bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical activity of the liver‐wort Conocephalum conicum.: Method of investigation and general characteristics of excitation
Authors: Paszewski A. , Dziubiska H. , Trębacz K. , Zawadzki T.
Published: April 2006

The excitation of the thallus of Conocephalum conicum L. produced by a tissue damaging stimulus (incision of thallus edge) was investigated. Changes in potential were measured with extracellular contact electrodes applied at various points of the thallus surface. Non‐stimulated plants showed no electrical activity. After stimulation a series of impulses occurred and were propagated all over the thallus. This plant electrical activity (PEA) depends on the magnitude of the stimulus. PEA is characterized by changes of frequency, time of duration and changes in the values of the amplitude. A similar phenomenon is well known in animal organisms as frequency coding. The general character of PEA does not depend on the kind of damaging stimulus (burn, puncture). PEA may also be induced by an electrical stimulus which does not damage the tissue.
Fixation and distribution of 14C in Populus deltoides during dormancy induction
Authors: Dickson Richard E. , Nelson Eric A.
Published: April 2006

Photosynthetically fixed 14C was analyzed in various chemical fractions from leaves and stems of cottonwood (Populus deltoides Bartr. ex. Marsh.) during dormancy induction. Dormancy was induced by 8‐h photoperiods and 20/14°C temperature regimes. Within 4 weeks under short days, terminal buds were set and leaf expansion and stem elongation had stopped. 14C2 was fed to a leaf at Leaf Plastochron Index 7 for 30 min. Either after this 30 min feeding period or after a 48‐h translocation period the plants were sampled, freeze‐dried, extracted and analyzed for14C. 14C‐fixation decreased during dormancy induction from 60% to 17% of the 3.7 MBq 14C applied at 0 week and 8 weeks, respectively. Percentage distribution of 14C in chemical fractions of source leaves reflected leaf age and translocation inhibition. In rapidly growing plants, considerable 14C was incorporated into leaf protein while most of the soluble14C‐sugars were either metabolized or translocated out of the leaf. After terminal bud set, the percentage of 14C in the protein and residue fractions decreased rapidly and that in the sugar fraction increased. Percent distribution in stems closely reflected changing metabolic pathways of carbon flow as influenced by dormancy induction. For example, the 14C in structural carbohydrates decreased in 5 weeks under short days from 65 to less than 10% of the 14C recovered in the chemical fractions, thus indicating cambium inhibition. At the same time the percentage of 14C in starch and sugar increased indicating storage. Short term (after 30 min) incorporation of 14C into the protein and starch fractions of leaves changed relatively little throughout the 8‐week induction period. In contrast the turnover rates of these fractions (14C present after 48 h) increased considerably after active growth of the whole plant stopped.
Relationships between CO2 concentration within the leaf and photosynthesis during deacidification in a CAM plant, Kalanchoë pinnatum
Authors: Nishida Kojiro
Published: April 2006

The CO2 concentration within the leaf of Kalanchoë pinnatum (Persoon) was measured during deacidification in the light. When the acidified leaf was treated with DCMU, the CO2 concentration within the leaf was increased about 3‐fold as compared to that of the non‐treated leaf, concomitant with a decline in deacidification. Low light intensity during deacidification also increased CO2 concentration within the leaf. From these experiments, it was concluded that in order for deacidification to proceed, CO2 released from malate must be fixed continuously by photosynthesis. Otherwise, an equilibrium for malate decomposition is soon established and results in suppression of deacidification. Thus, the CO2 concentration within the leaf seems to be one of the regulatory factors of deacidification.
Sucrose and ouabain effects on the kinetic properties of a membrane‐bound (Na++ K++ Mg2+) ATPase in sugar beet roots
Authors: Lindberg Sylvia
Published: April 2006

Kinetic studies of a microsomal (Na++ K++ Mg2+)ATPase from sugar beet roots (Beta vulgaris L. cv. Monohill) show that sucrose influences the MgATPase in different ways depending on the presence of K+ and/or Na+ 1) In the presence of the substrate MgATP and Na+ the effect of sucrose follows simple Michaelis‐Menten kinetics. 2) In the presence of substrate together with K+ or (K++ Na+), sucrose has little effect on the ATPase activity. 3) In the presence of Na+, onabain acts as an uncompetitive inhibitor with respect to MgATP. 4) In the presence of K+ or (K++ Na+), the inhibition by ouabain is somewhat depressed and shows non‐linearity when 1/v is plotted versus 1/MgATP. 5) Sucrose and Na+ activate in a competitive way, so that a successive increase of the Na+ level decreases the activation by sucrose. Both Km and V‐values are thereby changed. 6) The sucrose activation in the presence of Na+ is also influenced by ouabain. It is, therefore, suggested that Na+ may regulate the interference between the Na+/K+ pump and a sucrose sensitive system.
The effect of far‐red light on the photoperiodic regulation of carbohydrate accumulation in Allium cepa L.
Authors: Lercari Bartolomeo
Published: April 2006

Carbohydrate accumulation was induced in Allium cepa L. cv. Dorata di Parma by the addition of far‐red light throughout the 18 h day. Neither an 18 h‐day without far‐red nor the addition of far‐red light to a 10 h photoperiod could induce the carbohydrate accumulation. The accumulation of reducing sugar takes place both in the leaf‐blades and in the bulb; while there is accumulation of oligosaccharides only in the bulb. The results implicate phytochrome in the promotion of carbohydrate accumulation by far‐red light.
A semi‐lunar periodicity of neurotransmitter‐like substances from plants
Authors: Rounds Harry D.
Published: April 2006

Cardioacceleratory activity was found in ethanolic extracts of the leaves of Coleus blumei (Benth, var. verschaffeltii), Phaseolus vulgaris L., and Philodendron (Schott) sagittifolium. The cardioacceleratory activity fluctuated considerably from day to day and from sample to sample but displayed a consistent tendency to drop to very low levels shortly after full moon and new moon. The tendency to fall to low levels at semi‐lunar intervals is compared with similar findings in cockroach, mouse and human blood and complementary findings in cockroach nervous tissue.
The function of carotenoids during chloroplast development. V. Correlation between carotenoid content, ultrastructure and chlorophyll b to chlorophyll a ratio
Authors: Axelsson Lennart , Dahlin Clas , Ryberg Hans
Published: April 2006

The ultrastructural effect of carotenoid deficiency in wheat (Triticum aestivum L.) was studied after adding the herbicide SAN‐9789 to the growth medium. The presence of SAN‐9789 (28 mg I‐1) resulted in an almost complete absence of carotenoids. For plants grown in darkness the lack of carotenoids was accompanied by a reduction in partitions between primary thylakoids as well as a change in appearance of the plastoglobuli from small and black (osmiophilic) to large and greyish white (less osmiophilic). When plants were grown in weak red light (16 mW m‐2), the presence of SAN‐9789 also resulted in an almost complete absence of grana, a decrease in the ratio of chlorophyll b/chlorophyll a from 0.25 to 0.1, and an almost complete absence of prolamellar bodies. The greatest differences in carotenoid content, in amount of grana, in chlorophyll b/chlorophyll a ratio, and in number of prolamellar bodies, all occurred between 0.28 and 2.8 mg I‐1 of SAN‐9789. The change in appearance of plastoglobuli occurred at a lower SAN‐9789 concentration, between 0.028 and 0.28 mg I‐1. The ultrastructural responses to the SAN‐9789 treatment could be related to the effect on the carotenoid synthesis in different ways. The disappearance of thylakoid partitions was connected to a structural role of carotenoids, while the disappearance of the prolamellar bodies was dependent on the photoprotective role of carotenoids. The change in shape and size of plastoglobuli was not correlated to the presence of carotenoids. However, a connection to the accumulation of the carotenoid precursors is still possible.
Biological activity of 6‐(2,3,4‐trihydroxy‐3‐methylbutylamino)purine, an oxidation product of zeatin
Authors: Van Staden J. , Drewes S. E. , Hutton M. J.
Published: April 2006

6‐(2,3,4‐Trihydroxy‐3‐methylbutylamino)purine was identified as an oxidation product of cis‐zeatin and is biologically as active as the parent compound. A comparison of trans‐zeatin, cis‐zeatin and (±)‐dihydrozeatin indicated that trans‐zeatin and (±)‐dihydrozeatin were more active in the soybean callus bioassay than cis‐zeatin. Both the trans‐ and cis‐isomers of zeatin did, however, give an optimum response at 10‐5M. Dihydrozeatin was more active at concentrations of 10‐6 and 10‐5M than trans‐zeatin. The significance of the formation of 6‐(2,3,4‐trihydroxy‐3‐methylbutylamino)purine with respect to stereochemistry and the oxidation of cytokinins with an unsaturated isopentenyl side chain is discussed.
Dynamics of extractable carbohydrates in Pisum sativum. I. Carbohydrate and nitrogen content in pea plants and cuttings grown at two different irradiances
Authors: Veierskov B. , Skytt Andersen A. , Eriksen E. Nymann
Published: April 2006

When pea plants (Pisum sativum L. cv. Alaska) were grown in controlled environment rooms, a stock plant irradiance of 38 W m‐2 decreased the rooting ability of the cuttings compared to 16 W m‐2. Also the origin of the seeds was of importance. The experiments were done in 1976 (1975 seed lot) and 1979/80 (1978 seed lot). At 38 W m‐2 the 1975 seed lot produced 7.2 roots, whereas the 1978 seeds produced 20.7 roots per cutting. The content of fructose, glucose, inositol and sucrose was determined from an ethanol extract, and extractable starch from a perchloric acid extract. The irradiance treatment regulated the carbohydrate content of the plants at the time they were made into cuttings. Cuttings from 16 or 38 W m‐2 contained initially 6.8 and 8.5% carbohydrate, on a dry weight basis respectively. If the plants were not excised to cuttings, a stable level of carbohydrates was maintained throughout the growing period, whereas in the cuttings, the carbohydrate content increased five fold during the rooting period. The content of extractable carbohydrates did not show any correlation to the root initiation process, but might be of importance for the further growth of the new roots. The C/N‐ratio of the plants at the time they were made into cuttings reflected the pre‐growth condition and was not related to the rooting ability of the cuttings.
Dynamics of extractable carbohydrates in Pisum sativum. II. Carbohydrate content and photosynthesis of pea cuttings in relation to irradiance and stock plant temperature and genotype
Authors: Veierskov Bjarke , Andersen A. Skytt , Stummann B. M. , Henningsen K. W.
Published: April 2006

Rooting ability was studied for cuttings derived from stock plants of wild type pea seedlings and seedings of two mutants deficient in photosystem II activity and chlorophyll. Stock plants were grown at 15, 20, 25 or 30°C at 38 W m‐2. Cuttings were rooted at 20°C and at an irradiance of 16 or 38 W m‐2. The rooting ability seemed to be correlated with the initial carbohydrate content only at 38 W m‐2. Based on the findings of the present study it may be concluded that for pea seedlings the growth temperature is more important than photosynthesis as regards accumulation of extractable carbohydrates. During the rooting period carbohydrates are necessary for root formation, but the effect of the iradiance on the number of roots formed is not mediated by the carbohydrate content. Under specific rooting conditions it is possible to correlate the initial carbohydrate content with the rooting capacity of the cuttings within a phenotype, but not always when different phenotypes are considered. The results indicate a connection between the metabolic activity of the cuttings and their ability to form adventitious roots.
Interaction of triacontanol with gibberellin in control of lettuce seed germination
Authors: Lewak Stanislaw , Skowrońska Elżbieta
Published: April 2006

Triacontanol at concentrations from 2.3 × 10‐9M to 2.3 × 10‐7M did not affect the germination of lettuce (Lactuca sativa L., cv. Grand Rapids) seeds in darkness, stimulated by light at 25°C or by benzyladenine at 31°C. Stimulation of seed germination by gibberellin A3 (10‐5M) was significantly inhibited by triacontanol; the most effective concentration was 4.6 × 10‐8M. Pulse experiments demonstrated that triacontanol was ineffective when applied later than gibberellin, whereas an inverse sequence of treatment caused an inhibition comparable to that resulting from continuous treatment of seeds with both factors. Possible interaction of triacontanol with gibberellin receptor is discussed.
Glutamine synthetase in alder (Alnus glutinosa) root nodules. Purification, properties and cytoimmunochemical localization
Authors: Hirel B. , Perrot‐Rechenmann C. , Maudimas B. , Gadal P.
Published: April 2006

Chromatographic, kinetic and regulatory properties of glutamine synthetase (GS) were investigated in root nodules of Alnus glutinosa L. (Gaertn) grown in a culture chamber. By DEAE Sephacel column chromatography and polyacrylamide gel electrophoresis, a major form of the enzyme was identified. Molecular weight was about 360 000 for the native protein and 43 000 for the subunits. Optimum pH was about 7.3 and Km for glutamate and ATP were 0.9 mM and 0.5 mM, respectively. By immunofluorescent techniques GS was localized in the inner cortical cells but not in vesicles of alder root nodules.
Catalase activity and isozyme pattern of the metalloenzyme system, superoxide dismutase, as a function of leaf development during growth of Pisum sativum L. plants
Authors: Lastra O. , Gómez M. , López‐Gorgé J. , del Rio L. A.
Published: April 2006

The catalase activity and the isozyme pattern of the metalloenzyme system superoxide dismutase (SOD) have been determined in pea (Pisum sativum L., cv, Lincoln) leaves of different ages (apical, middle and lower), during several stages of plant development. Pea seedlings were grown in full nutrient solution in a phytotron. Catalase activity was determined polarographically, and superoxide dismutase isozymes (Mn‐SOD, Cu, Zn‐SOD I and Cu, Zn‐SOD II) were separated by acrylamide gel electrophoresis and their relative amounts quantified by densitonietry. The results indicate that the relative amounts of SOD isozymes are slightly different in leaves of different ages during plant growth and, interestingly, each molecular form of SOD shows a clearly distinct pattern during plant development. These changes in the relative percentages of SOD isozymes could be due to the induction of the distinct molecular forms of SOD by the metals Mn, Cu and Zn, translocated to the different leaves as a result of plant development. The relative percentage of the Mn‐SOD isozyme showed a similar pattern to that of catalase activity, suggesting a possible link between these two metalloenzymes at subcellular level, both cooperating to remove the toxic effects of O‐2 and H2O2.

An additional conclusion is that before a certain metalloenzyme can be used as a marker to assess the plant micronutrient status, it is essential to have a detalled study of its activity pattern in leaves of different age during plant development.
Effect of abscisic acid on the circadian leaf movements of Oxalis regnellii
Authors: Skrove D. , Rinnan T. , Johnsson A.
Published: April 2006

The effect of abscisic acid on the circadian leaf movements of Oxalis regnellii Mig. was investigated. Leaf stalks were cut and put into a nutrient solution, and the leaf movements automatically recorded. Continuous application of ABA (10‐5 or 10‐4M) to the solution did not alter the circadian period. However, the treatment delayed the rhythm and the amplitude was somewhat decreased. ABA pulses (4 h, 10‐4M) caused permanent phase shifts of the rhythm with delays and advances. Transient wilting of the stalks plus leaves did not produce permanent phase shifts of the rhythm. A wilting period of 4 h gave a (transient) 2 h advance as judged from the first maximum after the wilting treatment. This advance was independent of the time of application of the wilting. Wilting treatment for 8 h caused advances, the magnitude of which varied according to the timing of the wilting treatment. It is concluded that there was no connection between the (permanent) ABA effects and the (transient) wilting effects on the phase of the circadian rhythm. A direct action of ABA on the circadian oscillator is possible and the molecular mechanism might be via effects on ion permeability of the pulvini cells.
Involvement of photobleaching and inhibition of protochlorophyll(ide) accumulation in tentoxin effects on greening of mung bean seedlings
Authors: Wickliff James L. , Duke Stephen O. , Vaughn Kevin C.
Published: April 2006

Several types of evidence indicate that tentoxin‐caused reduction of chlorophyll accumulation in greening primary leaves of mung bean [Vigna radiata (L.) Wilczek cv. Berken] is due to both photobleaching and decreased protochlorophyll(ide) synthesis. Greening was greater under dim (2.5 μmol m‐2 s‐1) far‐red or white light than under bright (180 to 200 μmol m‐2 s‐1) white light in tentoxin‐treated tissues, whereas there was a positive correlation between fluence rate and greening in control tissues. Under continuous white light (100 μmol m‐2 s‐1) chorophyll(ide) accumulation was slower in tentoxin‐treated than in control tissues. This was caused by greater photobleaching of newly formed chlorophyll(ide), as well as by decreased protochlorophyll(ide) synthesis. Photobleaching did not affect protochlorophyll(ide) synthesis in control or tentoxin‐treated tissues. Chlorophyll(ide) was less stable in tentoxin‐treated than in control tissues during a 24 h period of darkness. Plastids of tentoxin‐treated tissues had all of the chlorophyll‐proteins of control plants. Etioplasts of tentoxin‐treated plants contained normal galactolipid contents, but galactolipids in these plants were greatly reduced in white light. Reduced chlorophyll accumulation caused by tentoxin is apparently the result of both photodestruction and of reduced synthesis of chlorophyll.
The effect of Ca2+‐stress on fluxes of Ca2+ and K+ in wheat and cucumber
Authors: Bengtsson Bengt
Published: April 2006

Fluxes of Ca2+ (45Ca) and K+ (86Rb) were investigated in 12‐day old intact plants of cucumber (Cucumis sativus L. var. Cilla) and 7‐day old intact plants of wheat (Triticum aestivum L. var. Svenno) which had been cultivated in nutrient solution. The rate of K+ uptake was affected by the external Ca2+ concentration, which reduced the uptake of K+ when present above and below a certain level. Pretreatment of roots in high [Ca2+] during a 24 h period decreased the rate of both K+ and Ca2+ uptake. Reduced availability of Ca2+ in the nutrient solution during 24 h reduced the uptake of K+ and Ca2+. Separation of the Ca1+ and K+ retained in the roots from the amounts transported to the shoots in plants pretreated with low [Ca2+], showed that the influx of K+ retained in the roots decreased while Ca2+ influx increased. The transport of both ions towards the shoot was, however, reduced. Reduction of available Ca2+ in the nutrient solution was suggested to change the composition of the membranes, maintaining their permeability properties and metabolically regulated functions. Leakage of K+ (86Rb) from the vacuolar and cytoplasmic compartment of wheat roots increased at reduced Ca2+ concentration in the nutrient solution.
Endogenous IAA and morphogenesis in tobacco petiole cultures
Authors: Cassells Alan C. , Long Roger D. , Mousdale David M. A.
Published: April 2006

Short duration (48 h) dark or high light treatment of the donor plants has been shown to influence the pattern of auxin metabolism in tobacco petioles in culture. In explants from dark treated donor plants there was a peak of IAA detectable at day 3 in culture. This was associated with reduced morphogenetic potential of the explant. Inclusion of 2,3,5‐triiodobenzoic acid in the medium prevented this IAA accumulation and eliminated the inhibitory effect of the dark pretreatment. Inclusion of IAA in the culture medium reduced the morphogenetic potential of explants from high light treated donor plants but had no effect on the morphogenetie potential of explants from dark treated donor plants. Explants cultured for one day on auxin‐free medium and then transferred to IAA‐containing medium were sensitive to auxin; those transferred after five days were insensitive. Studies on the interaction between media sucrose concentrations, endogenous IAA and peroxidase, and morphogenesis are reported. The results are discussed in relation to the influence of endogenous auxin on the receptivity of explants to exogenous (media) morphogenetic stimuli.
Role of ethylene in stimulating stylar abscission in pistil explants of lemons
Authors: Sipes Deborah L. , Einset John W.
Published: April 2006

Abscission in styles of excised Citrus limon (cv. Lisbon) pistils was stimulated by addition of 70 μM 2‐chloroethylphosphonic acid (ethephon) or 0.1 mM 1‐aminocyclopropane‐1‐carboxylic acid (ACC) to the defined medium of cultures. To study the relationship between ethylene and abscission, we used gas chromatography to analyze ethylene in cultures containing a test medium plus or minus abscission‐active chemicals. In the presence of ethephon or ACC, ethylene levels in sealed tubes increased rapidly, suggesting that these compounds stimulated abscission because they were converted to ethylene. In the presence of test medium or the inhibitor of abscission 2 μM picloram, the low ethylene levels found in sealed tubes did not differ strikingly in the two treatments. Ethylene production rates measured prior to abscission with test medium or in the presence of picloram were not markedly different either, although picloram completely inhibited abscission. Stylar abscission was delayed but not prevented by 50 μM aminoethoxyvinylglycine, an inhibitor of ethylene biosynthesis, and by hypobaric conditions (280 mm Hg) which removed ethylene from cultures. We concluded that ethylene is an important factor regulating stylar abscission in vitro and suggest that the inhibitory effect of picloram involves a process other than detectable ethylene production. Our results do not exclude the possibility that picloram affects enodgenous ethylene biosynthesis and/or metabolism and/or tissue retention.
The relationship between photosynthetic electron transport and photorespiratory 14CO2 release after DCMU treatment in the duckweed, Lemna gibba
Authors: Chaturvedi Rekha , Haugstad May K. , Nilsen Stein
Published: April 2006

The photosynthetic rate of Lemna gibba was measured as 14CO2 uptake at the beginning of and after 1 h DCMU treatment during the separate excitation of PS I (703 nm), mainly PS II (662 nm) and the combined excitation of both photosystems (662 + 703 nm) in 2 and 21% oxygen. The results show the Warburg effect. Photosynthesis was significantly reduced by DCMU whenever PS II was excited, at 662 nm and 662 + 703 nm. Photosynthetic enhancement was greater in 21 than in 2% oxygen in both the treated and untreated plants.

Photorespiratory 14CO2 release was only affected by DCMU treatment at 662 + 703 nm. It was significantly decreased in 21% O2 and significantly increased in 2% O2 as compared to the controls without DCMU. The 14C‐glycolate remaining in the plant after photosynthesis/photorespiration measurements was reduced whenever the electron supply to PS I was low.

These data support the hypothesis that a relationship exists between glycolate metabolism and photosynthesis via the electron transport chain where electrons from the oxidation of glycolate are donated to PS I when the electron supply from water is low.
Widespread occurrence of cholinesterase activity in plant leaves
Authors: Miura G. A. , Broomfield C. A. , Lawson M. A. , Worthley E. G.
Published: April 2006

In contrast to previous work, the distribution of cholinesterase was found to be ubiquitous in plant leaves. Cholinesterase activity was detected in 91% of the 70 species surveyed from 50 higher plants and three families of ferns. A radiometric assay was used to determine the hydrolysis of acetylcholine by leaf tissue slices in the presence and absence of 29 μM diisopropyl phosphofluoridate. The results obtained using this inhibitor as a criterion for cholinesterase activity were found to be consistent with previous studies using neostigmine as the inhibitor although there were some quantitative differences between the inhibitors. With some of the tested plants acetyl‐β‐methylcholine was also hydrolyzed, indicating that acetylcholinesterase rather than pseudocholinesterase was present at least in these cases. These findings demonstrate that the relative activity of cholinesterase in leaves can serve as an indicator of organophosphorous anticholinesterase contamination of the environment.
Energy metabolism of Plantago lanceolata, as affected by change in root temperature
Authors: Smakman Gerard , Rinie (J. J.) Hofstra
Published: April 2006

The long and short term metabolic effects of a shift in root temperature was investigated in Plantago lanceolata L. with special reference to the role of the cyanide resistant alternative pathway in root respiration. After a 10‐day period of growth at a 13°C root temperature, a decrease in root as well as shoot growth was observed, compared to control plants grown continuously at 21°C. Apart from an increase in shoot soluble and insoluble sugar level, no changes in metabolism were found, neither in root respiration, shoot photosynthesis, nor in root sugar and plant protein level.

Decreasing the root temperature from 21 to 13°C gave several clear short term changes in metabolism. Within one hour a decrease in cytochrome chain activity of the roots was found together with an increase in activity of the alternative chain. After 24 h a recovery to the initial level of both chains was observed. An increase in root temperature from 13 to 21°C gave an immediate increase in activity of both respiratory chains that was still present 24 h after the switch.

It is concluded that the activity of the alternative respiratory pathway in the root is strongly affected by a sudden temperature change in the root environment. This pathway acts in a way which is described by ‘the energy overflow model'. The presence of the alternative electron transport pathway should be taken into account in determinations of the respiratory Q10. Moreover, the length of time between the temperature change and respiration measurements is an important factor.
Mitotic activity and cell elongation in geostimulated roots of Zea mays
Authors: Barlow Peter W. , Hofer R.‐M.
Published: April 2006

Mitotic activity was investigated in the primary meristem of horizontally oriented excised root tips of Zea mays during the first six hours of their georeaction. The only statistically significant change that could be detected in the meristem was a decrease of the length of its upper half. No significant difference in mitotic activity was found between the upper and lower halves of roots kept continuously horizontal for 6 h. Cell proliferation thus seems relatively insensitive to changes in the redistribution of endogenous growth regulators that are believed to occur within the meristem during the onset of geotropism. In the zone of bending proximal to the meristem cell length was significantly greater in the upper half than in either the lower half or in the equivalent position in vertical control roots. Thus, cell elongation seems to be promoted in the upper half of the horizontal root. Thus, The differences in cell length were not accompanied by any change in the proportion of nuclei synthesising DNA in these elongating, non‐meristematic cells.
Effects of α‐aminoisobutyric acid and D‐ and L‐amino acids on ethylene production and content of 1‐aminocyclopropane‐1‐carboxylic acid in cotyledonary segments of cocklebur seeds
Authors: Satoh Shigeru , Esashi Yohji
Published: April 2006

In the cotyuledonary tissue of cocklebur (Xanthium pennsylvanicum Wallr.) seeds, AIB (α‐ aminoisobutyric acid) inhibited not only the endogenous ethylene production but also the ACC (1‐aminocyclopropane‐1‐carboxylic acid)‐dependent and IAA‐induced ones. The inhibition of the endogenous ethylene production by AIB was accompanied by the accumulation of ACC in the tissue. Thus AIB may act as a competitive inhibitor of the conversion of ACC to ethylene and thereby inhibit ethylene production. The promotion of ethylene production by D‐isomers of some amino acids, such as phenylalanine, valine, threonine and methionine was accompained by and increse in the ACC content, the degree of which was similar to that of the stimulation of ethylene production. Moreover, these D‐amino acids stimulated the conversion of exogenously applied ACC to ethylene. The corresponding L‐isomers failed to produce these effects. It seems likely that D‐amino‐acid‐stimulated ethylene production results from the increases of both the biosynthesis and degradation of ACC. Only for tryptophan did both D‐ and L‐isomers cause an increase in ethylene production and in ACC content in the segments. The mechanism of stimulation of ethylene production by the tryptophen isomers is possibly due to their conversion to IAA in the cotyledonary tissue.
Retardation of radish leaf senescence by polyamines
Authors: Altman Arie
Published: April 2006

The effect of polyamines and related metabolites on several parameters of leaf senescence was followed in detached radish (Raphanus sativus L. var. radicular cv. “Giant Butter”) leaves floated on test solutions in darkness. Leaf senescence was accompanied by a marked loss of chlorophyll, which started at 24–48 h of incubation. The polyamines, spermine and spermidine, and the diamines, putrescine and cadaverine, were highly effective in arresting chlorophyll loss over a period of at least 96 h. l‐arginine, and especially l‐ornithine, were less active. Polyaminens prevented the marked chlorophyll loss in dark‐incubated leaves, but did not compensate for the moderate chlorophyll loss when the leaves were aged in light. Polyamines were also highly effective in retarding earlier events of leaf senescence, prior to chlorophyll loss: both protein degradation and ribonuclease activity were inhibited by spermidine. Chlorophyll and protein loss in dark‐or light‐incubated suspensions of either “intact” or disrupted chloroplasts was not affected by polyamines. – It is concluded that polyamines are highly effective in preventing chlorophyll loss from detached leaves, possibly by controlling early senescence‐linked events which occur in darkness rather than by direct inhibition of chlorophyll degradation.
Replacement of photosynthetic electron transport inhibitors by silicomolybdate
Authors: Böger Peter
Published: April 2006

KCN‐treated spinach chloroplasts, their photosystem I being ineffective, exhibit a single reaction site for silicomolybdate. Using this heteropolyanion as electron acceptor, photosynthetic oxygen evolution is partially inhibited by ureas, triazines, or phenylpyridazinone herbicides, their inhibitory effect depending on the concentration of silicomolybate. Labelled atrazine attached to isolated chloroplast material is competitively replaced by silicomolybdate in the same manner as e.g. ureas complete with a triazine herbicide. – It is concluded (1) that silicomolybdate is bound and reduced at the herbicide‐binding protein, and (2) that the inhibition of silicomolybdate reduction by herbicides such as DCMU is due to loss of reaction sites for silicomolybdate.
Possibilities and constraints in the regeneration of trees from cotyledonary needles of Picea abies in vitro
Authors: Bornman Chris H.
Published: April 2006

Although use of embryonic or seedling tissues for mass clonal micropropagation in vitro in conifer reforestation programmes is questionable, there is a potential application in the regeneration of plants from scarce and costly seed derived from controlled pollination. In addition, in vitro culture shortens considerably the lag phase in numbers during the initial stages of vegetative propagation via rooted cuttings. Successive steps of the present technique are described whereby cotyledonary needles (secondary explants) were subcultured on a hormone‐free medium after administration of cytokinin or auxin to 14‐day‐old seedling (primary) explants of Picea abies. For bud induction, N6‐benzyladenine (BA) was applied either as a short‐duration (3 h), high‐concentration (125 μM) pulse or by vacuum infiltration and incubation in a BA‐containmg (5 μM) infusion medium. Induced adventitious shoots were elongated with the aid of far‐red light and rooted in vivo after a long‐duration (12 h), high‐concentration (625 μM) application of indolebutyric acid. Pulse and infusion treatments resulted in the induction of greater numbers of adventitious buds (average of 12 per needle) over a three to four week shorter culture period than was the case with the conventional inclusion of growth regulators in the agarified medium. No exogenous auxin was required in the bud‐induction programme; its inclusion even at nanomolar levels promoted histo‐ rather than morphogenesis. In cotyledonary needles, to the primary explants of which BA was applied as a pulse or by infusion, the cell divisions which gave rise to the meristemoids from which adventitious buds were produced, appeared to commence mainly in undifferentiated hypodermal layer cells but also in the mesophyll immediately below. By contrast, where BA was incorporated in the agarified medium the first divisions occurred mainly in cells of the epidermal layer.

A number of factors affected plantlet regeneration, for instance seed variability, age of seedlings, and mode of application of growth substances. It should also be accepted that the xeromorphic nature of the conifer leaf might impose physiological and morphological constraints on its culture in vitro that could militate against easy morphogenic manipulation. It is deemed essential that the current mean ratio of regenerated plants to cotyledonary needles of 1:1 be increased 10 to 20 fold in order to approach commercial feasibility.
Effect of gibberellic acid on K+ (Rb+) uptake and transport in sunflower roots
Authors: Benlloch Manuel , Fournier José M. , de la Guardia Manuel Díaz
Published: April 2006

Four‐week‐old sunflower plants (Helianthus annuus L. cv. Halcón), grown in different nutrient solutions, were used to study the effects of gibberellic acid (GA3) on K+ (Rb+) uptake by roots or transport to the shoot. Gibberellic acid application to the nutrient solution did not affect the exudation process of excised roots. When GA3 was sprayed on leaves 2 to 6 days before excising the roots, the rate of exudation and the K+ flux increased. When the exudation study was done keeping the roots in a nutrient solution in which Rb+ replaced K+, the GA3 effects were evident also on Rb+ uptake and transport. In intact plants, GA3 increased the Rb+ transported to the shoot but did not affect Rb+ accumulation in the root. It is suggested that these GA3 effects can be explained if it is assumed that GA3 acts on the transport of ions to the xylem vessels.
Influence of light on phosphoenol pyravate carboxylase in sorghum leaves
Authors: Vidal Jean , Godbillon Guy , Gadal Pierre
Published: April 2006

Upon greening of sorghum leaves (Sorghum vulgare Pers. cv. INRA 450) under white light illumination, phosphoenolpyruvate carboxylase activity increases. 17 times; at the same time, a new isoform of the enzyme appears.

The aim of the present work has been to identify the process responsible for the appearance of this isoform. Greening. of the leaves in the presence of D2O did not lead to a significant increase in the buoyant density of the enzyme. On the other hand, cycloheximide was a powerful inhibitor of the rise in PEP carboxylase activity. In order to clarify these conflicting data a procedure based on the immunoprecipitation of the enzyme and its quantification by gel electrophoresis was developed in order to estimate the amount of enzyme in leaf tissue. The results clearly demonstrate that light triggers an increased synthesis of the enzyme protein during greening of sorghum leaves.
Specific photoperiodic stimulation of dry matter production in a high‐latitude cultivar of Poa pratensis
Authors: Hay R. K. M. , Heide O. M.
Published: April 2006

Vegetative plants of Poa pratensis L. cv. Holt (origin 69°N) raised in short days gave large and significant increases in plant dry weight, plant height and leaf area upon exposure to continuous light, compared with 8‐h short days, at essentially identical daily inputs of radiant energy (8‐h summer daylight ± low intensity extension). For example, by the fourth harvest (after 26, 34 and 46 days at 21, 15 and 9°C, respectively), the dry weights of plants in long days were 81, 163 and 195% greater than those of the corresponding short‐day controls at the respective temperatures. Plant leaf areas in long days were between two and four times as large as control values by the end of the experiment. This was mainly due to increased leaf length caused by long‐day stimulation of cell extension and division. However, the photoperiod did not affect the partitioning of assimilates amongst leaves, culms and stolons. Most of these effects could also be brought about by exogenous gibberellin application to plants in short days. However, in contrast to the effect of long days, gibberellin treatment also induced stem internode elongation even in these vegetative plants. Examination by standard growth analysis procedures revealed that the observed increases in relative growth rate were due primarily to increased net assimilation rate followed, several days later, by increases in leaf area ratio when newly‐emerged leaves began to constitute a significant proportion of the leaf area. It is concluded that these reactions are of great adaptive significance for growth at the marginal temperatures prevailing at high latitudes.
Studies on some factors affecting solasodine contents in tissue cultures of Solanum nigrum
Authors: Bhatt P. N. , Bhatt D. P. , Sussex I.
Published: April 2006

Tissue cultures of Solanum nigrum L. were initiated from leaf explants on a solid medium containing inorganic salts [Murashige and Skoog (1962), Physiol. Plant. 15: 473–497], vitamins [Gamborg et al. (1968) Exp. Cell Res. 50:151–158], 3% sucrose and combinations of indoleacetic acid and benzyladenine. Solasodine content was determined in differentiated and undifferentiated (callus) tissues by a colorimetric technique and thin layer chromatography. Indoleacetic acid and sucrose in the medium markedly stimulated the production of solasodine in the tissue cultures. In the cultures grown in darkness the differentiated tissues produced significantly more (anywhere from 1.5 to 10 times) solasodine than the callus in several media. When sucrose concentration was increased to 4, 6 and 10% level in the medium which contained 10 μM benzyladenine as the sole growth regulator, a significant increase of solasodine production in cultures was found.
Possible roles of calcium and ammonium in the development of bitter pit in apple
Authors: Fukumoto Masashi , Nagai Koushiru
Published: April 2006

Apple trees (Malus pumila Mill. var. domestica Fuji/Malus prunifolia rootstock) showed a high susceptibility to bitter pit when supplyed with ammonium salt instead of nitrate (control) in the nutrient solution. When apple fruit was affected by bitter pit, a lower calcium as well as a higher nitrogen and ammonium‐nitrogen contents was observed in the fruit flesh near the calyx end. The activity of the mitochondrial Ca2+‐uptake of the fruit flesh near the calyx end was higher when the tree was grown with ammonium salt than when grown with nitrate. Both the activities of succinate: cytochrome c oxidoreductase and the mitochondrial Ca2+‐uptake per g of tissue were higher in affected fruit than in healthy fruit. Each of chlorpromazine, N‐(6‐aminohexyl)‐5‐chloro‐l‐napthalenesulfonamide (W‐7) and N‐(6‐aminohexyl)‐l‐naphthalenesulfonamide (W‐5), calmodulin antagonists, was infiltrated into the fruit for 20 min under reduced pressure (about 1 × 104 Pa). Few days later, numerous bitter pit‐like spots were observed in both fruit treated with W‐7 and chlorpromazine, while only a few spots were observed after the infiltration with W‐5, a less potent calmodulin antagonist. A possible mechanism for the occurrence of bitter pit is discussed.
Effect of bovine serum albumin on membrane potential in plant mitochondria
Authors: Diolez Philippe , Moreau François
Published: April 2006

The membrane potential in highly coupled potato (Solanum tuberosum L.) mitochondria, as measured by changes in safranine absorbance, was significantly increased by addition of bovine serum albumin. Purification of potato mitochondria on Percoll, in removing 50% of free unsaturated fatty acids, decreased the BSA‐de‐pendent membrane potential. The effect of added linoleic acid and of the natural accumulation of fatty acids during aging was studied. The response of membrane potential to addition of bovine serum albumin appeared to be directly correlated to the amount of free unsaturated fatty acids. Aging in vitro, in releasing free fatty acids, decreased respiratory control and ADP:O ratios and collapsed the membrane potential. During 2–3 h of incubation, addition of BSA completely restored membrane potential and oxidative phosphorylation.

It is concluded that both in fresh and in aged potato mitochondria the effect of bovine serum albumin on oxidative phosphorylation can be ascribed to an effect on membrane permeability to ions. BSA, in binding free unsaturated fatty acids, restored maximal membrane potential. The bovine serum albumin‐dependent membrane potential appears to be a sensitive criterion of the functional integrity of the inner mitochondrial membrane.
Effects of NaCl salinity in vivo and in vitro on ribonuclease activity of Vigna unguiculata cotyledons during germination
Authors: Filho Eneas Gomes , Prisco José Tarquínio , de Paiva Campos Francisco de Assis , Filho Joaquim Eneas
Published: April 2006

Pitiuba bean [Vigna unguiculata (L.) Walp.] seeds were sown in water or. in 0.1 M NaCl. Seedling growth and cotyledon nucleic acid mobilization were delayed by NaCl salinity. The differences in cotyledonary RNase activity between seeds sown in water and in NaCl solutions suggest that salinity delays the activation and/or de novo synthesis of the enzyme. Cotyledon extracts were subjected to gel filtration through Sephadex G‐100, and RNase activity measured. Only one cotyledonary RNase appeared during germination, and salinity did not induce any change in molecular weight of the enzyme. Salinity inhibited 45% of the specific activity of the RNase on the 5th day of the experimental period. The same salt concentration (0.1 M NaCl) added in vitro inhibited only 8 % of the specific activity of the enzyme. This difference may indicate that NaCl in vivo affects mainly the de novo synthesis of the RNase.
Turgor‐ dependent membrane permeability in relation to calcium level
Authors: Enoch Sarai , Glinka Zvi
Published: April 2006

The relationship between the inhibiting effect of Ca2+ and of low turgor pressure on K+ release from fresh‐cut discs of carrot (Daucus carota var. Nantes) storage tissue was studied. A range of Ca2+ concentrations in the tissue was obtained by adding 0.5 mM EDTA or CaSO4 at different concentrations to the medium. Calcium inhibited K+ release in fully turgid cells (2.5 μmol K+ g−1 h−1 in 0.5 mM EDTA vs 0.4 μmol K+ g−1 h−1 in 10 mM CaSO4). Less turgid cells, obtained by equilibration with 0.2 M mannitol, released K+ at only 30% of the rate of the turgid cells, yet the pattern of K+ release as a function of Ca2+ level was similar in both turgid and non‐turgid cells. Removal of calcium by EDTA occasionally injured cell membranes in the fully turgid discs but never in the less turgid ones. In view of the additive effect of Ca2+ and low turgor on K+ release regardless of the treatment order, it is suggested that the two factors exert their effect on membrane permeability independently of each other.
The effect of SAN 9789 and light on the germination of seeds from Taraxacum vulgare
Authors: Widell Karl‐Olof
Published: April 2006

Photoblastic seeds (achenes) of Taraxacum vulgare coll. were treated with a water solution of SAN 9789, 4‐chloro‐5 (methylamino) ‐2‐ (α,α,α‐trifluoro‐m‐tolyl) ‐3(2H) pyridazinone. SAN‐treatment increased the germination in darkness from 0 to 12%. An irradiation for 5 min with red light, giving a germination of 12% for seeds in water only, gave together with SAN treatment a germination of 60%. In both water and SAN, the effect of red irradiation could be reversed by a short irradiation (15 min) of far‐red light. If far‐red light was repeatedly given (5 min per h) it had hardly any effect on germination in water (4% germination), but for seeds in SAN solution, intermittent far‐red light had a stimulating effect (63% germination). If far‐red light was given continuously for 96 h, the germination in water was 1% and in SAN solution 17%. The results in the present paper indicate that SAN may broaden the concentration interval of Pfr for which germination is high.
Kinetics of photoautotrophic growth of Marchantia polymorpha cells in suspension culture
Authors: Katoh Kenji
Published: April 2006

Chlorophyllous, cultured cells of Marchantia polymorpha L. (HYA‐2 cell line) grow actively under photoautotrophic (lithotrophic) conditions. The maximum specific growth rate (μcell) was 0.64 day−1 and the doubling time was 1.08 days under optimum conditions (165 μmol m−2 s−1, 1% carbon dioxide enriched atmosphere, 25°C). The photosynthetic activity was 1.30 μmol CO2‐fixed (106 cells)−1 h−1 [66 μmol (mg chlorophyll)−1 h−1] in the exponential phase. The growth course has two distinct phases, an exponential and a linear one. The exponential phase is observed as long as the population density is sufficiently low (less than 7.9 × 106 cells ml−1), so that practically all individual cells directly receive the full incident light. The effect of light on the specific growth rate is a linear function of photon flux density. Linear growth occurs after the population density is so high that the incident light is almost completely absorbed by the cell suspension. The growth rate is a logarithmic function of photon flux density, in contrast to the specific growth rate, and saturates at high photon flux densities. The conditions of maximum growth, however, are not wellbalanced between cell mass production and cell division. Therefore, the maximum growth does not continue for a long time.