bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of the nucleotide pool during growth of suspension cultured cells of Nicotiana tabacum by high performance liquid chromatography
Authors: Meyer Reiner , Wagner Karl G.
Published: April 2006

In suspension cultured cells of Nicotiana tabacum L. cv. Wisconsin 38 the .concentration of 18 nucleotides and 3 nucleosides have been determined using a new procedure developed for the extraction, purification and HPLC separation of these compounds from plant tissue. The different nucleotide pools increase in size immediately at the onset of the batch culture and reach distinct maxima at the very beginning of the proliferative phase. The main component are the uracil nucleotides with UDP‐sugars as the predominant fraction followed by the adenine nucleotides; the energy charge is maintained at a high and constant value throughout the whole culture time. During the growth interval the increases in the nucleotide pools reveal that the cell proliferation phase is followed by an extensive phase of cell elongation. Whereas the concentration of the total nucleotides varies by a factor of about 3 along the growth curve, the ratio of uracil to adenine nucleotides is kept fairly constant indicating regulatory mechanisms for correlation of the individual nucleotide pools.
Nitrogen metabolism and senescence‐associated changes during growth of carnation flowers
Authors: Kenis J. D. , Silvente S. T. , Trippi V. S.
Published: April 2006

Nitrogen metabolism including nitrate reductase (EC 1.6.6.1), glutamate dehydroge‐nase (EC 1.4.1.2) and glutamate‐oxalacetate aminotransferase (EC 2.6.1.1) activities were studied during growth of petals taken from carnation flowers (Dianthus caryophyllus L. cv. Sir Arthur) together with senescence parameters (lipid hydroper‐oxides, soluble amino acids and permeability). A slight decline in nitrogen percentage on a dry weight basis was found together with a sharp decrease in nitrate reduct‐ase, glutamate‐oxalacetate aminotransferase and glutamate dehydrogenase activities during the maximum growth phase, which was characterized by increase in respiration, dry weight, length, organic nitrogen and DNA per petal. Changes generally associated with senescence, like lipid hydroperoxide and soluble ammo nitrogen accumulation and increases in permeability began to appear already during early growth. The results indicate that permeability and proteolysis may be closely related. The possible significance of the decrease in nitrogen percentage and enzyme activities during growth of petals is discussed.
Hydrogen peroxide metabolism as an index of water stress tolerance in jute
Authors: Chowdhury S. Roy , Choudhuri M. A.
Published: April 2006

Two species of jute plants Corchorus capsularis L. (cv. JRC 212) and C. olitorius L. (cv. JRO 632) were subjected to water stress for 2 and 4 days by withholding water. The relative water content (RWC) decreased in both plants under water stress but to a greater extent in C. olitorius. The C. olitorius seedlings also showed greater membrane injury than C. capsularis seedlings under water stress as was evident from injury index data. Water stress increased glycolate oxidase (EC 1.1.3.1.) activity more in C. olitorius than in C. capsularis. The activity of superoxide dismutase (SOD, EC 1.15.1.1.) and catalase (EC 1.11.1.6.) decreased under water stress and their decrease was higher in C. olitorius than in C capsularis. The level of hydrogen peroxide and lipid peroxidation also increased in both plants under water stress and the increase was higher in C. olitorius than in C. capsularis seedlings. Under comparable external water stress, C. capsularis seedlings showed lower membrane damage, lower H2O2 accumulation and lower lipid peroxidation than C. olilorius which may be taken as indicative of higher water stress tolerance capacity of the former.
Delayed luminescence of air‐dry soybean seeds as a measure of their viability
Authors: Vesetova T. V. , Veselovsky V. A. , Rubin A. B. , Bochvarov P. Z.
Published: April 2006

Delayed luminescence (DL) excited by visible light has been observed in air‐dry seeds of various plants. Changes in seeds of soybeans (Glycine max L. W.) which occur during natural and accelerated aging were reflected in subsequent loss of vigor and DL increase. The increase of the luminescence is caused by the changes in seed biopolymers, leading to a decrease in their ability to take up water. The method makes it possible to measure DL from a single seed. With aging, the DL was shifted toward higher intensities and there was greater variability. By monitoring the DL of seeds it may be possible to evaluate their quality and storage capability.
The role of abscisic acid in the ripening of grapes
Authors: Palejwala Vaseem A. , Parikh Himanshu R. , Modi Vinod V.
Published: April 2006

Ripening in grapes (Vitis vinifera L. cv. Thompson seedless) was accompanied by an increase in the levels of sucrose, glucose and fructose and a decrease in the levels of acids. The activity of glucose‐6‐phosphatase and fructose‐l–6‐bisphospbatase was lower in sweet grapes as compared to sour ones. Abscisic acid (10−6 M) stimulated the gluconeogenic process in sour grapes. The levels of some gluconeogenic enzymes were also elevated in its presence. Cyclohexitnide (0.036–1.8 mM) nullified the abscisic acid effect, suggesting that this effect involves de novo protein synthesis. The incorporation of [14C]‐leucine into proteins was enhanced about 80% by abscisic acid, confirming that abscisic acid promoted protein synthesis. Again, cycloheximide blocked the hormone mediated increase in the incorporation of radioactivity into proteins. The results indicate that one of the factors for sourness in certain mature ripe grapes may be that abscisic acid is not available.
Senescence of detached leaves in pigeon pea and chick pea: Regulation by developing pods
Authors: Grover Anil , Sinha S. K.
Published: April 2006

The senescence rate of the subtending leaves in deflowered and control plants of pigeon pea ICajanus cajan (L.) Millsp. cv., Prabhat] and chick pea (Cicer arietinum L. cv. JG 62) were examined during the course of natural and induced senescence, at several stages of pod growth. The leaves from the top 5 nodes on the main axis in pigeon pea and the top 8 nodes on the main axis in chick pea were used throughout the experiments. The natural senescence was characterized in leaves taken directly from the field‐growing plants. For the study of induced senescence, the leaves were excised from both control and deflowered plants at various stages of pod growth and placed in test tubes containing water under dark conditions. Senescence was assessed in terms of peroxidase activity and contents of tola] chlorophyll, soluble amino acids and total protein. During natural ageing in the field, the leaves from deflowered plants exhibited delayed senescence in both the species. In contrast, the rate of ageing during induced senescence was higher in the leaves of deflowered plants than in the controls. Although of the same chronological age when excised for induced senescence, the leaves of deflowered plants were evideatly metabolically different from the controls, due to the fact that deflowered plants did not support the development of pods. This difference probably determined the subsequent rate of induced senescence.
14C Translocation pathways in honeylocust and green ash: Woody plants with complex leaf forms
Authors: Larson Philip R. , Dickson Richard E.
Published: April 2006

Long‐distance transport in plants requires precise knowledge of vascular pathways, and these pathways differ among species. This study examines the 14C translocation pathways in honeylocust (Gleditsia triacanthos L.) and green ash (Fraxinus pennsylvanica Marsh.), species with compound leaves, and compares them with those of cottonwood (Populus deltoides Bartr. ex Marsh.), a species with simple leaves. The stem vasculature of honeylocust conforms to a 2/5 helical phyllotaxy and that of green ash to a decussate phyllotaxy. The plastochron is relatively long in both species – 2.5+ days in honeylocust and 4.5+ days in green ash. Consequently, the transition from upward to downward translocation from mature source leaves is abrupt and occurs close to the apex. Export of 14C from localized treatment positions within a leaf was found to vary both quantitatively and spatially. To determine export patterns, 14CO2 was administered to either individual leaflets of once‐pinnate or pinnae of bipinnate leaves of honeylocust, and to either individual veins of simple or leaflets of compound leaves of green ash. Transections of either the petiole or rachis base were then examined for 14C by micro‐autoradiography. In all cases, as treatment positions advanced acropetally in the leaves, the bundles translocating 14C were situated more dorsally in the basal petiole and rachis vasculatures. 14C was confined to the right side of the vasculature when structures on the right side of a leaf were treated. Compound leaves of both species mature acropetally. Thus, mature basal pinnae of honeylocust and basal leaflets of green ash translocate acropetally to younger leaf parts that are still rapidly expanding. All translocation pathways, both in the stem and leaf, conformed with vascular organization previously determined by anatomical analyses.
Biochemical changes associated with the ripening of hot pepper fruit
Authors: Gross Ken C. , Watada Alley E. , Kang Meung Su , Kim Soon Dong , Kim Kwang Soo , Lee Sung Woo
Published: April 2006

Hot pepper (Capsicum annuum L. cv. Chooraehong) fruit underwent a respiratory climacteric during ripening. However, the rate of ethylene production was low, reaching a maximum of approximately 0.7 μl kg−1 h−1 at the climacteric peak when the surface color was 30 to 40% red. Ripening was accompanied by a loss of galactose and arabinose residues from the cell wall. The content of uronic acid and cellulose in the wall changed only slightly during ripening. The average molecular weight of a cell wall hemicellulosic fraction shifted progressively toward a lower molecular weight during ripening. Total β‐galactosidase (EC 3.2.1.23) activity increased 50‐fold from the immature green to the red ripe stage. No polygalacturonase (EC 3.2.1.15) activity was detected at any stage of ripeness. Thus, the loss of galactose and arabinose residues from the cell wall, as well as the observed modification of hemicelluloses during ripening, seem to be unrelated to active polygalacturonase. Soluble polyuronide content remained relatively constant at approximately 60 μg (g fresh weight)−1 as fruit ripended.
Dicyclohexylamine uptake and effects on polyamine content in cultured cotyledons of radiata pine
Authors: Biondi Stefania , Bagni Nello , Sansovini Alba
Published: April 2006

Excised cotyledons of radiata pine (Pinus radiata D. Don) were cultured in the presence or absence of benzyladenine and two concentrations of dicyclohexylamine, a potent inhibitor of spermidine synthesis in animals and bacteria. Cellular levels of the drug and of putrescine, spermidine and spermine were determined by dansylation followed by thin layer chromatography. The rate of uptake of the drug was rapid during the first 6 h of incubation and then diminished; nevertheless, its cellular content increased with time in culture and uptake was greater if more was present in the medium. Cotyledons cultured on benzyladenine‐containing media accumulated more dicyclohexylamine than on benzyladenine‐free media and this resulted in toxic side‐effects. The drug had no significant effect on the elongation growth occurring in the absence of the hormone. In cotyledons treated with the drug, spermidine levels fell to zero after a 5‐ to 10‐day exposure. Putrescine increased transiently at 24 h and then declined significantly. Spermine levels also declined to 11% of control values by day 5 and remained low throughout. Except for a marked decrease in all three polyamines during the first 24 h of culture, all control cotyledons maintained significantly higher polyamine levels than dicyclohexylamine‐treated ones.
Stimulation of polysaccharide formation by 2,4‐dichlorophenoxyacetic acid in callus tissues of Arabidopsis thaliana
Authors: Gotô Nobuharu
Published: April 2006

A relatively high concentration of 2,4‐dichlorophenoxyacetic acid (45 μM) in solid culture medium stimulated the formation and secretion of mucilage polysaccharides by callus tissues of Arabidopsis thaliana L. Heynh. (line Estland). The mucilage was composed of at least two polysaccharides as revealed by gel chromatography on Sepharose 4B: the major component (87%) eluted in the void volume (molecular weight 2 × 106 or greater) and the minor component (13%) eluted in the molecular weight range from 2 × 104 to 4 × 105. Both polysaccharide components contained small amounts of uronic acids. The major polysaccharide consisted mostly of galactose (49%), arabinose (28%) and fucose (10%), whereas the minor one consisted of galactose (44%), xylose (18%), arabinose (14%) and rhamnose (14%). One of the components of the secreted mucilage seems to be an arabinogalactan.
Starch turnover in shoot‐forming tobacco callus
Authors: Thorpe Trevor A. , Joy Richard W. , Leung David W. M.
Published: April 2006

Tobacco callus grown under shoot‐forming conditions or in the presence of gibberellic acid, which inhibits shoot formation, was incubated in [14C]‐sucrose at three different periods in culture and then replanted. Evolution of 14CO2 occurred during the 10 day post‐incubation period. Most of the radioactivity was incorporated into the ethanol‐soluble fraction, which lost most of its label after 24 h. Starch was the major ethanol‐insoluble component and post‐incubation synthesis occurred in this fraction for 24 h or longer. Greater net synthesis of starch occurred in shoot‐forming tissue and the loss of label from starch began later than in tissue cultured in the presence of gibbe‐rellic acid. Newly synthesized starch was not immediately utilised in the organogenic process, but its utilization could be correlated with the shoot‐forming process.
Effects of Cd2+ and EDTA on young sugar beets (Beta vulgaris). I. Cd2+ uptake and sugar accumulation
Authors: Greger Maria , Lindberg Sylvia
Published: April 2006

Sugar beets (Beta vulgaris L. cv. Monohill) grown in a complete nutrient solution, were treated with Cd2+ (5 or 50 μM) and/or EDTA (10 or 100 μM) in different combinations. The Cd contents of five‐week‐old roots and shoots were determined by atomic absorption spectrophotometry, and the sucrose, glucose and fructose contents were measured enzymatically. The Cd2+ uptake in both roots and shoots shows a linear relationship to the concentration of free Cd2+ in the nutrient solution. This uptake is diminished in the presence of EDTA, suggesting that the Cd‐EDTA complex is unable to penetrate the membranes. The contents of glucose, fructose and sucrose in both roots and shoots decrease with increasing uptake of free Cd2+. This may be a secondary effect caused by the inhibition of photosynthesis in the presence of Cd2+. EDTA reduces the inhibition of Cd2+ on sugar formation and accumulation. In the presence of EDTA alone the sugar content increases somewhat. EDTA slightly influences the dry weights of whole plants. The ratio roots:whole plants increases. Cd2+ (≤ 50 μM) increases the dry matter portion of roots by ca 30%, but not that of shoots.
Some physiological and growth responses of kiwi fruit (Actinidia chinensis) to flooding
Authors: Savé Robert , Serrano Lydia
Published: April 2006

The effects of long‐term flooding on the growth of six‐month‐old Actinidia chinensis Planch cv. Abbot plants and some effects on stomatal behaviour and leaf water relations were examined under controlled conditions for 28 days. Flooding caused stomatal closure and decreases in transpiration rate, xylem water potential, osmotic potential and turgor potential. Flooding also caused inhibition of the dry weight increase of leaves plus stems and of roots, chlorosis and necrosis of leaves, production of hypertrophied lenticels and the appearance of a small number of adventitious roots on the submerged portions of the stems. Rapid and partial stomatal closure by flooding may not only be due to the passive mechanical response which follows leaf dehydration, since flooded plants showed an increase in xylem water potential and osmotic potential during the first days of the experiment. The marked intolerance of Actinidia chinensis to flooding has been a serious barrier to its culture in poorly drained soils, hence careful irrigation management is required.
Nitrogen fixation and biomass production in symbioses between Alnus incana and Frankia strains with different hydrogen metabolism
Authors: Sellstedt Anita , Huss‐Danell Kerstin , Ahlqvist Ann‐Sofi
Published: April 2006

Three different strains of Frankia, the pure cultures AvcI1 and CpI1 and a local strain (crushed nodule inoculum), were compared in symbiosis with one clone of Alnus incana (L.) Moench. Hydrogen metabolism, nitrogenase (EC 1.7.99.2) activity and relative efficiency of nitrogenase were studied as well as growth and nitrogen content of the plants. The local Frankia strain showed no measurable hydrogen uptake but high H2‐evolution. No H2‐evolution was detected in Frankia AvcI1 because of its hydrogenase activity. CpI1 also had hydrogenase, although only a very small H2‐evolution was detected at the end of the growth period. Hydrogenase activity was detected both in pure cultures and nodule homogenates of CpI1 and AvcI1. Growth, biomass production and nitrogen content were highest in alders inoculated with Frankia AvcI1 while the lowest values were found for alders living in symbiosis with the local Frankia strain. The presence of hydrogenase in Frankia seemed to be benefical for growth and biomass production in the alders. However, the strains also differed with respect to spore formation. The local strain, but not AvcI1 and CpI1, formed spores in the root nodules.
Growth, contents of K+ and kinetics of K+(86Rb) uptake in barley cultured at different low supply rates of potassium
Authors: Pettersson Sune
Published: April 2006

Plants of barley (Hordeum vulgare L. cv. Salve) were grown with 6.5–35% relative increase of K+ supply per day (RKR) using a special computer‐controlled culture unit. After a few days on the culture solution the plants adapted their relative growth rate (RGR) to the rate of nutrient supply. The roots of the plants remained in a low salt status irrespective of the rate of nutrient supply, whereas the concentration of K+ in shoots increased with RKR. Both Vmax and Km for K+(86Rb) influx increased with RKR. It is concluded that with a continuous and stable K+ stress, the K+ uptake system is adjusted to provide an effective K+ uptake at each given RKR. Allosteric regulation of K+ influx does not occur and efflux of K+ is very small.
Light‐mediated bioregulation of tillering and photosynthate partitioning in wheat
Authors: Kasperbauer M. J. , Karlen D. L.
Published: April 2006

The influence of plant population density on spectral distribution of light received by wheat (Triticum aestivum L. cv. Coker 797) seedlings was measured under field conditions, and effects of red and far‐red light on tillering and photosynthate partitioning were studied in controlled environments. Spectral distribution of light was measured in sunflecks at soil level in close‐, intermediate‐, and wide‐spaced field populations during the tillering stage. Close‐spaced seedlings received higher far‐red/red light ratios than wide‐spaced plants because of the larger amount of far‐red reflected from green leaves of the more numerous nearby plants. The far‐red/red light ratios in all population densities were higher in late afternoon than at noon. Close‐spaced plants developed fewer tillers, less roots and longer leaves than wide‐spaced seedlings under field conditions. In controlled environments, a higher far‐red/red ratio during photosynthetic periods resulted in fewer tillers and longer leaves; whereas, brief red or far‐red exposures at the end of each day had a more pronounced effect. Wheat seedlings that received 5‐min exposures to far‐red light at the end of the photosynthetic period each day for 20 consecutive days developed fewer tillers, longer leaves, less roots, and a higher shoot/root biomass ratio. The effects of far‐red light were reversed by red light. The light spectral shifts associated with field plant population densities and the responses to red and far‐red treatments under controlled environments suggest that phytochrome serves as a sensing mechanism that detects the amount of competition from other plants, and regulates the development of tillers and the partitioning of photosynthate between shoots and roots.
Control of Na+ and K+ transport in Spergularia marina I. Transpiration effects
Authors: Cheeseman John M. , Wickens Linda K.
Published: April 2006

In this paper we begin our study of factors controlling Na+ and K+ uptake in the halophyte Spergularia marina (L.) Griseb., with emphasis on plants growing at moderate salinity (0.2x sea water). The involvement of transpiration was considered first because of its potential to account for much or all of the transport of ions, and particularly of Na+, to the shoot under these growth conditions. Transpiration was constant with time through most of the light period, quickly dropping to 6% of the day time rate at night. 22Na+ uptake, on the other hand, showed much less day/night variation, and relative transport to the shoot was constant. After establishing that transpiration was linearly related to leaf weight, possible transpiration effects were further considered as correlations between leaf weight and transport to the shoot. Under constant, day‐time conditions, with linear effects of time and plant size removed, total transport of 22Na+ to the shoot (per plant) was not correlated to leaf weight. A similar result was found when transport was expressed per gram of root, and when partitioning of total label to the shoot was considered. Finally, the correlation was considered between leaf weight and a Na+/K+ enrichment factor defined as the Na+/K+ ratio in the leaves divided by that in the roots. This correlation was also insignificant. The results indicate that analysis of control of Na+ and K+ uptake and transport in this experimental system need not consider effects of transpiration.
Effects of salicylhydroxamate on respiration, seed germination and seedling growth in Avena fatua
Authors: Upadhyaya Mahesh K.
Published: April 2006

The effects of inhibitors of alternative respiration [salicylhydroxamate (SHAM) and propyl gallate (PG)] on germination, seedling growth and O2 uptake in Avena fatua L. (wild oats) were studied. SHAM did not inhibit germination or O2 uptake prior to germination. SHAM‐sensitive (alternative) respiration, therefore, cannot be a pre‐requisite for germination. Following germination, both chemicals inhibited seedling growth with the root being more susceptible than the shoot. SHAM concentrations that inhibited root growth by 90 to 95%, inhibited O2 uptake of 1 cm root apices by less than 15%. While sodium azide (a cytochrome‐oxidase inhibitor; 1 mM) alone inhibited O2 uptake by only 40 to 50%, in the simultaneous presence of SHAM (or PG), O2 uptake was inhibited by 90 to 99%. Thus: 1) respiration of wild oat seedling root apices is predominantly cytochrome‐mediated and incomplete inhibition of O2 uptake in the presence of azide alone is due to diversion of electrons to the alternative pathway and 2) even though these roots have little alternative respiration, they maintain the capacity to support a much greater flux of electrons via this path way. SHAM and PG at concentrations (0.05 to 0.4 mM) which inhibited O2 uptake significantly in the presence (but not in the absence) of azide had little effect on root growth suggesting that an effect(s) other than that on respiration is involved in the inhibition of root growth at higher concentrations. The effect of SHAM on wild oat root growth is not selective as it also inhibits growth of a number of crop species.
Salt balance of leaves of the mangrove Avicennia marina
Authors: Waisel Y. , Eshel A. , Agami M.
Published: April 2006

The contribution of each of the salt‐transporting processes to the NaCl balance of the leaves of the salt‐recreting mangrove Avicennia marina (Forssk.) Vierh. was quantitatively investigated. Transpiration rates, xylem sap concentration, leaf salt content, recretion rates and rates of salt retranslocation out of the leaves were continuously monitored during three day periods and the salt fluxes in and out of the leaves were calculated. The results indicated that salt filtration by the roots is by far the most important salt‐rejecting mechanism, preventing some 80% of the salt which is carried towards the root surface by the transpiration stream, from entering the shoot. Out of the remaining quantity of salts which enter the root xylem and reach the leaves, only 40% is removed by the salt‐recreting glands.
Enzymes of assimilatory sulfate reduction in leaves of Pisum sativum: Activity changes during ontogeny and in vivo regulation by H2S and cyst(e)ine
Authors: von Arb Christoph , Brunold Christian
Published: April 2006

Enzyme activities of assimilatory sulfate reduction were measured in leaves of Pisum sativum L., cv. Vatters Frühbusch, during their ontogenetic development, and during treatment with H2S and cyst(e)ine. Ribulose bisphosphate (RuBP) carboxylase (EC 4.1.1.39) and ferredoxin‐dependent nitrite reductase (Fd‐NiR, EC 1.7.7.1) were measured for comparison. In etiolated pea leaves, ATP‐sulfurylase (ATPase, EC 2.7.7.4), adenosine 5′‐phosphosulfate sulfotransferase (APSSTase), ferredoxin‐dependent sulfite reductase (Fd‐SiR, EC 1.8.7.1) and O‐acetyl‐L‐serine sulfhydrylase (OASSase, EC 4.2.99.8) activities were measured in appreciable rates, while neither RuBP carboxylase nor Fd‐NiR activities could be detected.

During the first 2–7 days after transfer into the light all enzyme activities increased. After reaching maximal activities, ATPase, APSSTase, and Fd‐SiR activities decreased in all leaves to low or indetectable levels during the following 3–6 days. RuBP carboxylase, Fd‐NiR and OASSase, on the other hand, decreased slowly and were still at high levels of activity at the end of the experiment.

Fumigation of pea plants with 1.5 μl l−1 H2S delayed the initial increase and the subsequent decrease of ATPase activity by 1–3 days. APSSTase activity decreased for 1–2 days, increased rapidly during the next 4–6 days and retained a high level of activity until the end of the experiment as did Fd‐SiR. One to two days after the beginning of fumigation the leaves started to accumulate high amounts of cyst(e)ine.

When pea plants with excised roots were placed on a nutrient solution containing cyst(e)ine, APSSTase activity decreased more on 0.2 and 0.5 mM than on 1.0 mM. Fd‐SiR activity was only slightly decreased on 1.0 mM cyst(e)ine. Neither Fd‐NiR nor RuBP carboxylase activities were affected.
Leakage of UV‐absorbing substances as a measure of salt injury in leaf tissue of woody species
Authors: Redmann R. E. , Haraldson J. , Gusta L. V.
Published: April 2006

Leakage of UV‐absorbing substances from leaf discs was used to determine salt and osmotic injury after treatment. A relative leakage ratio was calculated by dividing the UV absorption after treatment by the total absorption obtained after freeze‐killing the tissue. Time‐course results using Populus tremuloides Michx. leaves indicated 24 h as an appropriate treatment duration. NaCl and KCl caused more leakage than Na2SO4 and K2SO4 in P. tremuloides and Fraxinus pennsylvanica Marsh, the most sensitive species tested. Amelanchier alnifolia (Nutt.) Nutt. ex Roem. was more sensitive to K2SO4 than to KCl. Elaeagnus angustifolia L. and Caragana arborescens Lm. were the most tolerant to both salts. Tolerance to salts was greater in August than earlier in the growing season. Treatment of leaves with solutions of sucrose, PEG‐8000 and mannitol iso‐osmotic with KCl and NaCl showed that increased leakage was caused by specific ion effects, rather than osmotic effects.
Autumnal changes in total nitrogen, salt‐extractable proteins and amino acids in leaves and adjacent bark of black alder, eastern cottonwood and white basswood
Authors: Côtté Benoît , Dawson Jeffrey O.
Published: April 2006

Autumnal changes in total nitrogen, salt‐extractable protein and amino acid concentrations in leaves and adjacent bark of black alder [Ainus glutinosa (L.) Gaertn.], eastern cottonwood (Populus deltoides Bartr. ex Marsh.) and white basswood (Tilia heterophylla Vent.) were determined for trees growing on minespoils and a prairiederived loamy soil in central Illinois. The composition of free amino acids in foliage was also determined at peak concentration for each tree species during late senescence. Total nitrogen concentration in the leaves decreased slowly throughout most of the fall for all species. In the final stages of senescence, total leaf nitrogen concentrations were about halved in eastern cottonwood and white basswood but continued to decrease slowly in black alder. The concentration of salt‐extractable proteins in leaves of all species peaked early in the fall and then declined prior to leaf abscission. This decline coincided with an increase in the concentration of free amino acids in the leaves. The increase stabilized in both eastern poplar and white basswood but continued in black alder. Glutamine in black alder and eastern cottonwood, and asparagine in white basswood were the most abundant free amino acids at the time of peak concentration of total free amino acids in senescent leaves. Bark of trees of all species had higher nitrogen concentrations and higher proportions of salt‐extractable proteins to estimated total proteins after leaf senescence than during the preceding summer. Results indicate that autumnal fluxes in leaf and bark nitrogen fractions of alder can differ substantially from fluxes in other broadleaved winter‐deciduous trees in a way which suggests that alder does not effectively conserve leaf nitrogen through retranslocation to bark tissue.
Stimulation of cytokinins and chlorophyll synthesis in cucumber cotyledons by triadimefon
Authors: Fletcher R. A. , Arnold V.
Published: April 2006

Triadimefon [1‐(4‐chlorophenoxy)‐3,3‐dimethyl‐1‐(1,2,4‐triazol‐1‐yl)‐2‐butanone] changes the morphology and partitioning of dry matter in cucumber (Cucumis sativus L. cv. National Pickling) seedlings. The dry weights, potassium and cytokinin levels in the cotyledons and roots of the treated seedlings were higher, whereas the hypocotyl weights were lower than the controls. When etiolated intact seedlings or cotyledons excised from triadimefon‐pretreated dark‐grown seedlings were exposed to light, chlorophyll synthesis in the pretreated cotyledons was stimulated. Triadimefon does not have cytokinin‐like activity in the cucumber cotyledon greening bioassay, but appears to induce the plants to produce more cytokinims, probably by stimulating root growth. Hence it is proposed that the stimulation of chlorophyll production by triadimefon in cucumber cotyledons is mediated by maintaining high levels of potassium and cytokinins in the cotyledons.
Blue light regulation of stomata in wheat seedlings. II. Action spectrum and search for action dichroism
Authors: Karlsson Per Erik
Published: April 2006

The stomatal conductance response to low intensity blue light was studied in wheat seedlings (Triticum aestivum L. cv. Starke II, Weibull) under red background illumination. Reciprocity was shown to be valid for illumination times from 10 s up to about 2 min. The action spectrum, constructed from fluence rate response curves, showed a maximum peak at 445–450 nm, another peak at 470 nm, a slight shoulder at 420 nm and a plateau between 370–400 nm. The relationship with action spectra for other blue light responses is discussed. The blue light response of wheat stomata did not exhibit action dichroism (the direction of the electrical vector of polarized blue light did not influence the response of the guard cells).
Thigmomorphogenesis: Field and laboratory studies of Abies fraseri in response to wind or mechanical perturbation
Authors: Telewski Frank W. , Jaffe Mordecai J.
Published: April 2006

Field‐ and greenhouse‐grown Abies fraseri (Pursh) Poir. (Fraser fir) were analyzed for wind‐ or mechanically‐induced flexure changes. These changes included inhibition of stem and needle elongation, reinforcement of branch bases around the stem, and increased radial growth in the direction of the mechanical perturbation (MP). Mature trees exposed to high wind conditions were severely flag‐formed. These modified tree crowns had a lower drag than crowns of non‐flag formed trees in wind‐tunnel tests. In both field‐grown and greenhouse‐grown A. fraseri, MP induced a decrease in flexibility and increased elasticity of the stems. The increased radial growth of the stems overrode the increase in elasticity, resulting in the overall decrease in flexibility. The increase in radial growth caused by wind or mechanical flexure was due to greater cell divisions of the vascular cambium, resulting in increased numbers of tracheids. The decrease in stem elongation in these trees was due, at least in part, to a decrease in tracheid length. The potential biological and mechanical significance of these induced growth changes in trees are addressed. The data support the thigmomorphogenetic theory, which states that plants respond to wind and other mechanical perturbations in a way that is favorable to the plant for continued survival in windy environments.
Dormancy and seasonal changes of plant growth regulators in hazel buds
Authors: Rodríguez Ana , Sánchez‐Tamés Ricardo
Published: April 2006

Levels of indole‐3‐acetic acid (IAA), abscisic acid (ABA) and total phenolic compounds have been determined in hazel (Corylus avellana L. cv. Negreta) buds. IAA and ABA were quantified by flame ionization detector gas‐chromatography, and the phenolic content determined by a colorimetric technique. The highest level of free ABA occurs in autumn, approximately at the onset of winter dormancy, and it is lowest just before bud burst; suggesting that ABA plays an important role in the induction and maintenance of winter dormancy. The opposite result was obtained for IAA; the level of this regulator was low in autumn and showed a sharp increase just before budbreak. With respect to phenols, an apparent correlation can be observed between them and ABA in at least some of the fractions studied (acid and residual), so that they may enhance the inhibitory effect of ABA. The IAA/inhibitor balance showed a clear correlation with dormancy. In autumn (dormant buds), this balance is in favour of the inhibitors while the balance shifts towards IAA at the end of winter.
The dynamics of the flavour precursors, the S‐alk(en)yl‐L‐cysteine sulphoxides, during leaf blade and scale development in the onion (Allium cepa)
Authors: Lancaster Jane E. , McCallion Barbara J. , Shaw Martin L.
Published: April 2006

This study was undertaken to determine the patterns of accumulation and loss of the flavour precursors. (+) S‐1‐propyl‐L‐cysteine sulphoxide, (+) trans‐S‐1‐propenyl‐L‐cysteine sulphoxide, and (+) S‐1‐methyl‐L‐cysteine sulphoxide, during the development and senescence of the leaf blades and scales of a brown onion (Allium cepa L. cv. Pukekohe Longkeeper).

The levels of the flavour precursors were related to the ontogeny of the individual leaf blade and scale, and the ontogeny of the entire plant. Leaf blades which developed on a young or bulbing onion contained all 3 flavour precursors (total of about 50–70 mg leaf−1); but as each attached scale developed, the leaf blades lost their flavour precursors. All 3 flavour precursors increased in the developing scales and decreased in the senescing scales. Leaf blades which developed on an older, ripening onion contained, and then lost, only (+) S‐1‐propyl‐L‐cysteine sulphoxide, whilst the scales accumulated only (+) S‐1‐propyl‐L‐cysteine sulphoxide; (+) S‐1‐methyl‐L‐cysteine sulphoxide and (+) trans‐S‐1‐propenyl‐L‐cysteine sulphoxide were minimal. In the main scales of the onion, which did not senesce during ripening, there was a transition between these two patterns. These scales accumulated all 3 flavour precursors with (+) S‐1‐propyl‐L‐cysteine sulphoxide remaining constant at about 30 mg/scale; however there was a 10 fold loss of the other 2 flavour precursors (from 20 to about 2 mg/scale). The base plate (true stem) contained mainly (+) S‐1‐propyl‐L‐cysteine sulphoxide, which increased 5 fold in amount during bulbing. The other 2 flavour precursors were present at much lower levels.

A recycling of flavour precursors is suggested, with the leaf blades supplying flavour precursors to scales, and in turn older senescing scales recycling their flavour precursors to developing younger scales.
Phototransformation of protochlorophyll(ide) by a proplastid fraction from Euglena
Authors: Stürzl Erwin , Schiff Jerome A.
Published: April 2006

The phototransformation of protochlorophyll(ide) (Pchl(ide)) to chlorophyll(ide) (Chl(ide)) can be demonstrated in a proplastid fraction from Euglena gracilis Klebs var. bacillaris Cori if appropriate conditions are employed. Pigments were measured fluorometrically in acetone extracts of cell or organelles. Pchl(ide) and the phototransformation to Chl(ide) are at their highest levels in cells grown in darkness on normal or low vitamin B12‐containing medium (pH 3.5) to the late exponential phase (1.2–1.4 × 106 cells ml−1). Late exponential cells on low B12 medium yield a proplastid fraction that contains Pchl(ide) which is phototransformed to Chl(ide) when illuminated with red light (5.6 W m−2 for 4 min) in the presence of 10 mM Hepes, 20 mM TES, 0.5 mM potassium phosphate (pH 7.4), 70 mM sorbitol, 5 mM DTT, 5 mM ATP, 5 mM fructose‐1, 6‐bisphosphate, 10 mM malate and 2 mM MgCl2; intact organelles appear to be involved since deletion of osmoticum gives a lower activity, and addition of NAD(P)H is without effect. Phototransformation of Pchl(ide) to Chl(ide) in red light shows Bunsen‐Roscoe reciprocity between fluence rate and duration of illumination. Although mitochondria are present, they do not appear to be involved since inhibitors of respiration and uncouplers of oxidative phosphorylation fail to block the phototransformation. The percentage phototransformation of Pchl(ide) to Chl(ide) in late exponential normal B12 cells is 61 ± 10, and is 52 ± 3 in low B12 cells. About 67% of the activity in low B12 cells is recovered in the proplastid fraction incubated with the complete incubation mixture in saturating light. In both types of cells and in the proplastid fraction, the stoichiometry of conversion of Pchl(ide) to Chl(ide) is about 1:1 (mol/mol).
Effects of NH+4‐N and NO+3‐N on growth and metabolism of Sphagnum magellanicum
Authors: Rudolph Hansjörg , Voigt Jan Uwe
Published: April 2006

Photosynthetic CO2‐fixation, chlorophyll content, growth rate and nitrate reductase activity were used to examine the influence of NH+4‐N and NO−3‐N on Sphagnum magellanicum cultivated under defined conditions in phytotrons. NO−3‐concentrations up to 322 μM were found to be favourable. Increased NH+4 concentrations, however, resulted in growth inhibition and decreased chlorophyll content at concentrations ≧ 255 μM; e.g. 600 μM NH+4 caused a 20% reduction of nitrate reductase activity and net photosynthesis. For raised bog Sphagna an improved standard nutrient solution is proposed with the following ion concentrations (μM): 55 Na+; 17 K+; 95 NH+4; 22 Ca2+; 22 Mg2+; 2 Fe3+; 20 Cl−; 100 NO−3; 57 SO2‐4; 7.4 H2PO−4; trace elements: A‐Z solution (Hoagland) 50 μl 1000 ml−1; pH 5.8.
Influence of exogenously supplied potassium and sodium salts on the abscisic acid‐induced proline accumulation in barley leaf segments
Authors: Pesci P. , Beffagna N.
Published: April 2006

A stimulation of the abscisic acid (ABA)‐induced increase in proline was observed in leaf segments of barley (Hordeum vulgare L. cv. Georgie) if K+ or Na+ were supplied in the external medium as salts of monovalent anions such as NO3, Br, Cr and I, but not when sulphate or phosphate were used. To a lesser extent, the effect was evident also with RbCl, but it did not occur when chlorides of Li+. Cs+, NH4+, Mg:+ and Ca2+ were used. Both KC1 and NaCl in the concentration range 2–100 mM influence the ABA‐dependent proline accumulation to the same extent; the increase induced was about 100% at 10 mM, and reached a maximum between 60 and 100 mM. The effect is not due to the osmotic activity of the salts and does not seem to depend on changes in K+ and Na+ levels within the leaf tissue, but it is somehow linked to their external concentration. The existence of a specific interaction between ABA and K+ or Na+, possibly at the cell membrane level, is proposed.
Growth and solute accumulation in 3‐week‐old seedlings of Agropyron elongatiun stressed with sodium and potassium salts
Authors: Weimberg Ralph
Published: April 2006

Agropyron elongatum [Host. (Beauv.)] [cv. Arizona Glendale, was grown in liquid medium salinized with either NaCl, KCI, or a 50:50 mixture of these two salts at osmotic potentials ranging from 0 to –1.6 MPa. The amount of growth in 21 days was measured, and extracts were made of the shoots at this time. The extracts were assayed for low‐molecular‐weight organic compounds (glucose, fructose, sucrose, be‐taine, proline) and inorganic solutes (Na+, K+, Cl−, P.). The purpose was to determine if there was any correlation between the harmful effect of salinity on growth and the concentrations of solutes in tissues. Growth inhibition of A. elongatum was roughly proportional to the osmotic potential of the growth medium and was independent of the ionic composition of the salinizing salts. Total monovalent cation (the sum of Na+ and K+) concentrations and the ratio of these two cations in leaves were mainly a function of the ionic compostion of the salt in growth media, and, to a lesser degree, of osmotic potentials. F At an osmotic potential of –0.2 MPa, total monovalent cation in leaves was the same as in non‐stressed plants. However, if the salinizing salt contained NaCl, there was an increase in foliar Na+ with a balancing decrease in K+. At stress levels between –0.4 and –1,6 MPa, and, if the media were salinized with either 100% NaCl or a 50:50 mixture of NaCl and KCI, total monovalent cation concentrations remained constant at a value that was twice that in non‐stressed plants. Although total monovalent cation concentrations were equal in plants grown under these two salinity conditions, the K+/Na+ ratios shifted from a value of 1:2 in plants grown in 100% NaCl to 3:1 in plants subjected to the 50:50 mixture. If 100% KCI was used to salinize media, total monovalent cation was 80% of its concentration in NaCl‐treated plants in the range of –0.4 to ‐1.2 MPa. At –1.6 MPa due to 100% KCI, total monovalent cation was double that in plants subjected to ‐0.4 MPa. In the range of osmotic potentials from–0.2 to –1.2 MPa, the chloride:cation ratio was 1:2. At –1.6 MPa the ratio changed to 3:4. Proline started accumulating in leaves of A. elongatum when the tissue concentration of total monovalent cation exceeded 200 μ (g fresh weight)−1. Above this threshold value of total monovalent cation, the proline concentration of leaves was 6% of the amount of total monovalent cation that exceeded 200 umol (g fresh weight)1.
Salicylate‐collapsed membrane potential in pea stem mitochondria
Authors: Macri Francesco , Vianello Angelo , Pennazio Sergio
Published: April 2006

Salicylate, acetylsalicylate, benzoate and 3,5‐diiodosalicylate were examined for their effects on pea (Pisum sativum L. cv. Alaska) stem mitochondria and on a tonoplast‐enriched fraction. Salicylate collapsed the transmembrane electrochemical potential of mitochondria and the ATP‐dependent proton gradient of the tonoplast‐enriched vesicle preparation. Benzoate and acetylsalicylate did not show any effect, while 3,5‐diiodosalicylate inhibited both basal O2 consumption and ATPase activity of pea mitochondria. Salicylate seems to act as a protonophore. However, its effect is evident only at concentrations higher than those required by classical protonophores and, in addition, can be abolished after removing salicylate from the incubation medium. The activity of salicylate appears linked to the presence of the free phenolic hydroxyl on the benzene ring.
The influence of NaCl on Δ1‐pyrroline‐5‐carboxylate reductase in proline‐accumulating cell suspension cultures of Mesembryanthemum nodiflorum and other halophytes
Authors: Treichel Siegfried
Published: April 2006

Pyrroline‐5‐carboxylate (P‐5‐C) reductase (EC 1.5.1.2) was extracted from cell suspension cultures, which proved to be very suitable for investigation of proline accumulation. Proline accumulation in cell suspensions of M. nodiflorum L., as well as P‐5‐C reductase activity and substrate affinity, increased with progressive adaptation to NaCl stress. In vitro NaCl treatment inhibited enzyme activity and decreased substrate affinity, independent of pretreatment of the cells. NaCl concentrations below 100 mM did not inhibit enzyme activity of adapted cells. High substrate concentrations counteracted in vitro NaCl inhibition (up to 200 mM). Cycloheximide inhibited the increase of P‐5‐C reductase activity, as well as proline accumulation, after NaCl treatment, indicating stress‐induced de novo synthesis of the enzyme. The different reactions of P‐5‐C reductase upon salt treatment are discussed with respect to its possible role in the regulation of proline accumulation.
Localization of phytase and acid phosphatase isoenzymes in aleurone layers of barley
Authors: Gabard Kenneth A. , Jones Russell L.
Published: April 2006

The localization of acid phosphatase (EC 3.1.3.2) in aleurone layers of barley (Hordeum vulgare L. cv. Himalaya) grains was studied. Phosphatase (EC 3.1.3.26) activity, assayed with phytic acid as the substrate, is present in the dry grain at low leveis and increases during incubation in H2O at 25°C for three days. When aleurone layers are isolated from imbibed grain and incubated for 18 h in buffer with or without 50 μM gibberellic acid (GA3), the level of extractable phosphatase activity increases two‐ to threefold, and phosphatase is released into the medium. GA, promotes the release of phosphatase activity: aleurone layers incubated in GA, release twice as much phosphatase as layers incubated in buffer. Nine isoenzymes of phosphatase are found in aleurone layers of barley by non‐denaturing polyacrvlamide gel electropho‐resis. Six of these forms, isoenzymes 1,2,3,5,6 and 8, can be extracted from dry tissue, and after three days of imbibition in H2O an additional isoenzyme, isoenzyme 9, is found in aleurone extracts. When isolated aleurone layers are incubated for a further 22 h in buffer with or without GA3, isoenzyme 7 is found and yet another form, isoenzyme 4, is found in layers incubated in GA3. Eight isoenzymes are released from aleurone layers into the incubation medium. Isoenzymes 5 and 6 are released in buffer both with and without GA3, even when cycloheximide is present; cycloheximide inhibits the release of the other isoenzymes. Isoenzymes 1‐4, 7 and 8, on the other hand, are secreted into the incubation medium only when GA3, is present. Isoenzyme 9 is not released into the incubation medium. Acid phosphatase activity was localized in aleurone tissue using cytochemical, cell fractionation, and enzymatic methods. Cytochemical localization of ATPase (EC 3.6.1.8) in aleurone tissue showed the presence of enzyme activity in cell wall, protein bodies, endoplasmic reticulum, Golgi apparatus, and mitochondria. Analysis of organelle fractions isolated by density gradient centrifugation showed that the activity of acid phosphatase isoenzymes 1, 2 and 3 was prominently associated with the phytin globoid of protein bodies, and analysis of the activity released from the cell wall by enzymatic digestion showed that it was almost exclusively isoenzymes 5 and 6.