bluuebunny/crossref_metadata_2025_split huggingface dataset:
The dynamics of H+ efflux from the trap lobes of Dionaea muscipula Ellis (Venus's flytrap)
Authors: REA PHILIP A. 
Published: April 2006

Abstract. H+ efflux from the trap lobes of Dionaea muscipula Ellis (Venus's flytrap) was measured in vitro. FC, IAA, and 2,4‐D markedly increase the rate of H+ efflux within minutes of their addition to the incubation medium whereas ABA and DES cause the rate to decrease. Consequently, the H+ efflux mechanism of Dionaea is considered to be similar to the H+ extrusion pumps of other higher plants in this respect. However, the H+ extrusion mechanism of Dionaea may be unusual in that long‐term exposure of the trap lobes to known secretion elicitors— bactopeptone, NH4+, Na +, urea, thiourea, glycine or xanthine—also causes a large increase in the steady‐state rate of H+ efflux from the trap lobes. Since the observed H+ effluxes primarily correspond to the adaxial surface of the trap lobes and show similar time‐ and secretion elicitor‐dependencies to the responses seen in situ, it appears that the H+ effluxes measured in vitro bear a direct relationship to those observed in the intact, actively secreting plant.Three of the secretion elicitors that were tested— K+, NH4+, and urea—have rapid effects on the rate of H+ extrusion in addition to their long‐term effects. K+ and NH4+ cause a rapid acceleration of H+ efflux whereas urea causes a rapid deceleration or, at high external concentrations, reversal of the net flux. The effect of K+ is inferred to result from K+ ‐H+ exchange between the tissue and bathing medium. Studies with structural analogues of NH4+ and urea and inhibitors of the assimilation of reduced nitrogen suggest that the effects of NH4+ and urea result from the pH‐perturbing consequences of their metabolism subsequent to their absorption. These effects are considered to be auxiliary to the elicitation of secretion.It is proposed that H+ efflux from the trap lobes is mediated by a K+‐H+ exchange mechanism, the activity of which is modified by long‐term exposure to secretion elicitors and/or short‐term exposure to factors which alter the availability of endogenous H+ ions.
Abscisic‐acid‐induced turion formation in Spirodela polyrrhiza L III. Specific changes in protein synthesis and translatable RNA during turion development
Authors: SMART CHERYL C. , TREWAVAS ANTHONY J. 
Published: April 2006

Abstract The developmental process leading to the formation of the abscisic acid (ABA) induced turion of Spirodela polyrrhiza was accompanied by a repression of nucleic acid and protein synthesis. DNA synthesis in the developing lurion (induced by 10−4mol m−3 ABA) was inhibited within 3h of ABA addition, followed by a repression of protein synthesis after 24 h, while RNA synthesis was not inhibited until 3 d. The inhibitory effect of ABA on protein synthesis was found to be selective and the synthesis of several novel proteins appeared to be induced. These effects were specific to ABA‐sensitive tissue.The relationship between the changes in the protein and mRNA profiles during the development of the turion was investigated. The rapid general inhibition of protein synthesis at early stages of lurion formation could not be accounted for by the level of translatable mRNA, indicating an effect of ABA at the translational level. The specific alteration to the pattern of in vivo labelled proteins could have resulted, however, from control of the level of specific mRNAs for those particular proteins. Only after 3 d in ABA, when the developing primordium is committed to the turion developmental pathway, is there a total inhibition in the production of mRNA leading to the shutdown of all primary processes and the onset of the irreversible events leading to the dormant state.
Penetration of light into soil and its role in the control of seed germination
Authors: BLISS D. , SMITH H. 
Published: April 2006

Abstract Light transmitted through soil, and the leaf litter of two tree species, was measured using a spectroradiometer. In general, a greater penetration by longer wavelengths, especially far‐red, was noted. This was most marked in a dry sand sample. The effect was less in the case of clay‐loam aggregates. Moisture in the samples had an opposite effect in these two cases, causing an increase in transmission through sand but a decrease through clay loam aggregates. Reduction in particle size was found to reduce both the total light transmitted and the red/far‐red ratio (R : FR). Red wavelengths were also more attenuated by a layer of freshly fallen oak (Quercus rotrur) leaves than were far‐red wavelengths. A layer of Corsican pine (Pinus nigramaritima) needles however, was found to act as a neutral density filter over the 400 800 nm range.Prolonged exposure to soil‐filtered light was found to affect the germination of seven species tested. Plantago major demonstrated an approximately linear decrease in germination with increasing depth. Rumex obtusifotius showed an apparent threshold response at 4 6 mm depth, as did Cecropia obtusifolia but at a slightly greater depth. Digitalis purpurea germinated very poorly in darkness, yet was extremely photosensitive with very high germination even at 10 mm depth. Galiutn aparine and Chenopodium album showed a two‐phase response with germination reaching a peak at 2 mm depth.The implications for the function of the photoreceptor phytochrome in the control of germination are discussed in relation to soil‐transmitted light and with regard to the results of the germination tests.
Phase and amplitude relations between transpiration, water potential and stem shrinkage
Authors: WRONSKI E. B. , HOLMES J. W. , TURNER N. C. 
Published: April 2006

Abstract An electrical analogue describing the phase and amplitude relations between transpiration, water potential and stem shrinkage for trees was developed. Observations of shrinking and swelling at various heights up a Pinus radiata tree were obtained over several weeks in summer and autumn.The relative amplitude in shrinkage increased by a factor of two up the stem, but phase lags were small. The data obtained were used in conjunction with the electrical analogue of the How pathway to obtain an estimate of the relative magnitude of the capacitance of the living bark and the sapwood, and to predict phase lags between transpiration and leaf water potential, and lags in transpirational flux up the stem.The results suggest that if water potentials recover by dawn, phase lags in water potential down tree stems arc small and that the exchange between water stored in the sapwood and the transpiration stream is irreversible over the diurnal time scale.
Comparative ecophysiology of CAM and C3 bromeliads. IV. Plant water relations
Authors: SMITH J. A. C. , GRIFFITHS H. , LÜTTGE U. , CROOK C. E. , GRIFFITHS N. M. , STIMMEL K.‐H. 
Published: April 2006

Abstract An investigation was carried out into the water relations of CAM and C3 bromeliads in their natural habitat during the dry season in Trinidad. Measurements were made of xylem tension with the pressure chamber and of cell‐sap osmotic pressure and titratable acidity on crushed leaf samples. A steady‐state CO2 and H2O‐vapour porometer was also used so that changes in leaf water relations during individual day‐night cycles could be directly related to gas‐exchange patterns in situ.Xylem tension changed in parallel with transpiration rate and in general reached its maximum value in CAM bromeliads at night and in C3 bromeliads during the day. In addition, large nocturnal increases in cell‐sap osmotic pressure and titratable acidity (ΔH+) typically occurred in the CAM bromeliads. The C3‐CAM intermediate Guzmania monostachia showed slight nocturnal acidification, but had higher values of xylem tension during the day. Very high values of AH+ were observed in the CAM species when the tanks of the epiphytic bromeliads contained water: Aechmea nudicaulis showed a mean maximum ΔH+ of 474 mol m−3, the highest value so far observed for CAM plants. On some nights dew formed on the leaf surfaces of the epiphytes, partially curtailing gas exchange and leading to a marked decrease in xylem tension in both C3 and CAM species.Between‐site comparisons were also made for a wide range of habitats from arid coastal scrub to montane rain forest. Compared with values characteristic of other life‐forms, xylem tension and cell‐sap osmotic pressure were low for all bromeliads, and did not differ significantly in co‐occurring CAM and C3 bromeliads. Mean maximum xylem tension (10 species in total) ranged from 0.29 M Pa at the montane sites to 0.67 MPa at the most arid site, and mean minimum osmotic pressure (17 species) from 0.51 to 0.97 MPa. At the arid sites the bromeliads were exclusively CAM species, two of which (Aechmea aquilega and Bromelia plumieri) grew terrestrially in the undergrowth of the coastal scrub. Xylem tension in these species was low enough to indicate that they must be functionally independent of the substratum during the dry season. In the wetter part of Trinidad, no between‐site differences in leaf water relations were found along an altitudinal gradient in the Northern Mountain Range; seasonal differences in this area were also small. Overall, leaf water relations and gas exchange in the bromeliads were strongly affected both by short‐term changes in water availability and by longer‐term climatic differences in the various regions of the island.
Stimulation of chlororespiration by heat and high light intensity in oat plants
Authors: QUILES MARÍA JOSÉ 
Published: April 2006

ABSTRACTHigh irradiance and moderate heat inhibit the activity of the photosynthetic apparatus of oat (Avena sativaL.) leaves. The incubation of oat leaves under high light intensity in conjunction with high temperatures strongly decreased the maximal quantum yield of photosystem (PS) II, indicating the close synergistic effect of both stress factors on PS II inhibition and the subsequent irreversible damage to the photosynthetic apparatus. The PS I A/B protein levels remained similar to control values in leaves incubated under high light intensity or moderate heat, and decreased only when both stress factors were simultaneously applied. Immunoblot analysis of thylakoid membranes using specific antibodies raised against the NDH‐K subunit of the thylakoidal NADH dehydrogenase complex (NADH DH) and against plastid terminal oxidase (PTOX) revealed an increase in the amount of both proteins in response to high light intensity and/or heat treatments. In addition, these stress treatments were seen to stimulate the activity of electron donation by NADPH and ferredoxin to plastoquinone, the PTOX activity in plastoquinone oxidation and the NADH DH activity in thylakoid membranes. Incubation withn‐propyl gallate (an inhibitor of PTOX) inhibited the increase of NDH‐K and PTOX levels under high light intensity and heat, and slightly stimulated the activity of electron donation by NADPH and ferredoxin to plastoquinone. Antimycin A (an inhibitor of cyclic electron flow) increased the NADH DH activity and preserved the levels of NDH‐K and PTOX in thylakoid membranes from leaves incubated under high light intensity and heat. The up‐regulation of the PTOX and the thylakoidal NADH DH complex under these stress conditions supports a role for chlororespiration in the protection against high irradiance and moderate heat.
Functionality of resistance gene Hero, which controls plant root‐infecting potato cyst nematodes, in leaves of tomato
Authors: CABRERA POCH H. L. , MANZANILLA LÓPEZ R. H. , KANYUKA K. 
Published: April 2006

ABSTRACTThe expression of host genomes is modified locally by root endoparasitic nematode secretions to induce the development of complex cellular structures referred as feeding sites. In compatible interactions, the feeding sites provide the environment and nutrients for the completion of the nematode’s life cycle, whereas in an incompatible (resistant) interaction, the host immune system triggers a plant cell death programme, often in the form of a hypersensitive reaction, which restricts nematode reproduction. These processes have been studied in great detail in organ tissues normally infected by these nematodes: the roots. Here we show that host leaves can support a similar set of programmed developmental events in the potato cyst nematode Globodera rostochiensis life cycle that are typical of the root‐invading nematodes. We also show that a gene‐for‐gene type specific disease resistance that is effective against potato cyst nematodes (PCN) in roots also operates in leaves: the expression of the resistance (R) gene Hero and members of its gene family in leaves correlates with the elicitation of a hypersensitive response only during the incompatible interaction. These findings, and the ability to isolate RNA from relevant parasitic stages of the nematode, may have significant implications for the identification of nematode factors involved in incompatible interactions.
Enzymes of Heavy‐Metal‐Resistant and Non‐Resistant Populations of Silene cucubalus and Their Interaction with Some Heavy Metals in vitro and in vivo
Authors: MATHYS WERNER 
Published: April 2006

AbstractThe in vitro and in vivo effects of copper, zinc, cadmium, nickel, cobalt, and manganese on nitrate reductase, malate dehydro‐genase, isocitrate dehydrogenase, and glucose‐6‐phosphate dehydrogenase of zinc‐, copper‐ and non‐resistant populations of Silene cucubalus were investigated. During the in vitro experiments no resistant enzyme could be detected; enzymes of resistant and non‐resistant ecotypes had a similar sensibility to all the metals. Nitrate reductase was the most sensitive enzyme. During the in vivo experiments remarkable differences were found. The nitrate reductase and the isocitrate dehydrogenase of the zinc‐resistant population were activated when adding zinc to the culture medium, especially the nitrate reductase showed high activities at zinc concentrations where the nitrate reductase of the non‐zinc‐resistant populations was nearly completely inhibited. The zinc‐resistant ecotype had a real need for zinc.
Peroxidases as Indicators of Growth and Differentiation in Aspen Callus Cultures
Authors: WOLTER KARL E. , GORDON JOHN C. 
Published: April 2006

AbstractAspen (Populus tremuloides Michx.) callus tissue grown on a synthetic medium containing either an auxin (2,4‐dichloro‐phenoxyacetic acid) or cytokinin [6‐(3‐methyl‐2‐butenylamino) purine] differed in growth rate, total peroxidase activity, peroxidase isoenzyme expression, and in lignin, cell wall sugars and extractive content. Tissue treated with auxin increased more rapidly in fresh weight, but stopped growing sooner than did the cytokinin‐treated tissues. Lignification also proceeded more rapidly, and lignin formed a greater fraction of the cell wall weight in auxin‐treated tissue. For both treatments, peroxidase activity and growth rate were positively related (r = 0.96). Polyacrylamide gel electrophoresis showed some quantitative, but few qualitative, isoenzyme differences with hormonal treatment and growth rate.
Effects of Ionic Strength of Nutrient Solutions on Phosphate Uptake by Sunflower
Authors: PETTERSSON SUNE 
Published: April 2006

AbstractActive phosphate uptake by the roots of young sunflower plants was stimulated nonspecifically by increasing the total salt concentration of the uptake solution. Inhibition of active uptake by DNP‐treatment removed the salt stimulation. Independently of the rate of active uptake the amount of phosphate present in the free space of the roots increased as the salt concentration was raised. It is suggested that at low ionic strength of the nutrient solution the initial passive step of ion transport through the root free space can limit the overall uptake rate.
Activité néformatrice d'acides ribonucléiques extraits de tumeurs végétales
Authors: ROUSSAUX JACQUELINE 
Published: April 2006

AbstractRNAs extracted from crown‐gall tumors, induced by Agrobacterium tumefaciens (strain B6) on stems of Datura stramonium L., have been isolated by the phenol method and purified through Biogel P 60 columns. These RNAs have been transformed into complexes with l‐amino acids by incubation in a medium containing: Tris HCI buffer, pH 7.6, ATP, MgCl2, a mixture of l‐amino acids and a polypeptide synthetase purified from Alcaligenes faecalis. The inoculation of stems of Datura plants with these complexes induces the development of nodular outgrowths, whereas other complexes made from RNAs isolated from healthy Datura plants, from Agrobacterium tumefaciens, Escherichia coli and Alcaligenes faecalis do not cause any hyperplasia under our experimental conditions. The analysis of the results obtained, supported by histological studies of the outgrowths, suggests that these neoformations should be of tumoral nature.
Light Rquirements for Photoperiodic Sensitivity in Cotyledons of Dark‐grown Pharbitis nil
Authors: FRIEND D. J. C. 
Published: April 2006

AbstractThe light requirements for induction of flowering by a long dark period were investigated in dark‐grown seedlings of Pharbitis nil Chois, cv. Violet. The cotyledons bcame photoperiodically sensitive to a 24 h dark period by two 1 min red irradiations (6.3 μmol m−2 S−1) separated by a 24 h dark period. The reversibility of the effect of brief red irradiations, and the effectiveness of low energies of red irradiation suggest the involvement of phytochrome in the induction of photoperiodic sensitivity. Partial de‐etiolation occurred after these brief periods of red irradiation but the seedlings were not capable of net CO2 uptakeeven 7 h after the start of the main light period that followed the critical dark period. A changing response to the duration of the priod of darkness given between the two short red irradiations showed the the correct phasing of an endogenous photoperiodic rhythm is needed for the attainment of photoperiodic snsitivity.
The Effects of Age and Root Formation on the Life‐Span of Excised Cotyledons of Cucurbita pepo
Authors: MOHAMMAD A. M. S. , AL‐MASHHADANI Y. 
Published: April 2006

AbstractRoot initiation in Cucurbita cotyledons excised at various ages was studied in nutrient solution and water. The time required for root initiation depends on the age of the cotyledon and on the rooting medium. Nutrient solution favoured root formation. Maximum number of roots, maximal total root length, and maximum life‐span were found with cotyledons excised at an age of 14 days. Excision earlier or later resulted in less roots, less total root length, and shorter life‐span.
Respiration Rate and Mitochondrial Activity in Iris Bulbs
Authors: KOLLÖFFEL C. , VAN LOON‐LIEVE M. P. 
Published: April 2006

AbstractThe oxygen uptake of iris bulbs (Iris×hollandica‘Wedgwood’) which had been stored dry at 30 C (“retarded’ bulbs) was low (10 μmol O2 per h and bulb), the oxygen uptake of the intact bulb, the three outer fleshy scales and the remaining central part of the bulb increased three‐ to fourfold, nearly twofold and fourfold, respectively.Mitochondria were isolated from the scales of retarded and activated bulbs and their oxygen consumption with succinate, l‐malate (plus pyruvate). x‐ketoglutarate and NADH as substrate was measured polarographically. The oxidative capacity of mitochondria isolated from the scales of activated bulbs was only slightly higher than that from retarded bulbs when calculated on a tissue basis. No difference was found between the phosphorylation efficiency, respiratory control, cytochrome c deficiency, succinate dehydrogenase, malate dehydrogenase, succinate‐cytochrome c rductase, NADH‐cytochrome c reductase and cytochrome oxidase activity of the retarded and activated bulbs.The increase in the in vitro oxygen uptake of the scales after transition from 30 to 13 C was not accompanied by an equal increase in the oxidative capacity of their mitochondria suggesting that they are not responsible for this rise in oxygen uptake.
Effect of Abscisic Acid at Different Levels of Soil Water Potential on the Transpiration of Zea mays
Authors: TALHA MAHMOUD , LARSEN POUL 
Published: April 2006

AbstractThe effect of different levels of both exogenous abscisic acid (ABA) and soil water potential on transpiration from intact maize leaves was studied in growth chamber experiments. The transpiration rate showed a more consistent decrease with decreasing soil water potential than with increasing concentration of applied ABA. The effect of exogenous ABA on the transpiration rate was markedly lower at low than at high levels of soil water potential.
Manipulation of IAA‐Oxidase Activity and Auxin‐Deficiency Symptoms in Intact Cotton Plants with Manganese Nutrition
Authors: MORGAN PAGE W. , TAYLOR DANIEL M. , JOHAM HOWARD E. 
Published: April 2006

AbstractCotton (Gossypium hirsutum L. cv. Deltapine 15) seedlings were grown in solution culture in which the Mn2+ level was varied. Following an initial period, a series of shifts in manganese nutrition were employed, each lasting 14 days. Appearance was observed and fresh weight, IAA oxidase (IAAO), peroxidase and IAAO inhibitor levels were determined. After the initial 3 weeks of treatment, growth was negatively correlated with IAAO (or peroxidase) activity. All shifts in manganese nutrition resulted in predicted changes in IAAO activity, growth and plant appearance during a second 2‐week period of the experiment. Continuously deficient plants exhibited highest leaf abscission and IAA oxidase activity, and lowest growth of all treatments. Plants shifted from deficient to control levels of Mn2+ exhibited a marked decline in IAAO activity, increase in growth and absence of leaf abscission. Plants shifted from borderline deficiency to deficient Mn2+ exhibited a major increase in IAAO activity, reduction in growth and extensive leaf abscission. Control and borderline toxicity plants maintained normal IAAO activity, growth, and appearance. During a final 2‐week period, symptom expression was intensified. In particular, the initial borderline deficiency plants shifted to deficient levels of Mn2+ abscised most of those leaves that expanded after the shift in treatment. In addition, shifts of some plants to toxic Mn2+ levels during the third phase of the experiment produced a complete cycle of manipulation. Plants initially deficient in Mn2+ with high IAAO and low growth recovered growth and declined in IAAO when shifted to control Mn2+ and then suffered severe inhibition of growth and toxicity symptoms when shifted to high Mn2+.In all cases changes in enzyme activity, growth, leaf abscission and similar symptoms were most strongly expressed in the youngest tissue or that with the greatest potential for growth during the interval of a particular treatment. Since total growth, IAAO, leaf abscission, internode length and similar symptoms were consistently manipulated in both directions (increase or decrease in intensity or degree) by raising or lowering Mn2+ levels in the plant culture medium, we conclude that there is a causal relationship between IAAO and these responses that involves destruction of auxin.
Stimulation of Growth of Peppermint (Mentha piperita) by Phosfon, a Growth Retardant
Authors: CALABRESE EDWARD J. , HOWE KENNETH J. 
Published: April 2006

AbstractThe shoot growth and fresh weight of Mentha piperita grown in soil were stimulated at concentrations of 1.26 × 10−5M to 7.77 × 10−4M phosfon (2,4‐dichlorobenzyl tributyl phosphonium chloride) while higher concentrations resulted in retardation of growth. Concentrations of 6.30 × 10−7M to 3.78 × 10−5M caused retardation of growth in mineral nutrient solution, and even death at the highest concentrations. However, when the M. piperita plants were grown in mineral nutrient solutions at concentrations of phosfon which had been sequentially lowered from 2.52 × 10−8M to 2.52 × 10−12M, the shoot growth and fresh weight were stimulated as in the case of plants grown in phosfon treated soil.