bluuebunny/crossref_metadata_2025 huggingface dataset:
Uptake of l‐Phenylalanine in Synchronous Chlorella fusca. Characterization of the Uptake System
Authors: PEDERSEN ÅSE GRAN , KNUTSEN GJERT
Published: April 2006

Phenylalanine uptake in Chlorella fusca was measured, using the membrane filter technique. The cells were synchronized, and harvested at specific points of the life cycle. Experiments with autospores showed that the uptake followed saturation kinetics, with a Km= 5 μM. Vmax, was 0.1 nmol/min × 107 cells. The optimum temperature for the uptake was 40°C, and the activation energy was 1700 J/mol. The uptake showed a high specificity towards l‐phenylalanine; presence of the unlabelled stereoisomer did not inhibit the uptake. Uptake of l‐phenylalanine was inhibited in the presence of other analogues or other amino acids, but only if they were present in concentrations considerably higher than that of L‐phenylalanine. Variations in the ratio of Na4+ to K+ in the external solution during uptake experiments did not have any influence upon the uptake rate of l‐phenylalanine. The cells were able to take up the amino acid against a concentration gradient. At pool maximum the ratio between internal and external amino acid concentration was 1000/1. 2,4‐Dinitro‐phenol inhibited the uptake completely. Exchange between internal and external l‐phenylalanine could not be demonstrated. The Km value did not change during the life cycle of the cells. The uptake rate reached a maximum at the end of the light period, and fell to a minimum just before sporulation started. It is concluded that Chlorella fusca cells have a highly specific, active uptake system for l‐phenylalanine. The system is constitutive, independent on the K or Na concentration, and the mechanism of uptake does not change during the life cycle of the cells.
Effect of Ethylene on the Phenylalanine Ammonia‐lyase Activity of Carrot Tissues
Authors: SARKAR SUBODH K. , PHAN C. TON
Published: April 2006

Ethylene stimulated the activity of l‐phenylalanine ammonia‐lyase (PAL) in carrot (Daucus carota L.) tissues. It is also known to induce the formation of isochlorogenic acid. However, the induction patterns were different for isochlorogenic acid and PAL activity. Ethylene action seems to be indirect, as it did not affect the PAL activity of cell‐free extracts.
Effect of Cd on Photosynthesis and Transpiration of Excised Leaves of Corn and Sunflower
Authors: BAZZAZ F. A. , ROLFE G. L. , CARLSON ROGER W.
Published: April 2006

Detached corn and sunflower leaves exposed to various concentrations of Cd, supplied as CdCl2, exhibit reduced photosynthesis and transpiration. The reduction is dependent on the concentration of CdCl2 solution and generally becomes more pronounced with time. In sunflower, net photosynthesis and transpiration are completely inhibited within 45 min after the introduction of 18 mM Cd. Within two hours net photosynthesis is reduced to 40% and 70% of maximum after the introduction of 9 and 4.5 mM Cd respectively. In corn the trend of photo‐synthetic response to Cd is similar to that in sunflower except that the inhibition in corn is more pronounced at all treatment levels. A strong linear relationship between photosynthesis and transpiration inhibition is obtained in both species suggesting that Cd contamination induces stomatal closure.
Action Spectrum for the Timing of Photo‐Induced Cell Division in Adiantum Gametophytes
Authors: WADA MASAMITSU , FURUYA MASAKI
Published: April 2006

The photo‐induced cell division in single‐celled protonemata of the fern Adiantum capillus‐veneris was studied. When the protonemata were exposed to monochromatic light at 50 nm intervals between 350 and 750 nm, irradiations in the blue and near‐ultraviolet regions effectively induced cell division, while wavelengths longer than 550 nm showed no such effect. As reciprocity between duration and intensity was observed within the range of incident energy used, the action spectrum for the frequency of the photo‐induced cell divisions 24 h after irradiation was determined between 360 and 510 nm at 10 nm intervals. Furthermore, the previously known effect of phytochrome on the timing of the cell division was minimized by a short exposure to red light given immediately after the monochromatic irradiation. The resulting action spectra showed a peak in the neighborhood of 460 nm with shoulders and another peak in the near‐ultraviolet region.
Macromolecular Physiology of Plastids
Authors: NIELSEN OLE FREDERIK , GOUGH SIMON
Published: April 2006

The composition and amount of carotenoid pigments were determined in etiolated seedling leaves of 6 barley (Hordeum vulgare L.) mutants, comprising 1 xantha and 5 tigrina mutants. All mutants had on a mole basis approximately the same content of carotenoids as the wild type.

The mutants xan‐u21, tig‐n32, and tig‐33 contained significantly higher amounts of carotenes than the wild type, ranging from 32 to 68% of the total carotenoid content as compared to the 4–8% found in the wild type. In the mutants tig‐b23 and tig‐o34, only a slight increase in the amount of carotenes was notable. The carotene content and composition in tig‐d12 was indistinguishable from that of the wild type.

The carotenes extracted from xan‐u21, tig‐b23, tig‐n32, tig‐33, and tig‐o34 were characterized by adsorption chromatography and spectrophotometry. Mutant xan‐u21 is in the dark blocked in β‐carotene synthesis, and accumulates the aliphatic polyenes: phytofluene, proneurosporene, poly‐cis‐lycopenes, neo‐lycopene and lycopene. The other four mutants synthesize β‐carotene, but accumulate in addition various higher saturated carotenes, the main components being ζ‐carotene in tig‐b23, a lycopenic pigment in tig‐n32 and tig‐33, and lycopene in tig‐o34.

Accumulation of higher saturated carotenes appears correlated with specific aberrations of the membrane structure in plastids. The regulation of carotene and protochlorophyllide syntheses in etioplasts are closely linked as shown by the single gene mutants which affect both pathways. However, several mutants have been identified which cause defects in protochlorophyllide synthesis only.
Effects of Hydroxyproline and other Amino Acid Analogues on the Growth of Pea Root Segments
Authors: VAUGHAN D. , DEKOCK P. C. , CUSENS EVELYN
Published: April 2006

Changes in the lengths and growth rates of isolated 2–4 mm pea root segments, cultured in sucrose media under aseptic conditions, were paralleled by changes in invertase development and in chloride and leucine uptakes. The amino acid analogues o‐, m‐ and p‐fluorophenylalanine, azetidine‐2‐carboxylic acid and ethionine inhibited growth with corresponding changes in invertase activity and in chloride and leucine uptakes. In contrast hydroxyproline, which under the conditions used may be regarded as an analogue of proline, enhanced both the growth rate and duration of growth but had little effect on the several parameters of protein synthesis which were measured. No amino acid tested affected changes in growth, invertase activity or the uptake of chloride and leucine, but they prevented the effects of the corresponding analogues. The results show that although extension growth is dependent on continuous protein synthesis, only specific proteins, probably in the cell wall, play a key role in this process.
Die Hemmung der lichtinduzierten Chlorophyll‐, Carotinoid‐ und Anthocyansynthese durch Äthanol
Authors: LICHTENTHALER HARTMUT K. , THIESS DOROTHEA E.
Published: April 2006

The Inhibition of the Light Induced Chlorophyll, Carotenoid and Anthocyan Synthesis by Ethanol.

It is shown that already low concentrations of ethanol inhibit the light induced formation of pigments (chlorophylls, carotenoids, anthocyanins) in Raphanus‐seedlings.

The degree of inhibition depends on the ethanol concentration and rises with increasing incubation period. The inhibition of pigment synthesis is reversible, and immediately ceases when ethanol is removed. The formation of chlorophylls and anthocyanin is more repressed than that of carotenoids, and the formation of β‐carotene to a higher extent than that of xanthophylls. It is concluded that ethanol inhibits pigment formation by inhibition of protein synthesis. These results indicate that ethanol and other lower alcohols cannot be used for the solubilizing of organic compounds when these are applied to plant tissues.
Amino Acid Incorporation into Proteins by Plant Mitochondria in the Presence of Some Plant Growth Promoters, Metabolic Inhibitors and Synthetic Messengers
Authors: DE DILIP K. , ROY S. C.
Published: April 2006

The incorporation of 14C‐labelled phenylalanine into proteins of mitochondria prepared from 48‐h germinating seeds of Vigna sinensis (L.) Savi can be stimulated by gibberellic acid (GA3), kinetin and polyuridylic acid [poly(U)]. The incorporation is sensitive to various metabolic inhibitors which include rifampicin, actinomycin D, ethidium bromide, kanamycin, 5‐azauracil, 8‐azaadenine, and rotenone. They were used to study the effect of GA3 and kinetin on the sequential steps in protein synthesis (DNA ‐> RNA ‐> protein), which are variously affected by the inhibitors. The inhibitory effect of actinomycin D on the incorporation can be reversed by GA3 and kinetin, which implies that these two plant hormones act at the transcription level. With ethidium bromide the effect of hormones is not so convincing, though the trend is towards some release of inhibition. The plant hormones have apparently no effect on the incorporation sensitive to other inhibitors studied.

GA3 and kinetin can also stimulate the normal and polyadeny‐lic acid [poly(A)]‐directed incorporation of 14C‐labelled lysine into proteins by a mitochondria! preparation, lndole‐3‐acetic acid and 2,4‐dichlorophenoxyacetic acid can only stimulate the normal synthesis, which is not further stepped up by poly (A). The polynucleotide even seems to depress the action of IAA. This anomaly has been discussed.
Iron Deficiency in the Blue‐Green Alga Anacystis nidulans: Fluorescence and Absorption Spectra Recorded at 77°K
Authors: ÖQUIST GUNNAR
Published: April 2006

Low‐temperature (77°K) fluorescence and absorption spectra have been determined for whole cells and photosystem I particles of Anacystis nidulans grown in iron‐supplied or iron‐deficient inorganic media. Iron deficiency induces a decrease of F720 relative to F685 and F695 in the fluorescence spectra of both whole cells and photosystem I particles. This change is correlated to a reduction of preferentially the long wavelength absorbing fraction of chlorophyll a. The relative fluorescence intensity at 755 nm is increased by iron deficiency. No significant effects of culture‐age are found in the ratio between the three fluorescence bands (F685: F695: F720) of iron‐supplied A. nidulans.
Automatic Recordings of Action Spectra for Partial Reactions of Photosynthesis
Authors: HALLDAL PER , ÖQUIST GUNNAR , TIMNER LENA
Published: April 2006

Methods for automatic recordings of action spectra for partial reactions of photosynthesis are previously described. The present paper elaborates one of the descriptions and gives results from measurements. The method is based upon the recordings of changes in the absorption of certain dyes, which are used as electron acceptors or electron donors to photosynthetic reactions in illuminated chloroplasts or photosynthetic lamellae. By measuring the transmission changes continuously during a wavelength sweep of actinic light, which is corrected for equal numbers of light quanta at different wavelengths, an approximate integrated action spectrum of the selected partial reaction is obtained. A computer program gives the action spectrum after taking the first derivative of the curve and correcting it for changes with time in the rate of the dye reduction (oxidation) and the reverse reactions.

The action spectrum for photoreduction of 2,6‐dichlorophenol indophenol and cytochrome c by spinach chloroplasts has a peak at about the same wavelength as the absorption spectrum (677–680 nm). Details in the curves are observed at 650, 663, 673 and possibly at 695 nm. The action spectrum for mammalian cytochrome c oxidation by PSI particles of Anacystis nidulans has a peak at 683 nm (absorption spectrum at 679 nm). Shoulders are observed at 665, 677, 700, and 715 nm.
Permeability and Self‐Induction as Factors in Water Transport through Bean Roots
Authors: KUIPER F. , KUIPER P. J. C.
Published: April 2006

Water uptake of root systems of Phaseolus vulgaris was measured in a Scholander pressure cylinder at a constant pressure. Water uptake rises gradually till a steady state is reached after 15 to 60 minutes. This time course can be described as a transport process with the property of a self‐induction. The latter was not affected by temperature. It is concluded that the property of self‐induction is located in the cytoplasm or at the interface between cytoplasm and plasmalemma of the endodermal cells. It is suggested that cytoplasmic streaming controls the time course of water transport.
Half‐Life of sRNA from Primary Roots of Zea mays. A Contribution to the Cytokinin Production
Authors: KLEMEN FRANZ , KLÄMBT DIETER
Published: April 2006

Roots produce cytokinins, which could be generated from the catabolism of transfer RNA. To prove such a hypothesis, the half‐life of sRNA from primary roots of corn was measured. The shortest half‐life was estimated to be 3 days. Depending on growth, cells at the root tips are “moving” out of the growing region and become differentiated cells. Therefore the highest label at the root tip during the pulse incubation is moving backwards during the chase incubation. Prolonged chase increases the half‐life of sRNA successively, possibly due to decreasing metabolic activities of the originally labeled cells.
Iron‐Stress Response in Tomato (Lycopersicon esculentum) 1. Sites of Fe Reduction, Absorption and Transport
Authors: BROWN J. C. , AMBLER J. E.
Published: April 2006

T3238fer (Fe‐inefficient) and T3238FER (Fe‐efficient) tomato plants differ in their ability to utilize Fe and therefore can be used as test genotypes to locate sites of Fe uptake or to characterize changes that occur in roots in response to Fe stress (Fe deficiency). T3238fer does not respond to Fe stress. Release of hydrogen ions and reduction of Fe3+ to Fe2+ are two primary responses of T3238FER roots to Fe stress. Fe reduction sites were predominately in the young lateral roots, and between the regions of root elongation and maturation of the primary root. The use of BDPS (bathophenanthrolinedisulfonate) to trap Fe2+ did not affect the release of H+ ions or reduction by T3238FER roots. BPDS did not decrease Fe uptake until it exceeded the Fe concentration in the nutrient solution. A sevenfold increase in BPDS caused a threefold decrease in Fe taken up by the plant. Fe3+ is reduced to Fe2+ at root sites accessible to BPDS. Adding Zn decreased the response to Fe stress.

Iron stress initiates the development of lateral roots, and we propose that most Fe enters the plant through these roots. The iron moves through protoxylem into the metaxylem of the primary root and then to the top of the plant as Fe citrate. Root environmental factors that are competitive or inhibit Fe‐stress response, or genotypes that fail to respond to Fe stress, contribute to the development of Fe deficiency in plants.
Thermal and Ionic Factors in the Ultraviolet Photolysis of Plant Cell Membranes
Authors: SIEGEL S. M. , CORN CAROLYN
Published: April 2006

The exposure of red beet root tissue to ultraviolet (254 nm) at 2 × 106 erg × cm−2× min−1 (0.2 J × cm−2× min−1) causes release of betacyanin after a 20 minute induction period. Ultraviolet‐photolysis is temperature‐sensitive having a thermal threshold at about 10°C. Reduction in pigment release was effected by chlorides of Mg, Ca and Sr, but not by Li, Na or K. This effect was marked but not complete, even at 40 mM concentration.

It is concluded that photolysis is indirect, and involves a lytic factor, possibly an oxidant, derived from an original photochemical product.
Multiphasic Uptake of Sulfate by Barley Roots I. Effects of Analogues, Phosphate, and pH
Authors: VANGE MARTA S. , HOLMERN KARI , NISSEN PER
Published: April 2006

For sulfate uptake by barley roots, competition studies reveal that uptake and phase transitions are caused by interaction of ions with separate sites on or in the plasmalemma. Uptake is competitively, and unequally, inhibited by sulfate analogues but not by other divalent anions. In contrast, divalent phosphate and di‐ and trivalent pyrophosphate are equally effective in causing transitions. Phosphate is taken up mainly or entirely as H2PO4− by a similar but separate multiphasic mechanism. At pH 8, sulfate uptake is mediated by fewer phases than at low and intermediate pH.
Oscillatory Transpiration and Water Uptake of Avena Plants IV. Transpiratory Response to Sine Shaped Light Cycles
Authors: BROGÅDH T. , JOHNSSON A.
Published: April 2006

The transpiration rate of individual 6‐day‐old oat plants was forced to oscillate by cyclic sine‐shaped changes in the leaf irradiance (frequency 2 cycles h−1, amplitude and average value 1.4 mW cm−2, red light 620–800 nm). By means of a specially designed cuvette with three chambers the transpiration rate from three different segments of the leaf could be measured simultaneously. The leaf segments were illuminated individually and the illumination on each leaf segment could be modulated independently.

The experiments showed that there was a strong correlation between the transpiration rates from the different leaf segments, dependent on a coupling mechanism in the plant. The coupling phenomenon disappeared when the root system was eliminated or when the water potential of the root medium was lowered. It was experimentally shown that CO2 diffusion in the leaf could not be the primary cause for the coupling. Therefore the stomatal dependence on the leaf water potential was considered the most probable reason for the coupling.

The frequency of the forcing light cycles could be linearly changed during an experiment and this swept‐frequency technique was used to obtain a frequency response of one single oat plant. The technique made it also possible to study the strength of the coupling between different leaf segments.
Phylloquinone (Vitamin K1) Levels in Leaves of Plant Species Differing in Susceptibility to 2,4‐Dichlorophenoxyacetic Acid
Authors: JANSSON OWE
Published: April 2006

Plant species differing in susceptibility to 2,4‐dichlorophenoxyacetic acid (2,4‐D) were examined as to the level of phylloquinone (K) in the leaves. The K level was found to be considerably higher in several plants resistant or moderately resistant to 2,4‐D (Aegopodium podagraria L., Galium mollugo L., Lamium album L., Matricaria chamomilla L., Oxalis acetosella L., Stellaria media (L.) Vill., Viola arvensis Murr.) than in Chenopodium album L. and Sinapsis arvensis L. which are susceptible to 2,4‐D. Capsella bursa‐pastoris (L.) Med. and Plantago major L. (both moderately susceptible) and a few resistant or moderately resistant species (Agropyron repens (L.) PB., Anthriscus silvestris (L.) Hoffm., Triticum aestivum L.) had intermediate K levels. Cirsium arvense (L.) Scop. (susceptible) had a relatively high level of K. It is possible that a high K level in the plant can be of importance in the resistance to 2,4‐D.
Influence of Growth Conditions, Metabolic Inhibitors, and Phenolic Compounds on the ATP Pool in Fomes annosus
Authors: JOHANSSON MARTIN , HÄGERBY ELISABETH
Published: April 2006

The ATP pool of growing fungal mycelia, particularly Fomes annosus, has been determined. The ATP level varied during the different growth phases and correlated with the variations in the economic coefficient. Common uncouplers (at concentrations similar to those used in mitochondrial tests) decreased the ATP pool very rapidly. The size of the pool often fell 50–80% before the O2 uptake decreased below that of the control and was accompanied by an increasing exudation of inorganic phosphate. Phenolic compounds added to the medium stimulated the lacease activity, generally in combination with a decrease in the ATP level.
Lipid Composition of Whole Roots and of Ca2+, Mg2+‐activated Adenosine Triphosphatases from Wheat and Oat as Related to Mineral Nutrition
Authors: KUIPER P. J. C. , KÄHR M. , STUIVER C. E. E. , KYLIN A.
Published: April 2006

Lipid composition of whole roots of wheat (Triticum vulgare Vill. cv. Svenno Spring Wheat) and oat (Avena sativa L. cv. Brighton) and of cell wall fractions, mitochondrial fractions and microsomal fractions of these roots were studied. Lipid composition depended upon the level of mineral nutrition. In wheat total phospholipids, phosphatidyl choline and sulfolipid content was highest in the roots grown at the higher salt concentration, while the reverse was true for oat roots. In both species glycolipid and sterol content was lower in the high salt roots, at the same time as higher proportions of them were built into the microsomal fraction. Phosphatidyl choline content of the wheat root membrane fractions increased with the salt level, while the opposite occurred in the oat roots.

The phosphatidyl choline content may be correlated with the (Ca2+, Mg2+)‐stimulated ATPase activity.
The Initiation of an Endogenous Rhythm Affecting Flower Bud Formation in Pharbitis nil
Authors: PARASKA JOHN R. , SPECTOR CALVIN
Published: April 2006

When seedlings of Pharbitis nil are presented with an inductive dark period at varying times, they show a circadian fluctuation in the number of flower buds initiated. This study determines if this fluctuation is due to the plant's perception, at the time of the inductive dark period, of either a rhythmic, external, environmental stimulus or of an endogenous rhythm.

Using experimental designs in which the time of planting, the time of seedling emergence from the soil, and the time at which the presentation of an inductive dark period are varied, this fluctuation in flower bud formation is shown to be due to an endogenous rhythm initiated or synchronized by some event associated with the emergence of the seedlings from the soil. The results are inconsistent with the hypothesis that the plants are responding to rhythmic external stimuli.
Effects of Fluoride on Mitochondrial Activity in Higher Plants
Authors: MILLER J. E. , MILLER G. W.
Published: April 2006

The effects of fluoride on respiration of plant tissue and mitochondria were investigated. Fumigation of young soybean plants (Glycine max Merr. cv. Hawkeye) with 9–12 μg × m−3 HF caused a stimulation of respiration at about 2 days of treatment followed by inhibition 2 days later. Mitochondria isolated from the stimulated tissue had higher respiration rates, greater ATPase activity, and lower P/O ratios, while in mitochondria from inhibited tissue, all three were reduced.

Treatment of etiolated soybean hypocotyl sections in Hoagland's solution containing KF for 3 to 10 h only resulted in inhibition of respiration. Mitochondria isolated from this tissue elicited increased respiration rates with malate as substrate and inhibited respiration with succinate. With both substrates respiratory control and ADP/O ratios were decreased.

Direct treatment of mitochondria from the etiolated soybean hypocotyl tissue with fluoride resulted in inhibition of state 3 respiration and lower ADP/O ratios with the substrates succinate, malate, and NADH.

Fluoride was also found to increase the amount of osmotically induced swelling and cause a more rapid leakage of protein with mitochondria isolated from etiolated corn shoots (Zea mays L. cv. Golden Cross Bantam).

The results are discussed with respect to possible effects of fluoride on mitochondrial membranes.
Morphological and Physiological Effects of Maleic Hydrazide on Tobacco
Authors: BUSH L. P. , SIMS J. L.
Published: April 2006

Tobacco plants (Nicotiana tabacum cv. Burley 21) were cultured in the greenhouse to the 18‐leaf stage. The apical meristem was removed and subsequent axillary bud growth was removed by hand (controls) or axillary bud development was inhibited by application of maleic hydrazide. Compared with the controls, maleic hydrazide treated plants had a decreased stem diameter and stem weight, but an increased leaf weight and leaf weight/area. Plant height and leaf area were the same for both treatments. Maleic hydrazide inhibited translocation of 14C from a single leaf exposed to 14CO2. Respiration was greater than in the controls three days after application of maleic hydrazide, but 9 and 14 days after application there were no differences in respiration between the two treatments. Maleic hydrazide did not affect photosynthetic activity.
Growth and Dormancy in Norway Spruce Ecotypes (Picea abies) I. Interaction of Photoperiod and Temperature
Authors: HEIDE OLA M.
Published: April 2006

Growth and dormancy as affected by photoperiod and temperature have been studied in Norway spruce ecotypes of different latitudinal and altitudinal origin. First‐year seedlings were used.

In all ecotypes apical growth cessation and terminal bud formation occurred within 2 weeks after exposure to SD at temperatures of 18 to 24°C. At lower temperatures or at near‐critical photoperiods the response was delayed. The critical photoperiod for apical growth cessation varied from 21 hours in ecotype Steinkjer, Norway (64°N) to about 15 hours in ecotype Lankowitz, Austria (47°04′N). High‐elevation ecotypes also had longer critical pholoperiods than low‐elevation ecotypes from the same latitude.

A detectable growth depression resulted from as little as 1 or 2 SDs of 10 hours, and with 4 or more SDs apical growth cessation took place. In contrast to the situation in the shoot, root growth was not affected by photoperiod. Accordingly, the top:root ratio is drastically affected by photoperiod.

The critical photoperiod for cambial growth was shorter than that for apical growth in all ecotypes and cambial growth cessation was delayed for several weeks compared with cessation of apical growth. A transition to formation of late‐wood tracheids with thick walls and narrow lumens took place upon exposure to SD.

The photoperiodic effects were significantly modified by temperature, but the critical photoperiods were only slightly changed by temperature in the range of 12 to 24°C. However, a 10‐hour “night” at 4°C caused growth cessation in continuous light in four ecotypes tested.

Temperature optimum for apical growth under non‐limiting photoperiods (24 hours) was 21°C in all ecotypes, but with little difference among 18,21 and 24°C. The Q10 for apical growth was 3.5 in the temperature range 12 to 18°C. The growth potential as determined in 24‐hour photoperiods was not significantly different among the various ecotypes except for one northern eco‐type which was clearly inferior to the others. However, the growth of ecotype Steinkjer (64°N) was greatly suppressed even by the long midsummer days at 59°40′N, thus demonstrating the misleading impression one gets of the growth potential of northern ecotypes when they are moved southwards.
Distribution of Chlorophyll between the Two Photoreactions in Photosynthesis of the Blue‐Green Alga Anacystis nidulans Grown at Two Different Light Intensities
Authors: ÖQUIST GUNNAR
Published: April 2006

Anacystis nidulans was grown in white light of two different intensities, 7 and 50 W ·m−2. The in vivo pigmentations of the two cultures were compared. The ratio phycocyanin/chlorophyll a was 0.96 for cells grown at 7 W · m−2 and 0.37 for cells grown at 50 W · m−2. Phycocyanin‐free photosynthetic lamellae (PSI‐particles) were prepared, using French press treatment and fractionated centrifugation. Algae grown in the irradiance of 50 W · m−2 showed a chlorophyll a/P700 ratio of 260, while algae grown at 7 W · m−2 had a value of 140. Corresponding PSI‐particles showed values of 122 and 109 respectively. Light‐induced absorption difference spectra measured between 400–450nm indicated different ratios between cytochrome f and P700 in the two algal cultures.

Enhancement studies of photosynthetic oxygen evolution were carried out. When a background beam of 691 nm was superimposed upon a signal beam of 625 nm, good enhancement was observed for both cultures. With the wavelengths 675 and 691 nm together a pronounced enhancement could be detected only in algae grown at the higher light level.

Absorption spectra recorded on whole cells at 77°K revealed a small shift of the main red chlorophyll a absorption peak caused by light intensity.

It is proposed that the reduction of the phycocyanin/chlorophyll a ratio in high light‐grown cells is accompanied by an increased energy distribution by chlorophyll a into PSII.
Light‐Induced Changes in Pigment Composition of Photosynthetic Lamellae and Cell‐Free Extracts from the Blue‐Green Alga Anacystis nidulans
Authors: ÖQUIST GUNNAR
Published: April 2006

Anacystis nidulans was grown at two different levels of white light, 7 and50 W.m−2. The cells were disrupted through French press treatment, and phycocyanin‐free photosynthetic lamellae were obtained from the homogenate by fractionated centrifugation. Comparative absorption studies of the lamellae revealed that high intensity gave an increased carotenoid content relative to chlorophyll a. The spectral characteristics of the cell‐free supernatants were also analysed. The high light intensity gave increased contents of both pteridines (410 nm) and allophycocyanin (655 nm) compared with the contents in algae grown at the low light level.
Compounds Association with Cytokinin Activity in Fruitlets and Tracheal Fluid of Gossypium hirsutum
Authors: TAYLOR P. A. , KOSUGE T. , DeVAY J. E.
Published: April 2006

Compounds that account for cytokinin activity in fruitlets and tracheal fluids of cotton (Gossypium hirsutum L.) were determined using preparations purified by thin‐layer chromatography and gas–liquid chromatography and bioassayed with cultures of soybean stem callus tissue. At least five substances were found that stimulated growth of callus tissue. Among these, adenine and adenosine accounted for most of the growth stimulation of callus tissue. A compound with cytokinin activity was isolated with TLC properties similar to other known cytokinins, but its identity as zeatin, dihydrozeatin or N6‐(Δ2‐isopentenyl)‐adenine was not confirmed using GLC and GLC combined with mass spectrometry. It was estimated that less than 1% of the cytokinin activity of this unknown substance could have been due to N6‐substituted adenine derivatives.
Restoration of Photosynthesis in Dried Tobacco Leaf Tissue
Authors: GRAZIANI Y. , LIVNE A.
Published: April 2006

A comparison of 14CO2 fixation rates in dehydrating tobacco leaf tissue, either intact or epidermis‐free, shows that stomatal closure is the primary cause for photosynthetic reduction due to dehydration. Rehydration of the dried, epidermis‐free tissue was accompanied by restoration of photosynthetic activity. The restoration was not only affected by hydration level but was notably time‐dependent, apparently for reorganization of the photosynthetic apparatus.
Induction of Biplanar Growth in Fern Gametophytes
Authors: RAGHAVAN V.
Published: April 2006

In constant white light, protonemata of different ages of Asplenium nidus produce a fixed number of cells before they become biplanar. Protonemata with a lower initial cell number require a longer time to become biplanar than those with a higher initial cell number. Increasing the photoperiod or the light intensity reduces the cell number in the filament at the time of initiation of biplanar morphology. It is suggested that inductive light acts directly on cell metabolism to induce biplanar morphology, rather than indirectly by inducing mitotic activity.
Root Formation in Pea Cuttings III.
Authors: ERIKSEN E. NYMANN
Published: April 2006

Cuttings were either decapitated or both decapitated and disbudded at different time intervals. Cytokinin, at different concentrations, was applied to the cuttings in lanoline.

Higher concentrations of cytokinin inhibited root initiation during the early stage. However, the inhibitory effect of cytokinin disappeared during the later stage of root initiation.

Lower concentrations of cytokinin promoted the root initiation during the early stage. This effect was observed on cuttings which were only decapitated.

These results seem to indicate that the influence of cytokinin changes with the stage of development.

There seems to be an interaction between cytokinin and one or more other growth factors. A possible reason for this may be that cytokinin, in higher concentrations, produces inhibitory effects during the early part of root initiation by blocking the activity of auxin. The loss of the inhibitory effect of cytokinin during the later part of the initiation phase suggests that, at this stage, developing root primordia are capable of controlling the level of active cytokinin and thus do not react to the exogenous application of cytokinin.
Cold Hardiness of Plants: Correlation witb Changes in Electrophoretic Mobility, Composition of Amino Acids and Average Hydrophobicity of Fraction‐1‐protein
Authors: SHOMER‐ILAN ADIVA , WAISEL Y.
Published: April 2006

Cold‐hardening of cabbage plants, involves changes in Fraction‐1‐protein. Such changes are correlated with factors affecting hardening e.g. temperature, light, mineral nutrition and age. A 24‐h exposure to 5°C conditions induced the formation of a new protein with a different amino acid composition, lower average hydrophobicity and a higher hydrophility.
Activity Changes in Selected Enzymes from Soybean Leaves Following Ozone Exposure
Authors: TINGEY DAVID T. , FITES ROGER C. , WICKLIFF CARLOS
Published: April 2006

Soybeans [Glycine max(L.) Merr.] were harvested at various time periods after a 2‐h exposure to either 0 or 0.5 μ1/1 ozone to determine the effects of ozone on selected enzymes. Carbohydrate metabolism was modified by a depression of glyceraldehyde 3‐phaosphate dehydrogenase and an activation of glucose 6‐phosphate dehydrogenase. Ozone did not alter the levels of RNase, protease, acid phosphatase or esterase as might be expected if ozone enhanced leaf senescence. The activities of phenylalanine ammonia lyase, polyphenol oxidase and peroxidase were initially depressed and then stimulated following the ozone exposure. The reactions of soybeans to an acute ozone stress were more nearly akin to those elicited in response to other stresses than to the process of senescence.
Auxin Synthesis in Crown Gall Tumor Tissue: A Comparison of Three Putative Precursors
Authors: DAVIES FREDERICK S. , MAU SHIAO‐LIM CHEN , NOODÉN LARRY D.
Published: April 2006

Axenic crown gall tumor callus (from Vinca rosea L.) which is known to synthesize its own auxin is able to convert exogenous 14C‐indole or tryptamine to indoleacetic acid [5.4 and 10 × 10−6μmol × h−1× (g fr wt)−1 respectively], but little or no 3H‐tryptophan is converted [less than 6.4 × 10−8×μmol × h−1× (g fr wt)−1].
Lipid Peroxidation and Chlorophyll Destruction Caused by Diquat during Photosynthesis in Scenedesmus
Authors: VAN RENSEN J. J. S.
Published: April 2006

Lipid peroxidation and decrease in chlorophyll‐a and chlorophyll‐b content in Scenedesmus cells was followed in the course of time. Addition of diquat to the algae in the light causes lipid peroxidation and a decrease in chlorophyll content. This decrease is mainly due to chlorophyll‐a, the concentration of chlorophyll‐b remains more or less constant during the experiment. In the presence of N′‐(3,4‐dichlorophenyl)‐NN‐dimethylurea (DCMU), of cysteine, or during nitrogen‐flushing of the algal suspension, the lipid peroxidation caused by diquat is strongly suppressed. The decrease in chlorophyll‐a content caused by diquat is somewhat smaller in the presence of DCMU or during nitrogen‐flushing than with diquat alone, but is not influenced by cysteine. The chemical antioxidant butylated hydroxytoluene does not affect lipid peroxidation and chlorophyll destruction caused by diquat.
Effect of EMD‐IT‐5914 on Chlorophyll Synthesis in Leaves of Pennisetum typhoides Seedlings
Authors: HAMPP R. , SANKHLA N. , HUBER W.
Published: April 2006

EMD‐IT‐5914 (5‐dimethylamino‐methylene‐2‐oxo‐4‐phenyl‐2,5‐dihydrofurane‐carbonitril‐(3)) inhibited chlorophyll a formation almost completely and chlorophyll b and total carotenoids up to 80% of the control, but did not appreciably affect the activity of the enzyme system succinyl‐CoA synthetase/δ‐aminolevulinic acid synthetase. The activity of δ‐aminolevulinic acid dehydratase was not found limiting. In contrast, the herbicide strongly inhibited the activity of porphobilinogenase, and the reaction kinetics pointed towards a non‐competitive type of inhibition. The results are discussed in relation to the possible role of EMD‐IT‐5914 in chlorophyll biosynthesis.
Separation of Cytokinins from Danish Cabbage by Column Chromatography on Insoluble Polyvinylpyrrolidone
Authors: THOMAS T. H. , CARROLL J. E. , ISENBERG F. M. R. , PENDERGRASS ANN , HOWELL LYDIA
Published: April 2006

Chromatography of partially purified extracts of Danish cabbage (Brassica oleracea var. capitata L.) heads on polyvinylpyrrolidone columns using a weak phosphate buffer indicated a cytokinin complex containing nine components active in the modified Amaranthus betacyanin bioassay. Similar elution patterns were obtained with extracts of four different cabbage varieties but varietal differences occurred in the biological activity from each component peak. Paper and thin‐layer chromatography indicated the presence of both zeatin and zeatin riboside in the extracts but the other cytokinin‐active components were not identified. Separation of sweet‐corn extracts by this technique indicated that most of the cytokinin activity occurred in the elution volume where zeatin and zeatin riboside would normally occur.
Effects of Light on the Georeaction and Growth Inhibitor Content of Roots
Authors: PILET PAUL‐EMILE
Published: April 2006

The positive geotropic response of the apical segments prepared from the primary roots of Zea mays depends upon at least one growth inhibitor, produced by the root cap, moving basipetally into the extending zone of the root in which it accumulates in the lower part. Anjou maize reacts in both darkness and light while Kelvedon maize is, for the first few hours, geotropic only in light. The production (or activity) of the growth‐inhibiting substance — tested by using vertical half‐decapitated root segments — is quite similar to the georeaction. This finding provides strong evidence that, in the case of Kelvedon maize roots, the inhibitory substance may depend on light. Observations related to the root segment of Anjou and Kelvedon maizes of which the tips are exchanged, are in agreement with the above results.
Phenolic Content in Male and Female Carica papaya: A Possible Physiological Marker for Sex Identification of Vegetative Seedlings
Authors: JINDAL K. K. , SINGH R. N.
Published: April 2006

The phenolic composition was determined in the leaves, petioles and bark tissues of male and female plants of two papaya cultivars. The same kind of phenolics were isolated from the male and female plants. However, a marked difference was observed between the plant organs of different cultivars. The important free and bound phenolics extracted after acidic and alkaline hydrolysis were caffeic acid, gentisic acid, m‐coumaric acid, p‐coumaric acid, salicylic acid and quercetin. Four phenolic compounds were not identified. The amounts of free, acid‐hydrolysable and alkali‐hydrolysable phenolic compounds were considerably higher in male plants.
The Biosynthesis of 8‐Hydroxy‐6‐methoxy‐3‐methyl‐3,4‐dihydroisocoumarin and 5‐Hydroxy‐7‐methoxy‐2‐methylchromone in Carrot Root Tissues Treated with Ethylene
Authors: SARKAR SUBODH K. , PHAN C. TON
Published: April 2006

Biosynthesis of ethylene‐induced isocoumarin and eugenin in carrots (Daucus carota L.) was studied. Radioactive isocoumarin eugenin was isolated from these carrots fed with 1‐14C‐acetate and was isolated from ethylene treated carrots fed with 1‐14C‐acetate, 2‐14C‐malonate, and 3‐14C‐acetoacetate. Also, radioactive G‐3H‐5,7‐dihydroxy‐2‐methylchromone. A trapping experiment with 5,7‐dihydroxy‐2‐methyl‐chromone as trapping agent indicated that this compound was synthesized in carrots from acetate. From the results obtained, it was inferred that the biosynthesis of isocoumarin and eugenin must proceed via the acetate pathway.
The Effect of Light Intensity on Total Photophosphorylation and the ATP Level in Scenedesmus
Authors: OKKEH A. , TILLBERG J.‐E. , KYLIN A.
Published: April 2006

The dependence of in vivo photophosphorylation on light intensity was studied in the unicellular green alga Scenedesmus obtusiusculus. By selective use of the inhibitor DCMU, phosphorylation in (I) the complete system, (II) the pseudocyclic system alone, and (III) the true cyclic system alone, were followed. When the total binding of phosphate was studied, all reaction types became light saturated in about the same manner. The effect of DCMU on the level of ATP varied according to light intensity. As for the specific systems of photophosphorylation, the following ATP data were found: (I) In the complete system the level of ATP decreases with light intensity. (II) Under pseudo‐cyclic conditions light first increases and then decreases the ATP level. Under the atmospheric conditions used (i.e. CO2‐free nitrogen) this indicates a regulation between photophosphorylation and glycolysis, for which possible explanations are discussed. (III) In the true cyclic conditions light has little effect on the ATP level. The possibility is indicated that there is a structural difference between the non‐cyclic (site 1) and the pseudocyclic (site 2) sites of photophosphorylation on the one hand and the true cyclic site (3) on the other.
Tissue Culture of Maize I. Callus Induction and Growth
Authors: SHERIDAN WILLIAM F.
Published: April 2006

Callus induction and subculture was successful with mature embryos and stem sections of seedlings of Zea mays L. on Linsmaier and Skoog's medium modified to contain 4 mg/I of 2,4‐D and 1 g/I of casamino acids. — 2,4‐D was superior to NAA and IAA for both callus induction and growth. Callus subcultured on NAA formed abundant roots on agar‐solidified media and numerous root‐like primordia in liquid cultures. — Kinetin had no effect on callus induction in the presence of 2,4‐D and neither kinetin nor gibberellic acid stimulated callus growth during subculture. — Callus grew equally well on the medium of Linsmaier and Skoog, that of Schenk and Hildebrandt, and the B‐5 medium of Gamborg and Eveleigh containing 2% sucrose, 4 mg/I of 2,4‐D and 1 g/I of casamino acids. — The callus grew more rapidly at 25°C than at 30°C or 35°C. Little difference was noted at any temperature in callus growth in alternating light (16 h) and dark (8 h) or continuous dark. — Sucrose was superior to glucose and maltose in both liquid and agar‐solidified cultures. Lactose and galactose failed to support callus growth.
Studies on Auxin Protectors XII. Auxin Protectors and Polyphenol Oxidase in Developing Coffee Fruit
Authors: GRIFFIN BARBARA , STONIER TOM
Published: April 2006

The fruit of the coffee plant (Coffea arabica) was analyzed for auxin protector content. Ripe coffee berries were separated into pit and pulp, ground in buffer, and assayed for auxin protectors. The extracts were then subjected to gel filtration in order to determine the molecular weight of the protector(s). In the pit, a single protector was found with a molecular weight approaching 5000 daltons, while the pulp contained several auxin protectors, the largest of which appeared to be about 1000 daltons. Chromato‐graphic studies of various gel filtration fractions showed that protector activity was always associated with spots which exhibited a light blue fluorescence under UV.

The changing patterns during coffee fruit development were also investigated. Auxin protector production, and polyphenol oxidase (E.C. 1.10.3.1), an enzyme related to protector metabolism, were assayed at weekly intervals. In the unripe berry, an auxin protector was found with a molecular weight exceeding 200,000 daltons; as the berry ripened the amount of this protector gradually decreased until almost none was present in the ripe berry and the pattern changed to the pattern described above. Polyphenol oxidase content decreased as the berry ripened.

Commercially roasted pits, i.e., coffee “beans”, contained very high levels of protector activity. However, gel filtration studies showed this activity to be associated entirely with low molecular weight compounds.
The Role of Glumes and Gibberellic Acid in Dormancy of Themeda triandra Spikelets
Authors: MARTIN COLIN C.
Published: April 2006

Spikelets of Themeda triandra are dormant when mature and require an after‐ripening period in dry storage of approximately 12 months before full germination potential is realized. Successful germination of spikelets entails the splitting of the tough upper glumes by radicles. Dormany appears to result from a combination of embryo dormancy and mechanically resistant glumes. Glume removal from dormant spikelets increases germination while glume removal plus gibberellic acid increases germination even more.

During the after‐ripening period, the growth potential of spikelets and caryopses increases as measured by their ability to germinate in the presence of the osmoticum polyethylene glycol 6000. The inhibition of germination by decreasing osmotic potential of the germination medium significantly interacts with the promotion caused by gibberellic acid indicating that both factors affect germination by altering the growth potential of the embryos. The increase in growth potential during after‐ripening is probably related to the synthesis of gibberellin‐like substances. It is hypothesized that dormancy breaking during after‐ripening occurs because the growth potential of embryos increases and this consequently increases the ability of radicles to split the upper glumes during germination.
Comparison of Isocitrate Dehydrogenase Activity, Pyruvate Kinase Activity, and Polyphenol Content in Physiologically Different Pine Callus Tissue
Authors: COWLES JOE R. , FOWLER JO ANN , WALKINSHAW C. H.
Published: April 2006

During the growth of callus tissue of slash pine (Pinus elliottil Engelm.) several physiologically different types of tissue can be observed, often within the same culture. Different tissues were selected, based on color appearance, and used to determine isocitrate dehydrogenase and pyruvate kinase activity, and total polyphenol content. Isocitrate dehydrogenase and pyruvate kinase activity in yellow tissue was 3‐ to 5‐fold greater than in brown tissue, whereas the polyphenol content in yellow tissue was approximately 5‐fold less than in brown tissue. Dark brown callus, which also contained large amounts of polyphenols, did not have detectable enzyme activity. The differences in optimal concentrations of substrate and cofactors for the isocitrate dehydrogenase and pyruvate kinase reactions in yellow and brown tissues were very minor and therefore cannot account for the 3‐ to 5‐fold difference in enzyme activity between these tissues. Also, the addition of brown or dark‐brown tissue extract to the yellow tissue extract did not inhibit isocitrate dehydrogenase or pyruvate kinase activity in the yellow tissue extract.
Changes in Root Resistance as a Function of Applied Suction, Time of Day, and Root Temperature
Authors: SHIRAZI G. A. , STONE J. F. , CROY L. I. , TODD G. W.
Published: April 2006

Water uptake rate of decapitated root systems of cotton (Gossypium hirsutum L.), tomato (Lycopersicon esculentum L. cv. Rutgers), and kidney bean (Phaseolus vulgaris L.) plants shows an exponential increase with applied suction up to about —1 bar. The water uptake rate was higher on the descending path of applied suction than on the ascending path, indicating a hysteresis effect in the roots. The root resistance in a cotton plant increased between 3‐to 5‐fold during the photoperiod of 12 hours. The water uptake rate increased with increasing temperature of the root medium up to 30°C in cotton and 25°C in tomato and bean plants.