bluuebunny/crossref_metadata_2025 huggingface dataset:
Inter‐organ Control of Greening in Etiolated Cucumber Cotyledons
Authors: DEI MITSURU
Published: April 2006

Inter‐organ control of greening in etiolated cucumber (Cucumis sativus L. cv. Aonagajibae) cotyledons was investigated. Four‐ or six‐day‐old excised or intact etiolated cucumber cotyledons were illuminated under aerobic conditions. Excised cotyledons without hypocotyl hooks produced chlorophyll without a prolonged lag phase and the rate of chlorophyll formation was not depressed if they were illuminated immediately after excision. If the excised cotyledons were incubated in the dark before illumination, chlorophyll accumulation at the end of 6 h of continuous illumination was remarkably lowered as the dark period lengthened, especially in 6‐day‐old cotyledons. The rapid loss of chlorophyll‐forming capacity of excised cotyledons during dark preincubation suggests a stimulatory effect of hypocotyls on the greening in cotyledons. The treatment of excised cotyledons with bleeding sap in the dark for 18 h resulted in the promotion of chlorophyll formation during subsequent continuous illumination. Partial fractionation of bleeding sap with organic solvents and paper chromatography indicates that the active substances showed the same behavior as cytokinins. These facts add weight to the hypothesis that cytokinins from roots flow into cotyledons and stimulate greening.
Changes in Malate Content and in Enzymes Involved in Dark CO2 Fixation during Growth of Acer pseudoplatanus Cells in Suspension Culture
Authors: VANDERHOVEN C. , ZRŸUD J.‐P.
Published: April 2006

It has been reported in some cases that an increase in pCO2 stimulates growth in diluted cell suspension cultures. Experiments have been designed to study the pattern of dark CO2 fixation in sycamore cells grown in liquid suspension and to correlate this pattern with the culture growth phases. Comparisons were made between enzymatic activities, CO2 incorporation, malic acid content during lag, logarithmic and stationary phases of growth. Malic enzyme (NADP‐dependent) was at its maximum activity during early logarithmic growth phase, when biosynthetic capacities were at the highest. Phosphoenolpyruvate‐carboxylase activity was strongly correlated with the ability of cells to fix CO2. Malic acid content decreased soon after transfer of the cells to a new medium and increased at the onset of stationary phase. Under optimal conditions, the CO2 incorporation pattern did not change during growth, with an almost identical incorporation in the basic (amino acids) and acidic (organic acids) fractions. These observations have been discussed in relation to a possible effect of increased pCO2 in the cell environment.
Senescence‐Related Changes in the Lipid Transition Temperature of Microsomal Membranes from Algae
Authors: THOMPSON J. E. , MAYFIELD C. I. , INNISS W. E. , BUTLER D. E. , KRUUV J.
Published: April 2006

The phase behaviour of smooth microsomal membranes from senescing cultures ofScenedesmus quadricaudahas been examined by wide‐angle x‐ray diffraction. The algae were grown in Bristol's medium at 22°C under continuous illumination. The transition temperature, taken to be the highest temperature at which crystalline (gel) phase lipid can be detected, increased with culture age from a low of 0°C for young cultures to a high of about 70°C for 140‐day‐old cultures. This indicates that for young cultures the membrane lipid is entirely liquid‐crystalline (fluid) at physiological temperatures, but as the cultures age portions of the lipid become crystalline. The increase in transition temperature showed a close temporal correlation with loss of chlorophyll and loss of protein per g dry weight, and can thus be construed as an index of senescence. The unsaturated to saturated fatty acid ratio of the membrane lipid, while fluctuating with culture age, did not show any consistent trend that could be related to the change in transition temperature. Thus the formation of gel phase lipid does not appear to be due to a change in fatty acid saturation.
Application of the Entropy‐Enthalpy Relationship in Water Transport through Plant Roots
Authors: KUIPER F. , KUIPER P. J. C.
Published: April 2006

Water transport through plant roots is determined by a single layer of cells, so that water passes through a plasmamembrane‐cytoplasm‐plasmamembrane system. The water transport shows an exponential relationship with temperature in two phases with an abrupt transition. The Arrhenius activation parameters log A and E are calculated for the two phases of water transport below and above the transition temperature. Between log A and E two linear and parallel relationships are observed, one for each phase of water transport. The difference of log A between these two relationships is a measure for a change in entropy in cell water structure at the transition temperature. The change in entropy was small (13.4 J · mol−1· K−1) in comparison to the difference in activation energy E for water transport above and below the transition temperature. The role of the plasmamembrane and cytoplasm in determining the cell water structure is discussed.
The Antiranspirant Effect of Acetylsalcylic Acid on Phaseolus vulgaris
Authors: LARQUÉ‐SAAVEDRA A.
Published: April 2006

A series of experiments were carried out in order to elucidate whether acetylsalicylic acid (ASA) fed via petioles to beans could affect transpiration rate. In comparison with the water control it was found that a 10−3M ASA reduces transpiration as much as 43%, a reduction equivalent to 5 × 10−5M abscisic acid (ABA). Preliminary kinetics on the ABA, ASA and the water control on transpiration rate are presented and the results discussed.
The Uptake of Cytokinins by Protoplasts and Root Sections of Brassica campestris
Authors: DEKHUIJZEN H. M. , BOSSEN M. E. , VONK C. R.
Published: April 2006

The effect of cytokinins was studied on the incorporation of 14C‐labelled precursors into the nucleic acid fraction of protoplasts isolated from callus or roots of Brassica campestris. Protoplasts from callus and roots took up 14C‐uridine from the incubation medium and incorporated this precursor into the ribonucleic acid fraction during the experimental period of 16 h. Low concentrations of kinetin (10−8‐5 × 10−6M) did not stimulate the incorporation, and kinetin inhibited this process at higher concentrations (5 × 10−5M). This result led to an investigation on the uptake of cytokinins by protoplasts of roots. In contrast to a rapid uptake of radio‐actively labelled adenine and uridine. protoplasts from roots took up only small amounts of labelled kinetin. zeatin, zeatin riboside and zeatin nucleotides from the incubation medium.

Root sections took up far more adenine and kinetin than protoplasts from roots. The ratio between the amount of kinetin taken up and applied was much higher for the sections than for protoplasts, indicating that intact root cells took up kinetin far more rapidly than protoplasts. It is suggested that the plasmalemma and cell wall play an essential role in the uptake of cytokinins or that the differences in the uptake rates are related to differences between the rates of metabolism of cytokinins in root sections and in protoplasts.
Effect of Storage in Darkness and in Light on the Content of Membrane Lipids of Potato Tubers
Authors: LILJENBERG CONNY , SANDELIUS ANNA STINA , SELSTAM EVA
Published: April 2006

The lipid composition of tubers from the potato varieties Bintje and Desirée was investigated during storage. Storage in total dark ness after harvest gave only small changes in the amounts of triglycerides. monogalactosyl diglycerides and digalactosyl digtycerides. Storage in light resulted in changes in these lipids and in their fatty acid composition. The absolute amount and the relative content of linolenic acid in the galactolipids increased. A simultaneous and equivalent decrease in the percentage of linoleic acid took place without any marked percentage changes in the other major fatty acids. The light induced changes of the lipids, which occur simultaneously with greening of the tuber, are discussed and related to the development of thylakoid membrane systems in the plastids.
Accelerated Nitrate Uptake in Wheat Seedlings: Effects of Ammonium and Nitrite Pretreatments and of 6‐Methylpurine and Puromycin
Authors: TOMPKINS GARY A. , JACKSON WILLIAM A. , VOLK RICHARD J.
Published: April 2006

The experiments reported herein had two objectives. One was to determine if the slow rate of nitrate uptake which occurs upon initial exposure of nitrogen‐depleted wheat (Triticum vulgare cv. Knox) plants to nitrate was the result of insufficient reduced nitrogen. The second was to determine the impact of restrictions in ribonucleic acid or protein synthesis on both nitrate uptake and nitrate reduction.

Pretreatments of 14‐day‐old seedlings for a few hours in ammonium or nitrite did not result in an enhancement of the initial slow rate of nitrate uptake. Growth for two additional weeks in ammonium also failed to eliminate the induction period. The evidence indicates that the presence of nitrate, rather than a product of its reduction, was required to initiate development of the accelerated rate of nitrate uptake.

Puromycin (400 μg ml−1) and 6‐methylpurine (0.5 mM) prevented development of the accelerated phase of nitrate uptake. With both compounds, the relative restriction of nitrate uptake was greater than that of nitrate reduction as revealed by incorporation of 15N from labeled nitrate into reduced forms. The proportion of reduction which occurred in the root system under the imposed treatments could not be delineated precisely, preventing an unequivocal determination of the extent to which the two processes are coupled in the root system. The data nevertheless indicate nitrate reduction was closely associated with nitrate uptake.

Accumulation of nitrate in the shoots was markedly restricted in presence of 6 methylpurine. This effect most likely was a result of a severe restriction in the translocation of nitrate into the xylem, rather than an increase in the reduction rate in the shoots.
Effects of Ca2+ and Temperature on Potassium Uptake along Roots of Wheat, Rice and Cucumber
Authors: ZSOLDOS FERENC , KARVALY BÉLA
Published: April 2006

The differences in K+ uptake of different segments of excised roots of two thermophilic plants (rice, Oryza sativa L. cv. Dunghan Shali and cucumber, Cucumis sativus L. cv. Csemege Fürtös) and a non‐thermophilic plant (wheat, Triticum aestivum L. cv. Aurora) were investigated in the presence and absence of Ca2+, at 0 and 25°C, using radiotracer K+(86Rb+) technique. The K+ uptake exhibited different temperature‐ and Ca2+‐dependent distributions along the root axis for the different species studied. In the case of rice and cucumber an extraordinarily large K+ uptake occurred in the apical root portion at 0°C if Ca2+ was omitted. The presence of Ca2+ diminished this anomaly. For wheat normal K+ uptake patterns were observed under similar conditions. At 25°C Ca2+‐stimulated K+ uptake may appear in each root segment, depending upon species and composition of the uptake solution. The results indicate that there may be considerable differences in the compositions of the cell walls and membranes of root cells of thermophilic and non‐thermophilic plants, and in their ion‐exchange properties, especially in the apical region.
Interaction du photopériodisme et des effets de la zéatine, du saccharose et de ľeau dans la floraison du Chenopodium polyspermum
Authors: SOTTA BRUNO
Published: April 2006

Interaction of photoperiodism and zeatin, sucrose and water effects on the flowering of Chenopodium polyspermum

Root removal in Chenopodium polyspermum, a quatitative short‐day plant, enhances flowering under non‐inductive conditions. Presence of roots may be mimicked by zeatin applications on buds. Induction of flowering by short days may be counteracted by applications of zeatin, and appearance of flowers depends on the balance between number of inductive short days and zeatin quantity applied. Sucrose added in the culture medium or applied on buds acts as zeatin. Applications of water on buds may also delay flowering. These results show the plurifactorial regulation of the floral development of this plant. The relations between the non‐specificity of the induction and the specificity of the morphogenetic response are discussed.
Uptake of Nitrate by Mutants of Arabidopsis thaliana, Disturbed in Uptake or Reduction of Nitrate
Authors: DODDEMA HENK , HOFSTRA J. J. , FEENSTRA W. J.
Published: April 2006

A study of nitrate and chlorate uptake by Arabidopsis thaliana was made with a wildtype and two mutant types, both mutants having been selected by resistance to high chlorate concentrations. All plants were grown on a nutrient solution with nitrate and/or ammonium as the nitrogen source. Uptake was determined from depletion in the ambient solution. Nitrate and chlorate were able to induce their own uptake mechanisms. Plants grown on ammonium nitrate showed a higher subsequent uptake rate of nitrate and chlorate than plants grown on ammonium alone.

Mutant B25, which has no nitrate reductase activity, showed higher rates of nitrate and chlorate uptake than the wildtype, when both types were grown on ammonium nitrate. Therefore, the uptake of nitrate is not dependent on the presence of nitrate reductase. Nitrate has a stimulating effect on nitrate and chlorate uptake, whereas some product of nitrate and ammonium assimilation inhibits uptake of both ions by negative feedback. Mutant B 1, which was supposed to have a low chlorate uptake rate, also has disturbed uptake characteristics for nitrate.
Effect of Benzyladenine on DNA, RNA, Protein, and Chlorophyll Contents in Intact Bean Leaves: Differential Responses to Benzyladenine According to Leaf Age
Authors: NAITO KUNIHIKO , TSUJI HIDEO , HATAKEYAMA ISAO
Published: April 2006

Benzyladenine (BA) was applied to intact bean (Phaseolus vulgaris) leaves at different stages of their growth. Changes in the amounts of cellular constituents resulting from the different treatments were followed and compared. RNA, protein, and chlorophyll contents, dry weight, fresh weight, and leaf area per single leaf continued increasing when leaves were treated with BA from an early stage, whereas in untreated leaves all these values levelled off or declined with advancing age. Besides these changes, BA treatment induced an increase in the DNA content. Changes in RNA content was more remarkable in response to application or deprival of BA treatment than the corresponding ones in protein and chlorophyll contents. The pattern of response to BA varied greatly according to the age at which the leaf received the treatment. As leaves aged, they lost the ability to increase their area and fresh weight in response to BA. However, continuous treatment with BA from an early stage kept the leaves young and able to respond.
Rapid Effects of Abscisic Acid on Ion Uptake in Sunflower Roots
Authors: ERLANDSSON GUNVOR , PETTERSSON SUNE , SVENSSON SVEN‐BÖRJE
Published: April 2006

Short‐term effects of ABA, ABA + kinetin and kinetin on ion (86Rb‐potassium and phosphate) and water uptake in sunflower plants (Helianthus annuus var. californicus) were examined with a continuous‐recording technique. Ion uptake in the roots and transport to the shoots were also investigated by conventional tracer uptake experiments and by sap bleeding experiments with excised roots.

After addition of 5 × 10−6‐4 × 10−5M ABA to the root medium there was an immediate decrease (30–70%) in the rate of ion uptake which lasted 30–70 min. The rate of water uptake was not significantly affected as measured with this method. Ion transport to the shoots and to the bleeding sap of excised roots was decreased by ABA. ABA‐induced inhibition of ion uptake was abolished by the presence of kinetin, and uptake was slightly stimulated by 2 × 10−5M kinetin alone. We suggest that concentration gradients of ABA or rapid changes in the ABA‐kinetin balance in the roots affect ion uptake and transport.
The Importance of Roots in Regulating the Senescence of Soybean Primary Leaves
Authors: HSIA CHUNG PEI , KAO CHING HUEI
Published: April 2006

The role of roots in regulating primary leaf senescence of 14‐day‐old soybean seedlings was investigated. Compared with intact seedlings, the senescence of primary leaves is accelerated by removal of the root system but delayed if apical bud and the first trifoliate leaf are removed. No difference in senescence was found between intact seedlings and seedlings without roots, apical bud, and first trifoliate leaf. Lateral roots seem to play a predominant role in regulating primary leaf senescence. However, neither root nodules nor primary root play any function in senescence.

Results indicate that benzyladenine (BA) at optimal concentration (2 mg/1) completely replaces the roots to prevent the senescence of primary leaves, whereas gibberellic acid (GA) and abscisic acid (ABA) accelerate. The effect of indole‐3‐acetic acid (IAA) to replace roots in preventing senescence depends on the season the young seedlings are grown. Additional, though indirect, information of acropetal transport of ABA is provided.

In conclusion, it seems that cytokinins in lateral roots play a predominant role in leaf senescence and the normal supply of root cytokinins is important in leaf metabolism.
Daily Patterns under the Life Cycle of a Maize Crop
Authors: ANDRÉ M. , MASSIMINO D. , DAGUENET A.
Published: April 2006

Certain activities were studied daily in a self‐regulating growth chamber in four maize plants (Zea mays L. cv. INRA F7 x F2), which had been raised under completely artificial conditions. The transpiration pattern parallels that for photosynthesis, where a marked change occurs at flowering followed by a decline during cob formation. Respiration reaches a maximum at flowering and thereafter remains relatively stable. Final production figures are comparable with those obtained in field plants, but under artificial conditions the water requirement is halved. The results from this study increase our understanding of whole plant physiology and enable us to establish a closer correlation between plants raised in the laboratory and those in the field.
Varietal Differences in Rubidium Uptake Efficiency of Barley Roots
Authors: PETTERSSON SUNE
Published: April 2006

Uptake efficiency for Rb+ and SO2−4 was different in eight cultivars of barley, Hordeum vulgare L. Rb+ uptake was studied in more detail in low‐and high‐K+ plants of cv. Salve and cv. Hellas at different Rb+ concentrations in the experimental solutions.

The K+/Rb+ selectivity of the roots was strongly dependent on the experimental conditions, but changed similarly in the two cultivars. After six days the fresh weight of the shoots was c. 15% higher in ‘Salve’ than in ‘Hellas’. Root development and the average concentration of K+ in the plants were the same. Influx of Rb+ in the roots was up to 75% faster in ‘Salve’ than in ‘Hellas’. Experiments with short‐term Rb+ influx (10 min) + wash (5 min) indicated that the differences in Rb+ uptake efficiency were due to variations in Rb+ influx at the plasmalemma of the root cells. Efflux of 86Rb+ from 86Rb+‐labelled roots was higher in ‘Salve’ than in ‘Hellas’ during the initial 30 min in inactive solution, indicating that passive permeation (leakage) of Rb+ and probably also of K+ at the plasmalemma of root cells of cv. Salve is faster than that of cv. Hellas. The parallel differences between influxes and effluxes explain the comparatively small difference in net uptake between the two varieties.
Organogenesis and Plantlet Formation from Organ‐ and Seedling‐Derived Calli of Rice (Oryza sativa)
Authors: HENKE R. R. , MANSUR M. A. , CONSTANTIN M. J.
Published: April 2006

Callus was induced in different somatic organs of Oryza sativa L. Specific minimum 2,4‐dichlorophenoxyacetic acid (2,4‐D) concentrations in the medium were necessary for the induction of callus from different organs while high levels of 2,4‐D (6–10 mg/l) induced callus formation in each organ tested. The optimum 2,4‐D concentration for callus induction and growth for root‐derived calli was 2 mg/l and for leaf‐derived 6 mg/l. Root and shoot organogenesis were induced in both root‐ and leaf‐derived calli by sub‐culturing to a medium lacking 2,4‐D. Root organogenesis occurred at a higher frequency than shoot organogenesis. Shoot organogenesis rarely occurred in calli without differentiated roots. Increased age of callus cultures almost completely inhibited shoot development. The addition of the cytokinin 6‐γ,γ‐dimethylallyl‐amino purine partially restored the potential for shoot organogenesis. Whole plants were easily recovered from the calli and grown to maturity with some plants exhibiting phenotypic abnormalities.
Caractérisation de la glutamate déshydrogénase chez un halophyte obligatoire: le Suaeda maritima var. macrocarpa
Authors: BOUCAUD J. , BILLARD J. P.
Published: April 2006

Characterization of the glutamate dehydrogenase from an obligate halophyte: Suaeda maritima var. macrocarpa

The glutamate dehydrogenase (GDH), E.C. 1.4.1.3, of the obligate halophyte Suaeda maritima (L.) Dum. var. macrocarpa Moq. has been studied. NaCl increase in the culturing solution (0 to 23 g NaCl/litre) lowers the specific activity but does not affect the kinetic characteristics of the enzyme collected after purification on G‐25 Sephadex gel. In optimal conditions, GDH is activated by the addition of 25 mM NaCl in the incubation medium and inhibited with concentrations over 100 mM. The inhibitory activity of the salt induces both a modification of the affinity of the enzyme for substrate (competitive inhibition for ketoglutarate) and a modification of the catalytic potency (non‐competitive inhibition with NADH and ammonium ion). It is suggested that NaCl has a depressing influence on GDH synthesis. There is a fundamental difference between its short time action (in vitro) versus its continuous effect in the culturing solution.
The Photostability of Different Chlorophyll Forms in Dark Grown Leaves of Wheat
Authors: AXELSSON LENNART
Published: April 2006

The effect of denaturing treatments on the stability against high intensity irradiation (red light, 700 W m−2) was investigated in vivo for various chlorophyll forms in wheat. Three pigment forms were investigated: the 650‐form (protochlorophyllide) present in dark grown leaves; the 684‐form (chlorophyllide) formed within 5 s after photoreduction of the 650‐form; and the 673‐form (chlorophyll), into which the 684‐form has been transformed 25 min after photoreduction of the 650‐form. (The pigment forms are denoted by their absorption maxima in the red region before denaturation.)

Two denaturing treatments were used: heat treatment (water of 55°C for 2 min) and freezing and thawing (freezing in liquid nitrogen followed by thawing in water of 25°C). Heat treatment as well as freezing and thawing caused a shift in the absorption peak of the two nonesterified pigment forms. The peak of of the chlorophyllide 684‐form shifted to 673 nm and that of the protochlorophyllide 650‐form to 636 nm. The absorption maximum of the chlorophyll 673‐form was not affected by the above treatments.

Heat treatment as well as freezing and thawing had profound effects on the structural organization of the plastid pigments, as shown by a decrease in the photostability. For the 684‐form, heat treatment reduced the photostability by a factor of about 14 (half‐life in strong light changed from 170 s to 12 s). Freezing and thawing also reduced the photostability, although the effect was less pronounced (c. 3–4 times decrease in half‐life). Upon transformation of the chlorophyllide 684‐form into the chlorophyll 673‐form (the Shibata‐shift) the pigments became less sensitive to light, and were no longer “aggregated” by heat treatment. The “aggregating” effect of freezing and thawing was still present after the Shibata shift. The results thus verify a clear difference in structural organization of the 684‐form and the 673‐form, since the two pigment forms were differently affected by heat treatment. The 650‐form behaved similarly to the 684‐form, although it appeared to be slightly less aggregated by heat treatment. — The decrease in photostability, caused by heat treatment of the 684‐form, changed the kinetics for the photodecomposition from a first towards a second order reaction.
Effect of Temperature, Photoperiod and Several Growth Substances on the Cold Hardiness of Chrysanthemum morifolium Rhizomes
Authors: FAYYAZ MOHAMMAD M. , McCOWN BRENT H. , BECK G. E.
Published: April 2006

The effect of 14 combinations of photoperiod, soil and air temperature, and growth substance applications on the cold hardiness of Chrysanthemum morifolium‘Astrid’ rhizomes was evaluated. Both triphenyl tetrazolium chloride and regrowth tests were used to determine the viability of the cold‐stressed rhizome tissues. The rhizomes exhibited different degrees of cold hardiness under these environmental conditions. A combination of short photoperiod and low air and soil temperatures induced maximum cold hardiness. Low soil temperature accompanied by long photoperiods and warm aerial temperatures did not induce rhizome hardening, while some hardening in cool soils was evident under either short photoperiods or low aerial temperatures. Warm soils reduced rhizome hardening under the normally inductive short photoperiod‐cool aerial conditions. Since the induction of rhizome hardening was dependent on the induction of the aerial organs, the involvement of translocatable hardiness promoters is indicated. Foliar applications of low levels of gibberllic acid (GA3) or abscisic acid only slightly influenced rhizome hardiness.
Changes in Gene Expression from Diploid to Autotetraploid Status of Lycopersicon esculentum
Authors: ALBUZIO A. , SPETTOLI P. , CACCO G.
Published: April 2006

The activity levels of enzymes involved in photosynthesis, respiration and nitrogen metabolism were evaluated in a diploid and in the derived autotetraploid Lycopersicon esculentum. The autotetraploid exhibited, compared to the diploid, higher protein and reduced dry matter content; reduced rate of protein synthesis; enhanced activity of malate dehydrogenase, acid invertase, glutamate dehydrogenase, and nitrate reductase; decreased peroxidase activity; unchanged polymorphism of the above‐listed enzymes as revealed by electrofocusing, namely reduced CO2 fixation caused by lower ribulose‐1‐5‐diphosphate carboxylase and even lower phosphoenolpyruvate carboxylase activities in accordance with a smaller contribution of the C4 carboxylating cycle; lower activities of the two “key” enzymes of photorespiration ribulose‐1‐5‐diphosphate oxygenase and glycolate oxydase. The results suggest that the gene expression of the double gene dosage is enhanced in some cases and depressed in others, resulting in more unfavourable balance of the metabolic settlement.
Lipid Composition of the Roots of Plantago Species: Response to Alteration of the Level of Mineral Nutrition and Ecological Significance
Authors: KUIPER DAAN , KUIPER PIETER J. C.
Published: April 2006

In a study of the adaptation of Plantago species to their specific environment the lipid composition of the roots of several species: Plantago major L. ssp. major, Plantago major L. ssp. pleiosperma Pilger, Plantago lanceolata L., Plantago media L., Plantago maritima L., Plantago coronopus L. was studied as well as the effect of the nutritional regime. Upon exposure to low‐salt conditions Plantago major L. ssp. major L. and Plantago maritima L. maintained the level of free sterols in the roots, despite a depressed level of total sterols, and the root lipids were more saturated than under high‐salt conditions. Both factors may reduce nutrient leakage from the roots to the low‐salt condition. Upon exposure to low‐salt conditions, all Plantago species showed a decreased level of galactolipid (exception: Plantago coronopus) and a decreased level of sitosterol (exception: Plantago maritima); the latter being compensated by an elevated level of cholesterol + tocopherol in Plantago major ssp. pleiosperma, Plantago lanceolata and Plantago media. Plantago coronopus was the only species which under low‐salt conditions showed an increased level of free sterols, among which cholesterol was the most important; thus indicating a high degree of regulation of membrane permeability under alternating nutritional conditions. The level of sulfolipid was kept constant in all Plantago species, with the highest level observed in Plantago maritima. The role which various lipids may play in maintenance of membrane integrity under alternating nutritional conditions is discussed.
Concanavalin A Improves the Polyethylene Glycol Method for Fusing Plant Protoplasts
Authors: GLIMELIUS K. , WALLIN A. , ERIKSSON T.
Published: April 2006

An improved method for polyethylene glycol‐induced fusion of protoplasts isolated from auxotrophic mutants of Nicotiana tabacum L. cv. Gatersleben was developed. By using Petri dishes coated with concanavalin A the attachment of protoplasts induced by polyethylene glycol was strengthened. As a consequence of the stronger attachment more fusion products remained after the dilution and washing procedure. It was also found that a shorter treatment combined with a more rapid dilution of the polyethylene glycol solution was superior to previous fusion methods used for plant protoplasts.
On the Question of Stem Polarity with Respect to Auxin Transport
Authors: ZAJACZKOWSKI STEFAN , WODZICKI TOMASZ J.
Published: April 2006

The effect of section length and number of longitudinally contiguous cells upon polar transport of natural auxin from the pine stem cambial region was investigated with oat coleoptile curvature tests. Basipetal and acropetal efflux of auxin to agar declines with increasing length of the sections, but the polarity quotient varies little and is similar to the polarity of individual cells. An integrated system of cells produces a wave along the stem in the efflux of auxin from consecutive segments. The possible role of such waves in development of polarity gradients and of the morphogenic maps of orientation of cells in the stem cambial region is discussed.
Half‐life of tRNA Containing N6(Δ2‐isopentenyl)adenosine in Lactobacillus acidophilus ATCC 4963
Authors: HELBACH MAX , LEINEWEBER MICHAEL , KLÄMBT DIETER
Published: April 2006

tRNA containing N6‐(Δ2‐isopentenyl)adenosine may be precursors for the plant hormone cytokinin. To discriminate between tRNA containing and not containing cytokinin nucleotides, double labelling experiments were made by the use of [214C]‐mevalonic acid and [3H‐methyl]‐methionine. At a generation cycle of 2 h for Lactobacillus acidophilus ATCC 4963, the half‐lives of tRNA labelled with [3H‐methyl]‐methionine and [2‐14C]‐mevalonic acid are similar, namely 3 h. Isopentenylation of tRNA could be measured to be maximally 1:10.
Nodule Nitrate Reductase as a Source of Reduced Nitrogen in Soybean, Glycine max
Authors: RANDALL DOUGLAS D. , RUSSELL WALTER J. , JOHNSON DAVID R.
Published: April 2006

Hydroponically grown soybeans were fed 15N‐enriched NaNO3 at nine reproductive stages of development. The stem exudates contained excess 15N in the fully reduced nitrogen fraction. The soybean nodules had high nitrate reductase activity, whereas the roots had no detectable nitrate reductase activity. Based on these results, we concluded that the nodule nitrate reductase system has the potential of contributing significantly to the nitrogen economy of the plant.
Chlorophyllase in Phaeodactylum tricornutum Photosynthetic Membranes. Extractability, Small‐Scale Purification and Molecular Weight Determination by SDS‐Gel‐Electrophoresis
Authors: TERPSTRA WILLEMKE
Published: April 2006

The extractability of chlorophyllase is used as an indicator for the way in which the enzyme is incorporated in Phaeodactylum tricornutum photosynthetic membranes. Whereas with various aqueous solutions no appreciable amount of chlorophyllase is washed from the membranes even after chloroform‐pretreatment. the enzyme can be extracted with aqueous solutions after practically all the lipids have been removed by means of 80% acetone.

The proteins in an aqueous extract of the membranes thus treated were separated by electrophoresis on a 4% polyacrylamide gel; extraction of the active protein from several gels yielded a purified chlorophyllase solution.

As with the intramembraneous enzyme, activity of purified, solubilized chlorophyllase depends upon the combined presence of MgCl2 and dithiothreitol. The enzyme is inactivated upon heating at 56°C for 5 min.

After SDS‐gel‐electrophoresis of an enriched extract, enzyme activity could be localized in the gels. The molecular weight of SDS‐treated chlorophyllase, or of its principal subunit, was estimated to be about 38 kilodaltons.

The results are discussed in terms of the identity of prochlorophyllase.
Modalités du transport et du métabolisme de l'AIA 14C ou AIA 3H en relation avec la morphogenèse des bourgeons axillaires chez le Scrophularia arguta
Authors: MIGINIAC E. , SOSSOUNTZOV L. , DUGUE N.
Published: April 2006

Modes of transport and metabolism of
14
C‐IAA and
3
H‐IAA in relation to morphogenesis of axillary buds in Scrophularia arguta.

The main objectives of this study were to investigate the morphogenetic role of IAA on the growth and development of axillary buds. After foliar applications of radioactive IAA for 6 h on intact plants of Scrophularia arguta Sol. the characteristics of auxin transport were studied by liquid scintillation counting, thin layer chromatography and microautoradiography. The main part of the radioactivity moved at a mean rate of 7 mm/h. Over long periods of transport, the tracers accumulated at the base of the axis and in the roots. The nodes were a little richer in 3H or 14C than the internodes. This fact seemed to be correlated with the vascular organization of this part of the stem. A very weak proportion of tracers was found in axillary buds. The radioactivity was to about 50% associated with the IAA molecule; the rest corresponded essentially to indolyl‐4‐acetyl‐l‐aspartic acid and indolyl‐3‐aldehyde. Tracers were mainly concentrated in the phloem along the whole axis and, to a lesser extent in some of the young differentiating metaxylem vessels, and in the medullary rays. No radioactivity was found in the cambial zone and in the mature xylem, nor in the parenchymas. These results support the view of an indirect role of IAA on the axillary bud growth and morphogenesis.
The Effect of Gibberellic Acid and Guanosine Monophosphates on Extension Growth, Leaf Production and Flowering of Impatiens balsamina
Authors: SHARMA REETA , KUMAR SURINDER , NANDA K. K.
Published: April 2006

Gibberellic acid (GA3) increases the height of Impatiens balsamina under both 8‐ and 24‐h photoperiods. The height also increases with all guanosine monophosphates (GMPs) under 8‐h photoperiods but only with 5′‐GMP under 24‐h photoperiods. GA3 as well as GMPs increase the number of leaves under 8‐h but not under 24‐h photoperiods. GA3 as well as GMPs induce floral buds under strictly non‐inductive photoperiods and increase the number of floral buds under 8‐h photoperiods. The floral bud initiation occurs earlier when cGMP is used in combination with 100 mg/l GA3.
Isoperoxidases in Epidermal Layers of Tobacco and Changes during Organ Formation in vitro
Authors: THORPE TREVOR A. , THANH VAN MARIE TRAN , GASPAR THOMAS
Published: April 2006

The content and pattern of soluble isoperoxidases were determined in epidermal explants taken from different internodes of tobacco plants in the vegetative and floral states. There were qualitative and quantitative differences in the isoperoxidases, with a decrease in content and fewer bands being observed acropetally, i.e., in going from the base of the stem towards the apex. Epidermal explants from floral branches were grown in in vitro culture, with various media moditications, to form de novo floral or vegetative buds, roots or callus. Changes in soluble isoperoxidases were followed electrophoretically in relation to these varying morphogenetic pathways. In each of them, the number of bands increased on both the anodic and cathodic sides with time in culture. Compared to each other these four morphogenetic programmes were different in their peroxidase zymograms, mainly through varying kinetics in the development of activity of the isoenzymes. The changes observed during root and vegetative bud formation agree with previously published data, and the changes during floral bud formation agree with those observed in vivo.
Rapid Bioassay for Auxin
Authors: MEUDT WERNER J. , BENNETT HOWARD W.
Published: April 2006

A rapid bioassay is described for the detection of growth substances. The bioassay is simple to perform under ordinary laboratory or classroom conditions and the sensitivity to auxin is comparable to other bioassays, including those using Avena first internode sections. The bioassay is performed on isolated first internode sections from partly etiolated bean plants (Phaseolus vulgaris L. cv. Bush Burpee Stringless Bush Bean). The test material is applied to one side and near the base of the section. Auxin treatments induce curvature and the distance of the lateral displacement of the apical portion of the segment is proportional to the concentration applied. Routinely, the indole 3‐acetic acid response is measured 1 to 3 h after treatment. The sections also respond to gibberellic acid (GA3), which induces an increase in overall length, but unlike auxin, GA3 does not cause curvature. The test compounds are applied via a small filter paper disk that provides a convenient means for studying interactions of two or more compounds by co‐applications. Auxin‐induced growth can be monitored with a sensitive motion detector. Data are presented which confirm the usefulness of the assay.
Inhibition of Photosystem II in the Green Alga Ankistrodesmus falcatus by Copper
Authors: SHIOI YUZO , TAMAI HIROKO , SASA TSUTOMU
Published: April 2006

Copper strongly inhibited 2,6‐dichloroindophenol (DCIP) photoreduction in the broken cells of the green alga Ankistrodesmus falcatus (C303), and the activity lost could not be restored by adding 1,5‐diphenylearbazide (DPC). Inactivation of the DCIP Hill reaction reached 45% after incubation with 10 μM cupric sulfate for 20 min. In the same time, copper (13 μg/mg chlorophyll) was bound to the broken cells. Addition of 10 mM KCl reduced copper binding by about 53%. Fluorescence intensity at room temperature decreased upon addition of cupric sulfate and was partially restored by adding 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU), These results suggest that copper inactivates electron transport between the oxidizing side of the reaction center of photosystem II and the electron‐donating site of DPC. Further, the effect of light intensity shows that copper mostly affected the reaction rate of the dark step and had less inhibitory effect on the quantum efficiency of the primary reaction of electron transport in photosystem II.
Balance between Cyanide‐Sensitive and ‐Insensitive Respiration in Wheat Root Mitochondria, as Influenced by Salt Concentration in the Plant Growth Medium
Authors: MØLLER I. MAX
Published: April 2006

Mitochondria were isolated from 7‐day‐old wheat roots (Triticum vulgare Vill. cv. Svenno Spring Wheat) grown in either a full‐strength culture medium (100%) or in the same medium diluted 100 times (1%). Outer membrane integrity was assayed using the cytochrome c reduction assay. This indicated about 20% damage. Using an oxygen electrode the respiration of the mitochondria was measured with either malate or succinate as the substrate (both 40 mM). KCN (3 mM) and salicylhydroxamic acid (SHAM, 1 mM) were used as inhibitors. The properties of the isolated mitochondria (STATE 3 rate, ADP/O ratio, and KCN‐sensitivity) depend upon the ionic concentration of the growth medium of the roots. In the mitochondria isolated from roots grown in the 1% medium (1% mitochondria) there is a synergistic effect of KCN and SHAM. This means that electrons can be shifted from one pathway to the other when only one of the inhibitors is added. This flexibility between the electron pathways is almost nil in the mitochondria isolated from roots grown in the 100% medium (100% mitochondria). The maximal capacity of the alternative electron pathway (= rate in the presence of KCN) is higher in 1% (40 nmol O2 min−1 (mg protein)−1) than in 100% mitochondria (20 nmol O2 min−1 (mg protein)−1. In 100% mitochondria the alternative pathway seems to be operating at maximal capacity in the absence of KCN with both substrates and in both STATES 3 and 4. In 1% mitochondria the alternative pathway functions at >50% of its capacity in the absence of KCN.
Respiration of the Roots of Flood‐Tolerant and Flood‐Intolerant Senecio Species: Affinity for Oxygen and Resistance to Cyanide
Authors: LAMBERS HANS , SMAKMAN GERARD
Published: April 2006

The affinity of respiration for oxygen in the roots of six Senecio species studied was low compared with the affinity of cytochrome oxidase for oxygen. Half saturation values of approximately 22 μM oxygen were measured. Root respiration was to a large extent insensitive to cyanide in flood‐tolerant as well as in flood‐sensitive species. The evidence presented suggests that high activity of salicylhydroxamic acid (SHAM)‐sensitive oxidase in Senecio roots was the basis for the low oxygen affinity and for the high cyanide‐insensitivity of root respiration in the Senecio species. Methods are described to determine the in vivo activity of the SHAM‐sensitive oxidase. It was estimated that it contributed 70% to the total root respiration.

The presence of SHAM‐sensitive oxidase activity could explain a higher efficiency of root growth respiration under a low oxygen tension if this alternate oxidase was inhibited at a low oxygen concentration in the root medium. However, the SHAM‐sensitive oxidase was not specifically involved in either growth respiration or maintenance respiration. Its significance in regulation of the redox state of the cells is discussed.
Efficiency of Root Respiration of a Flood‐Tolerant and a Flood‐Intolerant Senecio Species as Affected by Low Oxygen Tension
Authors: LAMBERS HANS , STEINGRÖVER EVELIENE
Published: April 2006

A method was described to determine root growth respiration and root maintenance respiration rate of plants, grown in culture solutions of high and low oxygen concentrations, during linear growth. Root growth respiration of aerobically grown plants was three to four times lower in the flood‐intolerant Senecio jacobaea L. than in the flood‐tolerant species. Senecio aquaticus Hill. Root growth respiration of Senecio aquaticus Hill decreased by a factor two to three upon transplantation to a culture solution of low oxygen tension. The difference in root growth respiration between aerobically and anaerobically grown Senecio aquaticus Hill was ascribed to the presence of a highly active non‐phosphorylating oxidase.
Nitrogen Nutrition and Cytokinin Activity in Solanum tuberosum
Authors: SATTELMACHER B. , MARSCHNER H.
Published: April 2006

In water culture experiments with potato plants (Solanum tuberosum L. cv. Ostara), the influence of continuous nitrogen nutrition (constant supply of NO3−) and discontinuous nitrogen nutrition (interruption of NO3− supply, i. e., nitrogen withdrawal for 6 days) on the endogeneous cytokinin level in the roots, shoots and exudate of decapitated plants was studied. Harvests took place at intervals of 3 days. The chlorophyll formation test (cucumber cotyledons) and soya callus test were used to determine the cytokinin activity.

With continuous nitrogen, the cytokinin activity decreased slightly with time in both roots and shoots but rose in the exudate. With discontinuous nitrogen, the nitrogen withdrawal led to a temporary, pronounced increase in cytokinin activity in the roots; at the same time, the cytokinin activity in the exudate decreased sharply. It is assumed that this temporary increase in cytokinin activity in the roots is a reflection of increased meristem activity in the roots. In the shoots, the cytokinin activity decreased during the nitrogen withdrawal period. These nitrogen‐induced changes in cytokinin activity in the roots and shoots of potato should presumably have an important influence on the physiological age of the shoot, with all its consequences in the further development of the plant. Zeatin riboside was likely the main cytokinin component involved.
Characteristics of Zinc Uptake by Barley Roots
Authors: VELTRUP WERNER
Published: April 2006

The linear uptake of zinc by excised barley roots (Hordeum distichon L.) in the time range from 20–120 min is not continued over periods of 20–28 h. In concentration dependent uptake experiments with intact barley roots three phases in the range up to 1.38 mM zinc could be detected independent of the tested uptake period. The kinetic constants increased with higher phases and the transition points were lowered with increasing time. The presence of copper did not inhibit the uptake of zinc competitively. On the contrary a slight stimulation in the uptake rates was observed indicating an interaction with the transition site. It is concluded that zinc and copper are taken up by separate mechanisms.
Influence of Ammonium on the Growth and Development of Suspension Cultures of Pauľs Scarlet Rose
Authors: MOHANTY BIBEKANANDA , FLETCHER JOHN S.
Published: April 2006

In this work as in previous studies from this laboratory it was demonstrated that the presence of a trace amount of NH4+ (72.8 μmol) stimulated the growth of Pauľs Scarlet Rose on a defined medium containing NO3− (1920 μmol) as the only other source of nitrogen. A kinetic analysis of several growth parameters showed that the rate of increase of dry weight, fresh weight, cell number, and cell volume were greater during early stages of growth (days 0–8) when NH4+ was provided. During later stages (days 8–14) this relationship between the two cultures did not hold. The cells provided NH4+ continued to increase in fresh weight and cell volume, but the cells which were not provided NH4+ had a greater rate of dry weight and cell number increase. These differences led to 14‐day‐old cultures which were approximately equal in dry weight and cell number but differed by a factor of 2 in fresh weight. The presence of NH4+ speeded up the development and growth of the cells.
Rhythmic Production of CO2 by Tropical Orchid Flowers
Authors: HEW C. S. , THIO Y. C. , WONG S. Y. , CHIN T. Y.
Published: April 2006

Circadian rhythm of CO2 production was observed in some tropical orchid flowers. The tight bud showed relatively low respiration and no rhythmic changes. As soon as the flower opened, respiration increased and rhythmicity became apparent. The period for the rhythm was about 24 hours. Dark treatment and detachment dampened the amplitude of the rhythm without affecting the rhythmicity. In depollinated and pollinated flowers, the rhythmicity was less pronounced. Pollination and depollination appeared to stimulate respiration at the trough of the cycle. However, there was no significant difference in respiration per day between the untreated and treated flower. Both pollination and depollination hasten the senescence of orchid flowers.
Influence de la benzylaminopurine sur ľabsorption du phosphate par des disques de tubercules de pomme de terre
Authors: PENOT ANNICK HOURMANT et MICHEL
Published: April 2006

The Influence of Benzylaminopurine on the Absorption of Phosphate by Potato Tubers

Aging of disks of potato tuber in an aerated liquid medium induces a large increase of the rate of phosphate absorption. Experiments were performed with benzylaminopurine added to the aging solution at various times after slicing, and the rate of absorption was determined 24 h after slicing. The opposite experiment was also performed, with benzylaminopurine added at the beginning and withdrawn after different times. The addition of benzylaminopurine to the aging medium partially prevents the development of the phosphate uptake. The uptake mechanism is a metabolic phenomenon as shown by its sensitivity to temperature. The degree of inhibition depends on the benzylaminopurine concentration as well as on the time of aging. The results suggest that the cytokinin acts on a process which occurs all along the aging and underline the importance of the presence of benzylaminopurine during the first hours of aging.