bluuebunny/crossref_metadata_2025 huggingface dataset:
Sulfate deficiency stimulates release of dissolved organic matter in synchronous cultures of Scenedesmus obliquus
Authors: Soeder Cart J , Bolze Alfred
Published: April 2006

In synchronous cultures of the green alga Scenedesmus 276–3a suboptmal sulfate supply increases the concentration of dissolved organics considerably. The highest level of extracellular organic substances occurs at sulfate dosages which reduce growth by 50‐70% as compared to control cultures growing under standard conditions. Sulfate deficiency causes increased synthesis of carbohydrate and reduces the production of crude protein and chlorophyll almost simultaneously at incipient sulfur deficiency. Since the concentration of extracellular organic substance rises at the same time, this symptom of partial sulfur deficiency is interpreted as resulting from an imbalance between the production and utilization of photosynthetic products. Part of the excess carbohydrate is retained in the cells.
Growth and nutrition of three Salix clones in low conductivity solutions
Authors: Ericsson Tom
Published: April 2006

The ability of Salix aquatica Smith, S. fragilis L. and S. vlminalis L. to grow in low conductivity solutions was investigated. The effects of four different relative nutrient addition rates on the N, K, P, Ca, and Mg contents of the plants, on concentrations in the media, and on dry matter distribution between roots, stems, and leaves, were measured. No significant and persistent increase of concentration of any element resulting from the daily nutrient additions was measured in the media. Practically all nutrients were consumed by the plants at the same rate and in about the same proportions at which they were supplied. Linear regressions were found between any two of the three factors: relative rate of nutrient supply, nitrogen status, and relative growth rate. High nutrient addition rates favoured leaf development while low nutrient addition rates stimulated root growth. It is concluded that the decisive factor governing the mineral uptake rate in Salix is the rate of nutrient supply and that these clones are well suited for short rotation energy forestry in so far as their ability to absorb the mineral elements efficiently is concerned.
Seasonal variation of leaf tissue elasticity in four forest tree species
Authors: Roberts Stephen W. , Strain Boyd R. , Knoerr Kenneth R.
Published: April 2006

Measures of leaf tissue elasticity were determined by analyzing the turgor pressure‐water content relation developed from pressure‐volume experiments, in four naturally occurring forest tree species. The relation between the bulk tissue elastic modulus and tissue turgor pressure varied by species and varied with state of leaf maturation through the growing season. Although the values of the elastic modulus reported here agree in magnitude with values reported in general for higher plant tissue, the functional dependency of the apparent elasticity on tissue water status was more complex in this study than can be accounted for by current models.
Osmotic adjustment in indoor grown cassava in response to water stress
Authors: Ike I. F. , Thurtell G. W.
Published: April 2006

The water content‐water potential relation in stressed and unstressed cassava (Man‐ihot species) was examined to ascertain (i) the magnitude of osmotic adjustment in response to water stress and (ii) the mechanisms of such adjustments.

Water stress resulted in a displacement of the water content‐potential relation such that at any leaf water potential the water content was higher in the stressed plants. The osmotic potentials of turgid leaves (100% relative water content) were ‐0.97 and ‐1.00 MPa in the unstressed cultivars CMC 9 and MCOL 113 respectively. In the stressed plants, the values were‐1.13 MPa (CMC 9) and‐1.14 MPa (MCOL 113). The 0.14 to 0.16 MPa osmotic potential difference between the stressed and unstressed plants suggests that a stress‐induced osmotic adjustment occurred in both cultivars. The biiSk volumetric elastic moduli at turgor pressures above 0.10 MPa were 9.84 MPa (CMC 9) and 13.58 MPa (MCOL 113) in the unstressed plants. Tbe higher values found in the stressed plants, 14.56 MPa in CMC 9 and 16.91 MPa in MCOL 113, suggest a stress‐induced decrease in cell wall elasticity. Hence, the observed shift in the wafer content‐potential relations in the cassava involved both an osmotic adjustment and a decrease in cell wall elasticity. Increasing the number of stress cycles per plant did not cause a further displacement of the water content‐potential curves.
Manganese depletion in chloroplasts of Quercus rotundifolia during chemical simulation of lichen epiphytic states
Authors: Orús M. Isabel , Estévez M. Filar , Vicente Carlos
Published: April 2006

Incubation of Quercus rotundifolia branches in culture media containing lichen substances isolated from Evernia prunastri thallus produces inhibition of Hill reaction in chloroptasts isolated from the leaves of the branches. Incubation with lichen substances diminishes the amount of chloroplastic manganese through a chelation process. This decrease causes the loss of photosynthetic activity because the Hill reaction is restored upon addition of exogenous manganese to the chloropiasts.
Effect of gibberellic acid on growth and carbohydrate metabolism of developing tubers of potato (Solanum tuberosum)
Authors: Mares D. J , Marscfaner H. , Krauss A.
Published: April 2006

Potato plants (Solanum tuberosum L. cv. Ostara) were grown in aerated water culture in a controlled environment. When the tubers had reached a diameter of 1–3 cm. 14C‐labelled or unlabelled gibberellic acid (GA3) was applied to the surface of the stolons at points approximately 1 crn from the developing tubers, and treatment continued for 10 days. ‐ Significant quantities of GA3 moved into tuber tissue within 2–4 days of hormone application. This influx of GA3 was accompanied by a marked reduction in both the activity of ADPG‐pyrophospharylase and the ratio ADPG‐pyrophosphorylase/starch phosphorylase and an increase in the activity of UDPG‐pyrophosphorylase. Starch phosphorylase activity initially increased slightly but then fell, whereas the activity of starch synthase remained constant throughout the experiment. The soluble sugar composition of the tubers changed qualitatively towards a pattern characteristic of growing stolon tips prior to tuber initiation, but there was no clear evidence of net starch degradation. Changes in the activities of the enzymes were observed prior to noticeable effects of the hormone on tuber growth rate or the development of new stolons at the tuber eyes. ‐ GA3‐ treated tubers imported more 14C from labelled photosynthate than expected on the basis of growth rate. However, the capacity to convert solub#e‐14C to ethaTiol‐insoluble‐14C (predominantly starch) was reduced in comparison with non‐treated tubers. ‐ The observed changes in carbohydrate composition and enzyme activities indicate that GA3 induces a drastic change in potato tuber metabolism towards a pattern characteristic for the termination of the storage process.
Regeneration of whole plants from hypocotyl‐, root‐, and leaf‐derived tissue cultures of the pasture legume Stylosanthes guyanensis
Authors: Meijer E. G. M. , Broughton W. J.
Published: April 2006

Callus cultures were established on Murashige and Skoog medium from seedling hypocotyls and roots of Slylosanlhes guyanensis (Aubl.) Sw. cv. Cook and from leaves of 6‐month‐old) plants. Shoots developed in primary calli derived from seedling tissue with a number of benzyladenine or kinetin and naphthaleneacetic acid combinations. Shoot formation on primary leaf callus, occurred with 2.0 mg/1 benzyladenine and 2.0 or 1.0 mg/l naphthaieneacetic acid. Undifferentiated callus from all three sources was induced and maintained on medium with 2.0 mg/1 kinetin and 2.0 mg/1 2, 4‐dichlorophenoxyacede acid in the dark. Shoot formation and regeneration of whole plants from these calli were achieved at high frequencies. The most successful combination of phytohormones for the induction of shoot development in undifferentiated callus, was 2.0 mg/1 benzyladenine and 1.0 mg/1 naphthaleneacetic acid. The regenerated plants showed no phenotypic abnormalities.
Frost hardiness development in Pinus silvestris seedlings in response to fertilization
Authors: Hellergren J.
Published: April 2006

The effects of different levels of nitrogen on freezing survival, the amounts of chlorophylls and β‐carotene, the ratios Chl a/Chl b, and (Chl a + Chl b)/β‐carotene in hardened and unhardened seedlings of Scots Pine (Pinus silvestris L.) have been investigated. There was. no correlation between frost hardiness and nitrogen content in the unhardened seedlings. However, the hardy seedlings with the highest nitrogen content, showed a decrease in frost hardiness of 3°C. The amounts of chlorophylls and β‐carotene increased for all the treatments during hardening, except for the seedlings that had the highest nitrogen content; so that the effect of fertilizer was more evident in non‐hardened than in hardened plants. The ratios Chl a/Chl b decreased during hardening in all the treatments. This was an effect of a larger increase of Chl b than Chl a. The ratios of Chl a + Chl b/β‐carotene also decreased during hardening except for the plants that were fertilized with the second lowest amount of nitrogen. Since the amounts of Chl a and Chl b increase during hardening the amount of β‐carotene increases even more.

The growth rates of the seedlings were closely related to the nitrogen content for the different treatments. All plants were infected with ectotrophic mycorrhizae, which resulted in an enhancement of ion transportation from the soil to the plants. This is important when the supply of ions is low.
Inhibitory effect of methyl jasmonate and its related compounds on kinetin‐induced retardation of oat leaf senescence
Authors: Ueda Junichi , Kato Jiro , Yamane Hisakazu , Takahashi Nobutaka
Published: April 2006

The senescence‐promoting activities of methyl jasmonate and its related compounds were compared with respect to structure‐activity relationships. The activities were assayed by using oat (A vena saliva L. cv. Victor) leaf segments in the presence of 2 μg/ml kinetin. Dextrorotatory methyl jasmonate prepared from an authentic sample of the racemate mixture was less active than the naturally occurring levorotatory form especially at its low concentrations (0.1 to 2.5 μg/ml). The activity of jasmonic acid, the free acid form of methyl jasmonate, was much less than the methyl ester, and this relationship was true for the other compounds tested. The reduction of the unsaturated bond in the substituent at the C‐2 position and the keto group at the C‐3 position greatly reduced the activity. The length of the n ‐alkyl substituents at the C‐2 position had also a significant effect on the activity. From these results, it is concluded that the important functional groups for the high senescence‐promoting activity of the methyl jasmonate related compounds are the methyl acetate substituent at the C‐l position, the 2′cis‐pentenyl or n‐pentyl group at the C‐2, position and the keto group at the C‐3 position in methyl jasmonate.
Seasonal changes in frost hardiness in cloudberry (Rubus chamaemorus) in relation to carbohydrate content with special reference to sucrose
Authors: Kaurin Ase , Junttila Olavi , Hanson Jürgen
Published: April 2006

Monthly determinations of frost hardiness of cloudberry (Rubus chamaemorus L.) buds and rhizomes were done from October 1978 to October 1979. For buds LT50 (lethal temperature for 50% of the plant material) was calculated from the percentage of bud breaking and for rhizomes from visual estimations of the degree of coloring by triphenyltetrazolium chloride. The frost hardiness varied from—11.5°C in November to—4°C in May to July for buds and from—16°C in January to—3°C in June— July for rhizomes. Dehardening started in February while the plants were still covered with snow. In connection with the determinations of frost hardiness, carbohydrate analyses were done. There was a good correlation between the degree of frost hardiness and the amount of soluble carbohydrates determined with anthrone. Sucrose, determined by gas chromatography, seemed to be the sugar contributing most in this correlation.
Incorporation of label from root‐applied N6[8‐14C]furfiuryIadenine into the guanine nucleotide fraction of pea bud ribonucleic acid
Authors: Morris David A.
Published: April 2006

The pattern of incorporation of label into the nucleotides of axillary bud ribonucleic acid was investigated in Pisum sativum L. cv. Meteor following the application of N6[8‐I4C]furfuryladenine or of [8‐14C]adenine to the root system of decapitated plants and to cultured excised buds. When N6[8‐14C]furifaryladenine was applied to the root system label was confined to the guanine nucleotide moiety of the axillary bud ribonucleic acid; label from [8‐14C]adenine was incorporated preferentially into adenine nucleotide in the molar ratio adenine nucleotide/guanine nucleotide = 3.23. When isolated buds were incubated in media containing [8‐14C]adenine or N6[8‐14C]furfuryladenine, label was incorporated into both purine moieties of the ribonucleic acid. However, the relative incorporation into the guanine nucleotide fraction was considerably greater for N6[8‐I4C]furfuryladenine (adenine nucleotide/guanine nucleotide = 2.23) than for [8‐14C]adenine (ratio = 4.67).

It was concluded that the pattern of metabolism of adenine to guanine and its incorporation into the guanine nucleotide moiety of pea axillary bud ribonucleic acid, is influenced by the presence of a substitution in the N6 position of the adenine base.
Aspects of photoinduction of carotenogenesis in the fungus Verticillium agaricinum
Authors: Hsiao K. C. , Björn L. O.
Published: April 2006

An action spectrum for light induced carotenogenesis in Verticillium agaricinum (Link) Corda (ATCC 24668) was obtained by exposing mycelial pads to monochromatic radiation. Action maxima occurred at 290 (main peak) and 390 nm, and there was a minor peak at 483 nm. The results also showed interaction between the blue and UV light. Blue light partly reversed the UV light induction of carotenogenesis when given after, but not when given before UV light. This implies that there are at least two photoreceptors involved in carotenogenesis in Verticillium, but phytochrome is not likely to be one of them.
Inhibition of cytokinin‐induced plant growth by jasmonic acid and its methyl ester
Authors: Ueda Junichi , Kato Jiro
Published: April 2006

Effects of jasmonic acid, methyl jasmonate and ABA on cytokinin‐induced soybean (Glycine max Merrill cv. Kingen No. 1) callus growth and radish (Raphanus sativus L. cv. Comet) cotyledon growth were studied. Jasmonic acid and methyl jasmonate were powerful inhibitors of kinetin‐ or N‐phenyl‐N′‐(2‐chloro‐4‐pyridyl)urea‐induced soybean callus growth, the former being more effective than the latter, especially at low concentrations (0.45 to 4.5 μM). These compounds could completely eliminate kinetin‐ or N‐phenyl‐N′‐(2‐chloro‐4‐pyridyl)urea‐induced soybean callus growth at 45 μM. At low concentrations ABA had no effect but at 450 μM it completely eliminated callus growth induced by kinetin. Of the compounds tested ABA was the most powerful inhibitor of radish cotyledon growth in the presence or absence of kinetin. Jasmonic acid and methyl jasmonate were much less effective than ABA in this assay system.
Changes in the level of endogenous cytokinin‐like substances in Acer pseudoplatanus embryos during stratification and germination
Authors: Julin‐Tegelman Asa , Pinfield Neville
Published: April 2006

The bioassay used to detect and quantify cytokinin activity was the Amaranthus test. Free cytokinin‐like substances in embryos of Acer pseudoplatanus L. fruits increased during the first 20 d of fruit stratification at 5°C, but subsequently fell rapidly to values well below the amounts present in the embryos of freshly harvested fruits. These lower levels persisted throughout the remainder of a 60 d stratification period. Bound cytokinins fell during stratification from the highest detected levels present in freshly harvested material to values which were lower by about one third. No peaks of bound cytokinin activity were detected at any stage during stratification. In embryos from fruits stored at 17°C and unable to germinate, both free and bound cytokinins remained at a very low level throughout the 60 d period. Embryos from fruits previously stratified for 60 d showed increases in both free and bound cytokinins during the first 24 h of their incubation at 20°C in light, but after longer incubation periods up to 72 h, cytokinin concentrations decreased again to levels similar to those present at the commencement of the incubation period. Determinations conducted in 1979 and 1980 showed quantitative differences, but similar qualitative changes were observed in the two years. Most of the cytokinin activity was associated with compound(s) that co‐chromatographed with zeatin and zeatin riboside.
Allelopathic potential of dry fruits of Washingtonia filifera: Inhibition of seed germination
Authors: Khan M. Ishaq
Published: April 2006

The allelopathic potential of the dry fruits of Washingtonia filifera (L. Linden) H. Wendl. was investigated. Leachates from fruits inhibited the germination of lettuce, wheat, red cabbage and cucumber seeds. The inhibitory effect was partly neutralized by kinetin (20 mg 1−1) and gibberellic acid (50 mg 1−1). The effect of kinetin was more pronounced at 25°C than at 20°C. Substances inhibiting germination were localized in the pericarp of the fruit and were resistant to high temperature.
Effects of sulphur nutrition on nitrogen and carbon metabolism in lucerne (Medicago sativa L.)
Authors: DeBoer David L. , Duke Stanley H.
Published: April 2006

Studies were conducted with one‐year‐old plants of the perennial legume, lucerne (Medicago sativa L.), to determine the effects of various levels of S (0.3, 1.5, and 7.5 mM) on N2‐fixation, photosynthesis, herbage free amino acid pools and protein amino acids, levels of protein, and activities of key enzymes of leaf nitrogen and carbon metabolism. Sulphur deficiencies in the 0.3 mM S treatment, as determined by N:S ratios, did not appear until the second growth cycle. This treatment was severely S‐deficient by the end of the third growth cycle. Sulphur deficiencies did not occur in the other two treatments over three cycles of growth. By the middle of the second growth cycle acetylene reduction rates of plants grown with 0.3 mM S were lower than those of other treatments. At the end of the third growth cycle acetylene reduction rates of the 0.3 mM S treatment were ca. 30–35% that of the other treatments. There was no effect of S‐deficiency on photosynthesis, levels of leaf NADP‐isocitrate dehydrogenase and glutamine synthetase activity, or concentrations of leaf protein over the course of the experiments. Levels of NAD‐glutamate dehydrogenase, NAD‐malate dehydrogenase, and glutamate oxaloacetate trans‐aminase activity and concentrations of free methionine, arginine, urea, and ammonia increased, with S‐deficiency. Boron concentrations were very high (ca. 300 μg/g dry wt.) in S‐deficient plants. The mole percent methiomne in leaf protein decreased slightly and chlorophyll concentration decreased markedly with S‐deficiency. This study suggests that N2‐fixation is affected early during S‐deprivation of lucerne and that subsequent effects of S‐deficiency may be due to loss of fixed nitrogen.
Nitrate reduction in the wildtype and a nitrate reductase deficient mutant of Arabidopsis thaliana
Authors: Braaksma Fietje J. , Feenstra W. J.
Published: April 2006

A chlorate‐resistant mutant B25 of Arabidopsis thaliana (L.) Heinh. was isolated, which has very little or no in vitro nitrate reductase activity and grows poorly on a substrate with nitrate as the sole nitrogen source. The mutation of B25 (rgn) is monogenic and recessive, tightly linked to the marker gene an on chromosome 1. Nitrate induces cytochrome‐c reductase activity in the mutant but to a lower level than in the wildtype. After sucrose gradient centrifugation the greatest part of the cytochrome‐c reductase from induced wildtype is found as 8s type whereas cytochrome‐c reductase from B25 under the same conditions is found as 4s type. Nitrate reductase is found at the 8s position. It is suggested that B25 has lost the ability to assemble two 4s subunits showing cytochrome‐c reductase activity and a Mo‐bearing co‐factor into the functional nitrate reductase. Nitrate rather than nitrite is the inducing agent for nitrite reductase, since in B25 nitrite reductase is even more rapidly induced than in the wildtype after addition of nitrate. Both the wildtype and B25 contain a nitrate reductase inhibiting factor when grown on ammonium. This inhibiting factor is a small protein, possibly similar to the nitrate reductase inactivating enzyme reported for other plants.
The effect of NaCl salinity and water stress with polyethylene glycol on nitrogen fixation, stomatal response and transpiration of Medicago sativa, Trifolium repens and Trifolium brachycalycinum (subclover)
Authors: Sánchez‐Díaz M. , Aparicio‐Tejo P. , González‐Murúa C. , Peña J. I.
Published: April 2006

The objective of this study was to investigate the behaviour of different legumes against salinity and water stress, thus trying to discover simultaneous adaptations to both stresses. The nitrogen fixation, transpiration, predawn leaf water potential, and stomatal response of Medicago sativa L. (cvs. Tierra de Campos and Aragon), Trifolium repens L. (cv. Aberystwyth S‐184) and T. brachycalycinum Katzn. et Morley (=T. subterraneum L. cv. Clare) were compared at three levels of stress (0.05, 0.3 and 0.5 MPa of either NaCl or polyethylene glycol 6000) in nutrient solution. The plants were stressed for three days and then returned to control nutrient solution. The changes in the parameters analyzed were dependent on the proportion of stress treatments and the nature of the species, always being greater in plants from PEG than from NaCl solutions. Transfer of lucerne and subclover plants from NaCl at 0.05 MPa to a non‐saline medium resulted in an increase of nitrogen fixation above the level of the non‐salinized control plants, especially significant in lucerne. Analysis of possible inorganic impurities in commercial PEG suggest that such type of impurities are not responsible for the toxic effects reported. Plant damage resulting from PEG treatment was apparently due to penetrations of PEG (as determined qualitatively by using the tetraiodinebismuthic acid technique) or low‐molecular organic impurities into the plant. – The results are discussed as part of the adaptation of the different species to salinity and water stress. The best performance was given by “Tierra de Campos”.
Stomatal response and photosynthetic capacity of maize leaves at low temperature. A study on varietal differences in chilling sensitivity
Authors: Mustárdy L. A. , Vu Thanh Tam , Faludi‐Dániel Ágnes
Published: April 2006

The impairment of the turgor operated modulation of stomatal movement and changes in photosynthetic capacity were studied using two maize (Zea mays L.) varieties of different chilling sensitivity. In the tolerant variety stomatal opening exhibited characteristic transients, while in the more susceptible strain chilling induced a monotonous increase of stomatal apertures. Photosynthetic capacity of the leaves (expressed in terms of 14CO2 incorporation at 25°C) declined as a result of chilling regardless of stomatal opening. Nevertheless, tolerance was reflected in the preservation of a higher level of CO2 fixation capacity and in a more successful recovery.
Cytokinins in developing fruits of Moringa pterigosperma Gaertn.
Authors: Nagar P. K. , Iyer R. Indira , Sircar P. K.
Published: April 2006

The existence of cytokinins both as a free form and as a constituent of t‐RNA was investigated in young fruits of Moringa pterigosperma Gaertn. Purified methanol extract was separated into butanol insoluble and butanol soluble fractions. The cytokinin(s) in the butanol insoluble fraction was tentatively identified as zeatin nucleotide. The butanol soluble fraction contained cytokinins and was chromatographed on Sephadex LH‐20 with 35% ethanol. The two active fractions from LH‐20 column coincided with zeatin and zeatin riboside. Cytokinin per g tissue was high in early stages of fruit growth and then remained more or less constant. Alkaline phosphatase hydrolysis of t‐RNA hydrolysate of fruit tissue showed considerable cytokinin activity.
The uptake of potassium by Carex species from swamp habitats varying from oligotrophic to eutrophic
Authors: Veerkamp Mirjam T. , Kuiper Pieter J. C.
Published: April 2006

Short‐term potassium uptake by excised roots was investigated in Carex species from swamps, ranging from oligotrophic to eutrophic. The range of species from oligotrophic to eutrophic habitat is: C. rostrata Stokes, C. limosa L., C. lasiocarpa Ehrh., C. diandra Schrank, C. hudsonii A. Benn., and C. acutiformis Ehrh. After a short period of potassium starvation the species of the oligotrophic habitat showed a fast potassium uptake rate while the species of the eutrophic habitat showed lower uptake rates. Uptake by all species except C. rostrata and C. diandra was reduced at pH 4.0. Potassium uptake at low potassium concentrations was greatly increased by a period of starvation for potassium especially in the eutrophic species. The results on potassium stress are compared with the ecology of the species and with the reaction of the same Carex species to phosphate stress.
Enzymes of ammonia assimilation in legume nodules: A comparison between ureide‐ and amide‐transporting plants
Authors: Reynolds Paul H. S. , Blevins Dale G. , Boland Michael J. , Schubert Karel R. , Randall Douglas D.
Published: April 2006

Levels of amide and ureide biogenic enzymes were compared in the plant cytosol fractions of root nodules from soybean (Glycine max L. Merr., cv. Williams), pintobean (Phaseolus vulgaris L. cv. Pinto) and Lupin (Lupinus angustifolius L. cv. Frost). Enzymes of purine oxidation were found to be present in significant quantities only in ureide‐transporting pintobean and soybean nodules. The levels of these enzymes were low in lupin, but this amide‐exporter had significantly higher levels of asparagine synthetase. Enzymes of de novo purine biosynthesis and glycine biosynthesis were present at higher levels in pintobean and soybean, consistent with a role for de novo purine biosynthesis in ureide biogenesis. The low levels of these enzymes in lupin are consistent with a role in general purine and amino acid metabolism in these nodules, not directly related to the synthesis of transport compounds for fixed atmospheric nitrogen. Amino acid concentrations in soybean, pintobean and lupin nodules reflected the metabolic differences between amide and ureide plants. The comparative data presented are consistent with a pathway of ureide biogenesis using glutamine, glutamate and aspartate synthesized via reactions catalyzed by glutamine synthetase, glutamate synthase and aspartate aminotransferase in the de novo synthesis of purines followed by oxidation of these purines to produce the ureides allantoin and allantoic acid.
Uptake of calcium in wheat and cucumber roots
Authors: Bengtsson Bengt , Jensén Paul
Published: April 2006

Uptake of Ca2+(45Ca) was investigated in plants of wheat (Triticum aestivum L. var. Svenno) and cucumber (Cucumis sativus L. var. Cilla) cultivated in a nutrient solution with various Ca2+ concentrations. The adsorption of Ca2+ was higher in cucumber roots than in wheat roots especially at lower Ca2+ levels in the external medium. The intracellular fraction of Ca2+ was less than 20% of the total Ca2+ in wheat roots and less than 10% of the total Ca2+ in cucumber roots. The uptake of Ca2+ in cucumber was about 40 times higher than in wheat. Transport of Ca2+ in the roots towards the endodermis is suggested to take place mainly in the apoplastic pathway regulated by the availability of negatively charged binding sites along the cell wall continuum. Further transport of Ca2+ towards the stele may involve diffusion of Ca2+ into the symplasm in the vicinity of the endodermis. An active extrusion of Ca2+ towards the stele or towards the external medium is suggested to play a role in the regulation of Ca2+ uptake.
Lithium ions lengthen the circadian period of growing cultures of the diatom Skeletonema costatum
Authors: Østgaard Kjetill , Jensen Arne , Johnsson Anders
Published: April 2006

Turbidity measurements revealed that the circadian rhythm in the growth rate of the marine diatom Skeletonema costatum (Greville) Cleve was insensitive to temperature between 5 and 22°C. Growth of the alga was inhibited by lithium ions at concentrations higher than 2 mM. Lengthening of the circadian period was observed in the presence of 0.5–1.5 mM Li+. The results indicate that the lithium effect generally observed on circadian rhythms should not necessarily be ascribed to changes in an intercellular coupling of cellular oscillators.
Effect of α‐tocopherol on growth, membrane‐bound adenosine triphosphatase activity of the roots, membrane fluidity and potassium uptake in rice plants
Authors: Tànczos Otto G. , Erdei László , Vigh László , Kuipers Baukje , Kuiper Pieter J. C.
Published: April 2006

The effect of application of α‐tocopherol on the physiology of young rice seedlings (Oryza sativa L. cv. Dunghan Shali) was studied. Application of α‐tocopherol resulted in a growth stimulation of the shoots of 17.5% at the suboptimal 13°/8°C day/night temperature. Growth stimulation was accompanied by stimulation of K+‐uptake of the roots and by stimulation of the Ca2+‐stimulated ATPase activity of the microsomal fraction of the root cell membranes at low temperature in such a way that the non‐linearity (‘broken curve’) of the Arrhenius plot of control plants of this chilling‐sensitive species was absent and replaced by a linear relation, as in chillingresistant species. Application of α‐tocopherol also resulted in increased membrane fluidity, and the data are explained as a structural disordering effect of α‐tocopherol on the cell membranes of the rice seedlings.
Changes in water status during water stress at different stages of development in wheat
Authors: Teare I. D. , Sionit Nasser , Kramer Paul J.
Published: April 2006

The dynamics of stomatal resistance and osmotic adjustment in response to plant water deficits and stage of physiological development was studied in the leaves of spring wheat (Triticum aestivum L., GWO 1809). Plants were germinated and grown in pots in a growth chamber at the Duke University Phytotron to four physiological stages of development (4th leaf, 7th leaf, anthesis, and soft dough), during which time stomatal resistance, total water potential and osmotic potential were measured on the last fully developed leaf of water stressed and non‐stressed plants. Pressure potential was obtained by difference. Stomatal closure of the abaxial and adaxial surfaces were independent of each other, each having a different critical total water potential. The total water potential required to close the stomata on the last fully developed leaf were different at different stages of physiological development, decreasing as the plants grew older. The development of osmoregulation in wheat allows the closure of stomata during the vegetative stage at a high total water potential, but insures that stomata remain open from anthesis through the ear filling period to a lower total water potential.
Effects of a short‐day treatment on pool size, synthesis, degradation and transport of 3‐indole‐acetic acid in Scots pine (Pinus sylvestris L.) seedlings
Authors: Sandberg Göran , Odén Per‐Christer
Published: April 2006

The effects of a short‐day treatment on pool‐size, synthesis, degradation, and transport of 3‐indole‐acetic acid (IAA) in Scots pine (Pinus sylvestris L.) seedlings were studied. The short‐day treatment decreased the pool of free IAA in the needles but did not significantly affect the pool‐sizes of free IAA in the shoot‐axis, hypocotyls, cotyledons and roots. The bound alkali‐hydrolysable IAA‐pools were not affected by the short‐day treatment. The synthesis and degradation of radioactive IAA were also unaffected by the short‐day treatment. The transport of radioactive IAA was greatest from needles to roots, and this transport was significantly decreased by the short‐day treatment.
Precision and accuracy of indole‐3‐acetic acid analyses performed with the 2‐methylindolo‐α‐pyrone fluorescence assay and with a high performance liquid chromatography technique with spectrofluorimetric detection, exemplified on pine tissue (Pinus sylvestris L.)
Authors: Sandberg Göran , Dunberg Arne
Published: April 2006

The precision and accuracy of two versions of the 2‐methylindolo‐α‐pyrone (2‐MIP) assay and of a high performance liquid chromatography (HPLC) technique was assessed when applied to analysis of indole‐3‐acetic acid (IAA) in pine (Pinus sylvestris) tissue. In one version of the 2‐MIP assay total fluorescence at wavelengths > 450 nm was recorded, whereas in the other version fluorescence spectra were recorded and analyzed. Such analysis revealed the occurrence in some samples of fluorescent contaminants that impaired both precision and accuracy. The precision and accuracy of the 2‐MIP assay could be improved by additional sample purification, and the over‐all accuracy of the assay was finally verified, at a high level of sample purity, by successive approximation. The precision of the assay was then 14%. Successive approximation also verified that the HPLC technique was accurate at a less advanced stage of sample purity than the 2‐MIP assay, and had a precision of 14%.
Autolytic activities of the cell wall in rice coleoptiles. Effects of nojirimycin
Authors: Labrador Emilia , Nicolas Gregorio
Published: April 2006

Oryza sativa L. var. bahia coleoptile cell walls show sufficient autolytic activity for the release into the surrounding medium of amounts up to 60 μg of sugars per mg of dry weight of cell wall. The products released elute in Bio‐gel P.2 as mono‐ and polysaccharides with glucose as the sole component. The polysaccharide component releases tri‐ and tetrasaccharides on treatment with a glucanase specific for β (1–3) (1–4) linkages in the same proportion as that of the mixed glucan of the cell wall. This supports the hypothesis that the polysaccharide component originates from the cell wall glucan and that autolysis is therefore related to the processes of the loss of rigidity of the cell wall. Nojirimycin (a specific glucanase inhibitor and inhibitor of auxin‐induced elongation) decreases autolytic activity of the cell walls, reducing it to 30% of its normal value. Bio‐gel P. 2 elution of the products released in autolysis in the presence of nojirimycin shows that only the monosaccharide fraction was affected.
Potassium transport in wheat seedlings grown with different potassium supplies
Authors: Bérczi Alajos , Oláh Zoltán , Fekete Attila , Erdei László
Published: April 2006

Wheat seedlings (Triticum aestivum L. cv. Martonvásári 8) germinated and grown with different K+ supplies in a complete nutrient solution were examined. As controls, plants were grown in tridistilled water and 0.5 mmol/dm3 CaSO4 solution. The ionic states of the roots and shoots were followed from the 3rd to the 11th day after germination, with daily measurement of their K, Na, Mg and Ca contents. On the 11th day the K+(86Rb) influx of the excised roots was determined in the presence or absence of Ca2+ in an uptake solution of 1 mmol/dm3 KCl. The water contents of the plants and the K, Na, Mg and Ca contents of the excised roots were also measured before and after the uptake experiments of 1 h.

The rate of growth of the seedlings was practically independent of the ionic supply during the first 6 days. By the 7th and 11th days all plants (even those grown in tridistilled water) had reached the one‐leaf and the two‐leaf stage, respectively, but the water content of the roots of the control plants (about 86%) was significantly lower than that of other plants (about 95%). The lowest K content of wheat roots can be estimated as about 200 μmol (g dry weight)−1, which is about 10 μmol (g fresh weight)−1. Potassium seemed to be partly replaced by sodium. At high K contents in the roots and shoots, Na and Mg are expelled from both and, in addition, Ca is expelled from the shoots. The Ca content of the roots seemed to be unaffected by the K+ supply (or K content). The K+(86Rb) uptake of excised roots is interpreted on the basis of the negative feedback regulation by the K content of the roots. A possible Ca2+‐K+ exchange is also outlined.
Contrasting effects of simazine on the photosynthetic physiology and leaf morphology of two Populus clones
Authors: Akinyemiju O. A. , Dickmann Donald I.
Published: April 2006

Differential effects of simazine (2‐chloro‐4,6‐bis(ethylamino)‐s‐triazine) on the physiology of two Populus clones were investigated in a greenhouse study. Additions of 5 mg/pot simazine to young plants had no deleterious morphological or physiological effects on clone NC 5328 (P. x euramericana cv. I 45/51; Section Aigeiros), but reduced the rate of CO2 fixation, increased CO2 compensation concentrations and lowered the specific leaf weight of clone NE 388 (P. maximowiczü x P. trichocarpa cv. Kingston; section Tacamahaca). Abaxial leaf conductance to water vapor was not affected in NE 388. Deleterious effects of simazine on NE 388 were detected ca 48 h after exposure of plants to simazine and generally became more pronounced thereafter. Visual symptoms of injury were evident at ca 2 weeks after simazine application.

Toxic responses to simazine in clone NE 388 varied in different portions of the crown. Inhibition of photosynthesis and increased CO2 compensation concentrations were more pronounced in the region of recently matured leaves, but were somewhat less in the region of expanding leaves. Older mature leaves in the lower crown region showed no visual symptoms of injury and the rate of photosynthesis and CO2 compensation concentrations were largely unaffected.
Characterization of prolamellar bodies and prothylakoids fractionated from wheat etioplasts
Authors: Ryberg Margareta , Sundqvist Christer
Published: April 2006

Prolamellar bodies and prothylakoids from etioplasts of wheat (Triticum aestivum L. cv. Starke II, Weibull) were separated by sucrose density gradient centrifugation. Top‐loaded and bottom‐loaded sucrose gradients were compared. As a consequence of avoiding long time exposure of the membranes to low sucrose concentrations, separation in bottom‐loaded gradients, as compared to separation in top‐loaded gradients, resulted in a sharper and more narrow band of prothylakoids, and in better preservation of phototransformable protochlorophyllide, especially in the prothylakoids. In bottom‐loaded gradients, the prothylakoids were found concentrated in a band at a density of 1.20 g'ml−1. The prolamellar bodies were found at a density of 1.17 g'ml−1. In top‐loaded gradients the prothylakoids were found at a lower density than the prolamellar bodies. The prothylakoid fraction contained about 60% of the recovered protochlorophyllide and about 85% of the recovered protein. Absorption and fluorescence emission spectra revealed a higher amount of phototransformable protochlorophyllide, in relation to non‐phototransformable, in the prolamellar body fraction than in the prothylakoid fraction. Polyacrylamide gel electrophoresis indicated a high proportion of protochlorophyllide reductase in the prolamellar bodies. Chloroplast ATPase (CF1) was found predominantly in the prothylakoid fraction. Thus, our results strongly indicate the presence of phototransformable protochlorophyllide in the prolamellar bodies proper, while the main bulk of proteins are located in the prothylakoids.
Polyol accumulation by two filamentous fungi grown at different concentrations of NaCl
Authors: Adler L. , Pedersen Amelie , Tunblad‐Johansson Inga
Published: April 2006

The accumulation of polyols by Aspergillus niger (van Tiegh) strain S 1 and Penicillium chrysogenum (Thom) strain S 30 was followed during growth in media of different concentrations of NaCl. The major polyols found were glycerol, erythritol and mannitol. The total polyol pool increased in both organisms in response to raised salinity, and the proportion of glycerol and erythritol was markedly enhanced at high salinity.
Relation of source and sink during grain filling period in wheat and some aspects of its regulation
Authors: Herzog H.
Published: April 2006

The effects of changes in source‐sink relation and of cytokinin applications were examined with regard to the development of flag leaves and grain growth in two contrasting spring wheats, Triticum aestivum L., cv. Kolibri and Solo, grown in hydroculture at mean day/night temperatures of 21/19°C.

Lowering temperatures during the phase of ear differentiation decreased the ratio of source and sink size (flag leaf area/grains per ear) but hardly affected maximum chlorophyll content of the flag leaf (source activity), maximum rates of grain growth (sink activity), or final grain weight. Nevertheless, considerable differences were produced with regard to the duration of grain filling, the development and coordination of source and sink activities after maxima had been attained.

Changing the ratio of source and sink size during grain filling by spikelet removal affected final grain weight the less, the later the treatments began. Comparing, plants with identical source activities demonstrated that differences in grain weight were mainly due to different growth rates between day 16 and 40. Source activities were raised only temporarily (day 23) by spikelet removal done at day 2 or 14.

From this it may be concluded that changing the ratio of source and sink size influenced grain weight by creating different intrinsic growth potentials in the grains. These potentials might be estimated 3 weeks after ear emergence by DNA and RNA content per grain.

The effects of exogenous cytokinins were consistent with those due to spikelet removal suggesting that this hormone participates in a joint regulation of source and sink activity during grain filling.
Chlorophyll‐protein levels and degree of thylakoid stacking in radish chloroplasts from high‐light, low‐light and bentazon‐treated plants
Authors: Lichtenthaler Hartmut K. , Kuhn Gertrud , Prenzel Ursula , Meier Dieter
Published: April 2006

The level of 7 chlorophyll‐carotenoid‐proteins was determined in chloroplasts from radish seedlings (Raphanus sativusL. var. Saxa Treib) grown in high‐light (HL; 90 W m−2and low‐light (LL; 10 W m−2) growth conditions with and without application of the photosystem 2 herbicide bentazon (10−4M) and compared with the degree of thylakoid stacking.

The photosynthetic apparatus of HL‐chloroplasts contains higher proportions of the photosystem 1 chlorophylla‐proteins CPI and CPIa than LL‐chloroplasts or chloroplasts from bentazon‐treated plants.

In LL‐chloroplasts and in chloroplasts from bentazon‐treated plants a higher proportion of light‐harvesting chlorophylla/b‐proteins (LHCP1, LHCP2, LHCP3, LHCPy) is found. Bentazon treatment changes the proportion of LHCPs to about the same levels under both HL and LL‐growth conditions. The amounts of free chlorophyll found in bentazon chloroplasts (27–29%) is higher than in the HL or LL‐controls (16–18%).

The increase in degree of thylakoid stacking (% proportion of appressed membranes per total chloroplasts membranes) of LL‐chloroplasts as compared to HL‐chloroplasts of 7 to 9% (3rd to 5th day of illumination) is paralleled by a similar increase in the LHCPs of 5% and 8% (3rd and 5th day). The importance of light harvesting chlorophylla/b‐proteins as a prerequisite for thylakoid stacking is discussed.
Effects of viscosity on phototactic movement and period of cell rotation in Cryptomonas sp.
Authors: Uematsu‐Kaneda Hisako , Furuya Masaki
Published: April 2006

The swimming speed, the period of cell rotation, and the critical dark period between intermittent light pulses in the positive phototactic response of Cryptomonas sp. strain IAM CR–1 were measured in the presence of methyl cellulose, which slows down the cell movement by raising the viscosity of the medium. The cell rotated once while it swam one pitch of the helical path, irrespective of the rotational period. The period of helical movement (the rotational period) was 0.65 s and 0.45 s in the presence and absence of 4.5 g/liter methyl cellulose, respectively. The phototactic response to repeated pulses of light could no longer be induced when the dark interval exceeded 0.33 s in medium with 4.5 g/liter methyl cellulose and 0.23 s in medium without it. The ratio of the critical dark period between repeated light pulses to the rotational period was always about 0.5, although the rotational period was lengthened 1.4 times with methyl cellulose. Thus, the present results clearly demonstrated that it is this ratio which is crucial for phototaxis, rather than the absolute length of the critical dark period.
Salt‐spray stimulated growth in strand‐line species
Authors: Rozema Jelte , Bijl Frits , Dueck Tom , Wesselman Hans
Published: April 2006

The response to salt spray and soil salinity of two sand dune strandline species (Cakile maritima Scop. and Salsola kali L.) and two salt marsh strand‐line species (Atriplex hastata L. and A. littoralis L.) was compared in sand‐compost cultures. The growth of the salt‐marsh species remained unaffected, while the growth of the sand dune species Cakile maritima was strongly reduced by NaCl (150 and 300 mM) absorbed via the root system. All four species were resistant to airborne salinity, and under conditions of low soil fertility, salt spray increased the dry matter production, especially of the sand dune species. Mineral analysis revealed foliar uptake of Na, K, Cl, Ca and Mg. Na and Cl ions absorbed from seawater droplets induced succulence. Both salt spray and soil salt increased the methylated quaternary ammonium compound content in the shoot tissue. Under non‐saline conditions a considerable amount of these osmotic solutes was still present, while turgor pressure potential in these plants was rather low. The relation between salt, compatible osmotic solutes, turgor pressure potential and growth is discussed. Next to the major constituents of seawater, Na and Cl, especially magnesium and to a lesser extent, calcium, accumulated in the shoot tissue. Based on the positive growth response of the sand dune species to airborne salt, they should be termed ‘aerohalophytes’, whereas ‘soil halophytes’ should be used when referring to the Atriplex species, which are more specifically adapted to the increased salinity of salt marsh soils.
Induction of embryos in pollen cultures of Nicotiana sylvestris
Authors: Rashid A.
Published: April 2006

Induction of embryos in pollen cultures was possible when young buds from plants induced to flower at 15°C were given a cold treatment at 10°C for 15 days. Following selective isolation of embryogenic pollen the cultures raised were given cold treatment at 10°C for 12 or more days. In such cultures the embryos appeared at a frequency of 1.2% of the cultured pollen on mineral‐sucrose medium at pH 6.8.
Indolyl‐3‐acetic acid from shoots of Salix pentandra
Authors: Jensen Einar , Junttila Olavi
Published: April 2006

Indolyl‐3‐acetic acid from vegetative shoots of Salix pentandra L. has been isolated and identified by high performance liquid chromatography and combined gas chromatography‐mass spectrometry.