bluuebunny/crossref_metadata_2025_split huggingface dataset:
Respiration and Vitality of Binucleate and Trinucleate Pollen
Authors: HOEKSTRA FOLKERT A. , BRUINSMA JOHAN 
Published: April 2006

AbstractThe respiration and vitality of ungerminated bi‐ and trinucleate pollen were studied in order to determine the influence of relative humidity and temperature on metabolic activity. The gas exchange, germination capacity and staining with tetrazolium bromide were followed under standardized conditions.A constant respiration rate occurred under conditions of high relative humidity (97%). Per mg pollen, the trinucleate grains of Compositae and Gramineae respired 2 to 3 times as intense as 6 species of binucleate grains. Per unit of pollen protein the differences were even larger. In contrast to binucleate pollen, the longevity of trinucleate pollen was very short and the ability to germinate was lost twice as fast as the respiration capacity. This limits the use of tetrazolium bromide as an indicator of viability.At reduced relative humidities respiration was strongly restricted, but the longevity of bi‐ and trinucleate pollen considerably increased.Pollen of Gramineae, however, was very sensitive to changes in relative humidity; short exposure to low relative humidity decreased both the vitality and the capacity to respire.
Embryoid and Plantlet Formation from Stock Cultures of Nigella Tissues
Authors: BANERJEE S. , GUPTA S. 
Published: April 2006

AbstractEmbryogenesis could be induced within a short period in differentiated roots of Nigella sativa on solid Murashige and Skoog's medium containing casein hydrolysate (500 mg/1) and IAA (0.5 mg/1). Experimental root explants were taken from two different stocks: (i) previously differentiated from leaf callus and now being maintained through subcultures in liquid White's medium and (ii) freshly differentiated from leaf callus on solid Murashige and Skoog's medium + casein hydrolysate (100 mg/1) + IAA (0.5 mg/1). Fifty per cent of the embryoids produced 2n plantlets within 40–60 days.
Effects of Small Water Stresses on Cell Turgor and Intercellular Space
Authors: LEVITT J. , ZAKEN R. BEN 
Published: April 2006

AbstractA link was sought between small water stresses and the larger metabolic changes that accompany them. A simple infiltration weight method of measuring percentage intercellular space is described and its errors evaluated. It yielded values for leaves (16–35%) similar to those recorded elsewhere by the pycnometer method. The percentage of intercellular space decreased to 0–50% of the value in turgid leaves with a simultaneous loss of turgor only in the sunflower leaves. Turgor remained constant in the orange leaves. Similar results were obtained with the pycnometer method. Measurements revealed that the total or most of the decrease in the volume of sunflower leaves on loss of turgor was due to a decrease in area: the smaller decrease in the volume of orange leaves was entirely due to a decrease in thickness. It is suggested that the sclerophyll nature of the orange leaves is an adaptation to prevent a secondary O2‐deficit stress on exposure to a water stress.
Effects of Azide on Photophosphorylation in Isolated Spinach Chloroplasts
Authors: HAMLIN LEIF , TILLBERG JAN‐ERIC , SUNDBERG INGRID 
Published: April 2006

AbstractThe influence of sodium azide on open‐chain and flavine mononucleotide mediated cyclic photophosphorylation in isolated spinach chloroplasts was investigated under anaerobic conditions. Open chain phosphorylation was completely inhibited with DCMU both in the presence and absence of sodium azide in the experimental medium. Flavine mononucleotide mediated photophosphorylation was only slightly inhibited by DCMU in the absence of sodium azide but inhibited in two steps by increasing amounts of DCMU when sodium azide was present in the medium. The first step can be explained as being mainly an effect of DCMU on an open chain electron transport, with water and H2O2 as electron donors and with flavine mononucleotide — kept in an oxidized state by sodium azide — as the electron acceptor. The second step, as well as the comparatively insensitivity to DCMU in the absence of sodium azide, depends on cyclic photophosphorylation mediated by flavine mononucleotide.
The Spectral and Photochemical Properties of Subchloroplast Membrane Particles from Pinus silvestris
Authors: ÖQUIST GUNNAR 
Published: April 2006

AbstractIsolated chloroplasts from Pinus silvestris have been fractionated by a combination of digitonin and Yeda‐press treatment. Different subchloroplast particles have been isolated by differential centrifugation. The spectral and photochemical properties of the different fractions have been analysed. Photosystem I was enriched in the light particles (high Chl a/Chl b ratios, low Chl/P700 ratios, high F735/F685 ratios, high photosystem I activity and enrichment of long‐wavelength absorbing Chl a). The heavy fractions were enriched in photosystem II (low Chl a/Chl b ratios, high Chl/P700 ratios, low F735/F685 ratios and enrichment of short‐wavelength absorbing Chl a). The molar ratio Chl/P700 was about 1.5 times greater for Pinus than for Spinacia, and Pinus had relatively less long‐wavelength absorbing Chl a compared with Spinacia.
Multiphasic Uptake of Ammonium by Soybean Roots
Authors: JOSEPH R. ANTONI , VAN HAI TANG , LAMBERT J. 
Published: April 2006

AbstractUptake of ammonium by intact soybean (Glycine max Merr. cv. Amsoy) plants can be represented by 3 phases of a single, multiphasic mechanism in the range 1.78 × 10‐5‐3.57 × 10‐3M. Each phase covers a limited concentration range and obeys Michaelis‐Menten kinetics. The multiphasic pattern of NH4+ uptake is remarkably consistent at all stages of soybean growth (20, 40, 60 and 80 days).
Seasonal Changes in the Effects of Auxin on Rooting in Stem Cuttings of Ficus infectoria
Authors: ANAND V. K. , HEBERLEIN G. T. 
Published: April 2006

Abstract Ficus infectoria stem cuttings were treated with 10 and 100 μg/ml each of IAA, IBA, 2,4, ‐D and NAA at monthly intervals and planted to study their rooting response after recording morphophysiological status and cambial activty of the parent branches. Attempts were also made to surgically expose the cambium before auxin treatment to determine the relationship of seasonal variation in auxin effectivity to cambial activity. The results show that: (1) there are two distinct phases in the sensitivity of Ficus infectoria stem cuttings to auxin‐induced rooting; (2) the high rooting phase coincides with renovation of growth and high cambial activity starting in March and lasting through August and the low rooting phase coincides with winter dormancy and low cambial activity; (3) roots emerge in longitudinal rows in slitted auxin‐treated cuttings; (4) slitted auxin‐treated cuttings root profusely in June when cambial activity is high but not in October when cambial activity is low suggesting a close correspondence of seasonal variation between the rooting activity of auxin and cambial activity.
Métabolisme du γ‐Aminobutyrate chez Agaricus bisporus
Authors: BALDY PIERRETTE 
Published: April 2006

Abstractγ‐Aminobutyrate synthesis, the first step in this pathway, is catalysed by L‐glutamate‐1‐carboxy‐lyase (E.G. 4.1.1.15). The purification procedure and some of in vitro properties of this enzyme isolated from fruit‐bodies of Agaricus bisporus 19 Lge were investigated.Glutamate decarboxylase has been partially purified from a homogenate by a combination of ammonium sulfate fractionation and hydroxylapatite column chromatography. All kinetic studies were carried out manometrically in a nitrogen atmosphere at 35°C by conventional Warburg technique.The decarboxylase is a pyridoxal‐phosphate requiring enzyme. The pH optimum was found to be between 5.5 and 5.6 and the Km value for glutamate was calculated to be 4 × 10‐2M from a Lineweaver‐Burk plot. Of the amino acids tested the enzyme is specific for glutamate. γ‐Aminobutyrate is not carboxylated to form glutamate. Inhibition by malate, malonate, α‐ketoglutarate and NAD were found to be non‐competitive with respect to glutamate, and those by succinate to be uncompetitive. Fractionation of the subcellular components shows that the enzyme is localized in the hyaloplasm.The results are discussed in relation to the γ‐aminobutyrate bypath, a probable shunt to the Krebs cycle.
Differential Reactivity in Epidermal Cells of Begonia rex Excised and Grown in vitro
Authors: CHLYAH AVERIL , VAN MARIE TRAN THANH 
Published: April 2006

AbstractThin explants composed of the epidermis and underlying collenchyma excised from leaf veins of Begonia rex and cultured in vitro are capable of neoformation of unicellular hairs, roots and buds. Unicellular hairs were formed over the entire surface of the explant when 10−6M indole acetic acid or 10−7M naphthaleneacetic acid (NAA) was added to the basal medium; each epidermal cell was potentially involved. The epidermis was most sensitive to a NAA treatment during the first few days of culture but 30% of the explants could still react after 4 days of culture without NAA. When NAA (5 × 10−7M) and a cytokinin, zeatin (10−7M), were added together, roots were formed from epidermal tissue after numerous divisions in the original cells. Their initiation was not related to particular cells. Buds were formed when a cytokinin (10−6M) was added to the basal medium; bud meristems were formed from small groups of cells surrounding basal cells of glandular hairs. Hair formation was inhibited by either high (32–27°C) or low (12°C) temperatures applied continuously. 32–27°C seemed to inhibit elongation of the hairs specifically, whereas 12°C inhibited earlier phases in hair formation. This hypothesis was supported by short temperature treatments applied at different times during hair formation.
Regulators of Cell Division in Plant Tissues
Authors: GORDON M. E. , LETHAM D. S. , BEEVER J. E. 
Published: April 2006

AbstractThe cytokinins, 6‐benzylaminopurine and kinetin, markedly enhanced the yield of both free and membrane‐bound 80S ribosomes per unit weight of radish (Raphanus sativus) cotyledon tissue. The response was observed only after the induction of growth by cytokinin; during the lag period preceding cytokinin‐induced growth, ribosome yields from both control and cytokinin‐treated cotyledons were below detectable levels. Mannitol depressed both growth and ribosome yield to the same degree. The enhanced ribosome yield appeared to be an indirect effect of cytokinin and was probably a consequence of cytokinin‐induced growth. The effect of 6‐benzylaminopurine on ribosome yield was not reflected in enhanced levels of cytoplasmic ribosomal RNA, while recently synthesized ribosomes were found to be more readily recovered from cytokinin‐treated tissue than from control tissue. It was concluded that cytokinin‐enhanced ribosome yield resulted from enhanced ribosome recovery or extractability and that ribosome yield is an unreliable indication of ribosome level in plant tissue.
Rubidium Absorption by Corn Root Tissue after a Brief Period of Water Stress and during Recovery
Authors: PARRONDO ROLANDO T. , SMITH RICHARD C. , LAZURICK KENNETH 
Published: April 2006

AbstractIntact and excised samples of corn root tissue were subjected to water stress either by incubation in solutions of osmotica or by desiccation, after which they were transferred to CaSO4 solution for various time periods for recovery. Osmotic agents used were either mannitol or polyethylene glycol 6000 at concentrations adequate to depress rubidium absorption to less than 30% of that of controls. During 6 h following release from osmotic stress, rubidium absorption by samples from intact seedlings treated with mannitol increased to 44% of that of controls, while those treated with polyethylene glycol increased to 79% of that of controls. Recovery of root samples excised prior to stress was very nearly the same as that of samples from intact roots. When water stress was produced by desiccation, recovery was about the same as from polyethylene glycol, attaining a rate of 76% of that of controls after 8 h. Whereas desiccated samples almost completely regained their water content during recovery, none showed correspondingly complete recovery of ion absorption capacity. Finally, during the recovery period, the submerged controls, but not controls in humid air, showed an increase in ion absorption capacity with time, confirming that the widely observed “aging effect” or “washing effect” is due to submersion and not to time per se.
RNA Synthesis in Spring and Winter Wheat during Cold Acclimation
Authors: SARHAN F. , D'AOUST M. J. 
Published: April 2006

AbstractMarked increases were obtained in the levels of ribosomal and soluble RNA fractions in winter wheat submitted to cold acclimation temperatures. In comparison, the change in the rRNA and sRNA of spring wheat, grown under similar conditions, were less pronounced.With the cold acclimation treatment, sRNA accumulated by winter wheat shows an important change in its (G + C)/ (A +Ψ+ U) ratio, whereas no change in base composition is observed in the sRNA of spring wheat or the rRNA of both spring and winter wheat.It is suggested that in winter wheat, cold acclimation temperatures potentiate increased synthesis of specific sRNAs, this possibly being part of the increased capacity for protein synthesis associated with cold acclimation.
The Use of the Pressure Chamber Technique for Measurement of the Water Potential of Transpiring Plant Organs
Authors: MEIRI A. , PLAUT Z. , SHIMSHI D. 
Published: April 2006

AbstractThe existence of water potential gradients in flowering shoots and leaves of roses (Rosa sp., cv. Baccara) and along flag leaves of wheat (Triticum aestivum L.) were studied by means of the Scholander pressure chamber. In roses grown in greenhouse, the water potential measured in transpiring shoots was higher than in leaves detached from these shoots, whereas the potential differences between leaf and shoot after equilibration in the dark were small or negligible. A progressive decrease in water potential was found upon repeated measurement on the same organ; this decline was steeper in leaves than in shoots. Extrapolating this decline to excision time resulted in water potential values which, in transpiring shoots, were 3 to 5 bars higher than in leaves. Detopping the flower bud did not alter this pattern, indicating that the highest water potential in the shoot was in the stem. In field‐grown wheat, the water potential measured in a whole flag leaf was about 6 bars higher than that measured in the apical one‐third of the leaf, and this difference disappeared after equilibrating the detached leaf for 1 h in the dark. These potential differences indicate the presence of resistances along the water path in the organ. The results obtained by the pressure chamber represent the highest water potential in the organ, rather than the average water potential.
Effect of Na+, K+, Mg2+ and ATP on the Relative Electrophoretic Mobility of Sugar Beet Membrane Particles with NaK ATPase Activity
Authors: KARLSSON JAN 
Published: April 2006

AbstractElectrophoretic measurements on membrane coated particles were performed with a Zytopherometer. Tris‐HCl buffer 0.2 M pH 7.0 at 37°C with addition of different combinations of Na+, K+, Mg2+ and ATP was used as test medium. The membranes were of two types, an untreated preparation with low NaK ATPase activity and a deoxycholate treated preparation with high NaK ATPase activity. There was no marked difference in reaction between the two types of membranes. To both types of membranes Mg2+ gave a strong positive and ATP a slight negative addition to the membrane charge. In the presence of ATP Na+ gave a higher charge contribution than did K+ or a combination of Na+ and K+. This implies that K+ gives a higher affinity for ATP than Na+ does and or that ATP mediates a higher affinity for Na+ than for K+.
Growth Regulators and the Phytochrome‐Mediated Dormancy of Celery Seeds
Authors: THOMAS T. H. , PALEVITCH D. , BIDDINGTON N. L. , AUSTIN R. B. 
Published: April 2006

AbstractSeeds of five celery (Apium graveolens L.) cultivars germinated at 15°C in the light or dark but at 22°C only in the light. This light requirement was overcome by treatment with a mixture of the gibberellins GA4 and GA7 (GA4/7) but interactions of cytokinins, daminozide, ethephon, EDTA and N‐phenyl‐N′‐4‐pyridylurea (NC5392) with GA4/7 were observed. Varietal differences in response to GA4/7 concentration and the requirement for cytokinins were related to the upper temperature limits for germination of the different cultivars. Seeds of cultivars responding to low concentrations of GA4/7 appeared to contain less natural inhibitor than those requiring either high concentrations of GA4/7 or cytokinin in addition to low GA4/7. The cytokinin requirement for germination was partially removed by leaching the seeds with water. Interaction studies with applied hormones indicated that in seeds incubated in the light inhibition by abscisic acid was partially alleviated by N6‐benzyladenine but not by GA4/7 application. The implications of these results are discussed in relation to the involvement of natural plant hormones in the dormancy mechanism of celery seeds.
Increased Germination Rates of Baldcypress and Pondcypress Seed Following Treatments Affecting the Seed Coat
Authors: MURPHY J. BRAD , STANLEY R. G. 
Published: April 2006

AbstractThe effects of seed‐coat removal, warm‐water soaking, cold stratification, dry‐cold storage and acid treatment on the germination of baldcypress (Taxodium distichum (L.) Rich.) and pondcypress (Taxodium distichum var. nutans (Ait.) Sweet) seed were studied.Removal of the hard seed coat resulted in a prompt and high percent germination, indicating that there was no physiological embryo dormancy. Cold stratification, warm‐water soaking and acid treatment did not increase percent germination over the control after a 60‐day germination period. They did promote the rate of germination however, having a significantly higher germination at 30 days. Dry‐cold storage promoted the initial rate of germination, but resulted in a decreased percent germination below the control after 60 days.The above results suggest that moisture, and not cold, was the crucial component of stratification. The improved germination rate following acid treatment further suggests that any treatment which rendered the seed coat more permeable or softened it was more effective in increasing the rate of germination of baldcypress and pondcypress seed.
The Effect of Several Protein Amino Acids and Some Inorganic Nitrogen Sources on the Growth of Sphagnum nemoreum
Authors: SIMOLA LIISA KAARINA 
Published: April 2006

AbstractThe nitrogen metabolism of a bog moss, Sphagnum nemoreum Scop., has been studied in aseptic cultures. The effect of several protein amino acids, especially those found in peat, has been investigated. NH4NO3 (1.25 mM) was the best nitrogen source but NH4+ ions were more effectively utilized than NO3− ions when given as the only nitrogen source. Some of the amino acids (2.5 mM) allowed fairly satisfactory growth (arginine and alanine) when given as the only nitrogen source, but some of them were not utilized at all (leucine, lysine, isoleucine and methionine). Given at low concentrations (0.001 and 0.25 mM) together with NH4NO3 (2.5 mM), most of the protein amino acids failed to reveal any growth‐promoting or ‐inhibiting effect. Only lysine (0.25 mM) clearly inhibited growth under these conditions. The nitrogen metabolism of Sphagnum nemoreum seems to be rather flexible and this species is more tolerant of organic nitrogen, especially hydroxyproline, than the higher plants.
An Evaluation of Some Parameters Required for the Enzymatic Isolation of Cells and Protoplasts with CO2 Fixation Capacity from C3 and C4 Grasses
Authors: HUBER S. C. , EDWARDS G. E. 
Published: April 2006

AbstractVariable factors affecting the enzymatic isolation of mesophyll protoplasts from Triticum aestivum (wheat), a C3 gras, and mesophyll protoplasts and bundle sheath strands from Digitaria sanguinalis (crabgrass), a C4 grass, have been examined with respect to yields and also photosynthetic capacity after isolation. Preparations with high yields and high photosynthetic capacity were obtained when small transverse leaf segments were incubated in enzyme medium in the light at 30°C, without mechanical shaking and without prior vacuum infiltration. Best results were obtained with an enzyme medium that included 0.5 M sorbitol, 1 mM MgCl2, 1 mM KH2PO4, 2% cellulase and 0.1% pectinase at pH 5.5. In gerneral, leaf age and leaf segment size were important factors, with highest yields and photosynthetic capacities obtained from young leaves cut into segments less than 0.8 mm. To facilitate the cutting of such small segments, a mechanical leaf cutter is described that uniformly (± 0.05 mm) cuts leaf tissue into transverse segments of variable size (0.4–2 mm). Isolations that required more than roughly 4 h gave poor yields with reduced photosynthetic capacity; however, using the optimum conditions described, functional preparations could be roughly 2 h. High rates of light dependent CO2 fixation by the C4 mesophyll protoplasts required the addition of pyruvate and low levels of oxalacetate, while isolated bundle sheath strands and C3 mesophyll protoplasts supported CO2 fixation without added substrates. Rates of CO2 fixation by isolated wheat protoplasts generally exceeded the reported rates of whole leaf photosynthesis. Wheat mesophyll protoplasts and crabgrass bundle sheath strands were stable when stored at 4°C while C4 mesophyll protoplasts were stable when stored at 25°C.
Endogene Jahresperiodik der Blattbewegungen zweier Oxalis‐Arten
Authors: MÜLLER‐HAECKEL AGNES 
Published: April 2006

AbstractUnder natural light‐dark changes at the Arctic Circle special behaviour was observed in the leaf movement of Oxalis regnellii and Oxalis acetosella: (1) Advancing in the beginning of leaf rising. (2) Prolonging of the duration of day position. (3) Increasing positive phase‐andle differences. (4) Prolonging of the duratin of the daily moving‐time. From January to April all these features were running back. The winter behaviour has also been shown in artificial light‐dark changes (12:12), when plants were taken in the trial before mid winter. The reactions did not occur if the plants were put into artificial light conditions after mid winter. Criterions for an endogenous annual periodicity and its possible annual Zeitgebers under natural light‐dark changes are discussed. The positive correlation between the length of day position and the length of day‐time in the summer respectively the length of night‐time in the winter, as well as positive phase‐angle difference in spring and in autumn/winter, are judged as a criterion for a second oscillator.
Effect of Oxidized Nucleotide Coenzymes and Mercaptoethanol on Stabilization of Plant Dehydrogenase Activity in Crude Extracts
Authors: HAISSING BRUCE E. , SCHIPPER ARTHUR L. 
Published: April 2006

AbstractActivity loss of 6‐phosphogluconate, glucose‐6‐phosphate, and glyceraldehyde‐3‐phosphate dehydrogenases occurs in crude plant extracts prepared with insoluble polyvinylpyrrolidone (PVP) and a reducing agent, such as mercaptoethanol. Oxidized nucleotide coenzymes (1 mM), in addition to mercaptoethanol (100 mM), in the extraction buffer stabilizes activity of these dehydrogenases in extracts from both woody and herbaceous plants. PVP and mercaptoethanol alone equally stabilize malate dehydrogenase from most species tested. The mercaptoethanol and coenzyme treatment has proven useful in quantification, purification, and characterization of dehydrogenases in physiological investigations.