bluuebunny/crossref_metadata_2025_split huggingface dataset:
Extraction of tracheal sap from Citrus and analysis of its nitrogenous compounds
Authors: MORENO JOAQUIN , GARCÍA‐MARTINEZ JOSÉ L. 
Published: April 2006

AbstractTracheal sap was extracted from sections of stems (0.5 to 1.5 cm in diameter and 7.5 to 15.0 cm in length) of orange trees (Citrus sinensis (L.) Osbeck cv. Washington Navel) by using a combination of the vacuum and liquid displacement methods. The volume of sap obtained and its concentration of nitrogenous compounds were dependent on the volume of displacing liquid used for the extraction. Four ml of water‐saturated 1‐butanol extracted essentially all of the xylem fluid present in the stem sections without apparent production of artifacts.The time of sampling affected the nitrogen concentration of the tracheal sap, but not the content of xylem nitrogen per volume of stem material. The orientation of the stems in the tree and the diameter of the stems had an effect on their contents of xylem nitrogen, with southeastern orientation and thinner stems showing higher concentrations.We could not detect the presence of ammonium, nitrites or proteins in the tracheal sap of orange trees. Most of the nitrogen was present as amino acids and about 2% of the total in the form of nitrates. The qualitative composition of amino acids, as determined by TLC, was the same both in winter and spring tracheal sap. The main components of the sap were proline and arginine in winter, and these amino acids together with asparagine and aspartic acid in spring.
Efficiency and regulation of root respiration in a legume: Effects of the N source
Authors: LAMBERS HANS , LAYZELL DAVID B. , PATE JOHN S. 
Published: April 2006

AbstractA comparison was made of energy metabolism of nodulated N2 fixing plants and non‐nodulated NO3‐fed plants of Lupinus albus L. Growth, N‐increment, root respiration (O2 uptake and CO2 production) and the contribution of a SHAM‐sensitive oxidative pathway (the alternative pathway) in root respiration were measured. Both growth rate and the rate of N‐increment were the same in both series of plants. The rate of root respiration, both O2 uptake and CO2 production, and the activity of the SHAM‐sensitive pathway were higher in NO3‐fed plants than in N2 fixing plants. The rate of ATP production in oxidative phosphorylation was computed also to be higher in NO3‐fed plants. It is concluded that both carbohydrate costings and ATP costings for synthesis + maintenance of root material were lower in N2 fixing than in NO3‐fed plants.The respiratory quotient of root respiration was 1.6 in N2‐fixing plants and 1.4 in NO3‐fed plants. These values were slightly higher than the values calculated on the basis of CO2 output due to N‐assimilation and the experimental values of O2 uptake, but showed the same trend: highest in N2 fixing plants.Root respiration of NO3‐fed plants showed a diurnal pattern (both O2 uptake, CO2 production and the activity of the SHAM‐sensitive pathway), whilst no diurnal variation in root respiration was found in N2 fixing plants. However, C2H2 reduction did show a diurnal rhythm, which is suggested to be related to the diurnal variation in transpiration.Addition of NO3 to N2 fixing plants increased the rate of root respiration and the activity of the alternative pathway. This treatment did not decrease C2H2 reduction and H2 evolution within 4 days.Withdrawal of NO3‐supply from NO3‐fed plants decreased the rate of root respiration but had no effect on the relative activity of the alternative pathway.It is suggested that the higher rate of root respiration and the higher activity of the SHAM‐sensitive pathway in NO3‐fed plants is due to a larger supply of carbohydrates to the roots, partly due to a better photosynthetic performance of the shoots and partly due to a higher capacity of the roots to attract carbohydrates.
Transcription products associated with developing pea chloroplast membranes
Authors: STUMMANN BJARNE M. , KAUFMANN UWE , HENNINGSEN KNUD W. 
Published: April 2006

AbstractRNA fractions from leaves of pea (Pisum sativum L.) were labelled by placing dark‐grown shoots in 32P‐phosphate for 1 h in darkness and 3 h in light. Membrane‐associated RNA and soluble RNA was isolated from an organelle fraction containing plastids and mitochondria. A cytoplasmic RNA fraction was also isolated. These RNA fractions were hybridized to nuclear, chloroplast or mitochondrial DNA isolated from fully green leaves. The organelle RNA fractions hybridized significantly only to chloroplast DNA. This result suggests that at early stages of greening, light initiates transcription of part of the chloroplast DNA. Some of the newly transcribed RNA species are associated with the developing plastid membranes.
Substrate‐dependent modulation of ATPase activity by Na+ and K+ in roots of Plantago species
Authors: ERDEI LÁSZLÓ , KUIPER PIETER J. C. 
Published: April 2006

AbstractThe separate and combined effects of Na+ and K+ on ATPase activity of microsomal fractions from the roots of the halophytic Plantago maritima and the less salt‐tolerant Plantago coronopus were investigated in the presence of Mg+ATP or Ca+ATP (at equimolar ratios) as substrate. The ATPase activity in the presence of Mg+ATP was stimulated by Na+ and by K+ when they were added separately, but their combination reduced the enzyme activity. In the presence of Ca+ATP, however, the enzyme activity was stimulated by the combined addition of Na++ K+ as well, and their action was qualitatively additive, but experimentally lower. The two complexes as substrate probably served as allosteric effectors and induced different types of enzyme responses to monovalent cations.The Na+‐stimulation and K+‐stimulation of the ATPase activity could be separated by growing the plants under saline conditions. The Na+‐stimulation of the ATPase was lowered while the K+‐stimulation remained unchanged. The corresponding Na+ influx of the roots could also be blocked without influencing K+ influx of the roots. This kind of separation of ion fluxes and ATPases presumes a transport system model which possesses several units and which is accessible for regulation by hormones, lipids and divalent cations.
Influence of the excision of cotyledons on the content of indole‐3‐acetic acid, growth and flowering of Lupinus albus plants
Authors: ELKINAWY MAHASEN 
Published: April 2006

AbstractExcision of both cotyledons of Lupinus albus L. (L. termis Forssk.) seedlings at different morphological stages during the first 8 days after sowing, retarded significantly the growth of 16‐day‐old seedlings and decreased the content of IAA in the shoots. The effect was more obvious at the early excision (4 days after sowing). A pattern similar to that of control plants with intact cotyledons was attained when cotyledons were excised later than 8 days after sowing. It is believed that the cotyledons control the IAA content of the shoot during the early stages of development. At day 36 flower primordia were observed in controls but not in cotyledon‐less plants. At this time the IAA content of the shoot apices and the growth of cotyledon‐less plants were the same as in controls except for plants that lost cotyledons 4 days after sowing, which showed similar values at week 11, but did not produce flower primordia. The other cotyledon‐less plants produced flower primordia 4–11 days after controls. It is postulated that the cotyledons convey certain factor(s) to the developing axis at an early stage of the development which promote flowering.
Effect of vitamins on sprouting of purple nutsedge tubers
Authors: HUSAIN S. M. , AL‐ALI FAIZA AZIZ , SHAMSI S. R. A. 
Published: April 2006

AbstractVitamins of the B group and vitamin C were applied to purple nutsedge (Cyperus rotundus L.) tubers to study their effect on the sprouting rate, initiation and establishment of sprouts, growth of plantlets and development of orthotropic rhizomes in comparison with the corresponding effects of kinetin. Ascorbic acid up to 100 mg I−1 hastened sprouting, whereas vitamins of the B group and kinetin retarded sprouting; 100% tubers sprouted in all treatments within 10 days.Unlike kinetin, none of the vitamins resulted in the establishment of more than one sprout per tuber. Riboflavin and pyridoxine promoted root and shoot growth of the plantlets, whereas kinetin produced short, thick shoots and inhibited root growth, with increasing concentration.Ascorbic acid was only second to kinetin in the induction of orthotropic rhizomes, but the former resulted in an increase in rhizome length.
Stem pithiness in tomato plants: The effect of water stress and the role of abscisic acid
Authors: Aloni Beny , Pressman Etan 
Published: April 2006

The pith parenchyma in tomato (Lycopersicum esculentum) stems was found to be disrupted in response to water stress (stem pithiness). The process of the degradation starts at the upper part of the stem and proceeds downwards as the stress is prolonged. The damage to the stem tissue was found to be irreversible upon rehydration of the stressed plants. Scanning electron microscopy revealed that the protoplast of the affected cells is disrupted first, followed by degradation of the cell wall.Application of abscisic acid (ABA) induced pithiness in non‐stressed plants and also enhanced the effect of a short period of dehydration. Kinetin, although causing severe wilting, did not induce pithiness. However, when given after a short period of water stress or within the period of stress, kinetin enhanced pithiness development.In the course of the stress, ABA levels in the upper part of the stem and in the young leaves were higher than the levels found in the lower parts of the plant shoot. The increase in ABA levels was detected before any sign of pithiness.It is suggested that ABA might be the triggering agent of the cellular degradation process initiated by water stress.
Interactions between osmoregulation and the alternative respiratory pathway in Plantago coronopus as affected by salinity
Authors: Lambers Hans , Blacquière Tjeerd , Stuiver Bep (C. E. E.) 
Published: April 2006

Plantago coronopus L., a species from the coastal zone, was grown in culture solution with and without 50 mM NaCl. In addition it was transferred from a non‐saline solution to a solution containing 50 mM NaCl. Short term effects of NaCl on growth and various aspects of energy metabolism, including photosynthesis, shoot dark respiration, root respiration and the contribution of the SHAM‐sensitive alternative pathway to root respiration were investigated. The concentrations of soluble and insoluble non‐structural carbohydrates and of sorbitol a compatible osmotic solute in Plantago, in both shoots and roots were also determined.Growth of shoots and roots was largely unaffected by addition of 50 mM NaCl. Net photosynthesis, shoot dark respiration and the concentration of non‐structural carbohydrates in both shoots and roots were also unaffected by salinity. The rate of root respiration immediately decreased upon addition of 50 mM NaCl. This decrease was almost exclusively attributed to a decreased activity of the SHAM‐sensitive alternative pathway. The concentration of sorbitol in the roots increased quickly after addition of 50 mM NaCl, whilst the increase in sorbitol concentration in the shoots started later. The time course of the increase of sorbitol concentration was similar to that of the decrease in activity of the alternative pathway. During the first 12 h after exposure to 50 mM NaCl, the amount of carbohydrates which was saved in respiration, due to the decreased activity of the alternative pathway, was the same as that used for sorbitol synthesis in the roots. It is concluded that the activity of the alternative pathway decreased due to increased utilization of carbohydrates for sorbitol synthesis, according to a proposed ‘energy overflow model’.After 24 h, the sorbitol concentration in the cytoplasm of the root cells of plants transferred to a saline solution reached a level that was sufficient to compensate for 50 mM NaCl, assuming a cytoplasmic volume of ca. 10% of the total cell volume. The sorbitol concentration in roots of plants grown in a saline environment for several weeks was lower than that in roots of plants transferred to a saline environment for c. 24 h. It is suggested that sorbitol accumulated in roots of Plantago coronopus as an immediate reaction upon salinity, whilst other adaptations may occur thereafter.
Energy metabolism of Plantago lanceolata as dependent on the supply of mineral nutrients
Authors: Lambers Hans , Posthumus Freek , Stulen Ineke , Lanting Lineke , van de Dijk Siebren J. , Hofstra Rinie 
Published: April 2006

Plantago lanceolataL., a grassland species from a relatively nutrient‐poor habitat, was grown in nutrient‐rich and in nutrient‐poor culture solutions. Half of the plants were trensferred from high to low or from low to high nutrient conditions. Shoot growth was immediately reduced upon transfer to low nutrient conditions, whilst it reacted more slowly upon transfer of plants to high nutrient conditions. Root growth was less dependent on the supply of nutrients, but it was slightly reduced upon transfer of plants to high nutrient conditions.Photosynthesis was largely independent of the nutrient supply, apart from an initial increase upon transfer of plants to low nutrient conditions. Photosynthesis decreased with age in all treatments, and this decrease was not due to mutual shading. The decrease of photosynthetic rate was not accompanied by a decreased relative growth rate: it was compensated by a more efficient root respiration, since the activity of the alternative nonphosphorylating pathway continuously decreased in plants grown in a high nutrient environment.It is concluded that the alternative pathway was of significance in removal of carbohydrates, which could not be utilized for growth, energy production,etc., due to a temporary or structural imbalance between assimilate production and requirement. The alternative pathway also appeared to allowP. lanceolataplants to adapt to a changed environment as regards mineral nutrition.The experimental value for root growth respiration ofP. lanceolatagrown under high nutrient conditions was compared with a theoretical value, calculated from the biochemical composition of plant dry matter and the known energy costings for biosynthetic and transport processes. A good correlation between the experimental and theoretical value of root growth respiration was found if it was assumed that ion uptake requiredc. 1.0 molecule of ATP per ion per membrane passage.
Action of bicarbonate and Photosystem 2 inhibiting herbicides on electron transport in pea grana and in thylakoids of a blue‐green alga
Authors: van Rensen Jack J. S. , Vermaas Wim F. J. 
Published: April 2006

Bicarbonate (or carbon dioxide) is required for electron transport in isolated broken pea chloroplasts. The site of action of the bicarbonate ion is between the primary electron acceptor of Photosystem 2, Q, and the plastoquinone pool. After trypsin treatment the Hill reaction with ferricyanide does not require bicarbonate. Photosystem 2 inhibiting herbicides act also at this site. Therefore, a possible interaction of bicarbonate and these herbicides in their effect on photosynthetic electron transport was studied.The reciprocal of the Hill reaction rate in CO2‐depleted chloroplasts was plotted against the reciprocal of added bicarbonate concentration in the absence and in the presence of 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU), 2‐methoxy‐4,6‐bis (ethylamino)‐1,3,5‐triazine (simeton) or 4,6‐dinitro‐o‐cresol (DNOC). From these Lineweaver‐Burk plots we concluded that DCMU and simeton inhibit both bicarbonate binding and Vmax. There is a purely competitive inhibition of bicarbonate binding by DNOC. We suggest that DNOC may exert its inhibition of electron transport by removing bicarbonate from its binding site.In isolated thylakoid membranes of Synechococcus leopoliensis we did not find a bicarbonate effect nor inhibition by DNOC after Q, indicating that in the thylakoids of this blue‐green alga the binding site for bicarbonate and DNOC between Q and plastoquinone is absent.
Effects of bud removal in Scots pine (Pinus silvestris) seedlings
Authors: Gezelius Kerstin , Ericsson Anders , Hällgren Jan‐Erik , Brunes Laila 
Published: April 2006

One‐ and two‐“year”‐old seedlings of Pinus silvestris L., from which the buds had been removed, were studied for five weeks during the second and third growth period, respectively. Intact seedlings were used as controls. The seedlings were cultivated under controlled conditions in a climate chamber. The growth of the seedlings was determined and the one‐“year”‐old needles assayed for changes in net photosynthesis and ribulose bisphosphate carboxylase activity and in the levels of protein, Kjeldahl nitrogen, chlorophyll and starch.In the control the carboxylase activity and the content of protein, Kjeldahl nitrogen and starch in the needles increased in the beginning of the “summer” and decreased during the shoot growth period. The starch content was higher after bud removal (decapitation), since the carbohydrate could not be utilized for the growth of the new shoot. Decapitation did not affect the growth rate of the roots.The content of Kjeldahl nitrogen and total and soluble protein in the needles was higher in the decapitated seedlings during the period of shoot elongation in the control. Total nitrogen, but not protein, reached high levels, indicating accumulation of non‐protein compounds. The general course of the chlorophyll pattern was not affected. Higher ribulose bisphosphate carboxylase activity than in the control was observed in the later part of the experimental periods. The higher levels of protein and nitrogen as well as of carboxylase activity after decapitation support the interpretation that soluble protein, including the carboxylase, and possibly other nitrogen compounds in the older needles are used for growth of the shoot. The loss of protein and nitrogen and of carboxylase activity in the control did not seem to be due to mineral deficiency in the substrate.Despite higher levels of carboxylase activity and similar chlorophyll concentrations, light‐saturated net photosynthesis was lower after decapitation. The ratio between photosynthesis and photorespiration was not affected.
Translocation of labelled assimilates following photosynthesis of 14CO2 by the field bean, Vicia faba
Authors: Crompton Hilary J. , Lloyd‐Jones C. P. , Hill‐Cottingham D. G. 
Published: April 2006

When whole plants were exposed to 14CO2, almost the same amount of radioactivity was taken up initially by each leaf regardless of its position on the stem and of the presence of beans at that node. Thus, although developing beans are a powerful sink for assimilated carbon, they do not increase the CO2 uptake by adjoining leaves.The distribution of labelled assimilates 6 hours after feeding 14CO2 to a single leaf for 1 hour varied with both the position of the treated leaf and the stage of development of the plant. Before any flowers were set most of the radioactivity from all expanded leaves moved downwards to the roots and the stem below the treated leaf (lower stem). Later, during pod‐fill, the upper leaves maintained this supply to the roots and lower stem, whilst most of the carbon translocated from the lower and mid‐stem leaves went to the beans. However, we found no exclusive relationship between a leaf and the supply to beans developing on the same node.The amount of radioactivity moving out of a source leaf at a fruiting node increased over successive samplings up to 48 h; the pattern of distribution of the 14CO2 however remained virtually unchanged.
Cytophotometric study and statistical analysis of ploidy evolution in cultured tissues of Nicotiana tabacum
Authors: de Boucaud Marie‐Thérèse , Gaultier Jean‐Maurice 
Published: April 2006

Evolution of the ploidy in four strains of Nicotiana tabacum ev. P 19 was studied by cytophotometry after transformation of the cultured tissues into protoplast suspensions.The limits of these variations were analysed numerically and statistically. The method used is capable of wide application. It can be used to predict the evolution of the average ploidy level of a strain maintained on a given medium if the average ploidy level of the explant is known. Comparison is made relative to a standard of known ploidy (diploid protoplasts). Increase of the average ploidy level is faster when the explant is mainly diploid (leaf parenchyma) than when it is composed of more heterogeneous tissues as regards ploidy (shoot tip). The appearance of a random drift depends on the composition of the culture medium: it is immediate in one medium (MS2), but is preceded by a phase of relative stability in another medium (MS1) which is richer in kinetin.While the results presented specifically concern the strains cultured on media MS1 and MS2, the statistical method employed is applicable to cultures of any species for which one can experimentally justify a linear regression analysis.
Genotypic differences in the response of sugar beet plants to replacement of potassium by sodium
Authors: Marschner H. , Kuiper P. J. C. , Kylin A. 
Published: April 2006

The effect of replacing 50% or 95% of the potassium by sodium on growth and on potassium and sodium levels in three genotypes of sugar beet (MONOHILL; ADA; FIA) has been studied in water culture over a period from 2 to 9 weeks.In all three genotypes there was a preferential uptake of potassium compared to sodium. Nevertheless, at high sodium supply most of the potassium was replaced by sodium, particularly in the leaves. At the same supply the accumulation of sodium in the leaves increased in the following order: ADA < MONOHILL < FIA. Even with high dominance of sodium in the medium, the youngest leaves of FIA held about 0.5 mmol potassium per g dry matter, and potassium was evidently translocated from old leaves to the new growth.Effects of sodium on growth became more important with time. After 9 weeks, 50% replacement of potassium by sodium increased growth of all plant organs of the three genotypes. Replacing 95% of potassium by sodium depressed growth of the storage root in MONOHILL and particularly in ADA, with simultaneous enhancement of leaf growth in the latter. In FIA, however, this treatment further stimulated both leaf and, particularly, storage root growth. Sodium in comparison with potassium increased the sucrose concentration in leaves and storage roots. The highest sucrose concentration in the storage roots of ADA and FIA was obtained in the treatment with 95% sodium.The results demonstrate pronounced genotypic differences in sugar beet with respect to the response to sodium. FIA has the most natrophilic behaviour and might be a promising genotype for breeding programmes for adaptation of sugar beet plants to soils high in sodium.