bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in the Content of Phytyl and Geranylgeranyl Esters of Germinating Polytrichum commune Spores
Authors: LILJENBERG CONNY , KARUNEN PIRJO
Published: April 2006

Polytrichum commune spores contained esterified phytol and geranylgeraniol, 706 and 114 μg, respectively, per 100 mg dry weight of freshly collected spores. After storage for 9 months the level of esterified phytol of the spores was decreased by c. 600 μg, whereas the level of esterified geranylgeraniol was more or less unchanged.

The changes in the level of esterified prenols during germination follow the same pattern in freshly collected and in 9 month‐old spore material. An immediate steep decrease between 0 and 3 h was followed by an increase in the level of esterified phytol between 3 and 12 h and by a constant value for esterified geranylgeraniol during the same period. Between 12 and 48 h the level of both types of esterified prenols decreased. In the freshly collected spores the amount of esterified prenols increased after 48 h of germination, in the older spores after 72 h. Free phytol was found in trace amounts in dry and germinating spores and in the protonema.
Sprouting and Growth of Purple Nutsedge, Cyperus rotundus, in Relation to pH and Aeration
Authors: AL‐ALI F. A. , SHAMSI S. R. A. , HUSSAIN S. M.
Published: April 2006

The results of experiments on the sprouting and growth of purple nutsedge (Cyperus rotundus L.) in relation to pH and aeration are described. All pH levels between 2.2 to 9.0 allowed high sprouting percentage but the sprouted tubers did not survive at pH below 3 and survival beyond pH 7 was very poor. Post‐sprouting growth of nutsedge was optimal at pH 4.

Pre‐sprouting aeration of tubers stimulated early sprouting and produced vigorous shoots, whereas submersion of the tubers was inhibitory. Continuous aeration of the submerged tubers substantially removed the inhibitory influence on sprouting but the shoots remained weak. Seedlings grown in constantly aerated nutrient solution showed significantly better growth than in a non‐aerated one.
Hormonal Aspects of Senescence in Detached Tobacco Leaves
Authors: EVEN‐CHEN ZEEV , ATSMON DAN , ITAI CHANAN
Published: April 2006

The objective of the present work was to describe the simultaneous changes in endogenous levels of cytokinins, abscisic acid, indoleacetic acid and ethylene in detached, senescing tobacco (Nicotiana rustica L.) leaves. These measurements were related to changes in chlorophyll contents, 14CO2 fixation and proline contents — three parameters which have been considered to reflect senescence. Effects of exogenous hormonal treatments on these parameters, as well as on endogenous hormonal levels, provided further evidence for the interrelationships between hormones and for their roles in senescence.

Starting with actively growing attached leaves and ending with well‐advanced senescence in detached leaves, our data indicate a chronological sequence of three hormonal states: (a) cytokinins — high activity, abscisic acid, auxin and ethylene — low contents (actively growing, attached leaves); (b) cytokinins — low activity, abscisic acid — high, auxin and ethylene — low contents (apparent induction of senescence in detached leaves); and (c) cytokinins and abscisic acid — low, auxin and ethylene — high contents (senescence proper in detached leaves).
Water Potential and Component Potentials in Expanded and Unexpanded Leaves of Two Xeric Grasses
Authors: MAXWELL JAMES O. , REDMANN ROBERT E.
Published: April 2006

Water (ψ), osmotic (ψs+ψm) and pressure (ψp) potentials were measured in three leaf regions of Agropyron dasystachyum and A. smithii grown in the field. Spanner‐type thermocouple psychrometers were used to measure ψ and (ψm+ψm). Absolute water content (AWC) was measured gravimetrically. The ψ and ψp were slightly lower in the emerging leaf blade (EBI) than in the last fully emerged leaf blade (FEBI); (ψs+ψm) and AWC were similar in the two regions. A gradient as large as 0.7 MPa was observed between the EBI and the base of the same emerging leaf (EBs); the latter included the meristematic regions. Although (ψs+ψm) and ψp were generally higher in the EBs, the gradients diminished as the level of stress increased in the shoot. Under moderate water stress the ψp of the EBs remained constant relative to the ψp in the exposed blades. The large ψ gradient within the growing leaf could have resulted from high resistance imposed by poor vascular development in the intercalary meristem. Ability to maintain a relatively large ψ gradient may be of general significance in buffering the growing region of xeric grass leaves from extreme, short‐term fluctuations in water stress that occur in exposed leaf blades.
2,4‐D‐Induced Changes in the K+ Uptake of Wheat Roots at Different pH Values
Authors: ZSOLDOS FERENC , KARVALY BÉLA , TÓTH ILDIKÓ , ERDEI LÓSZLÓ
Published: April 2006

The effects of an auxin herbicide, 2,4‐D, at a concentration of 0.01 mM, on the K+ uptake and efflux of excised roots of wheat (Triticum aestivum L. cv. Rannaya) were investigated at different pH values. The K+ movement was monitored with a K+ (86Rb) tracer. In parallel experiments the ATPase activities of microsomal fractions were determined by the inorganic phosphate liberation method. 2,4‐D inhibited the K+ uptake especially at low pH, irrespective of whether Ca2+ was present or not. No marked changes were observed in the K+ efflux properties at pH values above 4. The inhibitory effect on K+ uptake exhibited a correlation with the hydrocarbon solubility of the herbicide, but not with the 2,4‐D‐induced decrease of the ATPase activity. It is suggested that 2,4‐D exerts a non‐specific effect on the lipid‐protein interactions, giving rise to a generalized alteration of the transport barrier properties of the plasma membrane even at as low a concentration as 0.01 mM.
Photosynthesis of Ivy Leaves (Hedera helix) after Heat Stress I. CO2‐Gas Exchange and Diffusion Resistances
Authors: BAUER HELMUT
Published: April 2006

For an analysis of the inhibition of the photosynthetic CO2‐uptake after heat stress attached leaves of Hedera helix L. were heat‐stressed for 30 min at various temperatures. Subsequently their photosynthetic CO2‐uptake, transpiration, respiration in light and darkness, and CO2‐compensation concentration were measured under optimal conditions.

After heat stress the stomatal resistance increased only corresponding to the raised CO2‐concentration inside the leaves (due to the reduced CO2‐uptake). The physical resistance between the mesophyll cell walls and the chloroplasts remained unchanged after heat stress. A non‐stomatal inhibition of the CO2‐uptake is indicated by a strong increase of the CO2‐compensation concentration after heat stress. This is hardly due to a stimulation of the respiration in light, as the CO2‐evolution into CO2‐free air in light was even reduced. Therefore, it must be concluded that the photosynthetic process itself is impaired after heat stress.
The Effect of Some External Factors on Nitrogenase Activity in the Free‐Living and Endophytic Nostoc of the Liverwort Blasia pusilla
Authors: RODGERS G. A.
Published: April 2006

The effects of pH, light intensity, temperature, oxygen and dehydration on nitrogenase activity in the free‐living and endophytic Nostoc sp. of Blasia are described. The endophyte exhibits greater nitrogenase activity at lower pH's than the free‐living alga. Maximal activity in the free‐living alga is attained at much lower light intensities than those required by the endophyte. Both algae have low activities below 10°C, the free‐living alga showing high activity above 12°C and the endophyte above 17°C. Increasing pO2 levels cause a decrease in activity in both algae. The free‐living alga is more tolerant to dehydration than the endophyte, although both algae are protected by mucilage. The results are discussed and possible benefits resulting from the symbiosis, with respect to nitrogen fixation rates, considered.
Content and Fatty Acid Composition of Steryl and Wax Esters in Germinating Spores of Polytrichum commune
Authors: KARUNEN PIRJO , LILJENBERG CONNY
Published: April 2006

Polytrichum commune spores contained 5.61 ± 0.52 mg steryl and wax esters, including volatile compounds, per 100 mg dry weight of spores. Volatile compounds were not found in 3‐h‐old sporelings. The content of the steryl and wax ester fraction, excluding the volatile compounds, is slightly increased during the first 6 h of germination. Thereafter, the content is decreased throughout the germination. Thus, 3‐day‐old sporelings contained 0.52 ± 0.05 mg steryl and wax esters per 100 mg dry weight of spores. In connection with protonema growth, steryl and wax esters were produced, and the 7‐day‐old cultures contained 5.09 ± 0.37 mg steryl and wax esters per 100 mg dry weight of spores. The main fatty acids of the steryl and wax ester fraction of dry spores and germinating spores as well as of protonemata were palmitic, oleic, linoleic and linolenic acids. Polyunsaturated C 20 acids were present only in trace or small amounts. Phytanic and phytenic acids were found in small amounts in dry spores, in 3‐ to 72‐h‐old sporelings, and in protonemata.
The Effects of Light and Temperature on Germination and Growth of Luffa aegyptiaca
Authors: OKUSANYA O. T.
Published: April 2006

The effects of light and temperature on the germination and growth of Luffa aegyptiaca were investigated both in the laboratory and in the field. The seeds germinated in both darkness and light but germination was better in the light.

At constant temperatures germination was best at 21°C, while alternating temperatures of 21 and 31°C and 15 and 41°C caused higher germination than the most favourable constant temperature. Constant temperatures of 15 and 31°C and alternating temperatures of 21 and 41°C resulted in very low germination, whereas no germination occurred at 41°C and at alternating temperatures of 31 and 41°C. Soil depth caused only a delay in seed germination, as it did not affect the total germination.

High temperature and high light intensity resulted in good seedling growth in terms of dry weight, leaf area and relative growth rate. High temperature and low light intensity caused increased plant height and high shoot weight ratio, both of which manifested in seedling etiolation. They also caused high leaf area ratio. Under low temperatures, irrespective of light intensity, growth was generally poor, but it was significantly poorer under low light intensity, which also caused high root weight ratio. High light intensity was principally responsible for high leaf weight ratio. The results help to explain the abundance of the species in newly cleared areas in Lagos and its environs.
Phloem Unloading in Stem Parts Parasitized by Cuscuta: The Release of 14C and K+ to the Free Space at 0°C and 25°C
Authors: WOLSWINKEL PIETER
Published: April 2006

By washing out 14C‐solutes or K+ from the free space of stem segments of Vicia faba L. and Urtica dioica L., efflux from stem tissues was measured. At 25°C the efflux of 14C or K+ from non‐parasitized stem parts was found to be comparable with the pattern known for parenchyma cells. The efflux pattern from parasitized stem parts kept at 0°C was also a normal one, but at 25°C a more complicated pattern was found. After addition of metabolic inhibitors, however, the efflux pattern appeared to be comparable with the pattern found in 0°C experiments. Also, after washing stem segments for several hours in water at 0°C, Phloem unloading was shown to start unimpeded after transfer to 25°C. Stem parts parasitized by Cuscuta can be regarded as a model system for studying the fundamental processes underlying movement out of sieve tubes in strong sink regions.
Effects of Organic Nutrients and Hormones on Growth and Development of Tissue Explants from Coconut (Cocos nucifera) and Date (Phoenix dactylifera) Palms Cultured in vitro
Authors: EEUWENS C. J.
Published: April 2006

The growth response (increase in weight) of cultured explants from seedling date (Phoenix dactylifera L.) and mature coconut (Cocos nucifera L. cv. Malayan Dwarf) palms to source and concentration of organic nitrogen. carbohydrate, auxins, cytokinins and gibberellins was examined. Growth was strongly stimulated by the presence of auxins (10−7 to 10−6M), cytokinins (10−6 to 10−5M), high concentrations of sucrose (0.2 M), and in the absence of NH4Cl, by organic sources of reduced nitrogen. Higher concentrations of auxin (2,4‐D or NAA at 10−6 to 10−5M) which still stimulated growth of Phoenix tissue, proved inhibitory to growth of freshly excised Cocos tissues.

Explants from both palms initiated roots when subcultured on a medium with increased levels of auxin (NAA, 2.5 × 10−6 to 2.5 × 10−5M) and reduced levels of cytokinin (6‐BAP, 5 × 10−8M). Isolated roots excised from these explants continued growth and produced new laterals when subcultured on media with GA3 (5 × 10−7M) and reduced levels of auxin, cytokinin, and either minerals or sucrose.
Cytokinins and Morphological Aspects of French‐bean Roots in the Presence of Rhizobium
Authors: PUPPO ALAIN , RIGAUD JEAN
Published: April 2006

Typical abnormalities were observed on French‐bean roots when the plants were cultivated in the presence of Rhizobium phaseoli, under hydroponic conditions. Substantial quantities of cytokinins were detected in the plant culture medium and their concentration remained high until the 9th day after inoculation, when the first nodules appeared. The presence of both partners, plant and bacteria, was required for this synthesis. Exogenous cytokinin production was responsible for morphological alterations of the roots observed before nodulation.
Allosteric Regulation of Potassium Uptake in Plant Roots
Authors: JENSÉN PAUL , PETTERSSON SUNE
Published: April 2006

In uptake experiments from nutrient solutions containing 2.0 mMK+labelled with86Rb+, the relationship between potassium uptake efficiency and internal potassium concentration of the roots, [K+]iwas found to be partly sigmoidal for intact plants of spring wheat (Triticum aestivumL.), glasshouse cucumber (Cucumis sativusL.), birch (Betula verrucosaEhrh.), lingonberry (Vaccinium vitis‐idaeaL.), Scots pine (Pinus silvestrisL.) and Norway spruce (Picea abies(L.) Karst.), The results were interpreted in terms of sigmoidal enzyme kinetics for allosteric regulation. Hill plots of the data gave straight lines at specific [K+]iintervals for the species. The slopes of the lines are the Hill coefficient, which could be regarded as a measure of the minimal number of allosteric sites. The Hill coefficient varied between ‐ 14.4 and ‐ 15.9. When divided by four, these values are fairly consistent with those in the literature. It is suggested that four active uptake sites interact with four groups of allosteric sites, each group containing four such sites, or that one active uptake site interacts with all the allosteric sites. Thus the results are evidence that the mechanism regulating K+uptake is basically similar for the investigated plants. It is the interval of [K+]imediating highly negatively cooperative allosteric regulation that differs among species.

For some of the species,ndecreased from about 15 and approached unity at high [K+]ivalues. This may indicate that only few sites are still available, making cooperativity unimportant. Alternatively high vacuolar [K+]iconcentrations may give rise to an incorrect evaluation of data from Hill plots, since the cytoplasmic K+content likely regulates the allosteric mechanism. Moreover, it is suggested that gene‐controlled carrier synthesis is responsible for the varying maximum K+uptake efficiency among species.
Thermolability of the Alternative Electron Transport Pathway in Higher Plant Mitochondria
Authors: CHAUVEAU M. , DIZENGREMEL P. , LANCE C.
Published: April 2006

Mitochondria from four plant species showing normal (Arum maculatum L., Arum italicum Mill., Sauromatum guttatum Schott) or induced (Solanum tuberosum L.) resistance to cyanide were submitted to temperature treatments up to 90 min at 45°C. The activity of the alternative, cyanide‐resistant electron transport pathway was specifically and deeply altered by temperature treatments. Hydrogen sulfide was released in direct proportion to the reduction of activity of the alternative pathway. Only a small fraction (≃ 20%) of the total labile sulfide content of the mitochondria was associated with the operation of this pathway. In cyanide‐resistant mitochondria, the cytochrome pathway was much more resistant to thermal inactivation than the alternative pathway. On the contrary, in cyanide‐sensitive mitochondria (with no alternative pathway) the cytochrome pathway was highly sensitive to temperature treatments.

These results indicate that the presence of a cyanide‐resistant alternative pathway is correlated with a higher degree of resistance to thermal denaturation of the cytochrome pathway. They also strongly suggest that iron‐sulfur proteins are regular components of the alternative pathway.
The Connection between High Energy and Low Energy Responses to Red and Far‐Red Light of Hypocotyl Elongation in Red Cabbage Seedlings (Brassica oleracea var. capitata‘Marner Septemberrot’)
Authors: OTTO KARL‐RONALD
Published: April 2006

Growth responses of hypocotyls of Brassica oleracea L. var. capitata caused by diurnal irradiation of various duration (0.5 h/d up to continuous irradiation) and various irradiance (0.3–1.5 W m−2) with red and far‐red light from sources characterized below can be described by the equation:

image

(W= relative effect, I= irradiance, t1= irradiation time per day, Ws= constant dependent on material and wavelength, α, B and ts, = constants dependent on wavelength.)

On the basis of that equation a possible connection between longtime and short‐time irradiation responses is discussed.
Action Spectra for Conversions of Phycochrome c from Nostoc muscorum
Authors: BJÖRN G. S. , BJÖRN L. O.
Published: April 2006

The reversibly photochromic pigment, phycochrome c, was extracted from the blue‐green alga Nostoc muscorum strain A. Action spectra were determined for in vitro conversions of the pigment from the short wavelength to the long wavelength form and vice versa. The action peak for the absorbance decrease at 650 nm is at 630 nm. During this decrease there is only a slight increase of the absorbance in the green region. Green and yellow light (maximum efficiency at 580 nm) completely restores absorbance at 650 nm. The observations are explained by the existence of three spectrally different forms of phycochrome c: Pc630 and Pc650 which equilibrate in darkness and Pc580 which is reversibly photoconvertible to Pc630. We have also measured the absorbance changes brought about by saturating irradiations with light of various wavelengths (“photostationary state spectrum”). Extreme photostationary states were obtained with about 650 nm and 500 nm light.
The After‐Effect of Water Stress on Chlorophyll Formation during Greening and the Levels of Abscisic Acid and Proline in Dark Grown Wheat Seedlings
Authors: BENGTSON CURT , KLOCKARE BIRGITTA , KLOCKARE RUNE , LARSSON STIG , SUNDQVIST CHRISTER
Published: April 2006

Cut seedlings of wheat plants (Triticum aestivum L. cv. Starke II Weibull) between 6 and 7 days old were water stressed in darkness by exposing them to air of 35% relative humidity 2.5 to 20 h. This treatment resulted in a water potential of ‐11 bars in the leaves after 20 h. The leaves were then rewatered and irradiated. The chlorophyll formation that took place in fully turgid leaves during the greening was markedly decreased in the case of the water‐stress pretreatmet. and especially the lag phase was prolonged. The longer the stress pretreatment the more evident was the subsequent effect on chlorophyll formation. However, no linear relationship was found between the amount of stress and the chlorophyll content. Protochlorophyllide regeneration from endogenously formed δ‐aminolevulinic acid was markedly decreased even after the shortest water‐stress period. However, protochlorophyllide accumulation from exogenously supplied δ‐aminolevulinic acid was only slightly decreased following the water‐stress pretreatment. Further more, the ratio of protochlorophyllide650 to protochlorophyllide628 was slightly reduced by the same conditions.

During the stress period both abscisic acid and proline were accumulated in the leaves. The content of abscisic acid increased up to six times the normal level during water stress lasting for 20 h. The increase of proline was about three‐fold for similar treatment. After rewatering the leaves the levels of both abscisic acid and proline rapidly declined and reached. 10 h later, the levels found in unstressed seedlings.

The increase in abscisic acid during water stress associated with impaired chlorophyll metabolism suggested that the after‐effect of water stress might be linked to chlorophyll metabolism through abscisic acid or some of its metabolites. The changes in proline content open the possibility that this substance could function as a reserve substance for the formation of chlorophyll after the discon tinuation of the stress.
Chasmogamous and Cleistogamous Pollination in Salpiglossis sinuata
Authors: LEE CHI WON , ERICKSON HOMER T. , JANICK JULES
Published: April 2006

Pollen from chasmogamous flowers of Salpiglossis sinuata L. could not be induced to germinate in vitro unless stigmatal extract was applied to the culture medium. The substance that induces pollen germination in the stigmatal extract is water‐soluble and heat‐stable. Crosses could not be achieved between chasmogamous and cleistogamous flowers because of structural incompatibility. Pollinated pistils of chasmogamous flowers release a large amount of ethylene. The burst of ethylene release is due to an interaction between pollen tubes and stylar tissue and is directly proportional to the quantity of pollen placed on the stigma. Cleistogamous flower buds also produce a burst of ethylene at the time of pollination within the closed flower. The ethylene release may be a cause of reduced corolla development associated with cleistogamous flowers.
Accumulation of Free Proline at Low Temperatures
Authors: CHU T. M. , JUSAITIS M. , ASPINALL D. , PALEG L. G.
Published: April 2006

The accumulation of free proline in the first leaves of barley, Hordeum distichum L., and wheat, Triticum aestivum L., in response to a range of low temperatures was examined with 10‐day‐old plants. In barley (cv. Prior) no proline accumulated at 8°C or above, but in wheat (cv. Gabo) proline accumulated at 12°C and lower temperatures. In barley, the first leaf survived for 29 days following transfer to 5°C and continued to accumulate proline throughout this period. In contrast, the first leaves of plants maintained at 20°C survived for 13 days only and accumulated no proline. Proline accumulation at low temperature was shown to be light‐dependent, both in intact plants and excised leaf sections, and the light requirement could not be replaced by supplying leaf segments with precursors of proline. Proline accumulation in response to water stress was not light‐dependent at 20°C but was at 5°C.

Inter‐specific and intra‐specific variation in the extent of accumulation in response to low temperature was also examined. Considerable variation was encountered but there was no clear relationship with geographical distribution or chilling sensitivity for the species and no correlation with accumulation in response to water stress in the cultivars of barley examined.
Effect of Magnesium on Chlorophyll‐Protein Complexes
Authors: ARO EVA‐MARI , VALANNE NIINA
Published: April 2006

The effect of Mg2+ during the isolation of chlorophyll‐protein complexes was studied in two moss species (Pleurozium schreberi and Ceratodon purpureus) and New Zealand spinach (Tetragonia expansa). When 2 mM MgCl2 was included in all the extraction and separation phases, the proportions of chlorophyll‐protein complex I. were very small in all plants studied. The withdrawal of Mg2+ considerably increased the proportions of CP I. The most pronounced increase in the chlorophyll present as CP I was found when Mg2+ was withdrawn from the gel, and this also increased the mobility of the CP II complex and free pigment zone. Exclusion of Mg2+ from the running buffer had very little effect. Although Mg2+ had little effect on the relative amount of chlorophyll in CP II, the withdrawal of Mg2+ from all the extraction and separation phases caused formation of polymers of CP II. In the mosses, the formation of polymers of CP II seemed to be more obvious in the species with large grana. Absence of Mg2+ from all the extraction and separation phases sometimes also produced a polymer of CP I.
Circadian Rhythmicity in Photoperiodic Regulation of Regeneration in Begonia Leaves
Authors: HEIDE OLA M.
Published: April 2006

The mechanism of photoperiodic regulation of regeneration in Begonia leaves has been studied by the night interruption technique in 24, 48, and 72‐h cycles. The response to 30 min red light interruptions in 48 and 72‐h cycles indicated a circadian rhythm in red light sensitivity with typical photophile and scotophile phases. In 24‐h cycles two types of response patterns were observed. With a main photoperiod of 3 h the usual response pattern with only one light‐sensitive phase near the middle of the dark period was found, whereas with 8‐h photoperiods two light‐sensitive phases were observed as previously reported by Zimmer in Begonia flowering studies (Gartenbauwissenschaft 38: 57, 1973). Reversion studies with FR indicate that the reactions are mediated by phytochrome. The results are discussed in relation to alternative hypotheses for photoperiodic timing.
The Significance of Oxygen Transport and of Metabolic Adaptation in Flood‐Tolerance of Senecio Species
Authors: LAMBERS HANS , STEINGRÖVER EVELIENE , SMAKMAN GERARD
Published: April 2006

Experiments were designed to provide information about the physiological basis of flood‐tolerance in Senecio species. The oxygen concentration in roots of S. jacobaea L., S. viscosus L. and S. vulgaris L. became almost zero after transplantation to a solution of low oxygen concentration, and it was concluded that the flood‐sensitivity of these Senecio species could be due to insufficient oxygen transport from the shoots to the roots.

The oxygen concentration in the roots of the flood‐tolerant S. congestus (R.Br.) DC., growing in a solution of low oxygen tension, was almost sufficient to maintain oxygen utilization at the rate observed in roots of plants, grown in an air‐saturated solution.

Oxygen utilization by roots of the flood‐tolerant S. aquaticus Hill, growing in a solution of low oxygen tension, was inhibited 50%. However, the oxygen concentration in the roots of this species remained high enough to maintain cytochrome oxidase activity and oxidative phosphorylation at the rate observed in roots from an air‐saturated environment. The activity of a second (“alternative”) oxidase must have been drastically reduced. Alternative NADH‐oxidizing enzymes, like nitrate reductase which was induced by anaerobiosis in roots of S. aquaticus, might replace the regulatory function of the alternative oxidase. — Thus, in S. aquaticus root porosity and root length contributed to the maintenance of an oxygen concentration which was sufficient for uninhibited cytochrome oxidase activity and oxidative phosphorylation rate in roots growing in a solution of low oxygen tension.
The Effect of Inorganic Salts on the Senescence of Dianthus caryophyllus Flowers
Authors: MAYAK SHIMON , KOFRANEK A. M. , TIROSH TSIPORA
Published: April 2006

Certain inorganic salts like KNO3, KCl, K2SO4, Ca(NO3)2 and NH4NO3 extend longevity of cut carnation flowers. The effect of KNO3 was studied in some detail. There is an osmotic adjustment in response to KNO3 treatment. The osmotic concentration change occurred in the external as well as in the internal compartments. The osmotic concentration change in the external compartment is well correlated with extension of longevity. The effect of KNO3 on the sensitivity to ethylene, and its significance in delaying senescence is discussed.
Zn2+‐Dependent Acid Inorganic Pyrophosphatase Activity as Related to Other Pyrophosphatases in Oryza sativa
Authors: KAR M. , PATRA H. K. , MISHRA D.
Published: April 2006

Acid inorganic pyrophosphatase on the one hand, and Mg2+‐dependent alkaline inorganic pyrophosphatase and Zn2+‐dependent acid inorganic pyrophosphatase on the other hand showed opposite trends in their activities in rice (Oryza sativa L. cv. Ratna) seedlings grown in dark and sun. The opposite trends in their activities were also noted in rice seedlings grown from gamma‐irradiated seeds and in detached rice leaves floated on water in dark. The ratios of Mg2+ dependent alkaline inorganic pyrophosphatase/acid inorganic pyrophosphatase and Zn2+‐dependent acid inorganic pyrophosphatase/acid inorganic pyrophosphatase changed significantly in response to the above physical treatments, but the ratio of Mg2+ dependent alkaline inorganic pyrophosphatase/Zn2+ dependent acid inorganic pyrophosphatase remained relatively stable. The conclusion is that Zn2+‐dependent acid inorganic pyrophosphatase activity is the same as that of Mg2+‐dependent alkaline inorganic pyrophosphatase and is different from that of acid inorganic pyrophosphatase, which requires no metal ion for activity. The acid and alkaline inorganic pyrophosphatase activities are due to separate enzyme proteins.
Protein Synthesis Related to Cold Temperature Stress in the Desiccation‐Tolerant Moss Tortula ruralis
Authors: MALEK LADA , BEWLEY J. DEREK
Published: April 2006

Incubation of hydrated Tortula ruralis (Hedw.) Gaertn., Meyer. Scherb. at temperatures down to 2°C resulted in an accumulation of polyribosomes and a decrease in single ribosomes. No changes in the levels of ribosomal subunits were detected. On rehydration of slowly dried moss, which contains no polyribosomes, these were reormed at 2, 8 and 20°C. Rapid incorporation of labelled leucine into protein was observed on reintroduction of the desiccated plant o water at 20°C and there was significant, but much reduced, ncorporation at 2°C. Previously undesiccated moss was also able o take up radioactive leucine and to synthesize protein at 2 and ‐2.5°C. Changes in the rate of protein synthesis at low temperature were not detected in cold hardened (winter collected or incubated at 2°C) T. ruralis. The moss appears to be adapted to survive freezing wear round and even summer‐collected moss can conduct protein synthesis at low temperatures: seasonal cold hardiness changes do lot appear to take place.
Nitrogen Metabolism of the Upper Three Leaf Blades of Wheat at Different Soil Nitrogen Levels
Authors: GROVER H. L. , NAIR T. V. R. , ABROL Y. P.
Published: April 2006

Some aspects of nitrogen metabolism, during grain development, of the upper three leaf blades on the mainshoot of wheat (Triticum aestivum L.) cv. Pusa Lerma, grown under three soil nitrogen levels (0, 30 and 120 kg ha‐1), were investigated. It was observed that these leaf blades were active in NO‐3 assimilation. Of the leaf blades, the flag lead blade had significantly higher nitrate reductase activity, higher amount of free amino acid and soluble protein content, whereas the content of NO‐3 was significantly lower than in the other two leaf blades. Application of soil nitrogen significantly enhanced the nitrate reductase activity (N30 over N0 and N120 over N30), free amino acid (N30 over N0 and N120 over N30), soluble protein (N120 over N0) and NO‐3 content (N30 and N120 over N0) in all three leaf blades. During the 35‐day period, viz. from 7 days prior to anthesis to 28 days after anthesis, the three leaf blades together reduced 280, 608 and 1397 NO‐3μmol under N0, N30 and N120, respectively.
Influence of Protein Factors on the Activation of NADP–malate Dehydrogenase by Dithiothreitol
Authors: VIDAL JEAN , JACQUOT JEAN PIERRE , GADAL PIERRE , VIDAL DIDIER
Published: April 2006

Leaves of Phaseolus vulgaris L. contained malate dehydrogenase activity dependent on NADP (E. C. 1.1.1.82); it could be detected in extracts only when a dithiol such as dithiothreitol was present. After the addition of dithiothreitol, the activity increased with time, passed through a maximum and then diminished. The activation rate and/or the maximum level of activity were essentially dependent on dithiothreitol concentration, pH, and temperature. The presence of bovine serum albumine or glycerol in the medium decreased the inactivation rate; equivalent results were obtained at low temperatures. A mathematical model was established showing an apparent first‐order rate for activation and inactivation only under conditions of alkaline pH near 8.3. These data allowed us to demonstrate that compounds other than dithiothreitol were necessary for the activation process. Evidence suggested that these compounds were protein factors of low molecular weights which increased the activation rate and the maximum level of activity when added to the incubation medium at pH 7.3. Their efficiency in the enzyme activation was higher at alkaline pH than at acid or neutral pH.
Electrochemical State of Potassium and Sodium in Free Cells of Acer pseudoplatanus
Authors: PENNARUN ANNE‐MARIE , VAN DE SYPE GHISLAINE , GRIGNON CLAUDE , HELLER RENÉ
Published: April 2006

The intracellular distribution of K+ and Na+ ions has been determined by compartmental analysis of isotope exchange. The simultaneous measurement of electrical potentials allowed us to show that the distribution of K+ was close to thermodynamic equilibrium while the internal concentration of Na+ was well below the value predicted for the equilibrium. The efflux of Na+ was more sensitive to temperature than its influx. Both ouabain and variations in the external levels of KCl produced weak and inconsistent effects, observations which would emphasize the difference between the Na+ extrusion mechanism of plants and animals. The Na+ extrusion system of Acer cells ceased to be functional in Na+‐depleted cells but recovered its function if the cells were placed in 10 mM NaCl, which suggests that the extrusion system was induced by the level of internal Na+ ions.
Gas Chromatographic–Mass Spectrometric Identification of 4‐Chloroindolyl‐3‐acetic Acid Methyl Ester in Immature Green Peas
Authors: ENGVILD KJELD C. , EGSGAARD HELGE , LARSEN ELFINN
Published: April 2006

Immature green peas were harvested from plants grown in water culture on Johnson's nutrient solution with radioactive chloride. Twenty five g of lyophilized peas were extracted with butanol, the extract chromatographed, first on Sephadex LH 20 and then on silica gel. The radioactive hormone was followed by scintillation counting without the use of any scintillant. The radioactive fractions were taken up in a few μl of chloroform and injected into a gas chromatograph interfaced with a mass spectrometer. Derivatization was not necessary. The electron impact mass spectrum showed the typical peaks of a chloroindolyl‐3‐acetic acid methyl ester: the molecular ion cluster at m/e 223, 225 and the characteristic indole fragment ions at m/e 164, 166 (M‐COOCH3)+. The chlorine atom was assigned to the 4 position of the indole ring after thin layer chromatography of radioactive extract and standards of four different chlorinated indolyl‐3‐acetic acid methyl esters.
Influence of Different Cytokinins on the Transpiration and Senescence of Excised Oat Leaves
Authors: BIDDINGTON N. L. , THOMAS T. H.
Published: April 2006

In order to investigate the possibility that cytokinins control transpiration indirectly through affecting leaf senescence, a direct comparison was made of the effect of different cytokinins on transpiration and senescence of oat leaves (Avena sativa L. cv. Forward). Senescence was assessed by measuring chlorophyll loss. The synthetic cytokinins N6 benzyladenine (BA) and kinetin delayed senescence and increased transpiration of oat leaves to a greater extent than did the naturally occurring compounds zeatin, Nb‐Δ2 isopentenyladenine (i6 Ade) and 6‐ø‐hydroxybenzyladenosine (hyd‐BA riboside).

During the early stages of the transpiration experiment zeatin showed similar or greater activity than BA. This period was longest when freshly excised leaves were used, was reduced when leaves were used after incubation in distilled water in the dark for 20 h and was eliminated by incubation in cytokinin solution in the dark. After this period the activity of zeatin declined relative to BA. The effect of cytokinins in increasing transpiration occurred only in the light; no effect was observed in the dark.

BA showed higher activity than zeatin in senescence tests but both cytokinins were less effective as the tests progressed, this decrease in activity being more rapid when older leaves were used.

The results are discussed in relation to the mechanisms by which endogenous cytokinins might control sensecence and transpiration in oat leaves and to the value of the oat leaf senscence and transpiration bioassays as tests for cytokinin activity of plant extracts.
Translocation and Metabolism of Injected Maleic Hydrazide in Silver Maple and American Sycamore Seedlings
Authors: DOMIR SUBHASH C.
Published: April 2006

Studies were conducted to determine the fate of 14C‐maleic hydrazide injected into the stem xylem of 1‐year‐old silver maple (Acer saccharinum L.) and American sycamore (Platanus occidentalis L.) seedlings. Maleic hydrazide was found to translocate to all parts of the plant within 1 day after treatment. The autoradiographs indicated that the radioactivity was accumulated in meristematic regions of the leaves. A significant amount (over 15% of the applied 14C) was exuded out of the roots into the nutrient solution after 30 days. The 14C in the nutrient solution was in the form of unchanged maleic hydrazide, whereas in plant tissue a metabolite possibly a conjugate with sugar was formed. With the passage of time, the amount of metabolite seemed to increase in proportion to that of maleic hydrazide. Approximately 30% of the applied 14C was unextractable with methanol after 30 days.
Investigation of Effects of Plant Growth Regulators on Liposome Fluidity and Permeability
Authors: PARUPS E. V. , MILLER R. W.
Published: April 2006

Naturally occurring plant growth regulators gibberellic acid (GA), indole‐3‐acetic acid (IAA), abscisic acid (ABA), ethylene and other growth regulating compounds such as 5‐methyl‐7‐chloro‐4‐ethoxycarbonylmethoxy‐2,1,3‐benzothiadiazole (TH) and 2,4 dichlorophenoxyacetic acid (2,4‐D), had no effect on the partition behavior of a piperidine based spin label in liposomes composed of pure or mixed phospholipids or a phospholipid‐sterol mixture. Although no effect on fluidity was observed, TH significantly increased the initial rate of swelling of soybean lecithin‐sitosterol liposomes in isotonic glycerol. IAA and ethylene did not influence this rate but ABA, GA and 2,4‐D inhibited the initial rate of swelling. Lipid composition of liposomes determined the extent and direction of the effects on swelling rates. The observed swelling behavior was, therefore, not related to fluidity of the bulk membrane lipids but was due, instead, to modification of the access of glycerol to the phospholipid bilayer surface or, alternatively, to the creation of polar channels into the liposomes.
The Effects of Age, Darkness and Nitrate on Poly‐β‐hydroxybutyrate Levels and Nitrogen‐Fixing Ability of Rhizobium in Lupinus angustifolius
Authors: GERSON T. , PATEL J. J. , WONG M. N.
Published: April 2006

The effects of age, darkness and nitrate on nitrogenase activity, poly‐β‐hydroxybutyrate (PHB) and β‐hydroxybutyrate dehydrogenase (BOHB DH) activity in Rhizobium lupini while in symbiosis with Lupinus angustifolius were assessed. It was concluded that PHB functions as a reserve material in root nodules and is involved in the maintenance of nitrogen fixation when the availability of photosynthates is restricted. PHB accumulation and the development of BOHB‐DH activity did not take place until the peak of nitrogenase activity had passed. All three parameters reached a steady level when the host plant was approximately 24 days old. Deprivation of photosynthates due to continuous darkness resulted in major losses of PHB and BOHB‐DH activity until N2‐fixation ceased. Nitrate addition without restriction of photosynthates resulted in diminished nitrogenase activity. Apart from a slight delay in accumulation. PHB levels were not affected. It was found important to standardize sampling since N2‐fixation was affected by plant culture and diurnal cycles.
Excitation of System I and System II in Photosynthesis as a Possible Control Mechanism of Glycolate Metabolism in the Blue‐Green Alga Anacystis nidulans
Authors: SØRENSEN L. , HOLMEN AA. T. , HALLDAL P.
Published: April 2006

Photosynthetic enhancement studies performed at 619 nm (excitation of Systems I and II) and at 446 nm (mainly excitation of System I) revealed an 18% photosynthetic enhancement simultaneously with a 31% reduction in glycolate excretion. This observation supports the hypothesis that some glycolate may be consumed in an oxidation process associated with System I when System II is poorly excited and the supply of electrons from the water splitting process of photosynthesis is low.
Growth and Composition of Rye Seedlings Cultured in Sea Water
Authors: SIEGEL S. M. , SIEGEL B. Z.
Published: April 2006

Two‐week‐old Balbo rye seedlings cultured in aerated sea water are similar in fresh weight and linear dimensions to plants grown in aerated fresh and brackish waters. No significant differences were found in dry matter, nitrogen, sulfur or phosphorus content but tissue chloride increased markedly. Most of the Cl uptake was retained as chloride, but a small quantity was water insoluble and possibly in organic combination.

We suggest that rye is a good prospect for development of lines suitable for sea water agriculture.
The Physiology of Rooting Populus Cuttings
Authors: OKORO O. O. , GRACE J.
Published: April 2006

Activity of endogenous cytokinin of cuttings was investigated in relation to the process of rotting. The levels of cytokinin in hardwood cuttings of easy‐to‐root Populus × euramericana (Dode) Guinier and difficult‐to‐root Populus tremula L. were monitored at various stages of root formation. In cuttings of P. tremula was found a higher cytokinin activity than in P. × euramericana and this condition persisted throughout the rooting period. There was a general initial decrease of cytokinin activity in both upper and lower halves of cuttings of both species. The declining level was reversed in the easy‐to‐root species when roots had formed and to a lesser extent in the difficult‐to‐root species when leaves expanded. In both cases this increase was relatively higher in the lower halves than in the upper halves.
Translocation and Metabolism of Leaf Applied Hexachlorophene in Peanuts
Authors: AUKEN OSCAR W. VAN , HULSE MICHAEL
Published: April 2006

Translocation, distribution, metabolism and photolysis of hexachlorophene (HCP) were investigated in peanut plants (Arachis hypogea L., Spanish type) grown under standardized conditions and treated with l4C‐ring‐labeled HCP. Treatment time ranged from 0–114 days. Autoradiographic analyses were performed on all plants. Selected plant tissues were extracted and chromatographed, using both thin layer and gas liquid chromatography.

No translocation of HCP was detected in the plant tissue. No HCP metabolites were found. Some HCP was lost from the leaves and inert controls at a specific rate per unit time. The rates were slightly different, being slower on the leaves than on the controls.

At the end of the 114‐day treatment and based on regression analysis of thin layer chromatographic plates, an average of 68% of the applied HCP remained unaltered on the treated plants and an average of 77% remained on the controls. This indicated that, respectively, 32 and 23% of the original HCP had been altered. This 9% difference was statistically significant. Upon further analyses of the above data, using gas chromatographic methods, as many as 14 peaks were found in the treated samples and the controls, including some parent material.

Ultraviolet photolysis seems to be the mechanism responsible for alteration of the HCP on the treated plants and controls. Two photolysis products have been identified by gas liquid chromatography‐mass spectral analysis. Twelve other electrophylic compounds have been found in various treated plant or control extracts.

Further analyses will be necessary to verify the identification and quantification of the other degradation products.
Chemical Control of Ripening in Banana
Authors: DESAI B. B. , DESHPANDE P. B.
Published: April 2006

A post‐harvest dip of banana (Musa paradisiaca L.) fruits into the aqueous solutions of abscisic acid and indoleacetic acid significantly hastened the banana ripening, judging from increases in total sugars, acidity, ascorbic acid and units of von Losecke's colour chart during storage at 20°C. The treatment of bananas with gibberellic acid and kinetin, on the contrary, retarded banana ripening as indicated by higher values for firmness, starch, cellulose and hemicellulose. The results obtained suggest that ripening of banana can be controlled chemically.
Photosystem II and Hypoxic Quiescence in Alligatorweed
Authors: QUIMBY P. C. , POTTER J. R. , DUKE S. O.
Published: April 2006

Stem cuttings of alligatorweed [Alternanthera philoxeroides (Mart.) Griseb.] were subjected to various light and chemical inhibitor treatments to obtain information about the physiological nature of the hypoxic quiescence induced by dark submergence. White or red light at 40 μE m−2 s−1 stimulated growth from submerged stem cuttings but far‐red at 5 μE M−2 s−1 did not. Photo‐system II inhibitors, such as 3‐(3,4‐dichlorophenyl) 1,1‐dimethylurea (DCMU) at 1.4 × 10−5M or 2‐chloro‐4,6‐bis(ethylamino)‐s‐triazine (simazine) at 10−5M, completely inhibited the growth that normally occurs in a submerged state under continuous white light at 40 μE m−2 s−1. These concentrations of DCMU or simazine did not reduce nonphotosynthetic growth from underwater nodes of emersed stem cuttings partially exposed to air in the light for 1 week. Hydrogen peroxide at 50 mg/1 added every other day partially relieved the simazine‐induced inhibition of growth from submerged, illuminated cuttings. These data indicated that sprouting and early growth of submerged, illuminated alligatorweed depended on the oxygen produced by photosystem II to support respiration and to overcome hypoxic quiescence.
Separation of Two Forms of Anthranilate Synthetase from 5‐Methyltryptophar Susceptible and ‐Resistant Cultured Solarium tuberosumCells
Authors: CARLSON JOHN E. , WIDHOLM J. M.
Published: April 2006

Potato cell suspension cultures (Solanum tuberosumL. cv. Merrimack) have been selected which are resistant to growth inhibition by D,L‐5‐methyltryptophan. Anthranilate synthetase activity in crude extracts from resistant cells was less sensitive to feedback inhibition by L‐tryptophan and D,L‐5‐methyltryptophan than the activity from the sensitive line. This altered feedback control apparently accounts for the cell's resistance to growth inhibition since there is a 48‐fold increase in free tryptophan in one of the resistant cell lines. Preparative polyacrylamide gel electro‐phoresis separated feedback‐sensitive and ‐resistant forms of anthranilate synthetase in extracts from both 5‐methyltryptophan‐susceptible and ‐resistant cells, with a predominance of the corresponding form in the respective cell type. The anthranilate synthetase activity from the 5‐methyltryptophan‐resistant line was inactivated more slowly by incubation of crude extracts at 50°C than the activity from the sensitive line. These results suggest the presence of two isoenzymes of anthranilate synthetase in cultured potato cells.