bluuebunny/crossref_metadata_2025 huggingface dataset:
Nutrient reserves of Salicornia europaea seeds
Authors: Austenfeld Franz‐Arnold
Published: May 2006

Seeds of Salicornia europaea L. were analyzed for their nutrient reserves. The content of potassium and sodium was 216 and 39 mmol (kg dry seeds)‐1, respectively. Calcium and magnesium accounted for 30 and 138 mmol (kg dry seeds)‐1, respectively. Whereas most of the alkali metals were water soluble, the alkaline earth metals were mostly acid soluble. The acid‐soluble calcium plus magnesium corresponded well with the acid‐soluble phosphate. Chloride was accumulated to a level equivalent to that of sodium. Carbonate was present at a concentration of 9 mmol (kg dry seeds)‐1. Carbohydrates accounted for 93 g (kg dry seeds)‐1, nearly half of which was derived from sucrose. Fructose and glucose were present only in traces. Total nitrogen was determined to be 55 g (kg dry seeds)‐1, 16% of which was diethylether soluble. The remaining nitrogen was separated into 39 g (kg dry seeds)‐1 ethanol‐insoluble and 8 g (kg dry seeds)‐1 ethanol‐soluble nitrogen. About 10% of the ethanol‐soluble nitrogen were derived from amino acids. Total lipid content was about 280 g (kg dry seeds)‐1. The alcoholic component of the storage lipids was glycerol and the glycerides were calculated from gas chromatography to be 66% of the total lipids. About 90% of the fatty acids consisted of unsaturated acids, linoleic and oleic acid, the majority (77%) of which was linoleic acid.
Differences between the flag leaf and the ear of a spring wheat cultivar (Triticum aestivum cv. Arkas) with respect to the CO2 response of assimilation, respiration and stomatal conductance
Authors: Knoppik D. , Selinger H. , Ziegler‐Jöns A.
Published: May 2006

The CO2‐ and H2O‐exchanges in the flag leaf and the ear of a spring wheat cultivar (Triticum aestivum L. cv. Arkas) were measured at CO2 partial pressures, pi(CO2), between 8 and 400 Pa under high photosynthetic photon flux densities (2000 μmol m−2 s−1). The experiments were carried out on each organ separately while attached to the intact plant, from the time of ear emergence through senescence. To study the contribution of the kernels to the gas exchange of ears, experiments were also carried out on sterilized ears (treatment A), and on ears from which the kernels were removed (treatment B).

Flag leaves and ears differed considerably with regard to CO2‐dependence of assimilation, response of stomata to varying pa(CO2), CO2 compensation point (and its temperature dependence), dark respiration, and dissimilation in the light (i.e. CO2 production which is not due to oxygenation of ribulose 1,5‐bisphosphate). The higher dark respiration of the ear originated mainly from the kernels and continued to some extent in the light. Thus, the CO2 compensation point was attained at higher CO2 partial pressures for the ear than for the flag leaf.

The CO2 uptake of the ear was not saturated at intercellular CO2 partial pressures below 180 Pa CO2, while that of the flag leaf reached saturation at about 80 Pa CO2. CO2‐saturated rates of CO2 uptake were 2.5 and 1.5 times the rates at natural CO2 partial pressure for ear and flag leaf, respectively. The stomatal conductance decreased with rising CO2 partial pressure above 35 Pa, in a more pronounced manner for the flag leaf than for the ear.
The acyl lipid composition of wheat leaves and moss protonemata using a new, non‐carcinogenic extraction solvent system
Authors: Somersalo Susanne , Karunen Pirjo , Aro Eva‐Mari
Published: May 2006

As chloroform has proved to be carcinogenic we were looking for an alternative solvent system for chloroform:methanol widely used in plant lipid investigations. The lipids from leaves of wheat (Triticum aestivum L. cv. Vakka) and from protonemata of the moss Ceratodon purpureus (Hedw.) Brid. were extracted with two petroleum ether:methanol solvent systems. The polar lipids were separated by two‐dimensional thin‐layer chromatography and the amounts of each lipid class were compared with those obtained from chloroform:methanol (2:1, v/v) extractions. The significantly higher amounts of phosphatidylinositol observed in petroleum ether:methanol (1:1, v/v) extraction suggest that the small amounts reported earlier in plants may be an artefact relating to the solvent system used. As petroleum ether:methanol (1:1, v/v) proved to be at least as good a solvent system as chloroform:methanol (2:1, v/v) we propose it as an alternative extractant for plant polar lipids.
Cytometry and flow cytometry of 4′,6‐diamidino‐2‐phenylindole (DAPI)‐stained suspensions of nuclei released from fresh and fixed tissues of plants
Authors: Sgorbati Sergio , Levi Marisa , Sparvoli Elio , Trezzi Federica , Lucchini Giovanni
Published: May 2006

Cytometry and flow cytometry were used to study characteristics of fluorescence of the DNA‐DAPI complex in nuclei released from different fresh and formaldehyde‐fixed pea (Pisum sativum L. cv. Lincoln) tissues. The two methods of isolation are compared and discussed as well as their possible use for quantitative analysis of DNA in plant tissues. With fixed tissues it is possible to obtain a number of nuclei sufficient for the flow cytometric analysis, even using small amounts of plant tissue.
Effect of short‐term dark incubation with sulfate, chloride and selenate on the glutathione content of spinach leaf discs
Authors: de Kok Luit J. , Kuiper Pieter J. C.
Published: May 2006

A 24 h incubation of leaf discs of spinach (Spinacia oleracea L. cv. Estivato) in darkness with 50 and 100 mM sulfate resulted in a two‐ to three‐fold increase in the level of glutathione (GSH), a compound which may serve as storage of excess reduced sulfur in the plant. The accumulated GSH was a small fraction (around 1%) of the sulfate taken up in the spinach leaf discs. Incubation of spinach leaf discs with 50 and 100 mM chloride resulted in only a 30% increase of the water‐soluble non‐protein‐SH; the uptake of electrolytes was comparable to that observed with sulfate. This indicated that the increase of the GSH level upon incubation with sulfate was rather specific and not due to salinity. Incubation with 50 mM Na2SO4 did not affect water‐soluble protein‐SH content after 24 h. Addition of 1 and 10 mM selenate, an inhibitor of sulfate reduction, strongly reduced sulfate‐induced GSH accumulation in spinach leaf discs, both in light and darkness. It was concluded that the sulfate‐induced SH accumulation was due to a substantial de novo reduction of sulfate in darkness and subsequent incorporation of the reduced sulfur into GSH. The role of the sulfate concentration at the reaction site of ATP sulfurylase in the regulation of sulfur assimilation in the plant is discussed with respect to the low affinity of the enzyme for sulfate.
Mechanism of phosphorus‐induced zinc deficiency in cotton. I. Zinc deficiency‐enhanced uptake rate of phosphorus
Authors: Cakmak Ismail , Marschner Horst
Published: May 2006

The effect of withholding Zn on the uptake, translocation and accumulation of P was studied in cotton plants (Gossypium hirsutum L. cv. Deltapine 15/21) grown in nutrient solutions under controlled environmental conditions. The influence of P on the uptake rate, translocation and distribution of 65Zn in the plants was also examined. Increasing the P supply resulted in severe Zn deficiency symptoms (interveinal chlorosis) as well as P toxicity symptoms, which were characterized by leaf puckering and grayish‐brown marginal necrosis. Zinc deficiency markedly increased the uptake and translocation rates of P over the whole concentration range tested (5x10‐5 to 1.25x10‐3M). Uptake and translocation rates of P increased with both level of P and severity of Zn deficiency. This often caused P toxicity symptoms on Zn‐deficient leaves. In contrast to P, the concentrations of K and Mg in the leaves were not affected by Zn deficiency. Similar results were obtained for sunflower (Helianthus annuus L.) and buckwheat (Fagopyrum esculentum Moench) plants. Higher P concentrations in Zn‐deficient leaves or shoots could not be attributed wholly to reduced shoot growth. This was also evident when Zn deficiency was compared with other micronutrient (Fe, Mn, and Cu) deficiencies. Only Zn‐deficient plants showed enhanced uptake and translocation of P. In experiments with 65Zn, a high P supply did not depress uptake and translocation of Zn. From the results obtained it is concluded that the P‐induced Zn deficiency in cotton, as well as in other species, is primarily caused by enhanced P uptake and translocation and not by inhibition of Zn uptake.
Mechanism of phosphorus‐induced zinc deficiency in cotton. II. Evidence for impaired shoot control of phosphorus uptake and translocation under zinc deficiency
Authors: Marschner Horst , Cakmak Ismail
Published: May 2006

Cotton (Gossypium hirsutum L. cv. Deltapine 15/21) plants were precultured for 19 to 25 days under controlled climatic conditions in nutrient solutions with different levels of Zn. With the onset of visual Zn‐deficiency symptoms the pH of the nutrient solution decreased from 6.0 to about 5.0. In contrast, Zn‐sufficient plants raised the pH of the nutrient solution to about 7.0. In short‐term studies it could be demonstrated that the Zn nutritional status of the plants remarkably influenced the uptake and translocation rates of mineral nutrients. Compared to Zn‐sufficient plants, P uptake rate in severely Zn‐deficient plants was increased by a factor of 2 to 3, whereas the uptake rates of K, Ca and particularly NO3 decreased. The accumulation of P in the roots of Zn‐deficient plants was either not affected or even lower than in Zn‐sufficient plants. Thus, Zn deficiency had a specific enhancement effect on root to shoot transport of P. This enhancement effect of Zn deficiency on uptake and transport of P was similar at nutrient solution pH values of 7.0 and 5.8; i.e. it was not the result of acidification of the nutrient solution. After application of 36CI, 86Rb and 32P to plant stems, basipetal transport of 36CI and 86Rb was not affected by the Zn nutritional status of the plants. However, in Zn‐deficient plants, only 7.8% of the 32P was translocated basipetally compared to 34% in the Zn‐sufficient plants. A resupply of Zn for 19 h to Zn‐deficient plants enhanced basipetal 32P transport. The results indicate that a feedback mechanism in the shoots is impaired in Zn‐deficient plants which controls the P uptake by roots and especially the P transport from roots to shoots. As a result of this impairment toxic concentrations of P accumulate in the leaves. The mechanism responsible is likely the retranslocation of P in the phloem from shoots to roots.
Stimulation of proton extrusion by K+ and divalent cations (Ni2+, Co2+ Zn2+) in maize root segments
Authors: Cocucci Sergio M. , Morgutti Silvia
Published: May 2006

Entry of the divalent cations Ni2+, Co2+ and Zn2+ into cells of maize (Zea mays L. cv. Dekalb XL 85) root tissue is accompanied by an acidification of the incubation medium, a decrease in both the pH of the cell sap and the level of malate in the cells, and by an inhibition of dark fixation of CO2. K+, on the contrary, induces only a very low acidification of the incubation medium, does not change either the pH of the cell sap or the malate level in the cells, and induces an increase in CO2 dark fixation. Different mechanisms are postulated for the stimulation of proton extrusion by divalent cations and K+.
Photosynthetic characteristics of the submerged macrophyte Ceratophyllum demersum
Authors: Best Elly P. H.
Published: May 2006

The photosynthetic and growth characteristics of Ceratophyllum demersum L. were investigated under laboratory conditions which simulated those encountered in the plants' normal environment. The carbon fixation rate of C. demersum measured with 14C at light and carbon saturation at pH 8.0 was 4.48 mg C (g ash‐free dry weight)−1 h−1. It was lower at pH 6.5 than at pH 8.0. The light use efficiencies in quiescent plants and actively growing plants were 6.3 and 8.7 × 10−9 kg CO2 J−1, respectively, with corresponding maximum photosynthetic rates of 2.67 and 4.36 mg C (g ash‐free dry weight)−1 h−1. Photorespiration in actively growing plants consumed 24% of the carbon fixed. Incubation with DCMU demonstrated that about one‐third was refixed. The optimum temperature for carbon fixation was 25°C. The C3‐photosynthetic pathway was the main operational route as indicated by the early photosynthetic products (largely C3‐acids) and the absence of Krantz anatomy and the chlorophyll a:b ratio (2.7). The maximum relative growth rates ranged from 0.025 to 0.041 g ash‐free dry weight (g ash‐free dry weight)−1 day−1 in the field (Lake Vechten, 1 to 3 m depth classes).
Identification of 4‐chloroindole‐3‐acetic acid and indole‐3‐aldehyde in seeds of Pinus sylvestris
Authors: Ernstsen Arild , Sandberg Göran
Published: May 2006

4‐Chloroindole‐3‐acetic acid (4‐Cl‐IAA) and indole‐3‐aldehyde (IAId) have been characterized as endogenous constituents in seeds of Pinus sylvestris L. by gas chromatography‐mass spectrometry. Quantitative estimates indicate that immature seeds contained 640 pg 4‐Cl‐IAA (g fresh weight)‐1 while mature seeds contained 340 pg (g dry weight)‐1. 4‐Cl‐IAA could not be detected in seeds five days after germination. The content of IAld increased from 127 pg (g dry weight)‐1 in mature seeds to 315 pg (g dry weight)‐1 after five days of germination.
Responses of Pinus clausa, Pinus serotina and Pinus taeda seedlings to anaerobic solution culture. II. Changes in tissue nutrient concentration and net acquisition
Authors: Topa Mary A. , McLeod Kenneth W.
Published: May 2006

Fifteen or 30 days of anaerobic growth conditions significantly reduced shoot and root nitrogen, potassium, phosphorus, iron and manganese concentrations in seedlings of pond pine (Pinus serotina Michx.), sand pine [P. clausa (Engelm.) Sarg.] and drought‐hardy and wet‐site loblolly pine (P. taeda L.) grown in a culture system using non‐circulating, continuously flowing solution. Calcium and shoot magnesium levels were least affected by anaerobic growth conditions – largely reflecting the passive nature of their uptake. Shoot and root nutrient content (mg nutrient pot‐1) followed similar trends, with wet‐site loblolly and pond pine seedlings least affected by anaerobic solution culture. Shoot biomass of wet‐site loblolly and pond pine seedlings was not affected by anaerobiosis, suggesting an increase in shoot nutrient utilization efficiency. Root biomass was significantly reduced by 15 or 30 days of anaerobiosis, with sand pine exhibiting the largest reduction in root dry weight (57%).

These results suggest that anaerobiosis interferes with net nutrient acquisition, even under the high nutrient conditions provided by solution culture. Sand pine suffered the largest reductions in shoot and root biomass and nutrient concentrations, showing earlier symptoms of waterlogging injury and nutrient stress than drought‐hardy loblolly pine seedlings. Whether net nutrient acquisition decreased because of the reduction in root surface area available for absorption and/or reduced uptake efficiency cannot be ascertained from these data.
Aerenchyma and lenticel formation in pine seedlings: A possible avoidance mechanism to anaerobic growth conditions
Authors: Topa Mary A. , McLeod Kenneth W.
Published: May 2006

Seedlings of pond pine (Pinus serotinaMichx.), sand pine [P. clausa(Engelm.) Sarg.], and loblolly pine (P. taedaL., wet‐site and drought‐hardy seed sources) were grown in hydroponic solution culture using a non‐circulating, continuously flowing design under anaerobic or aerobic conditions to determine whether flooding tolerance was correlated with enhanced internal root aeration. Transport of atmospheric O2from the shoot to the root of anaerobically grown loblolly and pond pine seedlings was demonstrated via rhizosphere oxidation, using both reduced indigo‐carmine solution and a polarographic, ensheathing Pt‐electrode. Stem and root collar lenticels were the major sites of atmospheric O2entry for submerged roots in these seedlings. No O2leakage was detected from roots of aerobically grown pine seedlings. Longitudinal and radial pathways for gaseous diffusion via intercellular air spaces in the pericycle and between ray parenchyma cells, respectively, were demonstrated histo‐logically in anaerobically grown loblolly and pond pines. Rhizosphere oxidation, and lenticel and aerenchyma development in roots of flood‐intolerant sand pine seedlings grown in anaerobic solutions were minimal. Only 15 days of anaerobic growth conditions were necessary to increase internal root porosities of loblolly and pond pine seedlings – although not to the extent found in seedlings treated for 30 or 75 days. Histological results indicated that root tissue in the secondary stage of growth was capable of forming intercellular air spaces, demonstrating a degree of internal plasticity – at least in the more flood‐tolerant loblolly and pond pine seedlings.
The influence of ectomycorrhiza on nitrogen nutrition and growth of Pinus sylvestris seedlings
Authors: Ingestad Torsten , Arveby Agneta S. , Käfar Monika
Published: May 2006

Ectomycorrhizal seedlings of Scots pine (Pinus sylvestris L. cv.), inoculated with the fungus Suillus bovinus (L. ex Fr.) O. Kuntze, and non‐mycorrhizal controls were grown in growth units with a circulating culture solution. Steady‐state nutrition and constant relative growth rates were achieved by means of varied relative nutrient addition rates and free access of nutrients. Typical mycorrhizas always formed within a short period of time after inoculation. The nutrition/growth relationships were in principle similar to previous studies under steady‐state conditions: there were close linear relationships between relative addition rate, relative growth rate and internal nitrogen concentration, i.e. an equilibrium established between nutrients added and taken up. This occurred when infected and uninfected seedlings were grown separately. When grown together in the same growth unit, there are indications that the fungus influenced the exudation pattern of the uninfected seedlings. More carbon was thus provided to the unspecified microflora in the cultivation system, and it was able to grow and withhold nitrogen from the seedlings. The mycorrhizal infection did not increase the specific uptake capacity of the roots, and the fungus constituted a sink for carbon. However, the nitrogen productivity (growth rate per unit of nitrogen per unit of time) was similar for mycorrhizal and non‐mycorrhizal seedlings, so that there might be mechanisms which compensate for the carbon cost.
Free space uptake and influx of Ni2+ in excised barley roots
Authors: Körner Lena E. , Møller Ian M. , Jensén Paul
Published: May 2006

The free space uptake and influx of Ni2+ (63Ni2+) was characterized in excised roots of 7‐day‐old, dark‐grown barley (Hordeum vulgare L. cv. Møyar). Most of the Ni2+ (63Ni2+) present in the roots after a typical experiment was removed by washing in CaCl2+, unlabelled NiCl2 or EDTA solutions. The amount of loosely bound Ni2+ increased during the first few minutes in the uptake solution, and then remained constant. A small fraction was tightly bound, probably mainly in the cell walls. Binding, both loose and tight, increased with concentration, as did influx. However, the lower the external Ni2+ concentration, the larger was the proportion of Ni2+ tightly bound compared with the total amount of Ni2+ taken up. Ni2+ influx was lowered by 85% with 2,4‐dinitrophenol, which may indicate that Ni2+ is actively absorbed across the plasmalemma.
Ornithine and arginine decarboxylases and polyamine involvement during in vivo differentiation and in vitro dedifferentiation of Datura innoxia leaf explants
Authors: Chriqui Dominique , D'Orazi Dario , Bagni Nello
Published: May 2006

The effects of exogenous ornithine, arginine and polyamines added to media leading to root, callus or bud initiation of Datura innoxia Mill. leaf explants growing in vitro were examined. Ornithine and arginine decarboxylase activities (ODC, EC 4.1.1.17; ADC, EC 4.1.1.19) as well as endogenous polyamine levels were also determined during the course of in vivo differentiation of the leaves and their subsequent in vitro dedifferentiation under rooting, callusing, or budding conditions. Decarboxylase activities were determined by measuring the 14CO2 released and the polyamines were quantified after dansylation by thin‐layer chromatography. In vivo, ODC and ADC activities decreased from shoots to young to old leaves. In vitro, synergistic effects between ornithine and indole‐3‐acetic acid on rhizogenesis were detected, while arginine was not effective. Exogenous putrescine also acted synergistically with auxin by promoting root growth. A close relationship was found between rhizogenesis, ODC activity and increase in endogenous putrescine and spermidine levels. ODC increased during the induction and time course of cell dedifferentiation and seemed to support these events, while ADC seemed to support only the later events involving redifferentiation.
The ambiguous role of 2,4‐dichlorophenoxyacetic acid in wheat tissue culture
Authors: Wernicke Wolfgang , Gorst Janet , Milkovits Lydia
Published: May 2006

The very basal, highly immature regions of dissected young leaves of Triticum aestivum L. cv. Kite formed adventitious roots on a nutrient medium supplemented with comparatively low concentrations (0.16 to 0.63 μM) of 2,4‐dichlorophenoxyacetic acid (2,4‐D). Higher concentrations (up to 640 μM) had to be applied to stimulate growth from more mature regions higher up the leaf. Yet, already at 2.5 μM roots were less distinct and more callus‐like, and eventually (at 10 to 640 μM) only a subculturable callus of apparently suppressed, slowly proliferating root primordia developed. Furthermore, at the most basal, highly immature regions growth was significantly retarded when the auxin concentration was raised. The leaf culture system appears to reflect the dual action of 2,4‐D known from herbicide research, namely growth stimulation from differentiating (or differentiated) cells, but growth suppression at or in the vicinity of apical meristems. Correspondingly, when the callus of apparently suppressed, slowly proliferating root primordia was transferred to media without 2,4‐D or with low concentrations (0.16–2.5 μM) rapid proliferation commenced, leading to profuse root outgrowth. The system demonstrates the ambiguous role which this auxin appears to have, at least in wheat tissue culture.
Effects of a brassinosteroid on growth and on H+‐extrusion in isolated radish cotyledons: comparison with the effects of benzyladenine
Authors: De Michelis Maria Ida , Lado Piera
Published: May 2006

We investigated the effect of 24‐epibrassinolide (BR) on the cytokinin‐bioassay based on growth of isolated radish (Raphanus sativus L. cv. Tondo Rosso Quarantino) cotyledons. BR stimulated growth of the cotyledons by about 50% when applied at saturating concentrations (3 μM). This effect was much lower than that of saturating concentrations of benzyladenine (BA) which was about 150% at 10 μM BA. The effects of saturating concentrations of BR and BA were additive. BR, but not BA, stimulated H+‐secretion by the cotyledons (measured as acidification of the incubation medium) slightly but reproducibly. These results indicate that the modes of action of the two phytoregulators are at least partially different.

BR‐induced stimulation of H+‐secretion was of similar amplitude to that induced by a concentration of fusicoccin (30 nM) such as to stimulate growth to the same extent as BR. These results suggest that BR‐induced stimulation of radish cotyledon growth might depend, at least in part, on BR‐induced acidification of the wall space, similar to that observed on Azuki bean epicotyls and maize roots.
Changes in accumulation of seed nitrogen compounds in maize under conditions of sulphur deficiency
Authors: Baudet Jacques , Huet Jean‐Claude , Jolivet Eugène , Lesaint Christiane , Mossé Jacques , Pernollet Jean‐Claude
Published: May 2006

Maize (Zea mays L., hybrid INRA 260) was grown in the greenhouse with mineral nutrition of different sulphate concentrations. Mature seeds from these plants were compared for their free amino acid and protein N forms. For the most S‐deficient sample, the Asx (asparagine + aspartic acid) content increased by 30% as compared with control, while methionine and cysteine decreased (by 25 and 30%, respectively), as well as glycine, lysine, histidine, arginine and tryptophan. In seeds lowest in S the non‐protein N to total N ratio was 77% higher than in the control. Free asparagine dominated in starved seeds (50 mol % of total free amino acids) and was ten‐fold more concentrated than in the control, where proline was the predominant free amino acid. Thus the Asx of non‐protein N reached 28% of the total mol Asx of the whole starved seed. Altered S nutrition had virtually no effect on the amino acid composition of the main protein fractions, but it significantly changed their ratios. Zeins, which are poor in S‐containing amino acids, showed 25% higher level than in seeds supplied with normal S. As a counterbalance, two glutelin subfractions rich in S‐containing amino acids, decreased by 36–71% under limiting S nutrition.

It is concluded that the plant reacts against S deficiency by modifying its N metabolism. Significant accumulation occurred of free asparagine, which is the main form of N transportation. The biosynthesis of seed storage protein occurred through the accumulation of the highest possible protein quantity allowed by the available S‐containing amino acids, i.e. proteins low in S‐containing amino acids were preferentially synthesized.
The distribution of nitrate reductase in tomato (Lycopersicon esculentum) leaves as affected by age
Authors: Doddema Henk , Stulen Ineke , Hofstra Jurien J.
Published: May 2006

The distribution of nitrate reductase (NR, EC 1.6.6.1.) in the leaves of single‐stem tomato plants (Lycopersicon esculentum Mill., cv. Vandenbergs Moneydor) was studied using an in vitro test. The activity decreased from young to old leaves. However, a low value (NR minimum) occurred in some leaves below the apex, usually in the almost completely expanded leaves, provided that the plants received sufficient nitrate to induce optimum NR activity in all the leaves. When insufficient nitrate was available there was NR in the young leaves only. The observed NR minimum coincided with a low value for soluble carbohydrates and amino acids. Since there was no extra export of labelled carbon from the leaves with the NR minimum, it is suggested that in the almost completely expanded leaves carbohydrates produced by photosynthesis are mainly used for the production of polysaccharides for new cell walls. Consequently, less are left for the production of keto acids, which can act as acceptors for reduced nitrogen. Therefore, less amino acids are produced, and this may result in a lowered protein synthesis, including a lowered synthesis of nitrate reductase.
Long‐term effects of plant hormones on K+ levels and transport in young wheat plants of different K+ status
Authors: Dhakal Min Raj , Erdei László
Published: May 2006

Long‐term effects of 1‐naphtaleneacetic acid (NAA), benzyladenine (BA), gibberellic acid (GA3), abscisic acid (ABA) and ethylene on K+ levels, K+ uptake and translocation to the shoot were studied in young wheat plants (Triticum aesticum L. cv. Martonvásári‐8) grown at different K+ supplies. Na+ levels and K+/Na+ selectivity were also investigated. Both in shoots and roots, NAA, BA and ABA decreased K+ and Na+ levels more effectively in high‐K+ plants than in low‐K+ plants. GA, and ethylene did not influence K+ and Na+ levels. K+/Na+ selectivity in roots of low‐K+ plants was increased in favour of K+ by BA, NAA and to a lesser extent by ABA. In high‐K+ plants only BA increased the K+/Na+ ratio, whereas the effects of the other hormones were the opposite (NAA) or less pronounced (ABA). K+(86Rb) uptake was inhibited by NAA and BA in low‐K+ plants but not in high‐K+ plants. K+(86Rb) uptake was inhibited throughout by 10 μM ABA. K+(86Rb) translocation to the shoot was influenced by the hormones similarly to the uptake patterns, with the exception of ABA, which inhibited translocation in low‐K+ plants but not in high‐K+ plants. The results show that hormonal effects may quantitatively and qualitatively be modified by K+ levels in the plant and that internal K+ concentration may play a role in the mechanisms regulating the effects of NAA, BA and ABA but probably not in those of GA3 or ethylene.
Long‐term effects of abscisic acid on K+ transport in young wheat plants of different K+ status
Authors: Dhakal Min Raj , Erdei László
Published: May 2006

The effects of abscisic acid (ABA) on growth, uptake and translocation of potassium ions, K+,Mg2+‐ATPase activity and transpiration were investigated in young wheat (Triticum aestivum L. cv. Martonvásári‐8) plants grown at different K+ supplies. Long‐term treatment with ABA (10 μM) reduced growth in high‐K+ plants, but had less effect under low‐K+ conditions. K+(86Rb) uptake was inhibited by about 70 and 40% in low‐ and high‐K+ plants, respectively. The stimulation by K+ of the Mg2+‐ATPase activity in the root microsomal fraction was lost with ABA treatment. It is suggested that the inhibitory effect of ABA on K+ uptake may be related to this effects on the K+,Mg2+‐ATPase. Translocation of K+ to the shoot was inhibited in low‐K+ plants only, and it was not affected in high‐K+ plants. In parallel to this, ABA treatment reduced transpiration by about 50% in low‐K+ plants, whereas a much smaller effect was seen in high‐K+ plants. These observations suggest that the regulation by ABA of the stomatal movements is strongly counteracted by high‐K+ status.
Biosynthesis of aromatic amino acids by highly purified spinach chloroplasts – Compartmentation and regulation of the reactions
Authors: Bagge Pia , Larsson Christer
Published: May 2006

The ability of chloroplasts to synthesize aromatic amino acids from CO2 was investigated using highly purified, intact spinach (Spinacia oleracea L. cv. Viking II) chloroplasts and 14CO2. Incorporation of 14C into aromatic amino acids was very low, however, and this was assumed to be due to lack of phosphoenolpyruvate (PEP), one of the substrates for the shikimate/arogenate pathway leading to aromatic amino acids in chloroplasts. Therefore, the glycolytic enzymes phosphoglycerate mutase (EC 2.7.5.3) and enolase (EC 4.2.1.11) were added to the 14CO2 fixation medium in order to convert labelled 3‐phosphoglycerate exported from the intact chloroplasts to 2‐phosphoglycerate and PEP. In this way a part of the glycolytic pathway was reconstituted outside the chloroplasts to substitute for the cytoplasm lost on isolation. The presence of both enzymes in the medium increased incorporation of 14C into Tyr and Phe more than ten‐fold and incorporation into Trp about two‐fold, while total 13CO2 fixation rates were not affected. Our results suggest that chloroplasts do not contain phosphoglycerate mutase or enolase, and that, in vivo, PEP is synthesized in the cytoplasm and imported to the chloroplast stroma for the biosynthesis of aromatic amino acids. The biosynthesis of all three aromatic amino acids was under feedback control. Using expected physiological concentrations (below 100 μM), each of the aromatic amino acids exerted a strict feedback inhibition of its own biosynthesis only.
Reinvestigation of the proposed red light effect on carotenogenesis in the fungus Verticillium agaricinum
Authors: Björn Gunvor S.
Published: May 2006

It has been claimed that the fungus Verticillium agaricinum (Link) Corda is able to form carotenoids after short‐term irradiation with very weak red light. A reinvestigation of this report has been performed on a larger scale. Comparison was made with samples treated with UV‐A light and with dark controls. The means and the se were calculated. Student's t tests and Mann‐Whitney's U tests have also been carried out. The conclusion of this investigation is that there is no effect of red light on carotenogenesis in V. agaricinum, while the effect of UV‐A light is easy to demonstrate under the same conditions.
Ontogenic variations in the alkaloids of Narcissus assoanus
Authors: Viladomat Francesc , Llabrés José M. , Bastida Jaume , Cusidó Rosa M. , Codina Carles
Published: May 2006

The distribution and ontogenic variations in the five alkaloids previously isolated from Narcissus assoanus Duf. (pseudolycorine, two new acetylated derivatives: I‐O‐acetylpseudolycorine and 2‐O‐acetylpseudolycorine, and two phenanthridines: assoanine and oxoassoanine) were studied. The alkaloids have been separated and quantified by high performance liquid chromatography, and the free amino acids phenylalanine and tyrosine were also analyzed. Comparing the results obtained for aerial parts and bulbs, we suggest that alkaloids are synthesized in the aerial part of the plant, and propose a likely biosynthetic pathway.
The regulation of enzyme activities of the nicotine pathway in tobacco
Authors: Wagner Roland , Feth Friedhelm , Wagner Karl G.
Published: May 2006

The activities of the three enzymes of the route ornithine to the N‐methyl‐Δ1‐pyrrolinium salt and of the eight enzymes of the route quinolinic acid to nicotinic acid (pyridine nucleotide cycle) were determined in the roots of different Nicotiana tabacum L. cultivars and for comparison in tomato (Lysopersicon esculentum L. cv. Vollendung) roots. Enzyme activities were further followed in different plant organs, dedifferentiated tissues, root organ cultures and in the roots after decapitation of tobacco plants. The data are in accord with the concept that the two routes are predominantly regulated by the enzymes putrescine methyltransferase (EC 2.1.1.53) and quinolinic acid phosphoribosyltransferase (EC 2.4.2.19), respectively. Further regulation involves the enzymes NAD+‐pyrophosphatase (EC 3.6.1.22) and nicotinic acid mononucleotide glycohydrolase; these findings confirm the suggestion that the transformation to nicotinic acid is performed along two routes: either via the synthesis and degradation of NAD+ or by a direct step through the action of a specific glycohydrolase.
Intraspecific differences in Cucumis sativus sensitivity to ultraviolet‐B radiation
Authors: Murali N. S. , Teramura Alan H.
Published: May 2006

Cucumber (Cucumis sativus L.) cultivars Marketmore, Lama, XPH 1187, XPH 1484 and Sprint 440 (N) were grown in a greenhouse under two levels of biologically effective ultraviolet‐B (UV‐B) radiation (daily dose: 0 and 11.6 kJ m−2 UV‐BBE) for 31 days. Significant intraspecific differences were observed in plant height, number of leaves, leaf area and total dry weight. Based upon total biomass accumulation, Marketmore was found to be the most tolerant, and XPH 1484 the most sensitive to UV‐B radiation. The dose response of accumulation of UV absorbing compounds (measured as absorbance of methanolic extracts) in leaf tissues showed an increase in UV absorbing compounds with UV‐B dose in Marketmore, Sprint 440 (N) and XPH 1187. In Lama and XPH 1484, however, doses below 8.7 kJ m−2 UV‐BBE produced no change in UV absorbing compounds. This study suggests that intraspecific differences in UV‐B radiation sensitivity in cucumber may be related to inherent differences in the accumulation of UV absorbing compounds in leaves.
Effect of benzyladenine on the polypeptide pattern of plastids in excised watermelon cotyledons
Authors: Longo Giovanna P. , Bracale Marcella , Rossi Gianfranca , Longo Claudio P.
Published: May 2006

We have shown in a previous paper that plastids of watermelon (Citrullus vulgaris Schrad., cv. Fairfax) cotyledons differentiate into amyloplasts when the cotyledons are grown in water and into prochloroplasts when they are grown in benzyladenine (BA) solution. In the present work we have tested whether this large difference in development of the plastids is accompanied by equally conspicuous changes in their polypeptide pattern. Cotyledons were grown for 4 days in the dark either on distilled water or on 10−5M BA. Alternatively they were transfered to 10−5M BA after 4 days of growth in water.

Plastids of control cotyledons had a rather simple polypeptide pattern. The only prominent protein bands were the two subunits of ribulose bisphosphate carboxylase (EC 4.1.1.39). Contamination with storage protein was present. Plastids from BA‐treated cotyledons had a much more complex polypeptide pattern. No storage protein contamination was observed. Polypeptide bands present only as traces in the control and having molecular weights of 32, 44, 48 and 49 kDa increased in intensity after an exposure of only 6 h to BA. The 32‐kDa band seemed to be most dependent on the presence of the hormone. Contrary to what was observed in plastids, BA seemed to have no influence on the polypeptide pattern of mitochondria.
Degradation and utilization of exogenous allantoin by intact soybean root
Authors: Imsande John
Published: May 2006

Allantoin is produced by soybean [Glycine max (L.) Merr. cv. Harper] nodules during nitrogen fixation. Decomposed nodules, therefore, may release allantoin into the surrounding soil. If the released allantoin were to be taken up by the plant without degradation, it is possible that the exogenous allantoin might repress subsequent nodulation. Using a hydroponic growth system, degradation of exogenous allantoin by soybean root was studied. In the presence of intact soybean root exogenous allantoin was rapidly degraded, yielding ca 2 mmol of urea per mmol of allantoin. Hydrolysis of urea to ammonia proceeded very slowly. Instead, the urea seemed to be taken up by the intact soybean root. The enzyme(s) required for the production of urea from exogenous allantoin could not be detected in the aqueous rooting medium. Therefore, these enzymes seem to be attached to the exterior surface of the intact soybean root. This study shows that exogenous allantoin can be readily degraded and assimilated by the growing soybean plant.
Ineffective utilization of nitrate by soybean during pod fill
Authors: Imsande John
Published: May 2006

The relative effectiveness of nitrate, allantoin, or nitrate plus allantoin as sources of nitrogen for the indeterminate soybean plant [Glycine max (L.) Merr cv. Harper] was studied throughout vegetative and reproductive growth. All plants were provided with 3.0 mM nitrogen and were grown hydroponically in growth chambers. During vegetative and early reproductive growth, plants given nitrate or nitrate plus allantoin grew faster than plants provided allantoin only. However, during pod fill, plants provided with allantoin or allantoin plus nitrate gained weight more rapidly than plants receiving just nitrate. More importantly, at maturity plants that had been provided with allantoin or allantoin plus nitrate during pod fill were 30% heavier in total dry weight, 50% higher in nitrogen content, and 50% higher in seed yield than plants that had received just nitrate. At full bloom, all plants were inoculated with the same culture of Bradyrhizobium japonicum, and twice each week throughout pod fill each plant was assayed for nitrogen fixation (acetylene reduction). Correlation coefficients obtained by linear regression analysis show a strong positive correlation between the measured rate of nitrogen fixation and maximum plant fresh weight (r = 0.83), total plant nitrogen (r = 0.81), or seed yield (r = 0.76). The fact that nitrogen fixation during pod fill stimulates plant growth and seed yield, coupled with the facts that nitrate blocks nodulation and is not used efficiently during pod fill by the soybean plant, may explain why seed yield of field‐grown soybeans usually does not respond to added fertilizer nitrogen. Thus, it is suggested that enhanced nitrogen fixation may be the key factor in improving soybean seed yield.
Root influence on in vitro growth of hyphae of the mycorrhizal mushroom Cantharellus cibarius replaced by carbon dioxide
Authors: Straatsma Gerben , Van Griensven Leo J. L. D. , Bruinsma Johan
Published: May 2006

The presence of a living root of tomato (Lycopersicon esculentum Mill. cv. Panase F) had a strong positive effect on growth in vitro of hyphal fragments of Cantharellus cibarius Fr. This was observed for 12 out of 14 fungal strains tested. Initial re‐growth of hyphae was independent of the presence of a root, but for the further development of strong mycelial growth 7 strains completely depended on the presence of a root. Five strains showed a considerably prolonged lag phase in the absence of a root and only 2 strains were independent. The presence of a root had no influence on the specific growth rates. Hyphal fragments of the totally root‐dependent strain S1 grew strongly in the absence of a root if they were brought into intimate mutual contact. Factor(s) stimulating growth were apparently produced by both roots and fungus. Volatiles from donor cultures of tomato roots of C. cibarius, Boletus edulis, and Tylopilus felleus stimulated growth of hyphal fragments in root‐less receiver cultures. This effect was prevented by the presence of a KOH solution. Donor cultures could be replaced by 0.5% CO2.
Flooding, gas exchange and hydraulic root conductivity of highbush blueberry
Authors: Davies Frederick S. , Flore James A.
Published: May 2006

Highbush blueberry plants (Vaccinium corymbosum L. cv. Bluecrop) growing in containers were flooded in the laboratory for various durations to determine the effect of flooding on carbon assimilation, photosynthetic response to varying CO2 and O2 concentrations and apparent quantum yield as measured in an open flow gas analysis system. Hydraulic conductivity of the root was also measured using a pressure chamber. Root conductivity was lower and the effect of increasing CO2 levels on carbon assimilation less for flooded than unflooded plants after short‐(i‐2 days), intermediate‐(10–14 days) and long‐term (35–40 days) flooding. A reduction in O2 levels surrounding the leaves from 21 to 2% for unflooded plants increased carbon assimilation by 33% and carboxylation efficiency from 0.012 to 0.021 mol CO2 fixed (mol CO2)−1. Carboxylation efficiency of flooded plants, however, was unaffected by a decrease in percentage O2, averaging 0.005 mol CO2 fixed (mol CO2)−1. Apparent quantum yield decreased from 2.2 × 10−1 mol of CO2 fixed (mol light)−1 for unflooded plants to 2.0 × 10−3 and 9.0 × 10−4 for intermediate‐ and long‐term flooding durations, respectively. Shortterm flooding reduced carbon assimilation via a decrease in stomatal conductance, while longer flooding durations also decreased the carboxylation efficiency of the leaf.
Cobalt inhibition of thigmomorphogenesis in Bryonia dioica: possible role and mechanism of ethylene production
Authors: Boyer Nicole , De Jaegher Geert , Bon Marie‐Claude , Gaspar Thomas
Published: May 2006

Rubbing‐induced inhibition of elongation in Bryonia dioica was completely prevented by 10−7M cobalt chloride. Cellular redistribution of peroxidases, mainly characterized by transiently enhanced membrane‐binding of soluble peroxidases, occurred as an immediate consequence of rubbing and was not inhibited by Co2+. Ethylene synthesis and 1‐aminocyclopropane‐1‐carboxylic acid (ACC) conversion readily increased upon rubbing and fell soon afterwards, but ACC conversion then increased again progressively. Co2+ did not drastically counteract these changes, except for the second rise in ACC conversion which was completely eliminated. The rubbing‐induced rise in ethyiene production and ACC conversion was closely correlated to microsomal ACC conversion and peroxidase activity, but only during the first hours after rubbing. The presented approach enables us to correlate stress‐induced ethylene production to membrane‐binding of peroxidases. It is suggested that ACC conversion in Bryonia dioica is triggered by two different, sequentially ordered mechanisms. The difference in the effects of Co2+ on elongation and ethylene production is discussed with respect to the role of ethylene in thigmomorphogensis.
Occurrence of acid and neutral carboxypeptidases in germinating cereals
Authors: Mikola Leena , Saarinen Sirpa
Published: May 2006

High neutral metallocarboxypeptidase activity (EC 3.4.17) has earlier been detected in young seedlings of rice (Oryza sativa L.) using benzyloxycarbonyl‐L‐phenylalanyl‐L‐alanine (Z‐Phe‐Ala) as substrate at pH 7. This finding was confirmed, and it was observed that the activity could be assayed with higher specificity and sensitivity by using Z‐Gly‐Ala or Z‐Gly‐Phe as substrate at pH 6.5–7. No corresponding activity was detected in seedlings of barley (Hordeum vulgare L. cv. Himalaya), oats (Avena sativa L.) or maize (Zea mays L.). The seedlings of the four cereals possessed similar activities of acid carboxypeptidases (EC 3.4.16; hydrolysis of Z‐Phe‐Ala and Z‐Ala‐Phe at pH 5.2 and of Z‐Ala‐Arg at pH 5.7). However, in endosperms of germinating rice and maize these activities were only about 1–5% of those in barley and oats. A corresponding, although less pronounced, difference was evident between the scutella of the two pairs of cereals. The possible relationship between neutral carboxypeptidase activity and ability to grow in anaerobic conditions is discussed.
Enzyme activities during imbibition and germination of seeds of tamarack (Larix laricina)
Authors: Pitel J. A. , Cheliak W. M.
Published: May 2006

Activities of six enzymes from extracts of separated embryos and gametophytes of tamarack [Larix laricina (Du Roi) K. Koch] seeds were assayed at various stages of imbibition and germination. On a per seed part basis, activities of 6‐phosphogluconate dehydrogenase (6‐PGD, EC 1.1.1.44), glucose‐6‐phosphate dehydrogenase (G‐6‐PD, EC 1.1.1.49), malate dehydrogenase (NAD+–MDH, EC 1.1.1.37), isocitrate dehydrogenase (NADP+–IDH, EC 1.1.1.42), soluble peroxidase (PER, EC 1.11.1.7), and acid phosphatase (ACP, EC 3.1.3.2) from both the embryo and gametophyte tissues generally increased slowly, following cold stratification for 30 days and imbibition under germinating conditions for 5 days, but then increased at a faster rate with emergence of the radicle and subsequent growth of the seedling. The rate of increase of enzyme activity was highest for PER. Soluble protein levels also increased with imbibition and germination, with about 3 times greater levels present in the gametophyte than in the embryo. Heat inactivation experiments showed that, except for G‐6‐PD, activities were stable up to 40°C. Inactivation occurred at lower temperatures for G‐6‐PD, while higher temperatures were required for PER. Incubation of extracts for 7 days at 4°C indicated that loss of enzyme activity was greatest for G‐6‐PD (3.9% remaining) and least for PER and ACP (94 and 95% remaining, respectively).
Controls on calcium ion fluxes in injured or shocked corn root cells: Importance of proton pumping and cell membrane potential
Authors: Rincon Magaly , Hanson John B.
Published: May 2006

Passive influx of 45Ca2+ into non‐growing corn root tissue (Zea mays L.) was increased as a result of actions (cutting, rubbing, chilling, heating, acidifying) or agents (cyanide, uncouplers) known to depolarize the cell membrane, and was decreased by actions (washing) or agents (fusicoccin) known to hyperpolarize it. These responses indicate the presence of Ca2+ channels which are voltage controlled. If the injuries were extensive, however, voltage control was lost and hyperpolarization with fusicoccin was expressed by increased 45Ca2+ influx. Control could be regained by tissue washing, and millimolar levels of external Ca2+ would protect against loss of control. Influx of Ca2+ was strongly inhibited by La3+, but only weakly by verapamil. Intact roots showed greater cold shock sensitivity in maturing cells than in growing cells. We conclude that corn roots normally restrict Ca2+ influx by a mechanism linked to hyper‐polarization of the plasmalemma.

Calcium ions which enter cold‐shocked tissue are partially extruded during the early phase of recovery by a process stimulated by fusicoccin and subject to uncoupling.