bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sugar and starch changes in pea cotyledons during germination
Authors: Monerri C. , Garcia‐Luis A. , Guardiola J. L. 
Published: April 2006

Changes in starch and sugar contents in the cotyledons during germination have been compared in a smooth (cv. Alaska) and a wrinkled (cv. Progress) cultivar of the garden pea (Pisum sativum L.). In both cultivars there was an initial accumulation of sucrose due to the hydrolysis of sucrosyl oligosaccharides, but galactose did not accumulate in the cotyledons. Starch mobilization in the Progress pea was linear with time and started before the rise in α‐amylase (EC 3.2.1.1) activity in the cotyledons; sucrose was synthesized in the cotyledons, and their excision from the axis resulted in an additional accumulation of this sugar. In the Alaska pea, the onset of starch hydrolysis coincided with the rise in α‐amylase activity; no accumulation of sucrose was found in excised cotyledons, whilst the sucrose content decreased continuously in attached cotyledons.The same sugars were found in the cotyledons of both cultivars, suggesting a common pathway for starch breakdown. Maltose, maltotriose and linear malto‐dextrins were not present and only trace amounts of glucose were detected, suggesting a degradation of starch by phosphorylase after an initial attack by α‐amylase. α‐Amylase activity in the cotyledons was higher in the presence of the axis, but was influenced by the water content of the cotyledons. Transient changes in α‐amylase activity correlated well with changes in the rate of starch hydrolysis, but after 2–3 days starch mobilization was reduced in excised cotyledons probably due to the resynthesis of starch.
Influence of fruit load and environmental factors on nitrate reductase activity and on concentration of nitrate and carbohydrates in leaves of eggplant (Solanum melongena)
Authors: Claussen W. 
Published: April 2006

Both the in vivo (+ nitrate) nitrate reductase (NR) activity (leaf disks incubated in the presence of KNO3) and the in vivo (− nitrate) NR activity (leaf disks incubated without KNO3) in leaves of eggplant (Solanum melongena L. cv. Bonica) were affected by rapidly growing fruits. Plants with a fruit load showed more pronounced diurnal variation in (+ nitrate) NR activity and higher (− nitrate) NR activity than plants without fruit. The higher (− nitrate) NR activity was accompanied by higher nitrate and lower sucrose and starch contents of leaves. The more pronounced diurnal changes in (+ nitrate) NR activity were paralleled by more pronounced diurnal variation in carbohydrate content of leaves. Fruit removal led to a decrease in both (− nitrate) NR activity and nitrate concentration in leaves, while the carbohydrate content increased. Plants supplied with ammonium instead of nitrate showed only slightly lower (+ nitrate) but no (− nitrate) NR activity. As for plants treated with nitrate, diurnal changes in (+ nitrate) NR activity were most pronounced in leaves of plants with fruit and this again was paralleled by a more pronounced diurnal variation in the carbohydrate concentration in the leaves.Increasing the oxygen level of the atmosphere to 50% led to a dramatic decrease in the (+ nitrate) NR activity and to an increase in both (− nitrate) NR activity and nitrate concentration, which was accompanied by decreasing carbohydrate contents of the leaves. Low light intensities and extended dark periods caused similar changes in NR activity and nitrate and carbohydrate concentrations in leaves. Increasing the nitrate concentration in the nutrient solution led to a rise in (+ nitrate) and (− nitrate) NR activity, but only the (− nitrate) NR activity paralleled the nitrate concentration in the leaves. This increase in the nitrate concentration was accompanied by a decrease in the carbohydrate content of the leaves.It is concluded that the level of and the diurnal changes in both (+ nitrate) and (− nitrate) NR activity and the concentration of nitrate in the leaves are dependent upon their carbohydrate status.
Spectral properties and chromophore rotation of phytochrome bound to substituted Sepharose
Authors: Sundqvist Christer , Ekelund Nils G. A. 
Published: April 2006

Brushite purified phytochrome from Avena sativa L. cv. Sol II was bound to phenyl Sepharose, octyl Sepharose, CNBr‐activated Sepharose and to anti‐phytochrome immunoglobulins immobilized on Sepharose. The spectral properties of phytochrome bound to anti‐phytochrome immunoglobulins and to phenyl Sepharose were similar to phytochrome in solution. Phytochrome bound to CNBr‐activated Sepharose or to octyl Sepharose showed reduced Pfr formation after red irradiation. The reversal to Pr with far‐red light was only partial but a further increase at 667 nm took place slowly in the dark. A peak at 657 nm was seen in the difference spectrum between CNBr‐activated Sepharose‐bound phytochrome kept in darkness and the identical sample immediately after a far‐red irradiation.The change in linear dichroism at 660 nm and 730 nm, induced by plane polarized red or far‐red light, was measured. It was computed that the long‐wavelength transition moment of phytochrome had an average rotation angle of 31.5° or 180°–31.5°. The substrate used for immobilization had a limited effect on the rotation angle. Phytochrome immobilized on CNBr‐activated Sepharose gave an angle of 27.8° and phytochrome immobilized on phenyl Sepharose gave an angle of 32.6°.
Sucrose release from soybean leaf slices
Authors: Anderson James Michael 
Published: April 2006

The release of photosynthate from leaf slices of soybean [Glycine max (L.) Merr. cv. Ransom II], to a bathing medium was studied to ascertain how p‐chloromercuribenzenesulfonic acid (PCMBS) can both stimulate and inhibit sucrose release. Soybean leaf slices released photosynthate to a bathing medium at a rate that was approximately linear with time. The photosynthate released was about 20% ionic and 80% non‐ionic, and sucrose represented about 75% of the total. Removal of Ca2+ from the medium increased the rate of release of all fractions, but amino acid release showed the largest increase. Sucrose was released at a rate estimated to be about 20% of the normal transport rate in intact leaves. The rate of sucrose uptake from 5 mM sucrose into soybean leaf slices was optimum at pH 6.3, and the rate of sucrose release was lowest at the same pH. However, sucrose uptake was found to be insignificant during release experiments. Sucrose release, but not amino acid release, was inhibited 75% by 1 mM PCMBS.The data support two components of sucrose release in leaves. The first is insensitive to the addition of PCMBS. This component probably represents leakage from phloem tissue. The second component is inhibited by PCMBS and probably represents release from the mesophyll. By comparing sucrose release from leaf slices of 12 different species of plants, 2 groups were found. In the first group, sucrose release was inhibited between 60 and 80% by PCMBS, and in the second group between 0% and 40%. The difference in the two groups can be explained by a relative difference in the size of the two components of sucrose release for each species.
Effects of salinity on ultrastructure and ion distributions in roots of Plantago coronopus
Authors: Harvey Diana M. R. , Stelzer Ralf , Brandtner Regina , Kramer Detlef 
Published: April 2006

Root cell structure and ion distributions have been examined in Plantago coronopus L. grown in the absence or presence of 110–125 mM NaCl. In both salt‐treated and control plants, the inner cortical cells often had membrane whorls projecting into the vacuoles. These structures appeared to be continuous with the endoplasmic reticulum. In roots grown in saline conditions, the parenchyma cells surrounding the xylem vessels showed very uneven wall thickenings and corrugations.In control roots, X‐ray microanalysis of frozen hydrated bulk specimens showed that there were three levels at which discrete reciprocal changes in Na/K levels occurred: the outer‐middle cortex, the endodermis and the xylem vessels. The first two of these were associated with high Mg, and the last with high Ca percentages. In the salt‐treated roots, the overall Cl percentages were much lower than in the culture medium, being severely limited at the epidermis. Na and, to a lesser extent, Cl percentages decreased radially inwards, while those of K increased. The Na:Cl ratio decreased radially inwards across the cortex. The analytical validity of the data is discussed in relation to differential elemental losses during analysis, specimen topography and analytical spatial resolution. The results are interpreted in terms of the proposed involvement of Mg2+‐ and Ca2+‐ATPases in ion uptake and regulation of translocation in Plantago coronopus roots.
Growth and accumulation of N, K+, Ca2+ and Mg2+ in barley exposed to various nutrient regimes and root/shoot temperatures
Authors: Jensén Paul , Perby Harald 
Published: April 2006

Six cultivars of spring barley (Hordeum vulgare L. cvs Salve, Nümberg II, Bomi, Risø 1508, Mona and Sv 73 608) were grown in water culture for three weeks with various combinations of mineral supply and differential roots/shoot temperatures during the growth period. Most important for growth and accumulation of N, K+, Ca2+ and Mg2+ was the mineral supply, followed by the root temperature and the choice of cultivar. Treatments with low mineral supply or low root temperature induced a uniform reduction in growth and accumulation of the ions studied. The effects of low mineral supply and low root temperature on growth and N accumulation was additive, which indicates that these factors exert their influence independently of each other.Roots grown at 10°C were smaller and Rb+(86Rb) influx was higher than in roots grown at 20°C. It is suggested that the control of Rb+(86Rb) influx is affected by the root temperature and the age of the plants. The higher 86Rb+ (86Rb) influx into the low temperature roots could not compensate for the smaller root size. However, the lower total mineral accumulation made up for the needs of the smaller plants and cannot explain the reduction in growth.
Variation in growth and accumulation of N, K+, Ca2+ and Mg2+ among barley cultivars exposed to various nutrient regimes and root/shoot temperatures
Authors: Perby Harald , Jensen Paul 
Published: April 2006

Six cultivars of barley (Hordeum vulgare L., cvs Salve, Nürnberg II, Bomi, Risø 1508, Mona and Sv 73 608) were exposed for three weeks to combinations of high and low mineral supply and differential root/shoot temperature. For all the parameters tested [fresh and dry weights, contents and levels of N, K+, Ca2+ and Mg2+, and influx of Rb+(86Rb)] the cultivar differences were influenced by the mineral supply, the root temperature and the age of the plants.The cultivar differences in N nutrition of three‐week‐old plants could partly be attributed to variation in root size, uptake of N and in use‐efficiency of the element. The cultivar variation in root‐shoot partitioning of N was small, except when low mineral supply was combined with a low root temperature. Similarly, cultivar differences in contents of K+, Ca2+ and Mg2+ were influenced by variation in uptake, use‐efficiency and root/shoot partitioning of the elements. Low root temperature increased cultivar variation in K+, Ca2+ and Mg2+ partitioning.The modern cultivar Salve was compared with Nürnberg II, which is derived from a German land race. Nürnberg II performed better than Salve when low root temperature and restricted mineral supply were combined. Otherwise Salve grew better, partly due to a more efficient use of N.Two high‐lysine lines, Risø 1508 and Sv 73 608, were compared with their mother lines Bomi and Mona. The differences obtained revealed no general effect of the high‐lysine genes on growth and mineral nutrition of up to three‐week‐old barley plants.
Conditions of induction of secondary dormancy in apple after breaking of primary dormancy by anaerobiosis and low temperature
Authors: Bulard C. 
Published: April 2006

Dormant embryos of Pyrus malus L. cv. Golden delicious, isolated from the fruits at harvest time or after a few months storage at 10 to 15°C, were kept under anaerobic conditions in order to eliminate primary dormancy. Germination tests were then carried out at different temperatures, using three modes of culture depending on the nature of the contact between the embryo and the medium. In CM the distal part of the two cotyledons was immersed in the medium. In RM only the embryonic axis was immersed. In C/2M the embryo was placed flat on the medium, the radicle and the external surface of one cotyledon being in contact with it.Results showed that primary dormancy was released progressively depending on the duration of the anaerobic treatment. After a treatment of 11 or 13 days the last symptoms of primary dormancy were only apparent when germination tests were carried out at high temperatures (26–30°C) or in CM mode of culture.When the embryos were kept at 4°C during 3 months inside the fruits, subsequent germination was inhibited at high temperature and in CM mode of culture. When the embryos were kept under anaerobic conditions (7 days) after the chilling treatmem inside the fruits, germination was no longer inhibited. It is concluded that the inhibition of germination at high temperature and in CM mode of culture is due to the persistence of traces of primary dormancy. Therefore, these conditions do not seem to induce secondary dormancy in apple embryos.After elimination of primary dormancy by anaerobiosis. only application of (±) abscisic acid (3.8 and 19 μM) inhibited germination. These results support the idea that ABA is an important factor in the induction of dormancy. However, the question remains whether this secondary embryo dormancy has the same characteristics as the original primary dormancy.
Benzyladenine effects on the development of the photosynthetic apparatus in Zea mays: Studies on photosynthetic activity, enzymes and (etio)chloroplast ultrastructure
Authors: Caers Marleen , Vendrig J. C. 
Published: April 2006

Primary leaf segments from 8‐day‐old dark‐grown, and from 4‐ and 8‐day‐old light‐grown seedlings of Zea mays L. cv. Fronica, were treated with 10‐bM benzyladenine (BA) in the dark for 14 h. The segments were then studied after an exposure to light for 14 h. Photosynthetic activity (O2 evolution and CO2 fixation) and chlorophyll accumulation were stimulated by BA in dark‐grown leaf segments with etioplastids in the earliest stage of development. In these segments BA stimulated the activities of ribulose‐1,5‐bisphosphate carboxylase (EC 4.1.1.39), phosphoenolpyruvate carboxylase (EC 4.1.1.31), NADP+‐malic enzyme (EC 1.1.1.40) and pyruvate, orthophosphate dikinase (EC 2.7.9.1). In segments taken from 4‐ and 8‐day light‐grown seedlings, BA did not enhance the photosynthetic activity nor the chlorophyll accumulation. The activity of the enzymes mentioned above, was significantly enhanced by the BA‐treatment.BA mainly affected grana stacking in mesophyll cell chloroplasts in primary leaf segments taken from 3‐ to 5‐day light‐grown seedlings. Stroma thylakoid development was stimulated only in leaf segments from 3‐day‐old plants. At the same time BA accelerated grana loss in chloroplasts of bundle sheath cells, a typical phenomenon of development in such chloroplasts. Stroma thylakoid length in these chloroplasts increased by a BA treatment in segments from 3‐ and 4‐day light‐grown plants. A significantly higher number of chloroplasts was only observed with segments taken from 8‐day light‐grown seedlings and treated with BA.The etiochloroplast number in segments taken from 8‐day etiolated plants was significantly higher in BA‐treated segments after 26 h illumination. In etiochloroplasts from both mesophyll and bundle sheath cells, BA enhanced grana stacking after illumination for 4 h or more, whereas stroma membrane length was significantly higher only after 26 h light.It is concluded that the effects of BA depend on the developmental stage. BA accelerates the development of mesophyll and bundle sheath cell (etio)chloroplasts, but does not affect the ultrastructure of mature chloroplasts.
The effect of the seed coat, embryonic axis and aeration conditions on starch degradation hi cotyledons of Lens culinaris
Authors: Revilla M. Angeles , Fernández‐Tárrago Jorge 
Published: April 2006

The influence exerted by the seed coat, the embryonic axis and aeration conditions on starch degradation and a‐amylase activity (EC 3.2.1.1) in lentil (Lens culinaris Medik cv. Castellana) cotyledons was studied over twelve days of seedling growth. The presence of the seed coat influenced starch degradation and amylase activity negatively. The starch content in attached cotyledons decreased with time; however, in detached cotyledons starch degradation was very slow. These differences were in accordance with the variations in dry weight. The axis exerted a promotive effect on amylase development during the first days of growth if aeration conditions were restricted. Moreover, in the last days, similar levels in attached and detached cotyledons were reached. When the detached cotyledons were placed under improved aeration conditions, the amylase levels reached were greater than under any other conditions.The low rates of starch degradation in detached cotyledons in spite of high amylase activity was not due to feed‐back inhibition of the enzyme system, but may have been due to osmotic stress.
Effects of stabilizing solutes on salt activation of phosphoenolpyruvate carboxylase from various plant sources
Authors: Shooter‐Ilan Adiva , Waisel Yoav 
Published: April 2006

Phosphoenolpyruvate carboxylase (PEP carboxylase EC 4.1.1.31) was extracted from various halophytic, semi‐halophytic and glycophytic plant species. When the enzyme of those extracts was substrate protected, and in the presence of 1.6 mM PEP in the reaction mixture, the activity of PEP carboxylase was increased by 100 mM NaCl, and the activity range in the presence of NaCl was expanded. No correlation could be established between the response of the enzyme to ions and various plant characteristics, such as taxonomic status, salt tolerance or carbon fixation pathways. Salt activation of PEP carboxylase was substrate (PEP) dependent, but the minimal substrate concentration varied in different species.Effects of the stabilizing solutes PEP, betaine, proline and glycerol on the kinetic properties of PEP carboxylase from Zea mays (L.) cv. Hazera were analyzed. In the absence of NaCl the slope of the Hill plot (nIt) tended to rise in the presence of these solutes. Stabilization of the enzyme with betaine or glycerol caused a decrease in K′. while K′ and VTO increased in the presence of PEP. NaCl (100 mM) caused an increase in both K′ and Vmax in the protected as well as in the unprotected enzyme, except for PEP protection, where K′ decreased somewhat. In the presence of the protectants, glycerol and PEP, the effect of NaCl on Vmax, was 2–4 times higher than its effect on the non‐protected enzyme.
Free amino acids and total nitrogen during shoot development in Scots pine seedlings
Authors: Gezelius Kerstin 
Published: April 2006

The concentration of free amino acids and total nitrogen was studied in needles, stems and roots of seedlings of Pinus sylvestris L. for five weeks during the second growth period (“summer”). In one group of seedlings the source/sink relation was disturbed through removal of the terminal buds. The seedlings were cultivated in artificial year‐cycles in a climate chamber.Total nitrogen increased in needles and sterns of intact seedlings in the beginning of the “summer” and decreased during shoot growth. In seedlings, from which the buds had been removed, nitrogen remained at high levels in the primary needles and accumulated in steins and roots. The results are consistent with utilization of nitrogen in older needles and in the stem during shoot elongation.The pool of free amino acids increased in the beginning of the “summer” and decreased after bud break in primary needles, stems and roots. Arginine and glutamine, in the roots also asparagine, were the dominating amino acids (amides included). Together, these compounds (plus glutamate and aspartate) contributed about 90% of the nitrogen in the amino acid pool in all organs. In primary needles and in the stem, arginine predominated at the end of hardening (75–85% of the amino acid nitrogen). Free amino acids contributed at most ca 10% of the total nitrogen in primary needles, where the ratio of free amino acid nitrogen: total nitrogen was highest at the end of dormancy and in the early “summer”. Free amino acids accumulated after bud removal in primary needles and especially in stems and roots. Glutamine became relatively more dominant than arginine in the different organs.The observations are consistent with the role of arginine and glutamine for storage and transport of nitrogen in conifers. Because of the low concentrations of amino acid nitrogen in the primary needles, arginine is not considered a major nitrogen reserve in needles of Scots pine seedlings.
Mitochondria from Zea mays leaf tissues: Differentiation of carbon assimilation and photorespiratory activity between mesophyll and bundle sheath cells
Authors: Petit Patrice , Cantrel Catherine 
Published: April 2006

A procedure was developed to obtain intact and purified mitochondria from mesophyll and bundle sheath tissues of Zea mays L. cv. I.N.R.A. 180, an NADP+‐malic enzyme type C4 plant. There was little cross‐contamination between the two mitochondrial fractions.Both types of mitochondria oxidized NADH, succinate and malate with respiratory control. In mesophyll mitochondria malate oxidation was highly sensitive to KCN (85–90% inhibition of first state 3) and showed good respiratory control. In bundle sheath mitochondria malate oxidation was less sensitive to cyanide (75‐80% inhibition) and showed poor respiratory control. Malate and NADH appeared to be the best substrates for respiratory activity. Mesophyil mitochondria could not oxidize glycine, whereas bundle sheath mitochondria could.The results indicate that mesophyll and bundle sheath mitochondria of Zea mays are differentiated, not only with respect to the decarboxylation of malate but also with respect to the decarboxylation phase of photorespiration.
Effect of light on photosynthetic capacity during cold acclimation in a cold‐sensitive and a cold‐tolerant potato species
Authors: Steffan Kenneth L. , Palta Jiwan P. 
Published: April 2006

The effect of low temperature acclimation at various light levels on the photosynthetic capacity of Solanum species was examined. Two species, Solanum tuberosum L. cv. Red Pontiac and Solanum acaule Bitt., which differ significantly in degree of frost‐tolerance and in their ability to acclimate to low temperature stress, were compared. Acclimation conditions included 5/2°C (day/night) temperatures, and either moderate (400 · mol · m−2· s−1) or low (40 · mol · m−2· s−1) photosynthetic photon flux densities. Several parameters of photosynthesis were measured in tissue pieces during acclimation treatments including chlorophyll content, chlorophyll a/b ratios and carbon dioxide‐saturated photosynthetic oxygen evolution during light‐limited and light‐saturated assays.Most measured photosynthetic parameters of low temperature‐grown plants of both species showed greater declines under the moderate light than the low light conditions. Chlorophyll a/b ratios were unchanged after low temperature exposures in both light level treatments. At low temperatures, the cold‐sensitive S. tuberosum demonstrated a greater inhibition of photosynthetic capacity in light‐ and carbon dioxide‐saturated assays than S. acaule at all light levels. In addition to a pronounced inhibition at the higher light level, S. tuberosum demonstrated a very strong inhibition of photosynthetic capacity at very low light levels. Our results suggest a correlation between ability to maintain essential metabolic processes during low temperature stress in the presence of moderate light levels and the ability to increase cold tolerance.