bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cyclic adenosine‐3′: 5′‐mono phosphate: Production and extracellular release from green and blue‐green algae
Authors: FRANCKO DAVID A. , WETZEL ROBERT G. 
Published: April 2006

AbstractCellular and extracellular levels of cAMP were analyzed in the blue‐green algae Microcystis aeruginosa, Anabaena flos‐aquae, and Synechococcus leopoliensis and the green algae Chlorella pyrenoidosa, Cosmarium botrytis, Pandorina morum, Scenedes‐mus communis, and Pediastrum biradiatum. On the basis of chromatographic analyses, and several biochemical assays, each alga produced cAMP and released it into the medium. Cellular cAMP (92–394 pmol g−1) and extracellular cAMP (8–440 pmol liter−1) varied greatly among species.
The effect of temperature on the germination‐promoting activities of cytokinin and gibberellin applied to celery seeds (Apium graveolens)
Authors: BIDDINGTON NORMAN L. , THOMAS TUDOR H. , DEARMAN ANTHONY S. 
Published: April 2006

AbstractCelery seeds (Apium graveolens L. cv. Lathom Blanching) made dormant by high temperature pretreatment (28–40°C) during imbibition in the dark, germinated at 22°C in the light after treatment with benzyladenine (BA). This BA‐induced promotion of germination increased with increasing pre‐treatment temperature from 32 to 38°C. whether BA was given before or after pretreatment.A mixture of gibberellins A4 and A7 (GA4/7) given before a 4 day high temperature pretreatment at 32°C partially inhibited the germination‐promoting activity of GA4/7 given after. It is suggested that gibberellin induces the formation of a thermola‐bile product which is necessary for germination, the precursor of which has a limited source.
Peanut and horse radish peroxidase isoenzymes. Intraspecies and interspecies immunological relatedness
Authors: CAIRNS EWA , HUYSTEE ROBERT B. VAN , CAIRNS WILLIAM L. 
Published: April 2006

AbstractThe presence of structural similarities in peroxidase isoenzymes was demonstrated by the technique of crossed immunoelec‐trophoresis. Isoenzymes found in the medium of peanut (Arachis hypogaea L.) cells grown in suspension culture were immuno‐precipitated in different arc systems according to the extent of relatedness of their antigenic determinants. Cross reactivity between isoenzymes in the medium was confirmed by demonstration that antibodies raised against only the glycoprotein fraction of the medium peroxidases would react also with the non‐glycosylated peroxidase isoenzymes that did not have affinity for Concanavalin A. Different peroxidase isoenzsmes from peanut leaves, peanut calli and peanut suspension cell medium share common antigenic determinants. Antibodies against peroxidase antigens from a different species, horse radish (Armoracia lapathifolia Gilib.), reacted with peroxidase antigens in the peanut cell medium. The results suggest a similarity of peanut peroxidases to horse radish peroxidase and. therefore, an evolutionary conservatism in peroxidase structure. The results also point to the potential utility of immunochemistry, including microcomplement fixation, to quantitate the structural similarities of peroxidase isoenzymes.
Changes in water potential and its components during shoot formation in tobacco callus
Authors: BROWN DANIEL C. W. , THORPE TREVOR A. 
Published: April 2006

AbstractShoot‐forming tobacco (Nicotiana tabacum L. cv. Wisconsin 38) callus maintains more negative water and osmotic potentials and more positive pressure potentials than non‐shoot‐forming callus. These differences are apparent by day 2 in culture, prior to any visible histological changes in the tissue, and are maximum by day 6, which is at the time of the first visible changes leading to organized development. The differences are maintained throughout the 28‐day culture period and are also evident in tissues grown under both low and high sucrose levels. Mannitol can partially replace sucrose in the maintenance of the above differences. It is suggested that the high water, osmotic and pressure potentials in the shoot‐forming tissue are maintained via (1) the accumulation of malate early in culture, (2) the presence of free sugars from the medium throughout the culture period, and (3) the degradation products of starch at the time of meristemoid formation and the succeeding organogentic phases.
In vitro phyllomorphic regeneration of shoot buds and shoots in Picea abies
Authors: JANSSON EVA , BORNMAN CHRIS H. 
Published: April 2006

AbstractNeedles (10–15 mm) of frost‐hardened 20–22‐week‐old (physiological age equivalent to 1 year) plants of Picea abies L. excised just after flushing, were induced to form adventitious shoot buds and shoots on media supplemented with BAP (6‐benzylaminopurine) and NAA (1‐napthaleneacetic acid). The addition of nanomolar concentrations (0.5–50) of NAA combined with 1–10 μM BAP considerably stimulated formation of pseudobulbils on the basal to mid‐part of the needle axis, as well as their subsequent development into shoot buds and shoots. On a medium containing 10 μM BAP, pseudobulbils that formed at the needle base did not develop further, but became necrotic and died with the omission of NAA. With 5 μM BAP + 50 nM NAA the initial phase of development was slow, but later showed good response and up to 22% of the needles produced shoot buds. Two to three shoots per needle could be excised and subcultured individually onto fresh media. It is concluded that the level of endogenous auxin decreases progressively from the needle's base to its tip, so that that concentration of exogenous auxin (50 nM NAA) which promotes pseudobulbil and shoot‐bud formation part‐way along the needle axis, simultaneously inhibits their induction at the needle base.
Effect of light intensity on the activity of starch synthesizing enzymes and starch synthesis in developing wheat grains
Authors: Mengel Konrad , Judel Günther‐Klaus 
Published: April 2006

The activities of starch synthesizing enzymes were investigated in wheat grains (Triticum aestivum L. cv. Kolibri) throughout the grain development period. Starch phosphorylase (E.C. 2.4.1.1.) activity was especially high during the early period of grain development, while starch synthase I (ADP glucose α‐glucan 4‐α‐glucosyl‐transferase, E.C. 2.4.1.21) had a maximum activity during the later stage of grain filling. The synthetic potential of starch phosphorylase measured in vitro was about 16 times higher than the quantity of starch actually produced. It is therefore suggested that starch phosphorylase is of substantial importance in grain starch synthesis, particularly in the early period of grain growth. The synthetic potential of starch synthase I measured in vitro made up 25 to 50% of the starch production and the synthetic potential of starch synthase II (UDP glucose α‐glucan 4α‐glucosyl‐transferase. E.C. 2.4.1.11) only about 5%.Reducing light intensity (shading) during the grain filling period depressed grain growth and starch production by about 20%. Starch phosphorylase was not significantly affected by the reduced light intensity if enzyme activity is calculated on unit grain weight and not as activity per grain. Starch synthase I activity, however, was depressed by shading during the later stage of grain development. The depressed starch production found under low light conditions, however, cannot only be explained by an affected starch synthase I activity, but probably was also related to other still unknown factors limiting grain growth under low light conditions. The poor starch production in the shaded plants was not due to an insufficient supply of assimilates.
Factors affecting the inhibitory effect of indolylacetic acid on root formation in pea cuttings
Authors: Eliasson Lennart 
Published: April 2006

Indol‐3yl‐acetic acid (IAA) present in the rooting solution for 1–4 days appreciably decreased the number of roots subsequently formed in pea stem cuttings. Removal of the lowest 10 mm of the cutting base after IAA treatment abolished the inhibitory effect of IAA almost completely. The number of roots formed from the remaining part of the base internode after excision of the basal centimeter of the internode 4 days after the cuttings were taken was similar to that of the control. It is concluded that the first root primordia, which develop near the cut surface, have an inhibitory influence on development of further roots. The inhibitory effect of IAA may be explained as a strengthening of this dominance phenomenon.Addition of charcoal to the rooting solution delayed the appearance of roots but increased the number of roots developed during a standard rooting period. Adsorption of stimulatory and inhibitory compounds at the surface of the cutting base is believed to be the reason for these results as no evidence of accumulation of inhibitory compounds in the solution was obtained. Charcoal reversed the inhibitory effect of IAA if added after the IAA treatment. This reversal was almost complete if the IAA treatment lasted for one day only but decreased drastically if the IAA treatment was extended over 4 days.
The ultrastructure of Anabaena azollae in Azolla pinnata
Authors: Neumüller Magnus , Bergman Birgitta 
Published: April 2006

The water fern Azolla pinnata R. Br. was collected in Northwestern India and its structure was examined using scanning and transmission electron microscopy. Emphasis was given to the symbiotic cyanobacterium. Anabaena azollae, and to its relationship to the hairs of the leaf cavities. The cyanobacterial filaments are loosely arranged and often adhere to the protruding hairs and the folded cell walls of the cavities. The vegetative cells show a typical bilayered cell wall. Thylakoids are few and evenly dispersed in mature vegetative cells and appear to lack phycobilisomes. Clusters of polyglucoside granules are distinguished between the thylakoids. Thylakoid membranes are often seen forming whirls and lattices. Polyhedral bodies (carboxysomes) appear particularly frequently in younger cells and in the proximity of polyphosphate bodies. Presence of structured granules, often positioned at both sides of the cross‐wall of neighbouring vegetative cells, suggest a positive nitrogen balance. A high frequency of heterocysts is noted, while spores are not observed.The outer cell wall of the unbranched, mostly two‐celled, hairs shows frequent invaginations. The cytoplasma of the mature hair contains numerous organelles, and is penetrated by an electron transparent network with blebs and vesieles appearing. The exchange of metabolites between the symbiotic partners is discussed in relation to the structures noted.
Water relations of cotton plants under nitrogen deficiency
Authors: Radin John W. 
Published: April 2006

Nitrogen deficiency in cotton plants (Gossypium hirsutum L.) increased the threshold water potentials for both stomatal closure and leaf senescence (defined as loss of chlorophyll and protein) during drought. These studies attempted to answer two questions: (1) What is the basis for the N/water interaction on senescence? (2) Is there a direct relationship between stomatal closure and senescence?Young and old leaves from N‐deficient and N‐sufficient plants maintained their relative sensitivities to water stress when excised leaf discs were floated on solutions of polyethylene glycol in dim light. In this leaf disc system, both leaf aging and N deficiency increased the threshold water potential for senescence. Leaf aging and N deficiency also decreased the concentration of exogenous abscisic acid necessary to initiate senescence in discs. A role for cytokinins in controlling senescence could not be clearly shown.In young leaves of both N‐deficient and N‐sufficient plants, stomata closed at water potentials much higher than those causing senescence. During leaf aging, the water potentials causing senescence increased more than those causing stomatal closure. The two processes thus occurred at about the same potentials in the oldest leaves. These data argue against a general cause‐and‐effect relationship between stomatal closure and senescence. Rather, each process apparently responded independently to absicsic acid accumulated during drought.
Comparative analysis of the effects of fusicoccin (FC) and of its derivative dideacetylfusicoccin (DAF) on maize leaves and roots
Authors: Radice Marco , Scacchi Alessandro , Pesci Piero , Beffagna Nicoletta , Marrè Maria Teresa 
Published: April 2006

In maize (Zea mays L. cv. DEKALB XL 640) leaf discs or root segments fusicoccin (FC) is by about 5‐10 times more active than its derivative dideacetylfusicoccin (DAF) in stimulating proton extrusion and the hyperpolarization of the transmembrane electrical potential (PD). Also the uptake by leaf discs in liquid medium and the affinity for a receptor present in cell free membrane preparations are by 3–5 times greater for FC than for DAF, while a much greater difference (by about two orders) in activity between the two substances is observed for their effects on leaf transpiration.FC reaches in the leaf tissue a concentration much higher than that of DAF. This is interpreted as due to the higher activity of FC in inducing stomata opening, thus accelerating the transpiratory water flow. The long distance translocation of both FC and DAF mainly depends on mass flow. Thus the initial stimulus on transpiration would induces an increase in concentration of the active substance in the reactive tissue, in a kind of autocatalytic cycle, resulting in the amplification of the difference in activity at cell level between the two toxins.The data on the promotion of H+ extrusion and the hyperpolarization of PD confirm the correlation and thus the possible cause‐effect relationship between FC (or its less active derivative DAF) binding to a receptor at the membrane, and the functions studied. The relationships between the “pathological” (transpiration and wilting) and the “physiological” (electrogenic proton secretion) effects of FC and DAF are also in agreement with the view that all of the known effects of FC and of its active derivatives can be explained as consequences of the activation of electrogenic proton extrusion.
Photosynthesis as related to xylem water potential and carbon dioxide concentration in Sitka spruce
Authors: Beadle C. L. , Neilson R. E. , Jarvis P. G. , Talbot H. 
Published: April 2006

Current‐year shoots of Sitka spruce (Picea sitchensis (Bong.) Carr.) were removed from the forest canopy. After steady‐state rates of net photosynthesis were obtained in a leaf chamber, the shoots were excised in air and removed at different times to establish a relationship between net photosynthesis and xylem water potential. The experiment was repeated at five ambient carbon dioxide concentrations.Net photosynthesis remained constant over a wide range of xylem water potential and increased linearly with ambient carbon dioxide concentration between 20 and 300 cm3 m−3. At low water potential net photosynthesis declined at each ambient carbon dioxide concentration and there was little difference in the potential (±0.05 MPa) at which zero photosynthesis was observed.There was a small increase in the CO2 compensation concentration at low xylem water potentials, but calculated mesophyll conductance still declined at low water potential after correction for this change in compensation concentration. Mesophyll conductance reached zero within the same range of water potential as net photosynthesis. The results suggested that the non‐stomatal contribution to the decline of photosynthesis was approximately 30% until almost complete stomatal closure occurred.
Relationship between tracheary element differentiation and the cell cycle in single cells isolated from the mesophyll of Zinnia elegans
Authors: Fukuda Hiroo , Komamine Atsushi 
Published: April 2006

A relationship between tracheary element differentiation and the cell cycle was studied in single cells isolated from the mesophyll of Zinnia elegans L. cv. Canary bird. Almost all nuclei of isolated mesophyll cells were at the 2 C level of DNA, indicating that almost all cells were initially in the G1 phase and that somatic polyploidy was absent. Cultured cells underwent partially synchronous DNA replication at 42 h and mitosis at 54 h of culture, and the first cell cycle time was approximately 58 h.The occurrence and timing of DNA replication and mitosis during cytodifferentiation to tracheary elements were investigated using microspectrophotometry, microfluorometry, tritiated thymidine autoradiography, and serial observation. More than 55% of the nuclei of the immature tracheary elements were at the 2 C level of DNA and were not labeled by continuous feeding with tritiated thymidine, providing clear evidence that these cells differentiated without interventing DNA replication. Some tracheary elements (approximately 30%) were formed after one round of the cell cycle, and others (less than 5%) were formed after passing through the S phase, but without intervening mitosis. All types of tracheary elements appeared simultaneously after 58 h of culture, and their patterns of increase in number were similar. From the results, we propose a hypothesis concerning the relationship between cytodifferentiation and the cell cycle.
Nutrition and growth of birch and grey alder seedlings in low conductivity solutions and at varied relative rates of nutrient addition
Authors: Ingestad Torsten 
Published: April 2006

Birch (Betula verrucosa Ehrh.) and grey alder (Alnus incana Moench) seedlings were grown with varied relative addition rates of all nutrients, up to optimum for vegetative growth. The root medium was basically distilled water to which the nutrients, contained in stock solutions in fixed proportions, were added every second hour and in exponentially increased amounts for consumption during the subsequent period. The nutrient weight proportions previously found to be required in birch (100 N:65 K:13 P) were used in all treatments. However, the nutrient proportions required in grey alder were found to be somewhat different (100 N:50 K:18 P). The use of the required proportions in the additions was important for maintenance of maximum growth, efficient nutrient utilization, and low concentrations in the root medium. Luxury consumption and inefficiency occurred at high concentrations. The results show that the nutrient requirements are sufficiently defined, for different relative growth rates, by the nutrient proportions and the relative addition rate.No clear relationships were found between conductivity or concentration in the root medium and the addition rate, net uptake rate, nutrient status, or relative growth rate. The results are in good agreement with data from low concentration and depletion experiments reported in the literature, showing that non‐limited uptake rates occur down to very low concentrations. Thus, there is strong evidence that concentration has been incorrectly used when applied as the treatment variable for plant nutrition in plant science and cultivation practice. The dominant factors in sub‐optimum and optimum nutrition are the amounts of nutrients available per unit of time, the growth rate, and the nutrient proportions. At low concentration levels, physical factors such as stirring and flow rate of nutrient solution and boundary layer effects are decisive for the rates with which the nutrients become available to the roots. Therefore, at low levels, concentration alone cannot be used as the factor determining nutrient uptake rate. At high levels, concentration is effective as a supra‐optimum factor and increased internal percentage contents cause decreased uptake efficiency, thus counter‐acting the concentration effect.Nitrogen effects dominated the stress indications when the internal nitrogen percentage content decreased from optimum to the level of the treatments in the beginning of the experiments. Leaf deficiency symptoms disappeared and the root/shoot ratio change ceased when nitrogen status stabilized. Strong linear regressions were found between any two of the variables: relative addition rate of nutrients, relative growth rate, and nutrient status.
Fusicoccin structure‐activity relationships: Stimulation of growth by cell enlargement and promotion of seed germination
Authors: Ballio A. , De Michelis M. I. , Lado P. , Randazzo G. 
Published: April 2006

The activity of a number of fusicoccin derivatives and analogues has been assayed on growth by cell enlargement and on proton extrusion in pea (Pisum sativum L, cv. Alaska) internode segments, on growth by cell enlargement in isolated squash (Cucurbita maxima Dechesne in Lam. variety Mantovana) cotyledons, and on germination of light‐requiring lettuce (Lactuca sativa L. cv. Grand Rapids) and of abscisic acid‐inhibited radish (Raphanus sativus L. variety Tondo Rosso Quarantino) seeds. A similar pattern of activity in the different tests was found for most fusicoccin derivatives and analogues. As with fusicoccin, the activity of its derivatives and analogues on growth of pea internodes is paralleled by the activity on the capability of the tissue to acidify the incubation medium.The obtained data are in full agreement with the view that the activity of fusicoccin on different physiological processes depends on its primary activation of a single system, involved in proton extrusion.
Changes in potassium fluxes in cells of carrot storage tissue related to turgor pressure
Authors: Enoch Sarai , Glinka Zvi 
Published: April 2006

The effect of increasing external osmotic pressure on potassium fluxes in aged and fresh‐cut discs of Daucus carota L. storage tissue was investigated. An increase of the external osmotic pressure by 5 bars of mannitol solution increased the rate of K+ net uptake of aged discs to 180% of their control rate. At 3°C and in 0.1 mM azide, in which a net efflux of potassium was observed, the mannitol treatment caused a reduction in the net efflux. In fresh‐cut discs, in which the capability of net influx was rather low and a substantial net release of potassium was noted, the increase in the external osmotic pressure by mannitol caused a 70% inhibition in the net efflux. This effect was also observed at 3°C.Measurements of separate fluxes confirmed the assumption that the mannitol treatment brought about two distinct effects on K+ fluxes: (a) raised the metabolically‐dependent influx and (b) lowered the membrane permeability‐dependent efflux. When a permeating solute (ethylene glycol) was used instead of mannitol, no effect on K+ flux was detectable. Reasons are given for relating the observed changes in K+ fluxes to the reduction in turgor pressure of the cells.
Adventitious rooting in hypocotyls of sunflower (Helianthus annuus) seedlings
Authors: Fabijan Dorothy , Taylor John S. , Reid David M. 
Published: April 2006

The effect of brief application (usually for 3 h) of various growth regulators and their antagonists on the production of adventitious root primordia in sunflower hypocotyls over a 3 day period, was investigated. Gibberellic acid inhibited, while an inhibitor of gibberellin biosynthesis promoted rooting. Low concentrations of cytokinins increased, but higher levels inhibited primordia formation. Auxin was able to stimulate or inhibit root production, depending upon the quantity applied, and triiodobenzoic acid applied to the top of the hypocotyls lowered the rate of root formation.From experiments in which benzyladenine, silver nitrate and benzyl isothiocyanate were supplied to the hypocotyl for various 3 h periods after root removal, we concluded that some of the important events necessary for adventitious root production occur during the first few hours after excision of the original root system. We also suggest that the hypocotyl cells on the first day go through a phase during which primordia production is blocked by endogenous ethylene and on the second day enter a phase during which endogenous ethylene promotes rooting.