bluuebunny/crossref_metadata_2025 huggingface dataset:
Factors Affecting Ethanol Induced Luminescence in Dark‐Treated Chloroplasts
Authors: SIGFRIDSSON BJÖRN
Published: April 2006

Abstracts

Dark‐treated chloroplasts emit light when treated with a high ethanol concentration. The ethanol treatment causes chlorophyll solvation. The light is red and emanates from a singlet excited molecule, probably a chlorophyll peroxide. It is quenched by acetone, sodium dodecyl sulfate treatment of the chloroplasts before the addition of ethanol, boiling, reducing substances and low pH. It is enhanced by ferricyanide and high pH. This is interpreted as a requirement for an organized structure and for an energy transfer system for light emission to occur.
Seasonal Changes in Water Potential and Turgor Maintenance in Sorghum and Maize under Water Stress
Authors: FERERES E. , ACEVEDO E. , HENDERSON D. W. , HSIAO T. C.
Published: April 2006

Leaf water (Ψ) and solute (ψ) potential were measured in field sorghum and maize under well irrigated (I) and dryland (NI) conditions throughout a season. Despite decreases in ψ due to slow soil water depletion and to apparent increases in liquid phase plant resistance, midday leaf turgor (ψp) in the NI sorghum was maintained at similar levels as in the I treatment throughout the season due to concomitant decreases in ψs. Osmotic adjustment was also observed in maize, although ψp was significantly lower in the NI treatment as compared to I during the final stages of grain filling. A seasonal shift in the ψ vs. relative water content relation of NI sorghum leaves was observed, more water being retained by the older leaf at any particular ψ. The major factor for turgor maintenance was a net increase in solutes per unit of tissue. The role played by increases in the proportion of tissue volume occupied by cell wall was also evaluated. No stomatal closure due to water stress was found in NI sorghum even though leaf ψ reached —20 bars late in the season. Under similar conditions, stomata closed at —14 to —16 bars in younger plants where water stress was made to develop much faster.
Somatic Hybridization of Nitrate Reductase Deficient Mutants of Nicotiana tabacum by Protoplast Fusion
Authors: GLIMELIUS KRISTINA , ERIKSSON TAGE , GRAFE REINHARD , MÜLLER ANDREAS J.
Published: April 2006

Protoplasts were isolated from two mutant cell lines of Nicotiana tabacum L. cv. Gatersleben and fused with the aid of polyethylene glycol. Both mutants lacked nitrate reductase and were thus auxotrophic for reduced nitrogen. The fusion resulted in a high frequency of hybrid cells which were detected by their regained ability to grow in media containing nitrate as sole nitrogen source. Thus, the two mutants were found to complement each other in the hybrids. In control experiments, back mutation and cross‐feeding were excluded as possible explanations for the occurrence of cell lines utilizing nitrate. A total of 1061 hybrid lines capable of sustained proliferation were isolated. Some of them were further characterized with respect to nitrate reductase activity, chlorate sensitivity, chromosome number, and shoot formation.

The results demonstrate that protoplast fusion can be used for the genetic analysis of cell variants of higher plants and that nitrate reductase‐deficient mutants provide efficient selective systems for hybrid cells.
Induction of Adventitious Buds on Embryos of Norway Spruce Grown in vitro
Authors: ARNOLD SARA VON , ERIKSSON TAGE
Published: April 2006

Adventitious buds were induced when isolated embryos of Norway spruce (Picea abies L.) were cultured on a defined medium containing 2iP. Anatomically different bud primordia were formed at high and low cytoldnin concentrations. The highest percentage of embryos forming bud primordia was obtained after 4–5 weeks on 2iP medium. Buds developed after transfer of the induced embryos to medium without growth regulators. Many of the buds developed into elongated shoots. No root primordia were observed in any of the induced embryos.
High Performance Liquid Chromatographic Analysis of Cytokinins in Sorghum bicolor Leaves
Authors: KANNANGARA T. , DURLEY R. C. , SIMPSON G. M.
Published: April 2006

High performance liquid chromatography with octadecylsilica (Bondapak C18/Poracil B) column packing was used to purify and separate cytokinins in Sorghum leaf extracts. The column size was 56 × 0.21 cm i.d. By gradient elution, using acidified water with increasing amounts of methanol, the major peaks of cytokinin activity, as determined by the callus tissue bioassay. were effectively separated from large amounts of extraneous impurities. These cytokinins were further separated on a microoctadecylsilica column (μBondapak C18, 30 × 0.4 cm i.d.) with a gradient of acidified water‐acetonitrile. Zeatin and zeatin riboside gave distinct ultra violet absorption peaks which could be used for quantitative estimation. Biological activity corresponded to the elution of these peaks. These two cytokinins are the major cytokinins in Sorghum leaves.
Effects of Season and Low Temperature on Polypeptides from Thylakoids Isolated from Chloroplasts of Pinus silvestris
Authors: ÖQUIST GUNNAR , MARTIN BJÖRN , MÅRTENSSON OLLE , CHRISTERSSON LARS , MALMBERG GUNILLA
Published: April 2006

Thylakoids isolated from pine chloroplasts were solubilized by sodium dodecyl sulphate and the polypeptides were separated by polyacrylamide gel electrophoresis. The chlorophyll‐protein complexes, P700‐CPa1 and LH‐CPa/b, had apparent molecular weights of 92,000 and 25,000, respectively. When the chlorophyll of P700‐CPa1 was extracted or photobleached, the apoprotein of P700‐CPa1 appeared as a pronounced peak in the polypeptide scan profile. The molecular weight of the apoprotein was 70,000. During autumn and winter the complex P700‐CPa1 was destroyed. This was primarily caused by bleaching of chlorophyll, as the 70,000 apoprotein increased in the scan profile when the complex P700‐CPa1 decreased. The winter destruction of P700‐CPa1 was less pronounced in old needles than in young. Freezing of frost‐hardened seedlings did not change the polypeptide scan profile, unless the temperature was lowered below the frost‐killing point followed by thawing and post‐treatment in light or darkness above 0°C. Again the main destruction occurred in the P700‐CPa1 complex, but in this case no significant increase of the apoprotein was observed. These alterations in the polypeptide scan profile of frost‐killed needles were not caused by the low temperature treatment as such, but they occurred after thawing of the needles.
The Effect of Dew on Plant Water Balance in Citrullus vulgaris and Cucumis melo
Authors: WENT FRITS W. , BABU V. RAMESH
Published: April 2006

A temperature gradient air‐leaf can be created purely by radiation loss with a sky‐radiator. Loss of radiation from leaf to an artificial sky causes water vapor condensation from a saturated atmosphere as dew on the leaves of plants. The condensed water was found to be taken up by the leaves of melon (Cucumis melo) and water melon (Citrullus vulgaris) bringing about a favorable water balance by reduction in the water saturation deficit and by increase of the water potential. In a number of individual experiments with matched plants a minimum 31% and maximum 117% increase of leaf fresh weight due to uptake of condensed water was noted.
Free and Bound Gibberellin Activities and Ent‐kaurene Synthesis during Induction of Cold Hardiness in Black Locust Seedlings
Authors: NOWAK JOANNA , BROWN GREGORY N.
Published: April 2006

The role of gibberellin in the development of cold hardiness in black locust (Robinia pseudoacacia L.) seedlings was investigated. Free and bound gibberellin activities were followed during induction of cold hardiness using ethyl acetate partitioning and pH variation, with subsequent paper chromatographic fractionation and gibberellin bioassay. While total gibberellin activity decreased during the induction of cold hardiness in black locust seedlings, no convincing evidence was found to support conversion of free gibberellin to a bound form. However, bound gibberellin activity did appear to be more stable than did free gibberellin activity during the final stages of cold hardening at freezing temperatures. Gibberellin synthesis was followed using 14C‐mevalonate conversion to ent‐kaurene in a cell‐free extract of the tissue. Ent‐kaurene synthesis decreased during cold hardening with no detectable synthesis in fully hardened seedlings. However, since growth cessation precedes development of cold hardiness, decreased gibberellin synthesis and corresponding trends in free and bound fractions might have been expected, and a cause and effect relationship is difficult to establish. Even so, a decline in one step in gibberellin synthesis and a greater stability of bound than free gibberelin activity are associated with induction of cold hardiness in black locust seedlings.
Hormonal Changes Associated with Growth and Development of Red Raspberries
Authors: VASILAKAKIS MILTIADIS D. , McCOWN BRENT H. , DANA MALCOLM N.
Published: April 2006

Analysis for gibberellin‐like substances (GA) and cytokinins in cold and non‐cold treated fall‐bearing and cold treated June‐bearing cultivars of red raspberries (Rubus idaeus L.) was made at the 10 and 20 node stages of growth (at 10 nodes, all plants were vegetative; at 20 nodes, only cold treated plants of fall‐bearing cultivars were flower induced).

Quantitative changes in GAs, as analyzed by the lettuce hypocotyl bioassay, were observed only in flower induced plants. In fall‐bearing cultivars at the 20 node stage of growth, there was a 100% greater activity in cold than non‐cold treated plants. Likewise, cold treated plants had a 60% greater activity at the 20 than at the 10 node stage of growth.

Major qualitative differences in GAs were observed between the 10 and 20 node stage of growth in cold treated fall‐bearing cultivars but not in cold treated plants of June‐bearing cultivars. Changes in compounds at Rf 0.3 and 0.5 accounted for 35 to 54% of the total increase in GA activity between flower induced and non‐induced stages of growth.

Cytokinin activity tested by the tobacco callus bioassay was greater at the 20 than at the 10 node stage of growth in all cultivars and treatments. However, cold treated plants of the fall‐bearing type had 70% greater cytokinin activity than non‐cold treated plants at both stages of growth.

It is suggested that gibberellins, possibly acting synergistically with cytokinins, are involved inflower induction in red raspberries.
Induction of Adventitious Buds on Buds of Norway Spruce (Picea abies) Grown in vitro
Authors: VON ARNOLD SARA , ERIKSSON TAGE
Published: April 2006

Resting vegetative buds of Norway spruce, Picea abies (L.) Karst., were induced to form adventitious bud primordia when cultured on medium ‐containing cytokinin. After transfer of the induced buds to medium lacking cytokinin, adventitious buds developed. The adventitious buds arose from meristems formed de novo in the needle primordia. No differences were found in the ability to form adventitious buds among buds collected from trees ranging from 5–50 years old.
Biochemical Changes in Excised Leaves of Oryza sativa Subjected to Water Stress
Authors: DWIVEDI S. , KAR M. , MISHRA D.
Published: April 2006

Excised rice (Oryza sativa L. cv. Ratna) leaves were used to compare the changes in the levels of various biochemical intermediates and enzyme activities during senescence in turgid and water‐stressed conditions. Chlorophyll, total protein and soluble protein content decreased but α‐amino nitrogen content increased during the senescence of turgid leaves. In the leaves subjected to water stress, these changes were accelerated, the acceleration being greater with higher degree of water stress. Starch, soluble sugars, total carbohydrates and non‐reducing sugar content decreased during senescence of turgid leaves. Water stress accelerated the changes in the levels of starch and non‐reducing sugar, but the changes in the levels of soluble sugars and total carbohydrates were retarded. Reducing sugar content increased at first and then decreased in the turgid leaves, and water stress accelerated the change. The decline in the catalase activity and the increase in the peroxidase activity with time was faster in the water‐stressed leaves than in the turgid leaves. Acid inorganic pyrophosphatase activity increased, but alkaline inorganic pyrophosphatase activity decreased during the senescence of turgid leaves, and such changes were accelerated by water stress. The results suggest that water stress does not accelerate all the processes connected with leaf senescence.
The Relationship of Some Glycosidases to the Endogenous and IAA‐induced Growth of Light‐grown Cucumber Hypocotyls
Authors: KATSUMI MASAYUKI , YAMAMOTO YURI
Published: April 2006

Some glycosidases in light‐grown cucumber (Cucumis sativus L. cv. Aonaga‐jibae) hypocotyl sections were examined with respect to their localization and relation to endogenous and IAA‐induced growth. Frozen‐thawed sections were used directly for measurement of enzyme activities, and β‐glucosidase, α‐ and β‐galactosidases and β‐xylosidase were assayed by using p‐ or o‐nitro‐phenylglycopyranosides as substrates. The order of the activity of these enzymes were β ‐glucosidase > β ‐galactosidase =α‐galactosidase > β‐xylosidase. No activity of α‐glucosidase was detected. High glycosidase activities were found in the youngest region of the hypocotyl, where the endogenous growth rate was highest. However, there was no significant difference in the activities of this region between seedlings at different growth stages. Among the enzymes tested, β ‐glucosidase showed a high correlation with the endogenous growth rate. β‐glucosidase was found to be mostly associated with the cell wall fraction, while β‐galactosidase was rather found in the soluble fraction of the cell. Separation of the epidermis from the section showed that a very high activity of β‐glucosidase was associated with the epidermis. In both whole sections and isolated cell wall fractions, IAA was shown to have no effect on the activities of β‐glucosidase and β‐galactosidase.
Conversion of Phosphatidyl Choline to Phosphatidic Acid in Freeze Injured Rye and Wheat Cultivars
Authors: HORVÁTH I. , VIGH L. , BELEA A. , FARKAS T.
Published: April 2006

The effect of exposure to freezing temperature (−15°C) on leaf phospholipid composition of hardened rye (Secale cereale L.) and hardened wheat cultivars (‘Miranovskaja 808’, ‘Bezostaja 1’, ‘Short Mexican’ and ‘Penjamo 62’), which differ in their resistance to frost, was investigated. Hardening took place under natural conditions. All the seedlings attained an equal level of linolenic acid in their leaves during hardening. Exposure to freezing temperatures resulted in a loss of phosphatidyl choline and accumulation of phosphatidic acid in the leaves. The ratio of phosphatidic acid to phosphatidyl choline, but not the level of poly‐unsaturated fatty acids in the leaves, was related to their ability to survive at low temperatures. As freezing injury is caused by the formation of ice crystals in both extra‐ and intracellular space, it is probable that the plasma membranes of the investigated cultivars differed with respect to their water permeability. It is concluded that the plants, depending on the degree of their resistance to cold, produce an unknown substance of lipidic nature upon exposure to cold, with the aid of which they adjust the transitional state of their membranes to the prevailing temperature and, at the same time, facilitate the efflux of water from the cells.
Cellulose Content in Fibers of Cottons which Differ in their Lint Lengths and Extent of Fuzz
Authors: BEASLEY C. A.
Published: April 2006

Three cottons differing in their extent of fuzz fibers (linters) and final length of lint fibers were analyzed for amount of fiber cell walls and fiber cellulose at various times postanthesis. Cellulose determinations were performed directly on whole fibers and on fiber cell wall preparations. The data suggest that the presence of fuzz fibers does not account for a rise, followed by a plateau, followed by a rise, in cellulose content expressed as a percentage of cell wall material. It is concluded that: (1) under our greenhouse conditions, all fuzz fibers are initiated by day eight after anthesis; (2) weight per mm length of all fibers increases up to the point of secondary wall deposition and increases even more rapidly after that; (3) deposition of secondary wall cellulose in fuzz fibers probably does not begin until after similar deposition begins in lint fibers; (4) the actual amount of cellulose in primary walls of all elongating fibers (fuzz and lint) is a constant value, about 1 × 10−16 mg/mm; and (5) secondary wall cellulose deposition in lint fibers begins very sharply, in advance of cessation of elongation, at a time closely related to final lint fiber length. It is speculated that: (1) cell wall preparation procedures may remove significant amounts of noncellulosic wall material, thus making it difficult to define all functional constituents on the basis of what is left in a cell wall residue; and/or (2) primary walls may lose to the cytoplasm some of their constituents in advance of secondary wall deposition, the extent of loss varying due to developmental age of the elongating fibers.
Regulation of Rubidium Uptake in Sunflower Roots
Authors: PETTERSSON SUNE , JENSÉN PAUL
Published: April 2006

Uptake of Rb+was investigated in 12‐day‐old intact plants of sunflower (Helianthus annumL. var.californicus) which had been cultivated or pretreated in nutrient solutions with various K+concentrations. The relationship between Rb+influx and K+concentration of the roots indicated regulation of Rb+uptake by allosteric inhibition of the uptake mechanism. A constant passive influx occurred contemporaneously with the active uptake as shown by experiments at 0°C or with 2,4‐dinitrophenol. The allosteric regulation of ion carrier activity occurred after a time lag of up to 1 h after the change of external solution. In experiments involving Rb+treatments of K+‐deficient plants, the synthesis of carriers for transport of Rb+could be demonstrated. A model including allosteric regulation of Rb+uptake in roots is discussed.
Gibberellin‐Growth Retardant Interactions on the Growth and Flowering of Clerodendrum thomsoniae
Authors: KORANSKI D. S. , McCOWN B. H. , STRUCKMEYER B. E. , BECK G. E.
Published: April 2006

Gibberellin‐growth retardant interactions on the vegetative growth and flowering of the vine Clerodendrum thomsoniae Balf. were studied using both exogenous treatments and biologically testing the acid fraction attained from the plant extract. The growth retardant, ancymidol, greatly retarded stem elongation and markedly increased flowering under inductive environments. Gibberellin A3 (GA3) application to the shoot tip stimulated vine growth, prevented flowering under inductive environments, and completely overcame ancymidol‐induced effects. In contrast to GA3, treatment with GA7 had little effect on vegetative growth but increased flowering under inductive environments. The elevated activity of gibberellin‐like compounds, as determined by bioassay, were similar except for a marked increase in levels in ancymidol‐treated plants grown under inductive environmental conditions. Microscopic examination of the stem tip indicated that the action of the growth regulators involved the induction of floral buds. Thus, in Clerodendrum, ancymidol appears to stimulate an unknown gibberellin(s) and simultaneously acts antagonistically with GA3.
Influence of Rate of Development of Leaf Water Deficits upon Photosynthesis, Leaf Conductance, Water Use Efficiency, and Osmotic Potential in Sorghum
Authors: JONES M. M. , RAWSON H. M.
Published: April 2006

This study reports the effect of rate of development of leaf water deficits in soil‐grown sorghum (Sorghum bicolor) on the relationship of net photosynthesis, leaf conductance, and water use efficiency to leaf water potential, and on the degree of solute accumulation (osmotic adjustment). Recovery of these processes on rewatering, and responses during a second stress cycle were also studied. The most rapid rate of stress (1.2 MPa day−1) resulted in no solute accumulation and the lowest rate of net photosynthesis and leaf conductance for any given leaf water potential during stress. Stress at 0.7 and 0.15 MPa day−1 led to equal solute accumulations of approximately 0.6 MPa, but net photosynthesis, leaf conductance, and water use efficiency at a given leaf water potential were lower with the faster rate of stress (0.7 MPa day−1). Additionally, leaf conductance at a given leaf turgor potential was lowest at the 1.2 MPa day−1 stress rate, slightly higher at the intermediate rate of stress, and clearly highest at the slowest rate of stress. Recovery of both net photosynthesis and leaf conductance upon rewatering was rapid, taking less than 3 days, but full recovery of osmotic potential took between 6 and 11 days. One slow stress cycle had no influence on relationships during a second cycle. The concept of a threshold leaf water potential for stomatal closure is discussed and the conclusion reached that stomatal closure occurs slowly over a wide range of leaf water potential (> 1.0 MPa), the range being greater for slower rates of stress.
Physiological Characteristics of Mycosphaerella ascophylli, a Fungal Endophyte of the Marine Brown Alga Ascophyllum nodosum
Authors: FRIES NILS
Published: April 2006

Mycosphaerella ascophylli Cotton, a fungal endosymbiont in the thallus of the marine brown alga, Ascophyllum nodosum (L.) Le Jol., was brought into axenic culture. Most of its nutritional requirements proved to be similar to those characteristic of marine saprophytic fungi: growth optimum at pH 7 to 8, good growth only with a high concentration of NaCl, ability to utilize nitrate as a nitrogen source and glucose, galactose and mannose as carbon sources. The fungus was more specifically characterized by a low temperature optimum (20°C, or lower), a requirement for both thiamin and biotin, and inability to metabolize xylose and fructose.
Correlation of the 680 to 672 nm Spectral Shift and the Halving of the Apparent Molecular Weight for Chlorophyll(ide) Holochrome from Barley
Authors: STUMMANN B. M.
Published: April 2006

Protochlorophyll(ide) holochrome was isolated from dark‐grown barley (Hordeum vulgare L.) leaves and photoconverted. When the chlorophyll(ide) absorption maximum had decreased from 680 to 676 nm the preparation was chromatographed on a Sephadex‐gel column under conditions which strongly inhibited a further decrease in the absorption maximum. The absorption properties of the column fractions and the shape of the chlorophyll(ide) elution‐profile indicated the presence of two distinct chlorophyll(ide)‐bearing molecular species with apparent molecular weights of c. 74,000 and 29,000 and absorption maxima at 680 and 672 nm, respectively. It is concluded that: (1) no long‐lived species with intermediate absorption maximum is formed during the 680 to 672 nm shift of the absorption maximum of newly photoconverted holochrome; (2) no long‐lived pigment‐protein complexes with intermediate molecular weights are formed during the approximate halving of the molecular weight; (3) the shift in the absorption maximum and the decrease in molecular weight are closely correlated.
Cytology of Callus of Cryptomeria japonica
Authors: MEHRA P. N. , ANAND MANJU
Published: April 2006

Callusing has been initiated from the cotyledons of 4‐week‐old seedlings of Cryptomeria japonica on Murashige and Skoog's medium supplemented with 22.8 μM IAA. Callus was grown successfully for more than 2 years on the same medium without any decline in growth vigour. The callus has shown differentiation of tracheids with reticulate thickenings but differentiation of root, shoot or whole plant has not yet been observed. Cytology of 2‐month‐old callus showed the presence of cells containing normal diploid chromosome complement of 2n = 22 and normal mitosis. However, the 6‐month‐old callus revealed majority of cells with normal diploid complement and the usual karyotype, but a few cells were noticed with aneuploid numbers ranging from 2n = 15–17. Anaphase bridges and lagging chromosomes have also been encountered.
Physiology of Rice Tungro Virus Disease: Involvement of Abscisic Acid‐Like Substance in Susceptible Host‐Virus Interactions
Authors: MOHANTY SUSANTA K. , MOHANTY SANTOSH K. , ANJANEYULU A. , SRIDHAR R.
Published: April 2006

Stunting was severe in susceptible rice (Oryza saliva L.) cultivar ‘Taichung Native 1’ infected with tungro virus (RTV) compared to less‐susceptible cultivar ‘IR 20’. The senescence of detached leaves of RTV‐infected susceptible cultivar incubated in water in dark was accelerated compared to the healthy leaves as measured by the loss of total chlorophyll content. The transpiration rate of RTV‐infected leaves of the susceptible cultivar was much lower than the healthy and RTV‐infected leaves of the less‐susceptible cultivar.

Partially purified extracts obtained from RTV‐infected leaves effectively inhibited GA‐induced α‐amylase synthesis in barley endosperms, and rice seedling growth, and they accelerated senescence of detached rice leaves. In all the three bibassays the ABA‐like activity was significantly greater in the extracts from the RTV‐infected susceptible cultivar than in extracts from the less‐susceptible cultivar.
Nitrogen Stress in Birch Seedlings
Authors: INGESTAD TORSTEN , LUND ANN‐BRITT
Published: April 2006

An account is given of experiments with birch (Betula verrucosa Ehrh.), in which experiments there was optimum availability of all other nutrients, while nitrogen was added in amounts corresponding to optimum as well as various non‐optimum consumption rates. At the beginning of the growth period the nitrogen concentration in the nutrient solutions was very low or zero in the sub optimum treatments. In the optimum and supra–optimum treatments the nitrogen concentration in the solution was varied up to high levels. The nutrient solutions were not changed but the nutrients taken up were replaced by frequent additions. The sub‐optimum nitrogen additions were carried out every second hour in amounts increasing exponentially day by day, and with a varied exponent.

During a lag phase the seedlings in the sub optimum treatments had rapidly diminishing growth rates, deficiency symptoms, and a relatively high root growth rate with formation of long, thin roots. When the growth rate later on had stabilized, a period was recognized during which measurements and sampling were carried out. At the end of the lag phase, or in the beginning of the experimental period, the nitrogen deficiency symptoms of the leaves disappeared and the various parts of the seedlings grew with the same rate, and in a good linear correlation with the rate of nitrogen supply.

The results indicate that nitrogen primarily influences the leaf area growth rate, which responds rapidly to a change in nitrogen availability. The following general growth response demonstrates the ability of the plants to adapt growth according to nitrogen supply, so as to create stable internal physiological conditions. Thus, there is a close agreement between the rate of nitrogen supply and consumption on one hand and growth rate on the other.

The characteristic nitrogen deficiency symptoms of the seedlings during the lag phase are very similar to those reported in the literature. During the stable period that follows, they disappear from the leaves in agreement with the fact that natural vegetation generally is green also when nitrogen is strongly growth limiting. It is concluded that the exponentially increasing amounts of nitrogen added to lie nutrient solution, also when the exponent is far below optimum, makes nitrogen available to the seedlings in a similar way as does the exponentially growing root system in. a solid medium. Birch seedlings are able to adapt growth rate to low nitrogen supply and thereby show a healthy appearance without acute deficiency symptoms. Some ecological and practical implications are discussed.
Effect of Light Intensity on Growth, CO2 Fixation, and Chlorophyll and Polar Lipid Production in Germinating Polytrichum commune Spores
Authors: KARUNEN PIRJO
Published: April 2006

The dry matter production in Polytrichum commune protonemata was increased when the light intensity was increased from 0 to 160 μE m−2 s−1, and at 160 μE m−2 s−1 production was about 200% of that found at 17 μE m−2 s−1. Production of chlorophyll (Chl) was increased by increasing light intensity from 0 to 17 μE m−2 s−1, but decreasing at light intensities above 17 μE m−2 s−1. At 160 μE m−2 s−1 the production of Chl was only about 50% of that at 17 μE m−2 s−1. The rate of CO2 fixation was low (0.31 μg CO2/mg Chi × h) at the light intensity of 17 μE m−2 s−1 as compared with that at 160 μE m−2 s−1 (0.83 μg CO2/mg Chi × h). Production of mono‐ (MGDG) and diglycosyl diglycerides (DGDG) was closely associated with that of chlorophylls. At the higher light intensity (160 μE m−2 s−1) production of glycolipids was about 60% of that at 17 μE m−2 s−1. Production of more polar lipids was less affected by light intensity. Light intensity also affected the fatty acid pattern of the lipid fractions. The effect was most pronounced in the MGDG fraction, where the proportion of C 18: 3ω3 + C 16: 3ω3 was higher at the higher light intensity.
Effect of Changed Environmental Conditions on Glycolipids of the Mosses Pleurozium Schreberi and Ceratodon purpureus
Authors: ARO EVA‐MARI , KARUNEN PIRJO
Published: April 2006

The effect of changed environmental conditions on the content of glycolipids and component fatty acids was studied in the moss species Pleurozium schreberi and Ceratodon purpureus. The mosses were collected from their natural habitats when frozen and covered by snow. After one week's exposure to rhythmic light (150 μE m−2 s−1, 12 h 17°C) no changes were observed in the absolute amount of fatty acids in either mono‐ (MGDG) or diglycosyl diglyceride (DGDG) fractions. Some changes were recorded in the content of individual fatty acids, however. The long chain, polunsaturated fatty acids (mainly 20:4ω6 and 20:5ω3 in P. schreberi and in addition 16:3ω3 and 18:3ω3 in C. purpureus) tended to decrease and the shorter chain, more saturated ones increased correspondingly. Under continuous light conditions (17°C) the total amount of fatty acids decreased in both MGDG and DGDG fractions, more significantly at 150 than at 75 μE m−2 s−1. This was due to the accelerated degradation and/or decreased synthesis of polyunsaturated fatty acids, which in this case was not totally compensated by the increase in shorter chain, more saturated ones.
The Intracellular Location of Particulate‐Bound Polyphenol Oxidase in Avocado Mesocarp
Authors: SHARON OSNAT , KAHN VARDA
Published: April 2006

Polyphenol oxidase of avocado mesocarp exists in a supernatant and a participate fraction. Isolation conditions were sought where maximal polyphenol oxidase activity could be retained in the particulate fraction. More polyphenol oxidase was associated with the 270–2000 g pellet than with the 2000–12,000 g pellet.

Analysis of the particulate polyphenol oxidase on linear sucrose density gradient revealed two relatively heavy peaks. The data showed that the major part of polyphenol oxidase was not a constituent of chloroplasts, chromoplasts or mitochondria. The closeness of the positions of polyphenol oxidase and of catalase in both the green and the yellow zones of the mesocarp established that most of the particulate polyphenol oxidase of avocado is associated with microbodies.
Cyanide‐Resistant Root Respiration and Tap Root Formation in Two Subspecies of Hypochaeris radicata
Authors: LAMBERS HANS , VAN DE DIJK SIEBREN J.
Published: April 2006

Root respiration of the tap root forming species Hypochaeris radicata L. was measured during tap root formation. A comparison was made of two subspecies: H. radicata L. ssp. radicata L., a subspecies from relatively rich soils, and H. radicata L. ssp. ericetorum Van Soest, a subspecies from poor acidic soils. Root respiration was high and to a large extent inhibited by hydroxamic acid (SHAM) before the start of the tap root formation, indicating a high activity of an alternative non‐phosphorylative electron transport chain. The rate of root respiration was much lower and less sensitive to SHAM when a considerable tap root was present. However, root respiration was also cyanide‐resistant when a tap root was present, indicating that the alternative pathway was still present. A decreased rate of root respiration coincided with an increase of the content of storage carbohydrates, mainly in the tap root. The level of reducing sugars was constant throughout the experimental period, and it was concluded that the activity of the alternative oxidative pathway was significant in oxidation of sugars that could not be utilized for purposes like energy production, the formation of intermediates for growth or for storage. Root respiration decreased after the formation of a tap root. This decrease could neither be attributed to a gradual disappearance of the alternative chain, nor to a decreased level of reducing sugars. No differences in respiratory metabolism between the two subspecies have been observed, suggesting that a high activity of the alternative oxidative pathway is not significant in adaptation of the present two subspecies to relatively nutrient‐rich or poor soils.
Fatty Acid Composition of Polar Lipids in Ceratodon purpureus and Pleurozium schreberi
Authors: KARUNEN PIRJO , ARO EVA‐MARI
Published: April 2006

The total amount of fatty acids in the mono‐ (MGDG) and diglycosyl diglyceride (DGDG) and more polar lipid fractions of frozen Ceratodon purpureus shoots was 4.6, 3.4 and 4.0 mg/g dry weight, respectively. The respective values for the tops of frozen Pleurozium schreberi were 2.6, 3.3 and 3.8 mg/g dry weight. The molar ratios MGDG/DGDG and MGDG + DGDG/chlorophyll were 1.3 and 3.7, respectively, for C. purpureus and 0.8 and 3.5 for P. schreberi.

In C. purpureus the main fatty acids in the MGDG fraction were C 18:3ω3 (44% of the total fatty acids) and C 16:3ω3 (26%); in the DGDG fraction C 18:3ω3 (70%); and in the more polar lipid fraction C 18: 3ω3 (26%) and C 16:0 (25%). The proportion of C 20 polyunsaturated fatty acids was 15, 12 and 19% of the total fatty acids found in the MGDG, DGDG and more polar lipid fractions, respectively.

In P. schreberi the proportion of C 20 polyunsaturated fatty acids was high in all polar lipid fractions (47, 42 and 25% in MGDG, DGDG and more polar lipid fractions, respectively). In addition, MGDG and DGDG fractions contained abundantly C 18:3ω3 (32 and 45%, respectively), and the more polar lipid fraction both C 18: 3ω3 (24%) and C 16:0 (27%).
Effect of Ammonium, Sucrose and Light on the Regulation of Nitrate Reductase Level in Pisum sativum
Authors: SIHAG R. K. , GUHA‐MUKHERJEE SIPRA , SOPORY SUDHIR K.
Published: April 2006

In shoot apices of 7‐day‐old dark‐grown peas the addition of ammonium along with the inducer nitrate resulted in a more than two‐fold increase in nitrate reductase activity. Individual amino acids, amides and amino‐acid mixture could not replace the ammonium effect. Ammonium also stimulated NADH‐glutamate dehydrogenase but not glucose‐6‐phosphate dehydrogenase. Sucrose caused a marked stimulation of nitrate reductase induction and showed synergistic effect with light. In presence of cordycepin and cycloheximide, induction of nitrate reductase was inhibited more if ammonium or sucrose was supplied along with the inducer. With actinomycin D, α‐amanitin or chloramphenicol, no differential inhibition took place in presence of ammonium. The inhibition of enzyme activity by chloramphenicol and 3‐(3,4‐dichlorophenyl)‐l,dimethyl urea was completely relieved by sucrose. Incorporation of 14C‐lysine was markedly stimulated by sucrose, but was not affected by ammonium. The effect of sucrose and light on 14C‐lysine incorporation was additive. Cordycepin and cycloheximide did not have any differential effect on 14C‐lysine incorporation in the presence of ammonium as well as sucrose. The inhibition of 14C‐lysine incorporation caused by chloramphenicol was relieved by sucrose. Sucrose also caused a marked increase in 3H‐uridine incorporation but ammonium had no effect. Actinomycin D and cordycepin blocked the sucrose dependent increase in 3H‐uridine incorporation.

The results suggest that ammonium mediated stimulation may depend on a regulatory protein(s) synthesized in response to ammonium, whereas sucrose acts mainly by an overall increase in RNA and protein synthesis. The effect of light does not seem to be dependent on photosynthetic light reactions.
Stem Nodules in Aeschynomene indica and Their Capacity of Nitrogen Fixation
Authors: YATAZAWA MICHIHIKO , YOSHIDA SHIGEKATA
Published: April 2006

There has been no report on stem nodules with nitrogen fixing activity. Aeschynomene indica produce nodules on the aerial parts, and the stem nodules proved to be capable of considerable nitrogen fixation [C2H4 produced c. 4 μmol (g fresh weight)‐1 h‐1]. The stem nodules embed reddish tissues, and a rod‐shaped bacterium was isolated from the tissues. The bacterium was ascertained to form root and stem nodules on seedlings of A. indica.
Content of Adenosine Phosphate Compounds in a Long‐Day Duckweed, Lemna gibba G3, under Different Light and Nutritional Conditions
Authors: KONDO TAKAO , NAKASHIMA HIDEAKI
Published: April 2006

The levels of ATP ADP and AMP as well as the energy charge were examined in the long‐day duckweed. Lemna gibba G3, under different light and nutritional conditions. ATP and ADP content, but not AMP, decreased slightly when the plant was cultured with a medium depleted of sucrose or was exposed to continuous darkness. The energy charge was not affected either by changes in the light conditions or by the depletion of sucrose from the medium, although increase of fresh weight changed drastically under these conditions. The levels of ADP and AMP and the value of the energy charge remained nearly constant throughout a 1‐day period when the plant was exposed to short‐day, continuous light and continuous dark. ATP content decreased gradually during the light period of the short day and thereafter remained constant during the dark period. When the plant was exposed to continuous light. ATP content decreased until the 8th hour after beginning of the continuous light, only to recover rapidly to its original level during the phase coinciding with the preceding dark period of the short day. Under continuous dark conditions the ATP content remained constant throughout the day. It was concluded that the diurnal rhythm of physiological activities previously reported cannot be related to the energy charge.
Chlorophyllase and Photsystem
Authors: TERPSTRA WILLEMKE , GOEDHEER J. C.
Published: April 2006

Preliminary experiments showed that Triton X‐100 at low concentrations (appr. 0.01%) induces reversible changes in some photosynthetic reactions in Phaeodactylum cells without influencing their absorption spectrum; presumably membrane permeability is effects. Although DC PIP can pass through the cell membrane in the presence of 0.01% Triton X‐100, only a very low PS I activity, measured as MV photoreduction by DCPIP‐ascorbate, is observed with whole cells.

MV photoreduction sensitized by membrane fragments isolated from Phaetdactylum, Euglena, Porphyridium and Synechococcus after French Press treatment is much higher with Phaeodactylum than with the other organisms. Spinach shroma membrane fragments show higher photosensitizing activity than grana fragments.

MV photoreduction in the above mentioned experiments is not influenced by DCMU (2 × 10−6M) or sodium azide (0.01–0.05 M); KCN (4 × 10−3M) has an inhibiting effect only with the blue‐green alga Synechococcus. The reaction mechanism of chlorophyll‐sensitized MV photoreduction is discussed.

Chlorophyll in an aqueous medium containing Triton X‐100 (JsO.01%) sensitizes the photoreduction of MV by DCPIP ascorbate. A similar reaction is observed with chlorophyll combined with solubilized Phaeocdactylum chlorophyllase: in the latter case the presence of both MgCl2 and DTT is required.

MV‐photoreduction is concluded to be a very unreliable procedure for determining PS I activity in membranes if these membranes have been prepared in (the presence of detergents.

The results support the hypothesis that (prochlorophyllase is a PS I protein.

The capacity of PS I to reduce MV in vivo is discussed.
Association of Plastoquinone‐9 and Phylloquinone K1 with Photoconvertible Protochlorophyllide Holochrome
Authors: LICHTENTHALER H. K. , SUNDQVIST C.
Published: April 2006

Protochlorophyllide holochrome was prepared from dark grown wheat seedlings in a saponin containing medium by precipitation with ammonium sulfale and differential centrifugaiion. During the different steps of purification the spectral properties and the photoconvertibility of prolochlorophyllide holochrome were measured concomitantly with its quinone and carotenoid content. Photoconvertible protochlorophyllide holochrome was enriched in quinones hut depleted of carolenoids compared with the whole etiolated leaf. The fractions containing long wavelength forms of photoconvcrtible protochlorophyllidc had a constant molar ratio of plastoquinonc. phylloquinone and protochlorophyllide of 1:1:2. The possibility of the prenylquinones to function as electron or hydrogen carriers between a hydrogen donor and protochlorophvliide is discussed.
Isolation and Mobilization of Storage Proteins from Apple Shoot Bark
Authors: O'KENNEDY BRENDAN T. , TITUS J. S.
Published: April 2006

Separation of the bark storage protein into three groups was achieved with minimal contamination from interfering cbromophores, using diethylaminoethyl cellulose column chromatography. Two of these groups were shown 10 contain neutral sugars in close association with the proteins. All three groups disappeared rapidly after the onset of growth. Polyacrylamide gel electrophoresis of the storage proteins showed the presence of eight prominent proteins. Ammo acid analysis of hydrolyzates of the proteins indicated that a large percentage of the protein nitrogen was in the form of basic amino acids.
Differentiation in Callus Cultures of Leaf of Two Species of Trigonella
Authors: SEN BASANTAK , GUPTA SUKUMAR
Published: April 2006

Callusing of leaf segment of Trigonella corniculata L. and Trigonelta foenum graecum L. was observed on Murashige and Skoog's (MS) medium and White's (W) medium supplemented with naphthalene acetic acid (NAA; 0.5 mg/1) and coconut milk (15% v/v). Root, shoot and development of isolated leaf occurred in the calli of both the species on MS medium containing NAA amd coconut milk. Omission of coconut milk with subsequent addition of casein hydrolysale (CH) increased the number of differentiated organs per callus. In both the materials higher differentiation rate was observed at low irradiance than at high irradiance or in complete darkness. Initially the cells were diploid but at the 5th passage the calli became mixoploid wilh predominantly diploid cell populations. The differentiated organs were diploid.
Interactions of Divalent Cations in Their Action on ATPases from Cucumber Roots
Authors: KAWASAKI T. , KÄHR M. , KYLIN A.
Published: April 2006

A microsomal fraction (10,000–30.000 g) was prepared from roots of Cucumis satirus L. (cv. Bestseller Fl) grown in solution culture. The ATPase activity was stimulated by Mg and Mn with optima between pH 6 and 7. Stimulation by Ca was obtained only above pH 7. Activations by Mg and Mn were inhibited by Ca, Mn and Mg interacted, so that Mn appeared strongly inhibitory for activation by Mg and Mg weakly inhibitory for activation by Mn: the simplest interpretation for this would be two separate enzymes. Cucumber accumulates and deposits Ca contrary to wheat and oat, which contain Ca‐activated ATPase in the pH region 6 to 7. The Ca data for cucumber are compared with earlier findings from wheat and oat and are tentatively related to known physiological differences.
The Effect of Abscisic Acid on the Uptake and Distribution of Ions in Intact Seedlings of Phaseolus vulgaris cv. Redland Pioneer
Authors: KARMOKER J. L. , VAN STEVENINCK R. F. M.
Published: April 2006

Abscisic acid (ABA) was found to increase the accumulation of 36Cl, total Cl, 22Na and total Na+ in roots of intact bean seedlings. After an initial promotion. ABA inhibited longdistance transport of these ions from the root to the shoot. However, it consistently inhibited both uptake and transport of 42K and total K+ in intact bean seedlings. A promotion of net 36Cl influx (ψoc) and its accumulation in the root (Q*v) concomitant decrease in transport index (long‐distance transport as percentage of total influx) showed that ABA stimulates ‐36Cl transport at the tonoplast. It inhibited H4 extrusion and net 86Rb influx which agrees with a cation exchange theory K+/Rb+ transport.
Diurnal Fluctuations in the Activity of the Enzyme Nitrate Reductase in Lemna paucicostata
Authors: DEVI S. LAKSHMI , MAHESHWARI S. C.
Published: April 2006

Diurnal fluctuations were observed in nitrate reducta.se activity in Lemna paucicostatu Hegelm, grown under 16‐h photoperiod. The enzyme activity showed a single peak in the middle of the photo period, i.e. 8 h after the onset of light. The activity decreased during the latter half of the photoperiod and reached a minimum level in the middle of the dark period. The peak in enzyme activity persists in continuous light as well as continuous dark, at least for a couple of days, suggesting the existence of endogenous rhythmicity
Effect of α‐Tocopherol, β‐Carotene, Monogalactosyldiglyceride and Phosphatidylcholine on Light‐Induced Degradation of Chlorophyll a in Acetone
Authors: VAN HASSELT PHILIP R. , DE KOK LUIT J. , KUIPER PIETER J. C.
Published: April 2006

The effect of α‐tocopherol, β‐carotene, monogalactosyldi‐glyceride and phosphatidylcholine on red light induced degradation of chlorophyll a was studied in acetone at 4°C. Monogalaclosyldi‐glyceride was ineffective up to a molar ratio of monogalactosyldi glyceride to chlorophyll of 1:10. α‐Tocopherol, β‐carotene and phosphatidylcholine inhibited chlorophyll degradation. Maximal protection by α tocopherol and β‐carotene was similar (76%) but on a molar basis a tocopherol was less effective. Protection by phosphatidylcholine was less than by a tocopherol and α‐carotene but the lipid was effective at a lower ratio of chlorophyll to protectant. Inhibition by phosphatidylcholine was independent of the degree of unsaturation of the fatty acids. Effects of β‐carotene and α‐tocopherol were additive at suboptimal concentrations, but addition did not increase the maximal protection of 76% by these substances alone. Phosphatidylcholine increased the effectiveness of α‐tocopherol and β‐carotene independent of their concentrations. It is suggested that interactions between lipids participate in the mechanism protecting chlorophyll a against photooxidation in the chloroplast membrane.
Analytical Procedures for the Sequential Extraction of 14C‐Labeled Constituents from Leaves, Bark and Wood of Cottonwood Plants
Authors: DICKSON RICHARD E.
Published: April 2006

A procedure for the extraction, separation, and measurement of photosynthetically fixed 14C in up to 8 chemical fractions (CHCl), amino acids, organic acids, sugars, protein, starch, hemicellulose, and residue) from small samples (1 to 100 mg) of cottonwood (Populus deltoides Bartr.) leaf material is described. The different chemical fractions are extracted in a sequence of chemical, ion exchange, and enzymatic steps. The 14C‐activity in these major fractions is then determined with liquid scintillation spectrometry. These major fractions (e.g., sugars, amino acids, organic acids) can be further separated into their individual chemical components by standard thin‐layer or gas‐ chromatographic methods for quantitative analysis if specific activities are desired. The major advantage of the procedure is that many chemical fractions can be sequentially separated with good reproducibility from a small amount of plant material without transfer of the material from the original homogenizer or centrifuge tube.