing degree and duration of stress at 38 W m−2 than at 16 W m−2. The differential rooting behaviour as a result of stress levels and irradiances is discussed in the light of available literature on adventitious root formation.
Frost‐induced phospholipid changes in cold‐acclimated and non‐acclimated rape leaves
Authors: SIKORSKA ELŻBIETA , KACPERSKA‐PALACZ ALINA
Published: April 2006

Freezing and thawing of winter rape leaves was found to cause a marked decrease of total phospholipid content in general, and that of phosphatidyl choline in particular. In the highly injured leaves the decrease of phosphatidyl choline was irreversible, and it was accompanied by a marked increase of phosphatidic acid. In the slightly damaged leaves no phosphatidic acid accumulation was detected, irrespective of phosphatidyl choline decrease. Instead of phosphatidic acid, the phosphatidyl glycerol or an unidentified P‐containing lipid increased after thawing in leaves hardened to the first (Tk50=−8°C) or to the second (Tk50=−13.5°C) level, respectively. Frost hardening was found to promote phospholipid recovery after freezing and to increase phospholipid content, including that of phosphatidyl choline and phosphatidyl ethanolamine. Possible association of frost hardening with modified phospholipase‐D properties is suggested.
Effect of root formation on 14C‐glycine uptake and incorporation into protein by attached and excised cotyledons of Helianthus annuus
Authors: MOHAMMAD A. M. S. , YOUSIF A. E.
Published: April 2006

Root formation was found to extend the life‐span of excised cotyledons of Helianthus annuus L. markedly. Excised cotyledons of 12‐day‐old plants attained longer life‐span, higher root number and total root length than cotyledons excised before or after 12 days. Protein content of attached cotyledons reached a maximum level 12 days after the commencement of germination followed by a decrease. Cotyledons excised 8 days after sowing showed maximum level of protein content 44 days after excision followed by a decrease. The increase was correlated with the full development of roots. The incorporation of 14C‐glycine into protein followed a pattern similar to the protein content, both in attached and detached cotyledons.
Somatic hybrid plants of Nicotiana glauca and Nicotiana tabacum obtained by protoplast fusion
Authors: EVANS DAVID A. , WETTER LESLIE R. , GAMBORG OLUF L.
Published: April 2006

Somatic hybrid plants were produced by fusion of protoplasts from cell cultures of the Nicotiana tabacum L. sulfur mutant Su/Su and from leaf mesophyll of Nicotiana glauca Graham. After fusion the N. glauca protoplasts failed to survive under the selected culture condition. From the hybrid cells light green shoots were produced. The hybrid plants exhibited intermediate characters between parental species with respect to leaf morphology, trichome density, floral structure and flower color. The chromosome number of 25 hybrid plants was 2n = 72 and both N. glauca and N. tabacum chromosomes were identified in the hybrids. Results of isoenzyme analysis showed bands of both parents and a specific (hybrid) band for aspartate amino‐transferase. Small subunit fraction‐1‐protein of somatic hybrids also consisted of the sum of N. glauca and N. tabacum bands. Leaf spot formation associated with the Su locus of N. tabacum was observed in somatic hybrids.
Cytoplasmic male sterility in barley
Authors: AHOKAS H.
Published: April 2006

The maternal male sterile barley msm1 with or without a dominant gene, Rfmla, which restores male fertility, was studied. Determined with SDS‐PAGE, the polypeptide pattern in the anthers of unrestored msm1 plants remains juvenile in the middle of anther development, two major zones being absent or weak. At the stage when anther development stops in msm1 plants, the anther proteins appear to be hydrolyzed to short‐chain peptides. Restored plants, heterozygous for the restorer gene, Rfmla, behaved like the near‐isogenic normal barley, cv. Adorra. The total leaf protein pattern of young leaf tissue and the chloroplastidic membrane protein pattern are normal in msm1 cytoplasm when studied with this technique.

Chlorophyll b is unnecessary for restoration by Rfmla, though the restored plants have a lower chlorophyll a/b ratio than an unrestored plant in the mature stem leaf.

Mature stem leaf pieces of unrestored msm1 plants were induced to senesce with 20 mM NaCl solution. This senescence was inhibited by exogenous kinetin. Leaf pieces of restored msm1 plants or those of near‐isogenic normal barley behaved in the same way in the NaCl solution as in distilled water. Many features of the physiology of restored plants can be explained as the functions of cytokinins.

Kernels of male sterile plants have a more rapid root elongation at germination than near‐isogenic normal barley.