bluuebunny/crossref_metadata_2025_split huggingface dataset:
A comparison between 3,5‐diiodo‐4‐hydroxybenzoic acid and 2,3,5‐triiodobenzoic acid. II. Effects on uptake and efflux of IAA in maize roots
Authors: Martin Hilary V. , Beffa Roland , Pilet Paul‐Emile 
Published: May 2006

An explanation is sought for the inhibition of maize root growth and gravireaction brought about by treatment with 3,5‐diiodo‐4‐hydroxybenzoic acid (DIHB). The effects of DIHB and 2,3,5‐triiodobenzoic acid (TIBA) on the uptake and efflux of [3H]‐indol‐3yl‐acetic acid (IAA) were tested using segments prepared from the elongation zone (2 to 7 mm region) of maize (Zea mays L. cv. LG11) roots.The uptake of [3H]‐IAA (21 nM) by root segments incubated in buffered solutions (pH 5.0) was measured over a 5‐min time‐course. No significant effect of DIHB at 100 μM was observed, whereas TIBA at 10 μM slightly stimulated the uptake of [3H]‐IAA. This experiment was repeated with the addition of non‐radioactive IAA (total IAA concentration 1.0 μM). Up to 3 min DIHB (100 μM) had no significant effect, but thereafter a slight stimulation of IAA net uptake was observed. Treatment with TIBA (10 μM) stimulated the accumulation of IAA in the segments.The effects of DIHB (10, 50, 100 μM) and TIBA (10 and 50 μM) on the efflux of [3H]‐IAA from segments that had been pretreated in [3H]‐IAA (22 nM) were then tested. Treatment with DIHB or TIBA at pH 5.0 inhibited IAA efflux; the inhibition by TIBA was more marked than that produced by DIHB. This experiment was repeated using DIHB (10, 50, 100 μM) buffered at pH 6.0, and an inhibition of IAA efflux was again observed.Both DIHB (10 μM) and TIBA (10 μM) inhibited the binding of [3H]‐NPA to a 5000–48000 g membrane fraction prepared from whole maize roots. The effects of the two substances were similar: 40% inhibition of specific binding by DIHB and 41% inhibition by TIBA. This indicates that DIHB, like TIBA, binds to the N‐1‐naphthyl‐phthalamic acid‐sensitive carrier for IAA efflux.It is concluded that DIHB, like TIBA, inhibits IAA transport at the level of efflux. The similarity between DIHB and TIBA as regards chemical structure and their inhibitory effects on IAA efflux and NPA binding strongly suggest that they act on the same carrier for IAA efflux across the plasmalemma.
Regulation of monocarpic senescence of Brassica campestris by the developing pods
Authors: Biswas A. K. , Mandal S. K. 
Published: May 2006

Senescence of Brassica campestris L. cv. B‐9 was studied with regard to seed maturation and source‐sink relationships. In normal control plants leaf senescence (as determined by the change in chlorophyll level) started and proceeded in a progressive manner from base to apex during the period of early pod setting. Complete yellowing of the leaves occurred well before the seed maturation and pod wall senescence. The pod wall always senesced before the attainment of final seed weight. In two different sets of acrocarpous plants containing 65 pods and 10 pods, respectively, leaf senescence was delayed during the pod filling period. It started non‐sequentially after complete yellowing and senescence of the pod wall. The degree of leaf senescence at the post‐pod filling stage was almost proportional to the number of pods present. When peduncles of the acrocarpous 10‐podded plants were removed after the pod filling stage of the plant, leaf senescence was delayed compared to plants whose pedicels were removed, although the senescence pattern of the upper three leaves was nonsequential in both cases. Defruiting at an early stage of development delayed leaf senescence, although the pattern of such senescence remained unaltered (i.e. nonsequential). Defoliation hastened the seed‐filling process and pod wall senescence. Plants containing fewer pods had higher average seed weight, although yield per plant was reduced.These results suggest that the pod wall serves as a temporary as well as intermediary storage organ and that foliar senescence is not directly related to seed maturation. The possible cause of uncoupling between foliar senescence and seed development is discussed.
The effect of different growth conditions on dark and light carbon assimilation in Littorella uniflora
Authors: Madsen Tom Vindbæk 
Published: May 2006

The effect of long‐term exposure to different inorganic carbon, nutrient and light regimes on CAM activity and photosynthetic performance in the submerged aquatic plant, Littorella uniflora (L.) Aschers was investigated. The potential CAM activity of Littorella was highly plastic and was reduced upon exposure to low light intensities (43 μmol m−2 s−1), high CO2 concentrations (5.5 mM, pH 6.0) or low levels of inorganic nutrients, which caused a 25–80% decline in the potential maximum CAM activity relative to the activity in the control experiments (light: 450 μmol m−2 s−1; free CO2: 1.5 mM). The CAM activity was regulated more by light than by CO2, while nutrient levels only affected the activity to a minor extent. The minor effect of low nutrient regimes may be due to a general adaptation of isoetid species to low nutrient levels.The photosynthetic capacity and CO2 affinity was unaffected or increased by exposure to low CO2, irrespective of nutrient levels. High CO2, low nutrient and low light, however, reduced the capacity by 22–40% and the CO2 affinity by 35‐45%, relative to control.The parallel effect of growth conditions on CAM activity and photosynthetic performance of Littorella suggest that light and dark carbon assimilation are interrelated and constitute an integrated part of the carbon assimilation physiology of the plant. The results are consistent with the hypothesis that CAM is a carbon‐conserving mechanism in certain aquatic plants. The investment in the CAM enzyme system is beneficial to the plants during growth at high light and low CO2 conditions.
Sensitivity of selected Frankia isolates from Casuarina, Allocasuarina and North American host plants to sodium chloride
Authors: Dawson Jeffrey O. , Gibson Alan H. 
Published: May 2006

Three experiments examined the effects of NaCl concentrations 0 to 500 mM on the growth of isolates of Frankia from Casuarinaceae and selected North American host plants. Four Casuarina isolates grew well in defined medium (pyruvate‐BAP) but not in a yeast extract medium. Conversely the non‐Casuarina isolates preferred the yeast‐extract medium, although two of them grew in the defined medium. When grown in their preferred medium, the Casuarina isolates were little affected by NaCl concentrations up to 200 mM but did not grow at 500 mM. The non‐Casuarina isolates, with the exception of an isolate from Purshia tridentata. were severely affected above 50 mM NaCl.Nitrogenase activity (C2H2 reduction) by the non‐Casuarina isolates could not be detected in low‐N medium although protein determinations indicated that a low level of nitrogen fixation had occurred. All four Casuarina isolates showed nitrogenase activity in culture, up to 200 mM NaCl, although at that concentration of NaCl, growth was affected more than that of cultures in N‐supplemented medium. All four strains showed a marked increase in nitrogenase activity up to 72 h after the addition of C2H2, with the magnitude of the effect and their subsequent behaviour being strain dependent.The results indicate that the isolates of Frankia from Casuarina and Allocasuarina, and that from Purshia tridentata, are more tolerant of NaCl than isolates from species not normally growing under sodic conditions. They provide optimism that these strains could successfully establish in saline soils if introduced with species of host plants tolerant to these soils.
Effect of photoperiod and temperature on the development of frost hardiness in three Alnus species
Authors: Tremblay Marie‐Francine , Lalonde Maurice 
Published: May 2006

The influence of short day and low temperature on cold acclimation of A. crispa (Ait.) Pursh, A. glutinosa (L.) Gaertn. and A. rubra Bong, was investigated. Two clones of each species originating from in vitro propagation were exposed to three daylength/temperature treatments. Periodically plantlets were exposed to controlled freezing temperature in order to evaluate their level of frost hardiness.Short day (SD) and cold temperature (CT) and long day (LD) and cold temperature (CT) were the most effective treatments for the development of frost hardiness in shoots and roots of the three species tested. Short day (SD) and warm temperature (WT) induced a significant increase in hardiness in shoots of all three species. However, this treatment did not trigger root hardening. A. crispa was found to be the hardiest species followed by A. glutinosa and A. rubra. Intraspecific variation was observed between the two A. glutinosa clones. A glutinosa clone AG8, a Russian provenance, showed a greater freezing resistance than A. glutinosa clone AG2, a German provenance.
Hydrogen metabolism of Casuarina root nodules: A comparison of two inoculum sources
Authors: Sellstedt Anita , Winship Lawrence J. 
Published: May 2006

Hydrogen metabolism was studied in three Casuarina species, C, equisetifolia Forst., C. glauca Sieb. ex. Spreng. and C. obesa Miq., either inoculated with the pure Frankia culture HFP CcI3 or inoculated with a crushed nodule inoculum made from C. glauca nodules. Nitrogenase (EC 1.7.99.2) activity and hydrogen evolution was measured on intact plants, while hydrogen uptake was measured on excised nodules and in nodule homogenates.Nitrogenase activity was highest in C. glauca inoculated with C. glauca nodules, while no hydrogen evolution was detected. Hydrogen evolution was highest in the symbiosis between C. equisetifolia and HFP CcI3, but the nitrogenase activity showed intermediate values compared to the other symbioses. Measured at a concentration of 93 μM H2, H2 uptake was highest in C. glauca inoculated with the C. glauca inoculum. H2 uptake activity in homogenates was 83% of the intact nodule rate. With phenazinemethosulfate as the electron acceptor, H2 uptake by nodule homogenates showed typical Michaelis‐Menten kinetics with a Km of 21.3 μM for H2.The data presented here indicate a host plant effect on the endobiont which alters the hydrogen metabolism.
The abilities of three Frankia isolates to nodulate and fix nitrogen with four species of Casuarina
Authors: Rosbrook P. A. , Bowen G. D. 
Published: May 2006

Three isolates of Frankia from nodules of Casuarina sens, strict. (JCT287. JCT295 and 20607) were compared in their abilities to nodulate and fix N, when associated with four species of Casuarina (C. cunninghamiana Miq., C. equisetifolia Forst., C obesa Miq. and C. glauca Sieb. ex Spreng) growing in a N‐deficient soil.All three Frankia isolates nodulated each of the four species of Casuarina. At 27 weeks after inoculation, growth (dry weight) of inoculated plants was 3.6 to 5.0 times greater than that of uninoculated plants. There were no significant differences in plant dry weight, the N concentration of shoots or roots, or the amount of N, fixed per plant among the Frankia isolates for each of the species of Casuarina studied. The infectivity and effectiveness in N, fixation of Frankia strain JCT287 with C. cunninghamiana was similar when two different defined media were used for culture of the inoculum.
Influence of growth retardants on the internode and ethylene production of sunflower plants
Authors: Sauerbrey EIke , Grossmann Klaus , Jung Johannes 
Published: May 2006

The growth‐retarding activity of the norbornenodiazetine tetcyclacis and the di‐oxanylalkenyl triazole LAB 150 978 as well as the ethylene‐forming compounds 2‐chloroethyl‐phosphonic acid (ethephon) and 1‐amino‐cyclopropane‐l‐carboxylic acid (ACC) on stem histogenesis and ethylene production of sunflower plants (He‐lianthus annuusL. cv.Spanners Allzweck) has been studied. The shoot growth of plants hydroponically grown and treated was reduced by the compounds. The shortening in the length of the 1st internode caused by tetcyclacis and LAB 150 978 was mainly induced by inhibition of cell division (the internode possessed fewer cortical cells per cell file). In contrast, ethephon and ACC decreased internode elongation mainly by reducing the rate of cell enlargement.The ethylene production of sunflower seedlings cultivated on agar nutrient medium rose with increasing concentrations of ethephon and ACC, the shoot length of the plants being progressively reduced.Tetcyclacis and LAB 150 978 inhibited both the formation of ethylene and shoot growth. It is suggested that in contrast to ethephon and ACC, tetcyclacis and LAB 150 978 do not achieve their growth‐retarding effect by influencing the production of ethylene.
Hydroxamate‐activated peroxidases in potato tuber callus. Interaction with the determination of the cytochrome and the alternative pathways
Authors: van der Plas Linus H. W. , Gude Henk , Wagner Marijke J. 
Published: May 2006

In potato (Solatium tuberosum L. cv. Bintje and Doré) callus a very active hydrox‐amate‐stimulated NADH‐dependent O2‐uptake develops during the growth of the callus, which is caused by a peroxidase. More than 95% of the peroxidase activity is found in the 40000 g supernatant. The total activity may be as high as 1000 times the respiratory acitivity of the callus tissue. At least two fractions, obtained by Sephadex gel filtration, can be distinguished showing this peroxidase activity, one of about 15 kDa and one > 50 kDa.The main properties of both fractions are:a) Hydroxamate at 0.2–0.5 mM gives half‐maximal stimulation. Maximal stimulation is observed with 1–3 mM benzhydroxamate (BHAM) and 1–15 mM salicylhydroxamate (SHAM). Higher concentrations, especially of BHAM, give less or no stimulation.b) Hydroxamates are not consumed during the reaction.c) Both NADH and NADPH can serve as the electron donor for the reaction. The affinity for NAD(P)H is very low (Km near 10 mM). In the absence of hydroxamates NAD(P)H is only slowly oxidized, with an even lower affinity.d) The peroxidase can carry out two reactions: an O2‐consuming and a H2O2‐consuming reaction. In both reactions one NAD(P)H is consumed. In the first reaction H2O2 is formed which can be consumed in the second reaction, resulting in an overall stoichiometry of 2 NADH consumed for each O2 molecule and in the production of H2O.e) The reaction is completely blocked by cyanide, superoxide dismutase (EC 1.15.1.1) and (excess) catalase (EC 1.11.1.6), but not by antimycin A or azide. This peroxidase‐mediated O2‐uptake might interfere with respiratory measurements. In experiments with isolated mitochondria this interference can be prevented by the addition of catalase to the reaction mixture. The use of high concentrations of hydroxamate is not allowed because of inhibitory effects on the cytochrome pathway. In intact callus tissue hydroxamates only stimulate O2‐uptake in the presence of exogenous NADH. In vivo the peroxidase does not appear to function in O2‐uptake, probably because of its localization (at least partly in the cell wall) and/or its low affinity for NADH. The use of hydroxamates in the determination of cytochrome and alternative pathway activity is discussed.
Endogenous polyamines in apple and their relationship to fruit set and fruit growth
Authors: Biasi Rita , Bagni Nello , Costa Guglielmo 
Published: May 2006

The distribution of free and bound polyamines was investigated from blooming until harvest on flower, fruitlets and fruits of Malus domestica Borkh cv. Golden Delicious, Relationships between polyamines and fruit set and growth were also investigated. The level of free polyamines was high only during the first weeks after full bloom and then decreased gradually. The amount of bound trichloroacetic acid‐insoluble polyamines was much higher than free polyamines. Bound spermine in particular showed a high value for almost 40 days after full bloom, while spermidine and putrescine were no longer detectable even a few days after full bloom.In relation to fruit set, it was possible to observe that abscission peaks took place when free polyamine levels were low or decreasing. Insofar as fruit growth is concerned, the most substantial variations in polyamine levels occurred very early in the season when fruit dry weight and protein amount were also changing rapidly and fruit diameter was almost impossible to measure.
Application of growth analysis to physiological studies involving environmental discontinuities
Authors: Wickens Linda K. , Cheeseman John M. 
Published: May 2006

In this report we consider the application of growth analysis techniques in environmental physiology, with particular concern for their ability to produce results which can be integrated with studies of short‐term metabolic responses at finer levels of organization. For purposes of illustration, we use responses of Spergularia marina (L.) Griseb. and lettuce (Lactuca sativa L. cv. Black‐seeded Simpson) to changes (environmental discontinuities) in the composition of a solution culture medium. Initial emphasis is on the use of cubic spline methods. It is concluded that while these may give apparently good fits to growth data, differentiation for determination of relative growth rate (RGR), and further transformation for such parameters as net uptake rate (NUR), are of questionable applicability. An alternative analysis based on the discrete estimation of RGR is considered.In any study, the requirements for both statistical and physiological confidence must be reconciled. In practice, and in the absence of mechanistic frameworks to which the results can be modeled, this is best accomplished by strictly adhering to the mathematical guideline that no more elaborate a description be applied than can be statistically justified.
Isolation and enzymological characterization of infected and uninfected cell protoplasts from root nodules of Glycine max
Authors: Kouchi Hiroshi , Fukai Katsuhiko , Katagiri Hiroki , Minamisawa Kiwamu , Tajima Shigeyuki 
Published: May 2006

Infected and uninfected cell protoplasts were isolated from soybean (Glycine max L. Merr. cv. Akisengoku) root nodules and purified by the use of nylon mesh filters and discontinuous Percoll gradients. Activities of the enzymes involved in carbon and nitrogen metabolism were measured in cytoplasmic fractions of purified protoplasts, as well as in the bacteroids isolated from infected cell protoplasts and in the cortical tissues after enzymatic digestion of the central zone of the nodules.A high degree of purity of both infected and uninfected cells was demonstrated by microscopic observations and assays of β‐hydroxybutyrate dehydrogenase (EC 1.1.1.30) and uricase (EC 1.7.3.3) activities and leghemoglobin contents.As a whole, higher specific activities of enzymes of glycolysis were found in the cortical and uninfected cells than in the infected cells. The activities of glycolytic enzymes were extremely low in the bacteroids. Invertase (EC 3.2.1.26) was highly localized in the cortex. However, activity of sucrose synthase (EC 2.4.1.13) was highest in the cytosol of infected cells. Alcohol dehydrogenase (EC 1.1.1.1) and lactate dehydrogenase (EC 1.1.1.27) activities were much higher in uninfected than in infected cells. Specific activities of enzymes for nitrogen assimilation, that is, glutamine synthetase (EC 6.3.1.2), glutamate synthase (EC 1.4.1.14), aspartate (EC 2.6.1.1) and alanine (EC 2.6.1.2) aminotransferase were several‐fold higher in uninfected cells than in the infected cells.The results are discussed in relation to the possible cellular organization of carbon and nitrogen metabolism in soybean root nodules.
Auxin‐induced delay of abscission: The involvement of calcium ions and protein phosphorylation in bean explants
Authors: Poovaiah B. W. , Friedmann M. , Reddy A. S. N. , Rhee J. K. 
Published: May 2006

Treatment with Ca2+ channel blockers such as lanthanum chloride and verapamil promoted abscission in pulvinar explants of bean (Phaseolus vulgaris L. ev. Pirate). In addition, auxin‐induced delay of abscission was markedly reduced in the presence of Ca2+ channel blockers. In vitro phosphorylation studies were performed using membrane preparations (130000 g pellet) from freshly excised as well as auxintreated and control (minus auxin) pulvinar sections. Auxin‐treated sections showed a 66 kDa phosphoprotein as well as Ca2+ ‐dependent phosphorylation that were not observed in control explants.Coomassie blue stammg of soluble proteins (130000 g supernatent) separated on SDS‐PAGE revealed the presence of 62. 55 and 47 kDa polypeptides only in the freshly excised pulvini. However. no distinct changes were observed in soluble protein profile between auxin‐treated and control explants. When soluble proteins were phosphorylated in vitro, Ca2+ promoted the phosphorylation of 92, 55. 40 and I7 kDa polypeptides only in freshly excised pulvmi. Ca2+‐dependent phosphorylation of soluble proteins was not observed in either the control or auxin‐treated explants. In addition. in vivo phosphorylation studies were performed using freshly excised. auxrn‐treated and control explants. Freshly excused segments and auxin‐treated ex‐plants showed similar phosphoproteins, which were different from those observed mcontrol.
Cytological abnormalities and aberrant microtubule organization during early divisions in mesophyll protoplast cultures of Medicago sativa and Nicotiana tabacum
Authors: Meijer Eltjo G. M. , Keller Wilfred A. , Simmonds Daina H. 
Published: May 2006

Karyokinetic and cytokinetic irregularities were examined in cultured mesophyll protoplasts of Medicago sativa L. cv. Regen S and Nicotiana tabacum L. cv. Wisconsin 38 during the early cell divisions. Spindle anomalies, laggine chromalids during anaphase, displaced phragmoplasts during telophase and incomplete cross‐walls following the completion of cytokinesis were scored in these cultures. The abnormalities, however, occurred at low frequencies when compared to those found in suspension culture‐derived protoplasts of Vicia hajastana. It is suggested that abnormalities are reduced because the mesophyll protoplasts regenerate a substantial cell wall prior to the onset of the first division.An entirely different class of cytological aberration occurring in 40–50% of the cells was caused by localized protruding of the cytoplasm (budding). The nucleus was often positioned at the site of constriction of the bud. The association of budding with mitosis has led us to postulate a mechanism which may be a cause of budding and to suggest a possible way to prevent it.
Effect of temperature on electron transport activities of glutaraldehyde‐fixed pea thylakoids
Authors: Nolan William G. 
Published: May 2006

Temperature‐induced changes in Hill activity of glutaraldehyde‐fixed pea (Pisum sativum L. cv. Alaska) thylakoids have been examined. Using ferricyanide as electron acceptor, a temperature‐induced change occurred at ca 12–14°C for both control and fixed thylakoids. In contrast to the controls, fixed thylakoids not only showed a change in slope of the Arrhenius plots but also a discontinuity which has not been observed in previous studies. A drop in activity coincided with the decrease in slope: the extent of the reduction depended on the concentration of glutaraldehyde used for fixation. Using a lipophilic electron acceptor, a temperature‐induced change also occurred at 12–14°C, but there was no reduction in activities of fixed thylakoids at temperatures above the change in slope.The results indicate that a temperature‐induced change in fixed thylakoids restricts the access of ferricyanide to its reductant(s) in the membrane but that fixation does not affect the temperature‐induced change per se. The results confirm that temperature has a general effect on the functioning of thylakoid membranes. The data demonstrate that calculations of the extent of inhibition by glutaraldehyde of Hill activity with ferricyanide should take into account the temperature at which assays are performed.