bluuebunny/crossref_metadata_2025 huggingface dataset:
Interpreting Leaf Water Potential Measurements with a Model of the Soil‐Plant‐Atmosphere Continuum
Authors: ELFVING DON C. , KAUFMANN MERRILL R. , HALL ANTHONY E.
Published: April 2006

A water flux model, which assumes that the dynamic functioning of the soil‐plant‐atmosphere continuum may be described by a series of steady states, was examined as a means for interpreting leaf water potential measurements in ‘Valencia’ orange trees (Citrus sinensis (L.) Osbeck). According to the model, leaf water potential should be related to transpirational flux, which in this experiment was estimated by the ratio of vapor pressure deficit of the atmosphere to leaf diffusion resistance (VPD/rleaf). Leaf water potentials decreased in a specific relationship with increasing values of VPD/rleaf provided that soil water was adequate and soil temperature was not too low, but regardless of season of the year or climatic or edaphic differences among 3 field locations. When soil water tensions exceeded 0.3 bar or when soil temperatures were lower than 15°C, deviations from the model occurred in the form of more negative leaf water potentials than predicted by VPD/rleaf. The model predicts from simple measurements made on intact plants that these differences were due to the modification of flow resistances by cool temperatures and the modification of both resistances and the potential of water at the source in the case of soil water depletion. The model may be a useful tool for interpreting plant water potential data under contrasting environmental conditions.
A Re‐examination of the Functional Significance of Aerenchyma
Authors: ARMSTRONG W.
Published: April 2006

Model roots of known length and internal porosity were assayed for ROL (radial oxygen loss) by the cylindrical Pt electrode technique and a series of curves were obtained which express the inter‐relationships between ROL and diffusion path length over a wide range of internal porosity levels.

The results indicate that internal porosity can exert considerable control on the amount of oxygen lost from roots, the more so the narrower the root.

Because radial oxygen loss is necessary for survival and competitiveness, doubt is therefore cast on the currently held view that aerenchyma formation furnishes the wetland plant with an oxygen diffusion pathway excessive to its requirements.

The results also suggest that cellular partitions and diaphragms in wetland species may impede gas transport far less than has hitherto been thought.
Long and Short Term Development of Frost Hardiness in Pinus silvestris, and Heavy Particle Adenosine Triphosphatase
Authors: BERVAES J. C. A. M. , KYLIN A.
Published: April 2006

The effect of different growth temperatures, of transfer between them, and of changes in outside temperature on frost hardiness and ATPase activity of Scotch pines (Pinus silvestris L.) were studied.

Plants which had been grown in the greenhouse and transported to outside “remembered” something of their earlier growing circumstances during a long period. They differed from the plants continuously grown outside in the level of hardiness, although changes in temperature caused similar fluctuations in the hardiness of both groups. It is evident that two mechanisms are present, the one causing a long term determination of the level of frost hardiness obtainable, the other causing a short term adaption.

The heavy particle ATPase activity as investigated below 20°C grouped itself according to the main temperature groups of the experiment. Above 30°C, the pretreatments had given rise to differences within the temperature groups. The level of the ATPase activity increased as the growing season came closer.
Effect of Fatty Acids on the Activity of Bacteriolytic Enzymes
Authors: HASKÅ GUNO , NORÉN BÖRJE , ODHAM GÖRAN
Published: April 2006

The ability of fatty acids to sensitize gram‐negative and gram‐positive bacterial cells to the action of bacteriolytic enzymes was studied. By synergetic effects between bacteriolytic enzymes and fatty acids isolated from Myxococcus such bacteria, which were otherwise resistant to the enzymes, could be lysed. Isobranched and unbranched acids with 11–15 carbon atoms were active and could sensitize Bacillus megaterium and Aerobacter aerogenes to the action of bacteriolytic enzymes from myxobacteria and to lysozyme. The sensitizing activity of tetradecanoic acid was enhanced with increasing concentration even after the solution was saturated. Neither ethylene diaminetetraacetate (0.1 and 1 mM) nor Triton X‐100 (1 0/00) could sensitize resistant bacteria to the action of bacteriolytic enzymes. However, they were active in combination and they could also increase the effect of tetradecanoic acid.
Triterpeneglycosides as Inhibitors of Fungal Growth and Metabolism
Authors: OLSEN ROLF A.
Published: April 2006

The inhibitory effect of the triterpeneglycosides aescin and avenacin on growth capability, leakage of organic and inorganic substances, and uptake of potassium ions in Ophiobolus graminis and Neurospora crassa was antagonized by the cations Ca2+ and Mg2+, the former having the greatest effect. The effect was different in the two fungi and was influenced by the buffer system.
Conversion of Digalactosyl Diglyceride (Extra Long Carbon Chain Conjugates) into Monogalactosyl Diglyceride of Pine Needle Chloroplasts upon Dehardening
Authors: BERVAES J. C. A. M. , KUIPER P. J. C. , KYLIN A.
Published: April 2006

Changes in lipid and fatty acid composition of pine needle chloroplasts were determined upon transfer of the trees from outside (‐5°C) to 32°C.

Within 7 1/2 hours after transfer, conversion of a portion of digalactosyldiglyceride into monogalactosyl diglyceride was observed. This portion consisted of a conjugate with extra long chain fatty acids (cerotic acid, 26: 0, and C26‐cyclo‐propane fatty acid). Only minor further changes in lipid and fatty acid composition were observed. Dehardening of the needles occurred within the same period. The data support the hypothesis that the degalactosidation reaction specifically depends on the fatty acid composition.

The extra long chain fatty acids may link different sub‐units of the chloroplasts and may contribute to an additional layer of H‐bonded water on the membrane surface because of the increased exposure of the galactose groups.
Evidence for the Transfer of Rhizobial Metabolites to the Polyploid Nuclei of Young Clover Nodules
Authors: BRUENING M. L. , WULLSTEIN L. H.
Published: April 2006

Autoradiography was used to provide evidence for the transfer of Rhizobium produced moieties to the host nuclei of young clover nodule cells. Cells of Rhizobium trifolii Dangeard were labeled with 3H‐adenine or 4,5‐3H‐l‐leucine and 3,4‐3H‐l.‐proline, washed free of external label, and allowed to nodulate young seedlings of white clover (Trifolium repens L. cv. White Dutch). Sections (0.5–1.0 μm) of young nodules up to four days old were autoradiographed using the dipping technique. Grain counts indicated movement of tritium from the leucine‐proline labeled rhizobia to the polyploid nuclei of two day old clover nodule cells. Acetylene reduction was not detected until approximately 24 hours after the transfer of tritium was observed. No transfer of tritium was observed with 3H‐adenine labeled rhizobia. It is hypothesized that nodulating rhizobia may induce clover nodule cells to initiate leghemoglobin synthesis by the transfer of a bacterially produced inducer.
Shoot Growth and Mineral Composition of Leaves and Fruits of Apple as Affected by Relative Air Humidity
Authors: TROMP J. , OELE J.
Published: April 2006

Shoot growth and water consumption of potted Golden Delicious trees were studied under a controlled environment with respect to two lewels of air humidity, soil moisture content, and the availability of nitrogen. In the high‐N treatment, high air humidity and high soil moisture content promoted growth; at the low‐N level, growth did not respond to the treatments. Water consumption was enhanced at low air humidity but was not afiected by the moisture centent of the soil.

In potted fruit&earing Cox's Orange Pippin trees exposed to two levels of air humidity, low humidity reduced shoot growth and, but to a much lower degree, fruit growth. It increased rhe spur‐leaf levels of N, Mg, and, for part of the experimental period, K and Ca, but affected hardly the mineral level in fruits. It is concluded that the amount of the minerals reaching the fruit is determined by the relative im‐portance of the xylem influx during the first few weeks after fruit set and the phloem influx occurring throughout. It is suggested that the xylem supply of the various minerals does not differ greatly; it is probably the main way for the influx of Ca, but for N, K, Mg, and P the phloem influx is com‐pletely dominating.
Reversal by Mercaptoethanol of Protective Effect of Solutes Against Frost Injury of Red Cabbage
Authors: KRULL EDWARD , LEVITT J.
Published: April 2006

In confirmation of Maximov's earlier results, non‐penetrating (sucrose) and penetrating (dimethylsulfoxide) substances lowered the frost killing temperature from ‐6°C in the control to ‐11° to ‐24°C, depending on the concentration. In contrast to his results, neither glycerol nor CaCl2 provided as good or as consistent protection.

The addition of 0.05 M mercaptoethanol overcame this protective effect either completely (low concentrations of protectant) or partially (high concentrations). The effect of the mercaptoethanol occurs during freezing and not during thawing. Since ethanol, without the mercapto‐(SH) group, does not counteract the protective effect, such protection must be related in some way to the sulfhydryl group — perhaps by an effect on the disulfide and sulfhydryl groups of the proteins.
The Effect of Gravity Compensation on Growth and Cell Wall‐loosening Enzymes in Helianthus annuus Hypocotyls
Authors: BARA METIN , GORDON SOLON A.
Published: April 2006

The effect of gravity compensation by the clinostat on the elongation, weight, and activity of two cell wall‐loosening enzymes (cellulase and β‐1,3‐glucanase) in Helianthus annuus hypocotyls was examined. Gravity compensation increases elongation (28.1 %) and weight (18.3 %). The activity of cellulase extracted from the apical sections is raised, but there is no significant effect on β‐1,3‐glucanase. The relationship between gravity compensation, changes in auxin level, and function of these two enzymes in respect to elongation is discussed.
Regulators of Cell Division in Plant Tissues XIV. The Cytokinin Activities and Metabolism of 6‐Acylaminopurines
Authors: LETHAM D. S. , PARKER C. W. , GORDON M. E.
Published: April 2006

Certain 6‐acylaminopurines have been shown to exhibit activity in several cytokinin bioassays. The active compunds included 6‐N,2′‐O‐dibutyryladenosine 3’:5′‐cyclic monophosphate, but adenosine 3′:5′‐cyclic monophosphate was inactive. The metabolites formed from [2,8‐3H] 6‐benzoylaminopurine by radish seedlings and excised radish cotyledons were investigated. When compared with zeatin, this amide showed considerable stability in vivo. Conversion to 6‐benzylaminopurine and its riboside was not detected but slight degradation to adenine was indicated. The principal metabolite was an unidentified compund.
Induction of Salt Sensitivity in Ophiostoma and Its Reversal by Imidazole Derivatives
Authors: FRIES NILS
Published: April 2006

Cells of the ascomycete Ophiostoma multiannulatum became sensitive to inorganic salts after a heat shock or a treatment with 2,4‐dinitrophenol. The induced sensitivity to chloride and bromide ions could be largely reversed by histidine and certain other imidazole derivatives. No other organic compounds tested except imidazoles possessed this ability. The sensitization is interpreted as a consequence of an injury to cellular membranes, in particular those of the mitochondria, and to an impaired oxidative phosphorylation.
Uptake of Uracil by Synchronous Chlorella fusca
Authors: KNUTSEN GJERT
Published: April 2006

Uptake of radioactive uracil by light‐dark synchronized Cblorella fusca Shihira and Krauss was studied. For the characterization of the uptake system autospores were used and the following results obtained. Autospores kept in the dark accumulated uracil against a concentration gradient in a process having an observed activation energy of 10 keal/mol in the 10–40°C interval. Addition of glucose to the reaction suspension did not affect the uptake, but, 100 γM dinitrophenol inhibited the process by 90%. Abrupt changes in rate were found upon changing the conditions from light to dark and vice versa, and the rates measured in light were about 2.5 times larger than those found in the dark.

Initial rates measured in the dark followed saturation kineties with half maximal rate found at 0.25 γM uracil, and with an apparent maximal rate of 1.7.10‐10 mol/10 min . 107 cells.

The effect of 14 pyrimidines on uptake was tested, and it was found that uracils which were substituted in the 5′ or 5′+ 6′ positions were strongly inhibitory. Of these, thymine and dihydrouracil were tested and shown to inhibit uracil uptake competitively.

Initial uptake rates, measured in the dark with 1.0 γM uracil, were recorded at intervals during the 24 h synchronous cycle. The uptake rate per ml culture was constant during the first 9 h, thereafter increasing to reach a peak value at 14 h. This peak was followed by a strong increase from 18 h onwards, this increase being concomitant with the sporulation process, and closely followed its time course.
Influence of Light of Different Spectral Compositions on Growth and Metabolism of Citrus Seedlings
Authors: ERNER Y. , GOREN R. , MONSELISE S. P.
Published: April 2006

Sour orange (Citrus aurantium L.) seedlings grown for six months under covers transmitting light of different spectral composition, were compared with others grown under a white cover (control) and outside in full daylight. The intensity of transmitted light was equalized under all covers and attained only 20% of full daylight.

Seedlings grown in daylight were shorter, had more internodes, smaller leaves, less chlorophyll and more ascorbic acid than the others.

Blue + far‐red covers (no transmission between 560–700 nm) enhanced seedling length, the protein and chlorophyll content and peroxidase activity of leaves. When also the wave‐range above 700 nm was cut out (blue) seedlings were the shortest, and leaves had very high protein and chlorophyll content, but much less ascorbic acid and lower peroxidase activity. Red + far‐red covers (no transmission below 500 nm) enhanced seedling length more than blue + far‐red; leaves contained as much protein as control, but had relatively high chlorophyll and peroxidase activity. Ascorbic acid was as low as in blue light.
Organic Nutrients in the Media for Propagation of Cymbidium in vitro
Authors: FONNESBECH MOGENS
Published: April 2006

Protocorms of Cymbidium (Orchidaceae) were grown on media containing different organic nutrients. Of the sugars tested sucrose was better than maltose, glucose and fructose, and sucrose had an optimum concentration of 3 to 4 %. D‐Mannose was significantly less effective than the other sugars. The amino acid mixtures casamino acids (casein hydrolysate) and tryptone increased growth while yeast extract was inhibitory and malt extract without effect. Optimal concentrations were 2 to 3 g · l‐1 casamino acids and 3 to 4 g · l‐1 tryptone. It was to some extent possible to substitute the amino acid mixtures with a single amino acid (glutamine at 300 mg · l‐1). Arginine was inhibitory and asparagine was without any effect. Vitamins proved to be unnecessary although there was a tendency towards increased growth with nicotinic acid and meso‐inositol. Purines and pyrimidines were added to the medium but with no effect. Liquid endosperm from coconuts (10 to 15%) increased growth while the liquid endosperm from Aesculus hippocastanum was inhibitory. On the basis of these results a revised medium is proposed for the in vitro propagation of Cymbidium.
Content and Aggregation of Ribosomes during Formation, Dormancy and Sprouting of Tubers of Helianthus tuberosus
Authors: BAGNI NELLO , DONINI ARNALDO , FRACASSINI DONATELLA SERAFINI
Published: April 2006

The ribosomes and their qualitative (monosomes‐polysomes) and quantitative variations over a whole vegetative period of the tuber of Helianthus tuberosus L. (cv. OB 1) were examined. Tubers in different phases of growth, dormancy and sprouting or slices of dormant tubers activated with 2 x 10‐6M indol‐3‐acetic acid were used. The ribosomes were analyzed by a linear sucrose gradient.

During flowering, polysomes of tuber disappeared almost completely and rRNA decreased in comparison with the level present at the beginning of tuber formation. After flowering, there was a new synthesis of monosomes and polysomes until the onset of dormancy; this last period was characterized by a marked increase in polysomes and a proportional increase in monosomes. The level remained almost constant till the break of dormancy. When the tubers sprouted, ribosomes, present almost exclusively as monosomes, decreased considerably; on the contrary the non‐photosynthetic sprouts contained many monosomes and polysomes.

The first phases of activation (3 h) of tuber slices were characterized by a RNA synthesis, which occurred during one hour, in the subunit region of the gradient. Successively (10 h of activation) the 32P incorporation was seen also in the polysome region and increased with time. Some possible interpretations of these last results are discussed.
Titration of Photophosphorylation in Spinach Chloroplasts with 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU)
Authors: SUNDBERG I. , KYLIN A.
Published: April 2006

The kinetics of the inhibition of photophosphorylation in chloroplasts from spinach (Spinacia oleracea) was investigated with 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU) in small concentration intervals, starting at 10‐7M. Plots of the reciprocal of photophosphorylation against concentration of DCMU gave essentially the same straight line with 2 mM nicotinamide adenine dinucleotide phosphate (NADP) together with saturating amounts of ferredoxin or with 4 mM K3Fe(CN)6 as the final acceptors for electrons. Practically complete inhibition was obtained at 3 x 10‐6M DCMU. With 0.1 mM flavin mononucleotide (FMN) and ferredoxin, the inhibition between 10‐7M and 10‐6M DCMU was a little slower than in the other two cases. At 10‐6M DCMU a break occurred to a new straight line in the plots, indicating that another reaction was inhibited. Total photophosphorylation without DCMU was about 77 μmol ATP per mg chlorophyll and hour. At the breaking point 20% remained, and inhibition was not complete even at 8 x 10‐6M DCMU. The inhibitor constant for the high‐DCMU reaction was in the order of 2 x 10‐5M; for the low‐DCMU reaction some complication made the “constant” appear negative. With phenazine methosulfate (PMS) added, DCMU was without effect on photophosphorylation. – As earlier shown by us, titration curves for intact cells of the microalga Scenedesmus show the break at 10‐6M DCMU; and above 6 x 10‐6M photophosphorylation in the algae is not further decreased by DCMU. The data are compared and their possible significance is discussed.
The Effects of Some Chelating Agents and Their Copper Complexes on Photosynthesis in Scenedesmus quadricauda
Authors: FÄNGSTRÖM INGEGERD
Published: April 2006

The effects on apparent photosynthesis in the green alga Scenedesmus quadricauda of four chelating substances, 8‐hydroxyquinoline (= oxine), β‐isopropyltropolone (=β‐thujaplicin), sodium dimethyldithiocarbamate and 3‐(β‐hydroxyethyl)‐C‐pentamethylene‐3‐aza‐dithiocarbamate have been investigated. The first three compounds mentioned had all an inhibitory effect on photosynthesis, measured as oxygen production with a manometric, a volumetric or a polarographic method. In combination with certain concentrations of CuSO4 bimodal dose response curves were observed, similar to those obtained on the growth of different microorganisms. Calculations of the amounts of different complexes that appeared in the nutrient solutions during the experiments are compared with the recorded degrees of inhibition. The results strongly indicate that the 1: 1‐complexes between Cu2+ and the chelating substances are the most toxic agents at low concentrations of these compounds.
Mechanisms of Sodium and Rubidium Uptake by Excised Barley Roots
Authors: NEUMANN‐GANMORE RUTH , WAISEL Y.
Published: April 2006

Accumulation of sodium and rubidium by excised barley roots was investigated. The concentration isotherm yielded one absorption shoulder. Nevertheless, it is suggested that two mechanisms take part in the uptake of sodium and rubidium: One non‐metabolic mechanism with an apparent participation at low external salt concentrations (< 1 mM) and at high concentrations (> 20 mM). Such a mechanism is almost unaffected by low temperature conditions and by metabolic inhibitors. Rubidium possesses a high affinity toward this non‐metabolic system. The second mechanism is sensitive to metabolic inhibitors and to low temperature conditions. It dominates at intermediate external concentrations (1–20 mM). Sodium possesses high affinity towards this mechanism. The two mechanisms operate in a parallel manner beyond a diffusion barrier (= plasmamembrane) surrounding the cells. It is assumed that both the metabolic and the non‐metabolic mechanisms operate in the entire concentration spectrum, but their relative contribution to the total uptake varies at different ranges.
Effects of Inhibitors of Protein and Nucleic Acid Synthesis on the Development of Ion Uptake Mechanisms in Beetroot Slices (Beta vulgaris)
Authors: VAN STEVENINCK R. F. M. , VAN STEVENINCK M. E.
Published: April 2006

Mechanisms for the uptake of K+, Na+ and Cl‐ develop sequentially in thin slices of beetroot tissue washed under aerobic conditions. Actinomycin D inhibited or prevented the development of K+, Na+ and Cl‐ uptake mechanisms when added to freshly cut slices, but had no effect on net ion uptake when added after the development of the ion uptake mechanisms. The use of puromycin as a specific inhibitor of protein synthesis was unsatisfactory as it caused leakage of pigments and excessive loss of ions from the disks.

Cycloheximide prevented the development of ion uptake mechanisms when added at the start of the experiment, but when added after the development of ion uptake mechanisms its inhibitory effect did not become apparent until after a certain time interval which varied from 3 hours for Cl‐ to 25 hours for K+ uptake in the same experiment. p‐Fluorophenylalanine caused an appreciable shortening of the time required for the development of Na+ and K+ uptake capabilities, while it completely prevented the development of a Cl‐ uptake mechanism. p‐Fluorophenylalanine‐induced early uptake of Na+ and K+, however, was followed by periods of net leakage of these ions.

It is suggested that the development of ion uptake mechanisms depends on the production of m‐RNA, which appears to be relatively stable after its synthesis. The synthesis and decay characteristics of specific proteins required for the ion uptake mechanisms appear to differ for each ion species.
Regeneration in Streptocarpus Leaf Discs and its Regulation by Temperature and Growth Substances
Authors: APPELGREN MAIGULL , HEIDE OLA M.
Published: April 2006

The formation of adventitious buds and roots in leaf discs of Streptocarpus x bybridus‘Constant Nymph’ were both stimulated by relatively low temperatures (12 and 18°C) applied to isolated discs or to the growing plants before leaf harvest.

Auxins also promoted both bud and root formation, the optimum concentration for rooting always being one to two orders of magnitude higher than the optimum for budding. Cytokinins had only a small stimulatory effect on bud formation. At higher concentrations it was inhibitory and even counteracted the stimulatory effect of auxin on bud formation. As usual, root formation was inhibited by cytokinin.

GA3 inhibited both bud and root formation but the inhibition was reversible by auxin. In presence of optimum auxin levels abscisic acid enhanced bud formation. It had little effect on root formation except for an inhibition at high concentrations.

The effects of exogenous auxin and cytokinin suggest that Streptocarpus leaves have a high and non‐limiting level of endogenous cytokinin with auxin as the limiting factor for both root and bud formation. This would also explain the exceptionally high regeneration ability of this plant.
The Role of Cytokinin in the Regulation of Growth, DNA Synthesis and Cell Proliferation in Cultured Soybean Tissues (Glycine max var. Biloxi)
Authors: FOSKET D. E. , SHORT K. C.
Published: April 2006

Changes in protein content and cell proliferative activity were followed after a cytokinin‐requiring strain of cultured Glycine max tissue was transferred to freshly prepared media which either contained or lacked cytokinin. Cell numbers doubled within the first two days after transfer, both in the presence and absence of cytokinin. However, after the second day no further increase in cell number was observed in the absence of cytokinin, while cell numbers continued to increase logarithmically in the presence of cytokinin. The size of the cell population attained after the first six days of growth was a function of the cytokinin concentration of the culture medium. However, the amount of 3H‐thymidine incorporated into nuclear DNA bore no relation to the rate of cell proliferation. Tissues cultured on medium lacking cytokinin incorporated the greatest amount of 3H‐thymidine per microgram of DNA, while the actively dividing tissues incorporated somewhat less. Using autoradiography and isopycnic CsCl gradient centrifugation, it was shown that the radioactivity derived from 3H‐thymidine was associated with nuclear DNA in the cytokinin‐deprived cells. Biochemical measurements demonstrated that cells cultured for six days without cytokinin had approximately twice the DNA content of the actively proliferating cells cultured on cytokinin‐containing medium. Furthermore, in autoradiographs labeled cells were found to average nearly three times as many silver grains per nucleus in tissues cultured without cytokinin as the cytokinin‐grown tissues. This suggests that the 3H‐thymidine incorporation in the non‐proliferating soybean cells results from nuclear DNA synthesis and that some of the cells became polypoid in the absence of cytokinin. These findings would be consistent with the idea that cytokinin acts as a specific trigger for cytokinesis.
Oscillatory Transpiration and Water Uptake of Avena Plants I. Preliminary Observations
Authors: JOHNSSON ANDERS
Published: April 2006

Oscillations in transpiration and water uptake of individual, young oat plants have been studied. The free‐running period of these oscillations was about 30 minutes. Conditions were reached under which the oscillations were sustained for about two days.

Short perturbations were given to the transpiration oscillations, the perturbations consisting of a short time increase or decrease in the illumination. The phase shifts of the oscillations as well as the amplitude effects caused by these perturbations were investigated.

Simultaneous recordings of transpiration and water uptake of a single plant showed that these functions were oscillating in phase. Both oscillations disappeared if the leaf was excised.
Phytochrome et germination des semences de Rumex
Authors: BIANCO J.
Published: April 2006

The Rumex alpinus L. achenes show a special type of positive photosensitivity: several red light irradiations are necessary to induce optimal germination. The achenes deprived of their pericarp lose their photosensitivity and germinate readily in the dark. By spectrophotometry in vivo, the presence of the Pr form of phytochrome is revealed in these seeds.

Short periods at extreme temperatures (30°C or 5°C) induce a good proportion of achenes to germinate. The gibberellins are inefficient on achene germination contrary to benzyladenine which exhibits some activity. A slight improvement of GA4 effects has been detected on scarified fruits.
Indole‐3‐Pyruvic Acid as an Intermediate in the Conversion of Tryptophan to Indole‐3‐Acetic Acid. II. Distribution of Tryptophan Transaminase Activity in Plants
Authors: TRUELSEN T. A.
Published: April 2006

Extracts from different organs of 30 plant species belonging to 16 families have been analysed for tryptophan transaminase activity. Only the brown alga Fucus spiralis was found to be devoid of the enzymes. Among the other plants tested, a difference in activity of two orders of magnitude was recorded. None of the genera or families investigated could be considered as particularly rich or poor sources of the enzyme. Extracts from leaves and stem tips contained generally more transaminase activity than extracts from stems and roots. The results are discussed in relation to other reports on the occurrence of the enzyme in plants.
The Effect of Storage Temperature on Shoot Growth, Flowering, and Carbohydrate Metabolism in Tulip Bulbs
Authors: MOE ROAR , WICKSTRØm ALF
Published: April 2006

Dry bulbs of the cvs. ‘Apeldoorn’ and ‘Paul Richter’ at stage G of flower development were stored at 5° or 21°C for 2, 4, 6, 8, 10, 12, and 14 weeks, respectively before being planted and forced at 18°C. Samples from each treatment were taken for carbohydrate analysis.

The low temperature treatment (5°C) was necessary to obtain satisfactory shoot growth and flowering after planting. The rate of shoot growth and the percentage of flowering bulbs increased with increasing duration of the 5°C treatment. Time of flowering was also precipitated. 12–14 weeks of low temperature treatment seemed optimal. High temperature (21°C), or a short period at 5°C (2–6 weeks), resulted in many non‐flowering bulbs, and a very slow shoot elongation when flowering occurred. In the latter case the tips or large areas of the perianths became white, the red pigmentation being prevented.

Paper chromatographic analysis of oligosaccharides revealed a substantially increased content of sucrose and fructosyl sucrose (DP ≤ 5) during the first 2–4 weeks of cooling. At the end of 12 weeks at 5°C, the content of oligosaccharides decreased.

The increase in the oligosaccharide content was accompanied by a corresponding starch decrease. High temperature storage (21°) led to comparatively slight changes in the sucrose and fructosyl sucrose content of the bulbs.

The significance of carbohydrate metabolism in relation to shoot elongation and flowering is discussed.
Effects of Daylength on Endogenous Gibberellins in Leaves of Solanum andigena
Authors: RAILTON I. D. , WAREING P. F.
Published: April 2006

Less gibberellin‐like activity was detected in extracts of potato leaves under short day than under long day conditions. Significant decreases in gibberellin levels were detected after two short day cycles. Using thin‐layer chromatography coupled with several solvent systems and various bioassays, at least four zones of gibberellin‐like activity, A, B, C and D were found in the potato leaf. Under long days only zones C and D were apparently present. However, preliminary purification using polyamide columns revealed that substances A and B were actually present in higher levels under long day than under short day conditions.

The chloroplasts of leaves exposed to short days contained less gibberellin‐like substances than those from leaves grown under permanent long day conditions.
Kinetics of Ion Uptake in Higher Plants
Authors: NISSEN PER
Published: April 2006

Single, multiphasic mechanisms located in the plasmalemma and the tonoplast are proposed to mediate ion uptake in cells of higher plants. There are no parallel uptake mechanisms and, normally, little or no free diffusion across the plasmalemma. The plasmalemma controls the rate of uptake at low external salt concentrations, while the tonoplast may become rate‐limiting at high concentrations.
The Effect of Sodium and Calcium on the Translocation of 14C‐sucrose in Excised Cotton Roots
Authors: JOHAM H. E. , JOHANSON LAMAR
Published: April 2006

The effect of sodium and calcium on the translocation of 14C‐sucrose in excised cotton roots (Gossypium birsutum) was studied. The roots were allowed to elongate in a modified Guinn's medium that was very low in calcium (6.25 × 10−2 mM) and sodium (8.70 × 10−3 mM). After a period of six days the roots were transferred to 20 × 100 mm Petri dishes that contained 10 × 40 mm Petri dishes as center wells. The roots were draped over the edge of the center well and extended into the outer dish. The outer Petri dish and its center well contained the same solution except that sucrose was supplied only in the center well. The sucrose used was spiked with uniformally labeled 14C‐sucrose. Four treatments were started which varied in their Na and Ca content.

Three and six day harvests were taken and the amount of 14C that had moved from the distal (in the center well) to the apical root section (in the outer dish) was determined. Increasing substrate Na or Ca caused an increase in 14C‐sucrose translocation and the effects of both ions were additive by the final harvest. These results were found to be independent of treatment effects on growth and respiration of the excised roots.

These data support the conclusion that Na may partially substitute for Ca in carbohydrate translocation. Thus, roots supplied the Low Ca‐High Na and High Ca‐Low Na treatments had equal translocation rates over a six day period. The highest translocation rate was obtained with the High Ca‐High Na treatment. Data from the High Ca‐High Na treatment on two successive three day periods indicate that Na may have a role in translocation other than that associated with substitution for Ca, or maintenance of tissue hydration.
Shoot Differentiation in Callus Cultures of Datura innoxia
Authors: ENGVILD K. C.
Published: April 2006

Datura innoxia Mill. callus cultures formed shoots in 2–4 weeks on media containing; a) gibberellic acid, b) indoleacetic acid, c) low concentrations of naphthylacetic acid, d) low concentrations of 2,4‐dichlorophenoxyacetic acid, e) benzylaminopurine, f) no growth substance.

Benzylaminopurine promoted shoot differentiation. Gibberellic acid inhibited shoot formation weakly, but inhibited proper leaf blade formation.

Root differentiation was rare.

The callus cultures of Datura innoxia grew rapidly (100‐fold in 4 weeks) on a slightly modified Murashige and Skoog medium (0.5 mg/l thiamin · HCl, pH 5.5, no glycine) in light at 30°C. Callus grew well on any single one of the growth substances NAA (10−5M), 2,4‐D (10−6M) or BAP (3 × 10−6M). Growth was less and more erratic on GA or IAA. The callus cultures did not grow significantly better when BAP was combined with one of the auxins or with GA.
Isolement d'une alcool déshydrogénase chez Rhizobium et rôle dans le métabolisme indolique
Authors: RIGAUD JEAN , TRINCHANT JEAN‐CHARLES
Published: April 2006

Rhizabium meliloti contains an alcohol dehydrogenase (E.C.1.1.1.1.) which can be isolated by breaking the cells. This soluble enzyme was purified 16.1‐fold by fractional precipitations with ammonium sulfate followed by gel filtration on Sephadex. The activity of the enzyme was tested with various aldehydes as substrates in the presence of NADH. Indole‐3‐acetaldehyde (IAAld) can be reduced to tryptophol (Tr‐ol), and the optimal pH for this reaction is ca. 6.5. The reaction can be reversed, and Tr‐ol is oxidised in the presence of NAD, but is was found that the yield was very poor; the optimal pH was ca. 8.6. This alcohol dehydrogenase is responsible for Tr‐ol formation in Rhizobium, but under our experimental conditions tryptophol cannot really be considered as a precursor of IAAld and indole‐3‐acetic acid.
Ethylene as a Cause of Transient Petiole Epinasty in Helianthus annuus during Clinostat Experiments
Authors: PALMER J. H.
Published: April 2006

Petiole curvature and elongation growth in Helianthus annuus L. have been recorded for plants rotating with their stems parallel to the horizontal axis of a clinostat at 8 revolutions per hour over 72 hours. When rotation was continuous, dorso‐convex curvature (epinasty) developed in the first 12 hours and was followed by recovery (straightening) in the next 36 hours. Thereafter the petioles remained straight. These changes in shape are due to brief consecutive increases in the elongation growth of the upper and lower halves of the petiole. Plants exposed to 10 μl per liter ethylene after 200 hours on the clinostat, developed similar petiole epinasty, followed by straightening when the exposure to ethylene ceased. Interrupting rotation of the plant for 1 hour in 4, did not change the petiole response, whereas the alternation of 4 hour stationary and rotation periods, delayed the straightening process. The axillary angle between the stem and petiole increased from about 40° to 63° during either continuous rotation or rotation with 1 or 4 hour stationary periods. When detached leaves were inverted, the rate of ethylene release approximately doubled after 4 hours and continued to increase thereafter. The results indicate that the development of transient petiole epinasty on the clinostat, is due to ethylene production caused primarily by the disorientation of the plant, rather than to the rotation process.
Changes in Transpiration, Net Carbon Dioxide Assimilation and Leaf Water Potential Resulting from Application of Hydrostatic Pressure to Roots of Intact Pepper Plants
Authors: JANES B. E. , GEE G. W.
Published: April 2006

Hydrostatic pressures varying from 0 to 6.0 bar were applied to roots of intact Capsicum annuum L. cv. California Wonder plants growing in nutrient solution and the rates of transpiration, and net CO2 assimilation, apparent compensation point and leaf water potential measured.

Increasing the pressure on the roots of plants with roots in solution with either ‐0.5 or ‐5.0 bar osmotic potential with 1 bar increments resulted in a decrease in transpiration. With the application of 1 or 2 bar pressure the rate of transpiration returned to near or above the original rate. An application of 3 or 4 bar pressure reduced the rate of transpiration of all plants. The transpiration of plants with roots in solution with ‐0.5 bar osmotic potential remained at the reduced rate for as long as these pressures were maintained. The transpiration of plants with roots in solution with ‐5.0 bar was only temporarily suppressed at these pressures. Changing the applied pressure from 3 or 4 bar to 0 resulted in a rapid increase in transpiration which lasted approximately 15 minutes. This was followed by a decrease in transpiration to a rate lower than before the pressure was applied. The pattern of response was similar for plants at low or high light intensity or at normal or low CO2 concentrations. When leaf diffusive resistance was 6.0 s cm−1 or greater, changes in net CO2 assimilation were similar to those of transpiration. The apparent CO2 compensation point increased as pressure was applied and decreased with a release in pressure. Leaf water potential increased with an increase in pressure and decreased with a decrease in pressure. The changes in leaf water potential were frequently but not always proportional to changes in pressure.

It is postulated that the respouses noted were due to changes in resistance to flow of water from xylem terminals through the mesophyll cells and stomatal cavities to the atmosphere.
Effect of Potassium Supply on the Acropetal Transport of Water, Inorganic Ions and Amino Acids in Young Decapitated Sunflower Plants (Helianthus annuus)
Authors: MENGEL KONRAD , SIMIC RADOMIR
Published: April 2006

The effect of potassium supply on the exudation rate and the content of ions and amino acids in exudation sap was studied using young decapitated sunflower plants (Helianthus annuus L.). Plants were grown originally in a complete nutrient solution. After decapitation one set of plants was transferred to a nutrient solution without potassium and another set to a solution with potassium, all other nutrients remaining the same for both treatments.

During an experimental period of 3 days the plants supplied with potassium showed exudation rates which were more than twice as high as plants in the nutrient medium without potassium. The potassium supply affected the potassium and nitrate contents of the exudation sap. Both were lower in the treatment without potassium. The calcium and magnesium contents of the exudation sap were not significantly influenced by the potassium treatment, whereas the phosphate content was higher in the treatment without potassium. At the beginning of the exudation period the potassium supply did not affect the content of amino acids in the exudate, but later the plants supplied with potassium showed higher contents of amino acids in the exudation sap.

As the absence of potassium reduced the exudation rate considerably the acropetal transport of all exudation sap constituents analysed in this experiment was markedly reduced.
Effect of Certain Nucleic Acid and Protein Inhibitors on Carotenogenesis in Verticillium agaricinum
Authors: MUMMERY ROSEMARY S. , VALADON L. R. G.
Published: April 2006

Cycloheximide, actinomycin D, puromycin, 5‐fluorouracil and 5‐fluorodeoxyuridine, all inhibitors of nucleic acid and protein synthesis, have been used to investigate at which level light affects carotenogenesis. The first three compounds inhibited both total protein and total carotenoids whereas the other two inhibited protein but not carotenoids. The results suggest that ribosomal RNA or possibly AMP‐rich RNA must be implicated in the light effect.

A scheme involving protein synthesis is proposed to account for the results obtained.
Carbon Dioxide and pH Requirements of Non‐Photosynthetic Tissue Culture Cells
Authors: NESIUS KNEELAND K. , FLETCHER JOHN S.
Published: April 2006

Maximum growth of suspension cultures of Paul's Scarlet rose required a low pH (5.2 to 5.4) during the division phase (day 0 to 7) and a higher pH (5.8 to 6.0) during the expansion phase (day 7 to 14).

The fresh weight increase was reduced by approximately 22%, but the dry weight was not influenced when cells were grown for 14 days in a CO2 deficient environment. Kinetic studies showed that the first five days of growth was the critical period of nonautotrophic CO2 fixation when cells were grown in medium buffered at pH 5.4. The phosphoenolpyruvate carboxylase activity was highest (0.50 × 106 cpm min−1· g−1 fresh weight) during the period when nonautotrophic CO2 fixation appeared to be critical for growth.
Studies on the Flowering Mechanism in Lemna
Authors: KHUDAIRI A. KARIM , MAENG JUESON
Published: April 2006

The dark reaction of the short day plant Lemna perpusilla was investigated. It was found that 3‐phosphoglycerate and pyruvate (10−6M) increased the flowering rate in the presence of nitrates. Pyruvate‐2‐14C was added to the culture solution during two hours of the dark reaction and 14C was incorporated into serine, aspartate and glutamate. It was postulated that pyruvate reacted with a nitrogen source forming an intermediate, possibly aspartate, which was further converted into serine. L. perpusilla failed to flower when the dark period was interrupted with red light and as a result endogenous serine accumulated in a high concentration. The dark reaction of L. perpusilla, in which serine was involved, required (1) oxygen, (2) ATP, (3) moderate temperature, and (4) an enzyme system.
Synchronous Cultures of Chlamydomonas reinhardti: Properties and Regulation of Repressible Phosphatases
Authors: LIEN TORLEIV , KNUTSEN GJERT
Published: April 2006

De novo synthesis of phosphatase (derepression) in orthophosphate deprived synchronously growing Chlamydomonas reinhardti has been demonstrated by using a double labelling isotope technique coupled with cellulose acetate electrophoresis. Repressed and derepressed phosphatase exhibited different enzymatic properties as pH optimum, electrophoretic pattern, Km and Ki values. Especially the acid phosphatase was located near the cell surface.

Inorganic, cold TCA‐extractable 32P, decreased during the first 1–2 h after phosphate deprivation when there was little or no net synthesis of phosphatase.

Results of experiments with additions of orthophosphate and cycloheximide to derepressed cells, indicated that the derepressible enzyme was relatively unstable, while its m‐RNA was relatively stable.
Changes in Urease Activity in Apple Trees as Related to Urea Applications
Authors: SHIM KYUNG‐KU , SPLITTSTOESSER WALTER E. , TITUS JOHN S.
Published: April 2006

Changes in urease (E.C.3.5.1.5.) were followed during the growth of 1‐year‐old MM 106 and 9‐year‐old Golden Delicious apple trees (Malus pumila Rehd.). Urease was found in leaves, roots, and bark with actively growing tissues containing more activity than senescing tissues. The urease activity in the leaves declined steadily during leaf senescence but abscised leaves still contained about half of their initial urease activity. In the bark the urease activity changed only slightly. Urease activities in the leaves and bark of apple trees were always greater in those trees which had received an application of urea. In senescing apple leaves, urea induced a rapid increase in urease activity. The changes in total activity and specific activity of urease were parallel and suggests that urease was synthesized de novo. After urease activity reached a maximum, a rapid decline occurred. Urease was inhibited by low concentrations of ammonia and this decline may be due to product inhibition.
Response of Cowpeas to Salinity and (2‐Chloroethyl) trimethyl‐ammonium Chloride (CCC)
Authors: IMBAMBA S. K.
Published: April 2006

Recent investigations have demonstrated that the growth retardant, (2‐chloroethyl) trimethyl‐ammonium chloride (CCC) inhibits several aspects of vegetative growth. In solution culture experiments, reduction in plant growth and dry matter production was confirmed in cowpeas, Vigna unguiculata L, (cv. Makueni II), when treated with CCC. The growth retardant had negligible effect on the rate of transpiration per unit leaf area although it slightly increased the relative water content of leaves. Stomatal opening was suppressed by CCC treatment but the number of stomata per unit leaf area was increased by the growth retardant. Variations in mineral element content (K, Ca, N and Na) of shoots are presented and discussed in relation to CCC treatment.
The Influence of the Synthetic Growth Regulator α‐Chloro‐(β‐(3‐chloro‐o‐tolyl) propionitrile on Some Phytochrome‐mediated Processes
Authors: DIERICKX P. J. , VENDRIG J. C.
Published: April 2006

In intact Sinapis alba seedlings the synthetic growth regulator α‐chloro‐β‐(3‐chloro‐o‐tolyl)propionitrile (PRB‐8) inhibits the phytochrome‐mediated anthocyanin synthesis, carotenoid synthesis and L‐phenylalanine ammonia‐lyase activity. This action was compared with that of other auxins and with that of α‐chloro‐β‐(3‐chloro‐o‐tolyl)propionitrile‐homologues. From the results it appeared that PRB‐8 and some other o‐tolyl derivatives are more inhibitive than other known auxins.
Triterpeneglycosides as Inhibitors of Fungal Growth and Metabolism 6. The Effect of Aescin on Fungi with Reduced Sterol Contents
Authors: OLSEN ROLF A.
Published: April 2006

The amount of sterols in the mycelia of Ophiobolus gra‐minis and Neurospora crassa was reduced by cultivating the fungi in the presence of inhibitors of the sterol synthesis. The hypocholesteraemic compounds β‐diethylaminoethyl‐(2.2‐diphenylpentanoate) hydrochloride (SK & F 525‐A) and 2.2‐diphenyl ‐1 ‐(β‐ dimethylaminoethoxy)pentane hydrocchloride (SK & F 3301‐A) were particularly effective in reducing the sterol contents. At the same time, the growth yield was reduced. Aescin had a reduced inhibitory effect on the radial growth of the mycelia with decreased sterol contents, the leakage of UV‐absorbing substances and K+ ions was reduced to small amounts, and the inhibition of the K+ uptake was nullified.