bluuebunny/crossref_metadata_2025 huggingface dataset:
Half‐Life of sRNA and its Consequence for the Formation of Cytokinins in Lactobacillus acidophilus‐A.TCC 4963 Grown in the Logarithmic and Stationary Phases
Authors: LEINEWEBER MICHAL , KLÄMBT DIETER
Published: April 2006

Cytokinin nucleotides are normal constituents of transfer RNAs. The formation of free cytokinins might be connected with the normal hydrolysis rate of those RNAs. To get an impression about the cytokinin production by this pathway, the half‐life of sRNA from Lactobacillus acidophilus grown in the logarithmic and in the stationary phases has been estimated. At the generation cycle of two hours the half‐life of sRNA is 3 to 4 hours during the logarithmic phase, and 10 to 12 hours during the stationary phase.
Effects of Carbon Source, Gibberellins and Ethylene on Wall‐Bound Invertase Activity in Callus of Convolvulus arvensis
Authors: KLIS F. M. , de GROOT C. , VERWER R.
Published: April 2006

The growth rate of Convolvulus callus on a sucrose‐containing medium appeared to be largely independent of the activity of cell wall invertase. The increase of this enzyme activity which occurs upon subculturing was unaffected within the first 24 h by the presence of the substrate sucrose. Neither substitution by glucose or fructose, nor complete deletion of the carbon source had any effect.

Gibberellins apparently were not involved in the initiation and/or control of the increase of wall‐bound invertase activity occurring upon subculturing. Exogenous ethylene was unable to mimick this effect of subculturing but when applied immediately after subculturing it had a synergistic effect on the increase of invertase. Inhibition occurred, however, when exposure to ethylene was delayed until after 24 h of incubation. These findings suggest a role of ethylene in the control of wall‐bound invertase activity.
Comparative Studies on Water Uptake and Water Permeability of Potato Tissue under the Effect of Indoleacetic Acid, Chloramphenicol and Actinomycin D
Authors: ÖNDER NURTEN
Published: April 2006

The water uptake of potato tuber tissue under the influence of chloramphenicol and actinomycin D was compared with that of indoleacetic acid. Both antibiotics decreased the water absorption as compared to the effect of indoleacetic acid. This decrease, in the early hours (3 to 6 h), is due to diminished water permeability. In the later period (6 to 48 h), it is instead a result of a reduction in wall extensibility.
The Uptake of 2‐Deoxy‐dGlucose by Isolated Ricinus Cotyledons
Authors: GUY MICHA , REINHOLD LEONORA
Published: April 2006

The uptake of the non‐metabolizable glucose analogue, 2‐deoxy‐d‐glucose (DOG) has been followed in isolated cotyledons of Ricinus communis L. Within 2 min of immersion in a labelled DOG medium, DOG phosphate (DOG‐P) was detectable in the tissue. DOG uptake was relatively rapid for 30 min after which it slowed down but nevertheless continued for many hours; DOG was eventually accumulated against a concentration gradient. Internal DOG‐P concentration also rose for the first 30 min, but then reached a plateau. The relationship between uptake and external concentration was close to linear during the first hour, and subsequently curvilinear.

Analysis of “wash‐out” curves indicated that after very rapid exit from the surface and free space of the tissue, the half‐time for exit of the remaining 85% of the absorbed DOG was approximately 250 min. By comparison, the half‐time for exit of sorbitol was 30 min. No DOG‐P could be detected in the wash‐out solutions.

When cotyledons were transferred to labelled medium after preloading in non‐labelled DOG, the specific activity of the internal DOG pool rose faster than that of the DOG‐P. Both curves flattened out when their specific activity was less than half that of the external medium. Addition of d‐glucose to the medium depressed DOG‐P formation, but only when the incubation period was less than 45 min.

Arguments are presented for concluding (a) that DOG uptake is mediated by a specific uptake mechanism; (b) that more than one internal DOG pool is involved; and (c) that the observed phosphorylation is not a necessary step in the entry process into either of the pools, whether the latter are in series or in parallel.
The Effect of Hadacidin on Bud Development and its Implications for Apical Dominance
Authors: LEE PETER KUNG‐WOO , KESSLER BEZELAL , THIMANN KENNETH V.
Published: April 2006

Hadacidin, which is known to inhibit the enzyme adenylo‐succinate synthetase, was applied locally to lateral buds on decapitated Pisum sativum L. plants. In controls the buds grew out normally, but the treated buds were almost completely inhibited. After a delay, the buds overcame the inhibition, and their subsequent outgrowth could be further hastened by the local application of a cytokinin. The inhibition, unlike that due to IAA, was not transported to a second bud, and it could be largely reversed by kinetin or dimethylallylaminopurine. Adenine itself produces little or no reversal, however. There was some reversal by aspartic acid, which is known to reverse, at least partially, the hadacidin inhibition of the isolated enzyme. It is deduced that lateral bud development is dependent on the synthesis of a cytokinin, which may take place by a biochemical route similar, but probably not identical, to that for adenine. It follows that this synthesis takes place locally in the bud itself.
Aspects of the Effect of ABA on the Water Status of Barley and Wheat Seedlings
Authors: MIZRAHI Y. , SCHERINGS S. G. , ARAD S. MALIS , RICHMOND A. E.
Published: April 2006

The effect of abscisic acid on plant growth and survival during water deprivation was studied in barley and wheat seedlings. Under conditions of both limited and ample water supply, treatment with abscisic acid greatly reduced transpiration and, in addition, suppressed root growth. In water‐deprived seedlings, abscisic acid increased the total dry matter, reflecting improved efficiency in water‐use. In addition, the growth period and survival of water‐deprived seedlings were markedly prolonged. In field trials, however, abscisic acid had no significant effect on waterdeprived seedlings. Possible reasons for this lack of response are discussed.
Qualitative Characterization of Some Peptides Inducing Morphogenesis in the Nematode‐ Trapping Fungus Arthrobotrys oligospora
Authors: NORDBRING‐HERTZ BIRGIT , BRINCK CARITA
Published: April 2006

Some peptides inducing capture organ formation in Arthrobotrys oligospora were characterized with regard to their amino acid contents. The N‐terminal, C‐terminal and total amino acids were determined as their dinitrophenyl‐derivatives by thin layer chromatography on silica gel in two different solvents. The amino acid composition was further confirmed by gas‐liquid chromatography.

The peptides investigated had a high proportion of non‐polar and aromatic residues. Thus, leucine, isoleucine, valine, proline, and tyrosine were present in all the peptides. In addition, phenyl‐alanine, glycine, and alanine occurred in some preparations. Tyrosine, valine, and phenylalanine were found in N‐terminal position, and leucine or isoleucine were C‐terminals.
Redistribution of Potassium, Calcium, Magnesium, and Manganese in the Plant
Authors: VAN GOOR B. J. , WIERSMA D.
Published: April 2006

The extent of redistribution in apple was described by calculating the fruit/leaf ratio of the cation content. It was found that the redistribution diminishes in the sequence K > Mg > Ca ∼ Mn. These results are more or less in agreement with those found elsewhere.

Investigations were made to see whether it was possible to account for the differences in redistribution by the phloem by means of the solubility of these cations in the sieve tube sap. As model plants Yucca flaccida and Ricinus communis were used, plants from which it was possible to obtain phloem sap in a rather pure state. It was found that the addition of potassium and magnesium as a chloride in the usual investigated range of concentrations did not give precipitation. With calcium and manganese, however, a precipitate soon occurred. Manganese was demonstrated to be less soluble than calcium. For Ricinus the maximum amount of calcium and manganese the sieve tube sap could contain before precipitation set in was higher than for Yucca sap.

The results confirm the possibility that the redistribution of the different cations in the plant can be related inter alia to their solubility in the sieve tube sap.

It was also found that the calcium in the phloem sap is present in ionic condition. Thus the normal laws of solubility should be applicable.
Resistance and Sensitivity of Chloroplast Ribosomes to Streptomycin in Mutants of Chlamydomonas reinhardi
Authors: BOSCHETTI ARMINIO , NIGGLI VERENA , OTZ URSULA , WIEDMER THERESE
Published: April 2006

In a mendelian (sr3) and an uniparental (sr35) streptomycin resistant mutant of Chlamydomonas reinhardi the influence of streptomycin on protein synthesis on the chloroplast and cytoplasmic ribosomes was investigated in vitro. Hetero‐, mixo‐ and phototrophic agar cultures and heterotrophic liquid cultures were used.

Protein synthesis on the cytoplasmic ribosomes, measured by the activity of glyceraldehyde‐3‐phosphate: NADP dehydrogenase (EC 1.2.1.9), was not inhibited, but rather stimulated by streptomycin.

Protein synthesis on the chloroplast ribosomes of sr3, measured by the activity of ribulose‐1,5‐diphosphate carboxylase (EC 4.1.1.39), was greatly inhibited by streptomycin, especially in hetero‐ and mixotrophic cultures. In sr35 the chloroplast ribosomes were resistant to streptomycin.

Heterotrophically grown cultures of sr3 and of a streptomycin‐sensitive strain are yellow in the presence of streptomycin and form no or only reduced thylakoids on solid media. But 70‐S organelle‐ribosomes are present in a normal amount.

The relationship between chloroplast protein synthesis and thylakoid formation is discussed.
L'Indole et le Tryptophane “régulateurs” de croissance, en culture “in‐vitro”, pour les tissus de parenchyme médullaire de Tabac, normaux et tumoraux
Authors: BEAUCHESNE GILDAS
Published: April 2006

Indoleacetic acid, tryptophan and indole promote growth of pith tissues of tumorous Nicotiana glauca×N. langsdorffii amphidiploïd hybrid, but only indoleacetic acid gives the potentiality of continuous development to the tumorous tissues after some days of contact on a medium without growth substances. In combination with 6‐benzylaminopurine, tryptophan and especially indole are promoting substances like auxin for the non‐tumorous pith tissues of tobacco, and allow a considerable organogenesis.
The Regulatory Role of the Embryo on the Development of Isocitrate Lyase Activity during Germination of Ponderosa Pine Seeds
Authors: BILDERBACK D. E.
Published: April 2006

The specific activity of isocitrate lyase rapidly increased in the megagametophytic tissue of cold‐stratified seeds of ponderosa pine (Pinus ponderosa Laws) prior to and after germination. When the embryo was removed at germination, isocitrate lyase activity continued to develop. However, in the total absence of the embryo, only a small increase in the specific activity of the enzyme was observed. The development of the enzyme was inhibited by cycloheximide, actinomycin D and abscisic acid.

The embryo produced an unidentified factor which enhanced the development of isocitrate lyase activity in the megagametophytic tissue. This embryo factor could not be replaced by the hormones indoleacetic acid (IAA), gibberellic acid (GA3) or benzylaminopurine (BA). Indoleacetic acid had little effect upon enzyme development. Gibberellic acid and benzylaminopurine inhibited isocitrate lyase development in the megagametophytic tissue of the seed.
Stimulation by Ethylene of Axis and Hypocotyl Growth in Bean and Cocklebur Seedlings
Authors: GOTÔ N. , ESASHI Y.
Published: April 2006

Effects of ethylene on the elongation of bean (Phaseolus vulgaris) embryonic axes and hypocotyls, and of cocklebur (Xanthium pennsylvanicum) hypocotyls were studied. In the bean axes, exogenous ethylene was promotive in stimulating longitudinal growth during the early germination period, but thereafter it turned inhibitive. This transition of the ethylene action is likely involved in the appearance of newly differentiated tissues in the hypocotyl, which are negatively sensitive to the gas. The ethylene stimulated elongation of the axes was hardly affected by light or by the presence of the cotyledons. In the bean hypocotyl segment unit, elongation was stimulated by ethylene in its limited zone, when the concentration of ethylene and the exposure times to ethylene were adequate (0.3 to 30 μl/l, 6 to 8 h): Elongation in the much younger region near to the elbow was inhibited by ethylene treatment, whereas the treatment of the upper region of the shank with ethylene finally resulted in significantly increased growth as compared to the untreated controls. In the continuing presence of ethylene over 3 days, the elongation of every region was retarded markedly and radial growth was induced in most regions of the shank from just below the elbow. These ethylene responses occurred independently of red light irradiation, but the ethylene promotion of elongation was lost by shortening the segment height, by removing the hook portion from the segment unit, or with its natural disappearance as a result of ageing. Fundamentally, similar effects of ethylene was observed in cocklebur hypocotyls.
Agglutinating Effects of Concanavalin A on Isolated Protoplasts of Daucus carota
Authors: GLIMELIUS KRISTINA , WALLIN ANITA , ERIKSSON TAGE
Published: April 2006

The agglutinating effects of Concanavalin A (Con A) on protoplasts isolated from cell suspensions of Daucus carota were studied. Con A was shown to agglutinate the plant protoplasts in a manner similar to the way some animal cells are agglutinated. The agglutination process is dependent on the Concanavalin A concentration, protoplast density, treatment time, the temperature, and the membrane condition, α‐D‐Methylgluco‐pyranosid completely inhibited Con A induced agglutination. The results are discussed in relation to membrane structure and morphology.
Endogenous Sugar Levels and Their Effects on Root Formation and Petiole Yellowing of Detached Mustard Cotyledons
Authors: LOVELL P. H. , ILLSLEY ANN , MOORE K. G.
Published: April 2006

Detached cotyledons of Sinapis alba rooted readily in water in petri dishes in the light. The addition of (6 × 10−2M) galactose, mannose or 2‐deoxy‐D‐glucose to the culture medium proved toxic to cotyledon growth. Of the other sugars tested that were not toxic, sucrose was the most inhibitory to root formation and increased petiolar yellowing to the greatest extent. Glucose was more inhibitory than fructose which in turn increased petiolar yellowing more than methyl‐D‐glucose.

Sucrose, glucose, or fructose at 6 × 10−2M in the culture medium gave rise to very substantial increases in the cotyledon petiole of reducing sugar and starch with smaller increases in sucrose. Methyl‐D‐glucose had much less effect on internal sugar levels. It was found that the higher the internal level of glucose the more rapid the rate and final extent of petiolar yellowing. In general, the degree of petiolar yellowing was inversely related to the ability of the cotyledon to root. Methyl‐D‐glucose differed from the other sugars in that it delayed and reduced root formation but had very little effect on petiolar yellowing.
Induction of Isocitrate Lyase in Synchronous Cultures of Chlorella fusca
Authors: AASBERG KARL ERIK , LIEN TORLEIV , KNUTSEN GJERT
Published: April 2006

Isocitrate lyase (ICL) of Chlorella was induced with acetate, and induction kinetics followed in autospores and 6 h old cells of a synchronous culture.

The enzyme could not be induced in illuminated cells. With both cell types 1.2 mM acetate was the optimal inducer concentration. Freeze‐thawed cells and acetone powders were used for measurement of activity. With the former the time course of increase in activity was different at the two cell ages. With 6 h old cells the activity fluctuated: There was first a period of increase, then one with decrease and again one of increase. No such variation was found with freee‐thawed autospores or with acetone powders of both cell stages. Darkening 6 h old cells for different periods of time before induction reduced the peak of activity, leaving the rate of the third phase unchanged. Illumination of darkened cells before induction increased the peak. Increasing the duration of both treatments increased their respective effects.

Acetone extracts taken at different times after start of induction inhibited the ICL activity of a test preparation. The inhibition decreased concurrently with the variation in the ICL activity‐found‐when freee‐thawed cells were used in the enzyme assay.

The inducibility, taken as the rate of the third phase, was measured at different times during the 24 h synchronous cycle. Using three different acetate concentrations and both methods of cell preparation, we found that the inducibility was constant for 17 h whereafter it increased rapidly to a final level.
Embryogenesis and Organogenesis in Pumpkin Explants
Authors: JELASKA SIBILA
Published: April 2006

Embryogenic callus was induced by culturing explants of pumpkin hypocotyls on Murashige‐Skoog‐medium with the addition of 3% glucose and one of the following growth substances (or combinations of them): β‐indolylbutyric acid, 2,4‐dichlorophenoxyacetic acid, β‐indolylacetic acid, α‐naphthyl‐acetic acid, adenine (natural), kinetin, autoclaved water‐melon sap and yeast extract (Difco). A large number of embryoids and adventive buds were produced. These were able to develop to normal plants.

The 17 strains of embryogenic tissue obtained have maintained their embryogenic characteristics for more than 3 years. The induction of embryogenic callus in pumpkin seems to be strongly dependent on the genetic constitution of each individual plant.
Relationship of Auxin Transport to Branch Dimorphism in Cordyline, a Woody Monocotyledon
Authors: FISHER J. B. , BURG S. P. , KANG B. G.
Published: April 2006

Lanolin containing 3H‐IAA was applied to apical cut ends of stem segments and decapitated plants of Cordyline terminalis, a monocotyledon possessing true secondary growth. Distribution of extracted label showed that: 1) in horizontal stems up to 7 times as much label accumulates in the lower surface compared to the upper surface, and this ratio increases with distance from the cut apical surface; 2) in upright stems most label (62%) occurs in the cambial and cortical regions, external to the primary and secondary vascular tissues; and 3) in upright stems having the cambium and cortical regions removed by a girdle, label accumulates above the girdle (c. 10 times greater than the control). These data are in accord with a theory of branch dimorphism derived from morphological studies, which suggested that high auxin levels initiate and maintain rhizomes and low levels initiate leafy shoots.
Multiphasic Uptake of Sulfate by Barley Roots
Authors: HOLMERN KARI , VANGE MARTA S. , NISSEN PER
Published: April 2006

Uptake of sulfate by excised barley roots increases upon their washing in aerated water or dilute CaCl2 solutions. Washing increases the values for Vmax and the sulfate concentrations required for transition between the lower phases, but the KM‐values remain essentially constant. At low sulfate concentrations, phase transitions do not occur in the absence of calcium or other divalent cations. These ions are about equally effective in enhancing short‐term sulfate uptake. Phase transitions were not principally altered by sulfhydryl or protein reagents. These concentration‐dependent transitions appear unrelated to temperature‐dependent phase transitions as evidenced by similar multiphasic patterns at low and high temperature.
The Excretion of the β‐Carboline Alkaloid Harman in Passionfruit
Authors: COPELAND L. , SLAYTOR M.
Published: April 2006

By feeding (methylene‐14C)‐L‐tryptophan, a biosynthetic precursor of the alkaloid harman, to Passiflora edulis it can be shown that the concentration of (3‐14C)‐harman initially increases and then decreases. By feeding (3‐14C)‐harman, the decrease has been further investigated and found to be due to excretion and not catabolic reactions.
The Effect of CO2‐Concentration on the Occurrence of a Number of Acids from the Citric Acid Cycle in Tomato Leaves
Authors: MADSEN ERIK
Published: April 2006

Examination of the effect of CO2‐concentration and time of day on the content of malic acid, citric acid, aconitic acid, isocitric acid, succinic acid and fumaric acid in tomato leaves, revealed that the total content of these acids will rise with the CO2‐concentration up to 0.10 vol% CO2. In the morning up to 0.22 vol% CO2 was needed for optimal effect.

Samples of leaves picked at 1 a.m. showed the lowest content of these acids. At 9 a.m. the content had increased, and at 4 p.m. the increase was considerable. The content of malic and citric acid constituted 36 and 34% of the total acid content. In the afternoon and the night the aconitic acid represented 14% and in the morning 20% of the total acid content. Isocitric acid, fumaric acid and succinic acid occurred only in relatively small concentrations.
Supraoptimal Temperature Effects upon Agrostis palustris
Authors: DUFF D. THOMAS , BEARD JAMES B.
Published: April 2006

Agrostis palustris turfs cut weekly at 1.3 cm were subjected to successive four‐week periods with day‐night temperature regimes of 20–10, 25–15, 30–20, 35–25 and 40–30°C. Plants grown at 40–30°C exhibited a growth character distinctly different from those grown at 20–10°C. They were more upright and bristle‐like in growth habit. The percentage dry weight of leaf blade tissue increased 67% and weight per unit area increased 53% between 20–10 and 40–30°C. Reduced leaf blade width was noted first at 30–20°C while leaf blade length reduction first occurred at 35–25°C. Weekly yields were significantly reduced at the supraoptimal temperature regimes of 35–25 and 40–30°C. Chlorophyll content was lowest at 20–10 and 40–30°C, the lowest and highest temperature regimes studied. Shoot density appeared to decrease under the 35–25°C regime, but no dead plants were observed. The apparent decrease in shoot density was attributed to the upright growth habit. Density decreased at 40–30°C upon death of individual plants. A community of grass plants maintained as a turf was found to change in form quite rapidly in response to temperature.
Nitrite Uptake by Nitrogen‐Depleted Wheat Seedlings
Authors: JACKSON W. A. , JOHNSON R. E. , VOLK R. J.
Published: April 2006

Intact, 14‐day‐old nitrogen‐depleted wheat (Triticum vulgare cv. Blueboy) seedlings were exposed to solutions of 0.5 mM KNO2, 0.05 mM CaSO4 and 1 mM sodium 2‐[N‐morpholino]‐ethanesulfonate, pH 6.1. Nitrite uptake was determined from depletion of the ambient solution or from incorporation of 15N in the tissue. An initial nitrite uptake shoulder was followed by a relatively slow uptake rate which subsequently increased to a substantially greater rate. This accelerated phase was maintained through 24 h. Nitrite accumulated to a slight extent in the root tissues during the first few hours but declined to low values when the accelerated rate was fully developed, indicating an increase in nitrite reductase activity paralleling the increase in nitrite uptake capacity. About 50% of the nitrogen absorbed as nitrite was translocated to the shoots by 9–12 h.

Development of the accelerated nitrite uptake rate was restricted in excised roots, in intact plants kept in darkness, by 400 μg puromycin ml−1 and by 1 mM L‐ethionine. When puromycin and L‐ethionine were added after the accelerated phase had been initiated, their effects were not as detrimental as when they were added at first exposure to KNO2. The two inhibitors restricted translocation more than uptake. The data indicate an involvement of protein synthesis and a requirement for movement of a substance from shoots to roots for maximal development of the accelerated nitrite uptake phase. A requirement for protein synthesis in the transport of soluble organic nitrogen from roots to shoots is also suggested.
Endogenous Growth Substances in Normal and Dwarf Mutants of Cortland and Golden Delicious Apple Shoots
Authors: JINDAL K. K. , DALBRO S. , ANDERSEN A. SKYTT , POLL LEIF
Published: April 2006

Endogenous growth substances in the shoots of dwarf mutants of Cortland (Cortland 65–6 and Cortland 65–7) and Golden Delicious (Golden Auvil Spur and Yellow Spur) were investigated in relation to dwarfism. The shoots were extracted at three stages of growth, namely: 1) rapid elongation growth, 2) formation of terminal bud, and 3) cessation of cambial growth. The growth substances were partially separated by thin layer chromatography and bioassayed using the Avena first internode and Lepidium seed germination tests.

Shoot extracts from the normal Cortland and Golden Delicious plants contained higher levels of auxins at all stages of growth than those from dwarf mutants. Growth‐promoting activity was found in two zones on chromatograms developed with isopropanol: ammonia: water (10:1:1 v/v/v):Rf 0.4 to 0.5 and Rf 0.8 to 0.9.

The Lepidium seed germination test showed the presence of a highly inhibitory zone between Rf 0.3 and 0.4 in the extracts of dwarf and normal plants. However, the peak of germination inhibition activity was sharp for dwarf mutants and less for extracts of normal growing plants at 3 stages of growth. The inhibitory substance(s) was further purified on TLC plates by successive separations in different solvent systems. Two substances which inhibited the Lepidium seed germination were found, one close to the Rf value of synthetic abscisic acid and the other appeared to be similar to xanthoxin in Rf value, biological activity and UV absorption spectra.
Chloroindolyl‐3‐acetic Acid and Its Methyl Ester Incorporation of 36Cl in Immature Seeds of Pea and Barley
Authors: ENGVILD K. C.
Published: April 2006

Immature seeds of pea and barley were harvested on plants grown in solutions containing 36Cl−, but no other chlorides. Autoradiography of two‐dimensional thin layer chromatograms (silicagel) of butanol extracts of freeze‐dried seeds showed the presence in both species of several radioactive compounds besides Cl−. One compound, present in pea and probably in barley, cochromatographed with a mixture of 4‐ and 6‐chloroindolyl‐3‐acetic acid methyl esters. Another, detected in pea, but probably not in barley, cochromatographed with a mixture of 4‐and 6‐chloroindolyl‐3‐acetic acids.
Proteinase Inhibitors in Germinating Barley Embryos
Authors: KIRSI MARKKU
Published: April 2006

The activities of trypsin inhibitors and Aspergillus‐proteinase inhibitors have been assayed in barley embryos germinating in different conditions.

The Aspergillus‐proteinase inhibitor activity increased about 20‐fold during 6 days at 20°C both in separated embryos germinating on nutrient agar and in the embryos of undissected grains germinating on agar with or without mineral salts. Significant inhibitor activity was also present in root tips at later stages of vegetative growth. Whether any changes occurred in the molecular weight distribution of the inhibitors present in the seedlings was studied by gel filtration on Sephadex G‐75; only minor changes were observed.

The trypsin inhibitor activity per seedling remained roughly constant in all cultures. In gel filtration experiments all the activity appeared to be due to the inhibitor species present in resting embryos.
Field Studies of Photosynthesis as Affected by Water Stress, Temperature, and Light in Birch
Authors: HARI PERTTI , LUUKKANEN OLAVI
Published: April 2006

This study continues the investigations previously conducted as laboratory experiments. The results from the present study confirm our earlier observations made on alder seedlings concerning the effect of water stress, temperature and light on the net uptake of CO2.

A variable that we could call the physiological water stress is proposed as a measure of the intrinsic factor of photosynthesis during and after drought. A physiological water stress builds up and discharges slowly and interacts strongly with temperature. Our model for the effects of physiological water stress, temperature, and light intensity explains satisfactorily the net uptake of CO2 in birch in the field. Thus, our earlier results concerning the effects of physiological water stress on photosynthesis are not artifacts generated by the unnatural laboratory environment.
Nitrite Uptake Patterns in Wheat Seedlings as Influenced by Nitrate and Ammonium
Authors: JACKSON W. A. , JOHNSON R. E. , VOLK R. J.
Published: April 2006

Nitrite and nitrate uptake by wheat (Triticum vulgare) from 0.5 mM potassium solutions both showed an apparent induction pattern characterized by a slow initial rate followed by an accelerated rate. The accelerated phase was more rapid for nitrate uptake, was initiated earlier, and was seriously restricted by the presence of equimolar nitrite. The accelerated phase of nitrite uptake was restricted by nitrate to a lesser extent. The two anions seem not to be absorbed by identical mechanisms.

Ammonium pretreatments or prior growth with ammonium had relatively little influence on the pattern of nitrite uptake. However, prior growth with nitrate eliminated the slow initial phase and induced development of the accelerated phase of nitrite uptake. A beneficial effect was noted after 3 h nitrate pretreatment and full development had occurred by 12 h nitrate pretreatment. The evidence suggests that a small amount of tissue nitrite, which could be supplied either by absorption or by nitrate reduction, was specifically required for induction of the accelerated phase of nitrite uptake.

Cycloheximide (2 μg ml−1) seriously restricted development of the accelerated phase of nitrite uptake, but its effect was not as severe when it was added after the accelerated phase had been induced by prior exposure to nitrite or nitrate. However, translocation of 15N from the absorbed nitrite was sharply decreased under the latter conditions, indicating a difference in sensitivity of the uptake and translocation processes to cycloheximide.

Potassium uptake was greater from KNO3 than from KNO2 and in both instances it was enhanced during the early stages of the accelerated phase of anion uptake. Moreover, addition of NaNO3 to KNO2 substantially increased potassium uptake. A coupling between anion and potassium uptake was therefore evident, but the coupling was not obligatory because the accelerated phase of nitrite uptake could occur in absence of rapid potassium uptake.
Action du diméthylsulfoxyde sur l'absorption du 42K et du glucose‐14C (U) par des disques foliaires de Zea mays et Pelargonium zonale
Authors: CHAMEL ANDRÉ , CARLIER GEORGES
Published: April 2006

42K and 14C (U)‐glucose uptake by foliar discs of maize (Zea mays L.) and pelargonium (Pelargonium zonale L.) is inhibited by dimethyl sulfoxide (DMSO) at concentrations of 5 and 10%. This effect increases with the duration of the absorption and appears with varied concentrations in K or glucose. In most cases, this inhibitory effect is less with aged discs than with freshly cut discs. Besides, the DMSO (10%) enhances the exsorption of 42K by foliar discs of maize. The effects of DMSO and two osmotic agents, mannitol and polyethylene glycol 1000, on the uptake and water content of discs are compared. It seems that the effect of DMSO on the uptake is not only an osmotic effect. It may also be related to other actions of this substance in affecting an active uptake.
Properties of Mg2+‐Stimulated and (Na++K+)‐Activated Adenosine‐5′‐Triphosphatase from Sugar Beet Cotyledons
Authors: KARLSSON JAN , KYLIN ANDERS
Published: April 2006

Sugar beet leaf homogenate contains Mg2+‐stimulated ATPase activity with the highest specific activity in the 25,000–30,000 ×g‐fraction. This fraction also has (Na++ K+)‐activated ATPase activity. Both activities have two pH optima, one stable at pH 7.9 and one variable at lower pH. When optimal conditions of Na+ and K+ were tested with 64 combinations of these ions, at least two mountains of activity were revealed.

The (Na++ K+)‐ATPase had a high specificity for ATP. It had lost about 50% of its original activity after 56 days of storage at −85°C. The activity drop was most pronounced at high ionic concentrations in the test medium.

The (Na++ K+)‐ATPase shows four peaks of activity when tested at constant ionic strength. The idea is put forward that the four peaks reflect two ATPases, one in the tonoplast and one in the plasmalemma, which undergo conformational changes in relation to the ionic milieu.
Raising the Maximum Permissible Air Velocity in Controlled Environment Plant Growth Chambers
Authors: O'LEARY JAMES W. , KNECHT GEORGE N.
Published: April 2006

Phaseolus vulgaris L. plants were grown in two naturally lighted, outdoor controlled environment plant growth chambers. The approach velocity to the plant growing zone was 75 cm s−1 in one chamber and 225 cm s−1 in the other. The lower air velocity represents the presently considered maximum permissible air velocity in controlled environment plant growth chambers. The humidity in both chambers was near saturation. After three weeks' growth in these chambers, there were no significant differences in fresh or dry weights of the plants or any parts thereof. The high air velocity reduced the transpiration rate as predicted by energy budget considerations and significantly lowered the average leaf temperature of the crop by three degrees. The data strongly support the hypothesis that the maximum permissible air velocity in controlled environment plant growth chambers can be raised considerably if the humidity is maintained high.
A Proposal for the Use of Standardized Methods for Chlorophyll Determinations in Ecological and Eco‐physiological Investigations
Authors: LINDER SUNE
Published: April 2006

The various methods for chlorophyll determination, found in the literature, may give chlorophyll values differing by as much as 20%. Not only the choice of solvent and equations but also the routines and conditions for processing of samples can be large sources of errors.

In the present paper some recommendations are given concerning sampling and storage of plant material, extraction and determination of chlorophylls.

A simple and fast method for chlorophyll determinations is described and recommended as a suitable method for most ecological and eco‐physiological investigations in which chlorophylls are determined. The principle of the method is that the total amount of chlorophylls is determined in a colorimeter calibrated for chlorophyll measurements. Results from a prototype of the “Chlorophyllometer” are presented and compared with spectrophotometric determinations.
Induced Heat Sensitivity of Wheat Roots and Protecting Effect of Ethanol and Kinetin
Authors: SKOGQVIST INGRID
Published: April 2006

Wheat seedlings were subjected to heat shock for 2 min at 45°C. The seedlings were then incubated at 25°C or higher temperatures (usually 35°C). At 25°C the root tips survived the heat shock, but not at temperatures above 34°C, unless they had been pretreated with ethanol or kinetin, After 1 h in ethanol and after more than 15 h in kinetin the root meristem survived a high incubation temperature after the heat shock. Immediately after heat treatment the glyceride content in treated root tips was higher than in untreated roots. The same was observed after heat treatment of root tips pretreated in ethanol and kinetin. The content of ether extractable lipids was not changed by the heat shock.
Release of Volatile Mercury from Vascular Plants
Authors: SIEGEL S. M. , PUERNER N. J. , SPEITEL T. W.
Published: April 2006

Volatile, organic solvent soluble mercury has been found in leaves and seeds of several angiosperms. Leaves of garlic vine (Pseudocallyma alliacium), avocado (Persea americana) and haole‐koa (Leucaena glauca) release mercury in volatile form rapidly at room temperature. In garlic vine, the most active release is temperature dependent, but does not parallel the vaporpressure temperature relationship for mercury. Mercury can be trapped in nitric‐perchloric acid digestion fluid, or n‐hexane, but is lost from the hexane unless the acid mixture is present. Seeds of haole‐koa also contain extractable mercury but volatility declines in the series n‐hexane (90%) > methanol (50%) > water (10%). This suggests that reduced volatility may accompany solvolysis in the more polar media. Gas chromatographic analysis shows that the volatile compound is not dimethyl mercury.
Cytokinins in Xanthium strumarium: A Rapid Response to Short Day Treatment
Authors: HENSON I. E. , WAREING P. F.
Published: April 2006

Following a single inductive short day, cytokinin activity in extracts of leaf laminae, buds and root exudate of Xanthium strumarium L. (as measured by the soybean callus bioassay) declined to between 10 and 25% of the level detected under long‐day conditions. Additional inductive cycles, up to five, produced little further change. Cytokinin activity of petiole extracts fluctuated and did not decline to the same extent as that of leaf laminae, buds or exudate.
Diurnal Cycling in Root Resistance to Water Movement
Authors: PARSONS LAWRENCE R. , KRAMER PAUL J.
Published: April 2006

The occurrence of diurnal changes in root resistance of cotton was studied by measuring the flow of water through 35‐to70‐day‐old root systems under a pressure of 3.10 bars or a vacuum of 0.88 bar. The volume of exudate obtained under constant pressure or constant vacuum was 2 to 3 times greater near midday than near midnight indicating that the root resistance apparently was 2 to 3 times greater at night than during the day. The salt concentration of the exudate also cycled; the concentration was lowest at midday and highest at night, hence there was little diurnal variation in the total amount of salt moved per hour. The cycle for volume of exduate, salt concentration, and apparent root resistance had a period of 22 to 26 hours at 24°C. The cycle gradually died away 2 to 3 days after removal of the shoots.

The diurnal variations appeared to be controlled by signals from the shoots because the phase of the cycles could be reset by changing the light‐dark cycle under which the plants were grown. Cycling was eliminated by exposure to 8 or more days of continuous light before removing the shoots, and cycling could not be entrained by a 6 hour light‐6hour dark cycle. Bubbling nitrogen gas through the nutrient medium stopped cycling. A possible role of ion or growth regulator action is discussed.
Metabolism‐linked Binding of Rubidium in the Free Space of Wheat Roots and its Relation to Active Uptake
Authors: IGHE ULF , PETTERSSON SUNE
Published: April 2006

Components of the initial uptake and active transport of rubidium were studied in potassium‐starved and potassium‐rich wheat plants. A metabolism‐linked component of the initial uptake in the root was identified by means of DNP‐treatment. It was shown that there is a direct proportionality between the magnitude of the metabolism‐linked component of the initial uptake and the rate of active uptake.

It is suggested that, in the free space, this metabolism‐linked ion binding represents an initial step of the active ion transport preceding the subsequent carrier‐mediated transport across the plasmalemma.
Iron Deficiency in the Blue‐Green Alga Anacystis nidulans: Changes in Pigmentation and Photosynthesis
Authors: ÖQUIST GUNNAR
Published: April 2006

Phycocyanin‐free photosynthetic lamellae (PSI‐particles) were prepared from Anacystis nidulans, grown in complete and iron‐deficient media. French press treatment and fractionated centrifugation were used. Absorption studies of the particles revealed an iron deficiency‐induced shift of the main red chlorophyll a absorption peak from 679 to 673 nm as reported before for whole cells. The shift may reflect a changed distribution between different chlorophyll a forms. Action spectra for photo‐oxidation of mammalian cytochrome c with photosynthetic lamellae revealed an iron deficiency‐induced shift, corresponding to that found in the absorption spectra. As photo‐oxidation of cytochrome c is mediated by PSI, it is believed that chlorophyll a also after the shift towards shorter wavelengths, is active in PSI.

A decreased photosynthetic capacity of PSI, due to iron deficiency, was shown by time course studies of photosynthetic oxygen evolution, by photo‐oxidation studies of P700 and mammalian cytochrome c, by photo‐reduction studies of NADP and by combined studies of light‐induced and chemical oxidation of P700. The ration chlorophyll a/700 was also determined for whole cells, lyophilized cells and PSI‐particles. Iron deficiency caused an increased ratio in all studied fractions. The results of this work imply that energy is transferred with less efficiency within the photosynthetic units of PSI in iron‐deficient A. nidulans than in iron‐supplied algae.
Sorbitol in Tracheal Sap of Apple as Related to Temperature
Authors: WILLIAMS M. W. , RAESE J. T.
Published: April 2006

The influence of dormant‐season temperatures on levels of sorbitol was determined in an effort to provide further information on the possible role of sorbitol in dormancy of apple tress (Malus sylvestris Mill.). Two‐year‐old shoots were collected throughout the dormant season; sorbitol and sugars were determined in tracheal sap extracted under vacuum and in ground dried wood extracted in a soxhlet apparatus. Sorbitol and sugar trimethylsilyl derivatives were detected by gas chromatography. Levels of sorbitol in the sap generally increased during subfreezing temperatures and decreased during warm periods throughout the dormant season. Early peak increases in sap sorbitol appeared to coincide with the beginning of leaf senescence. Postharvest levels of reducing sugars, sorbitol, and particularly sucrose in the wood, increased as the temperature decreased during the dormant season, and the sugar levels decreased with warming temperatures in the spring. Our data indicate that sorbitol and sucrose are important reserves of storage carbohydrates in resting apple trees.
Titration of Photophosphorylation, Oxidative Phosphorylation and Glycolysis in Scenedesmus with Desaspidin: Regulation between Pathways and Sites for Photophosphorylation
Authors: KYLIN ANDERS , OKKEH ASSAD
Published: April 2006

Narrow concentration intervals were used, covering 10−6– 10−4M desaspidin. The interaction with glycolysis involves three steps, the inhibitor constants (Ki:s) being in turn 2.7 × 10−5M, 1.3 × 10−4M, and high. About 18% of total glycolysis is inhibited in each of the two first steps, and 65% left for the third reaction. After compensation for glycolysis, oxidative phosphorylation may show a sudden jump to about 10% inhibition at 1.5 × 10−5M desaspidin, the possible Ki of the reaction starting here being very high. Correcting for glycolysis, desaspidin affects total Photophosphorylation in two steps, with the Ki values of 7.8 × 10−5M and 4.6 × 10−4M respectively. Inhibition in the first step is about 27% of the total photophosphorylation.

By applying 10−6M DCMU[/3‐(3, 4‐dichlorophenyl)‐l, l‐dimethy lurea], one can abolish non‐cyclic photophosphorylation. Desaspidin then reacts in a single step with a Ki of 1.4 × 10−4M. At 5 × 10−5M DCMU, also the pseudocyclic photophosphorylation is abolished. The remaining, true cyclic photophosphorylation has a single Ki of 2.3 × 10−5M for desaspidin.

Under non‐cyclic conditions, the true cyclic process contributes about 25% to total Photophosphorylation. Under pseudocyclic conditions, no cyclic photophosphorylation occurs. Under true cyclic conditions, the non‐cyclic and pseudocyclic processes are inoperative. This indicates a regulative system, so that either (1) the (non‐cyclic + true cyclic), (2) only the pseudocyclic, or (3) only the true cyclic systems can be traced, dependent on the level of DCMU applied. There are two sites for non‐cyclic Photophosphorylation, one of them common to the pseudocyclic pathway. Cyclic photophosphorylation has a third site, different from the other two.
Carbohydrate Availability and Shoot Formation in Tobacco Callus Cultures
Authors: THORPE TREVOR A.
Published: April 2006

Tobacco callus grown on a shoot‐forming medium containing sorbitol or no carbon source survived, but did not produce shoots. Transfer of tissue from a sucrose medium to carbohydrate‐deficient media and vice versa suggested that the growth of the tissue was a function of a total period in contact with available carbohydrate. Both starch and free sugars in the tissue were utilized during shoot initiation. Furthermore, it appeared that the continuous availability of carbohydrate was required for shoot primordium growth and/or their development into leafy vegetative shoots in dark‐grown cultures.
Carbohydrate Metabolism and Translocation in Healthy and Cocoa Swollen Shoot Virus‐Infected Cocoa Plants
Authors: ADOMAKO D. , HUTCHEON W. V.
Published: April 2006

Analyses of cocoa swollen shoot virus‐infected and healthy cocoa (Theobroma cacao L.) plant tissues were made to determine the effect of virus infection on the metabolism and transport of carbohydrates in affected plants. Starch, sucrose and reducing sugars were found to accumulate in infected tissues. Translocation of photosynthates (mainly as sucrose) to the stem and root system, as estimated by the overnight loss of carbohydrates from the leaves and by 14CO2 tracer experiments, was as efficient in the infected plants as in the healthy. Infected plants showed a higher diurnal turnover of carbohydrates in their leaves and, on unit leaf area basis, higher levels of 14C‐labelled assimilates suggesting that they have a greater photosynthetic capacity than the healthy plants. The rate of respiration, as determined by the proportions of organic acids, amino acids and other intermediary metabolites formed from translocated 14C‐labelled sugars, was generally higher in infected than in healthy plants. It is concluded from available data showing the presence in infected tissues of mineral nutrients, protein N and amino acids at the same concentrations as in healthy plants, and from the relatively high rates of photosynthesis and respiration that a high rate of metabolic activity is maintained in the host‐virus system. Some factors possibly contributing to the stunted growth of infected plants are discussed in the light of these findings.
Thermal Denaturation Properties of Deoxyribonucleic Acid and Chromatin during the Life Cycle of Spirogyra
Authors: SASAKI KIMIKO , TAKAYA KATSURO
Published: April 2006

Half melting temperature (Tm) of DNA prepared from the nuclear fraction of vegetatively growing cells of Spirogyra was 86°C in the standard saline‐citrate solution and 68°C in the dilute saline‐citrate solution, and the major Tm values of soluble chromatin were 68°C and 78–80°C in the dilute saline‐citrate solution. The Tm value of DNA prepared from the nuclear fractions of conjugating and zygote cells was 88°C in the standard saline‐citrate solution and 70°C in the dilute saline‐citrate solution, and the major Tm values of soluble chromatin were 72°C, 78–80°C, and 84°C in the dilute saline‐citrate solution. The Tm values of DNA prepared from cells arrested at different stages of the life cycle of Spirogyra were raised by combining with different fractions of histones. The results agreed with an altered structure of the nucleoprotein complex during the life cycle of Spirogyra.