bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of Freezing Damage in Apple Bark and Pine Needles
Authors: BERVAES J. C. A. M. , KETCHIE D. O. , KUIPER P. J. C.
Published: April 2006

The time course of freezing damage in pine needles and in bark of apple trees was followed at different subzero temperatures. From these data the killing rate by freezing was determined for trees which differed in degree of cold hardiness.

The activation energy of the killing reaction was also calculated. The killing rate was lowest in cold‐acclimated trees, but the activation energy of the killing reaction was very high indicating a high degree of structured water in the cells. Non‐acclimated trees showed uniform low values of the activation energy of the killing reaction at all subzero temperatures studied.

It is suggested that intracellular supercooling could be a part of the mechanism of frost protection in cold‐acclimated apple trees within the – 30 to – 20°C range, but not in the –20 to –10°C range.
Phytoluminography: Imaging Plants by Delayed Light Emission
Authors: SUNDBOM E. , BJÖRN L. O.
Published: April 2006

It is demonstrated that photographic images of plants can be produced in the absence of external illumination using an image intensifier. The image is produced by the weak delayed light emission (afterglow) from photosynthetically active chloroplasts.

We propose the use of such “phytoluminographs’ for the study and diagnosis at an early stage of disturbances due to parasites, mineral deficiency, herbicides, frost etc.
The Spectral Response of Light Dependent Chlorophyll b Formation
Authors: VIRGIN HEMMING
Published: April 2006

Dark grown seedlings of barley will obtain a high ratio chlorophyll a/chlorophyll b when exposed to intermittent light (1 min of incandescent light or one electronic flash every hour). Such material has been exposed to monochromatic light of different wavelengths for 1 h. The ratio a/b gets a minimum in light of 670 nm, indicating the highest rate of chlorophyll b formation at this wavelength. The possibility is discussed that the light absorber (and also precursor) could be a short‐lived chlorophyll a form, existing prior to the forms in the Shibata‐shift. Chlorophyll b formation in darkness is discussed from the findings that the rate of formation of chlorophyll b is higher in intermittent light than it should be, calculated from the rate in continuous light, where the saturation intensity is rather low.
The Role of Abscisic Acid in Flower Abscission of Lupinus luteus
Authors: PORTER N. G.
Published: April 2006

The role of abscisic acid in the control of flower abscission in Lupinus luteus L. was examined. Using a modified extraction and purification technique, endogenous abscisic acid levels in the upper flowers of an inflorescence were found to increase markedly some days before abscission could be detected. When abscisic acid was injected into flower‐bearing nodes or fed via the roots, no increase in the abscission rate was obtained at any position in the flowerhead. Application of abscisic acid to only the leaves resulted in a marked increase in flower abscission. The role of abscisic acid per se as a primary controlling factor of flower abscission in yellow lupin is questioned.
Site of in vivo Regulation of Tree Stem Elongation by Bark‐Banded Morphactins
Authors: NEUMANN PETER M. , BACKHAUS RALPH , DOSS ROBERT P. , SACHS ROY M.
Published: April 2006

Morphactin ester applied as a bark band to stems of Monterey pine seedlings (Pinus radiata D. Don) at first stimulated and then inhibited the rate of stem elongation over a 20‐day period. The inhibition was caused by a direct action of morphactin on the shoot rather than by indirect action on the root system. 14C labelled morphactin applied to the bark accumulated in the shoot apices and the amount accumulated could be related to the inhibition of growth. More than 70% of labelled material isolated from roots and shoot apices was in the form of a metabolite similar to the carboxylic acid derivative of the morphactin ester. A preparation of 14C labelled acid derivative applied to the bark was translocated to the shoot apex and to the roots and inhibited stem elongation.
Phytochrome Control of Longitudinal Growth and Phytochrome Synthesis in Maize Seedlings
Authors: DUKE STEPHEN O. , NAYLOR AUBREY W. , WICKLIFF JAMES L.
Published: April 2006

The active, far‐red light absorbing, form of phytochrome was found to inhibit growth and phytochrome levels in the mesocotyl and coleoptile of 4‐ to 5.5‐day‐old seedlings of Zea mays L. Short, low‐irradiance red or far‐red light treatments were used to produce different proportions of active phytochrome at the end of highdirradiance white‐light periods, which left different levels of total phytochrome in the plants. After light treatments which left relatively high levels of spectrophotometrically assayable phytochrome in the seedlings, apparent phytochrome synthesis in the subsequent dark period was low regardless of the proportions of each form of the pigment present at the beginning of the dark period. In light treatments producing relatively low levels of assayable phytochrome, levels of apparent phytochrome synthesis in both red and far‐red treatments and differences between apparent synthesis in red and far‐red treatments were maximal. No simple correlation was found between growth and apparent phytochrome synthesis. However, growth and total phytochrome levels were positively correlated in both organs. Using a subtractive method of correlation, in which only phytochrome effects were plotted, strong linear relationships between phytochrome levels or longitudinal growth and Pfr levels were found in those light treatments leaving greater than 8% of dark control levels of phytochrome in the tissues. Using this technique non‐linear, inverse relationships between Pfr and apparent phytochrome synthesis was found, indicating that modes of phytochrome control over phytochrome synthesis and growth differ. Our results are consistent with the view that in vivo assays of “bulk’ phytochrome reflect levels and states of the physiologically active phytochrome fraction under our experimental conditions in maize.
Photoautotrophic Growth and Photosynthesis in Cell Suspension Cultures of Chenopodium rubrum
Authors: HÜSEMANN WOLFGANG , BARZ WOLFGANG
Published: April 2006

A method is described for growing cell suspension cultures of Chenopodium rubrum photoautotrophically for prolonged periods of time. By using a two‐tier culture vessel the growth medium with the cells was separated from the CO2 reservoir. Definite CO2 concentrations were established by a K2CO3/KHCO3 buffer. Photoautotrophic growth in C. rubrum cell suspension cultures was correlated with the CO2 level. At 0.5% CO2 the cell cultures contained 68 μg chlorophyll/g fresh weight and showed an increase in fresh weight of about 80% in 18 days. At 1% CO2 an increase in fresh weight of 165% in 18 days was observed. The chlorophyll content rose up to 84 μg/g fresh weight.

The photoautotrophic growth was also greatly influenced by the 2,4‐D content of the medium. Cell growth was enhanced by lowering the auxin concentration. Best growth was attained (210% increase in fresh weight) at 10−8M 2,4‐D.

The photosynthetic activity of the cells was measured by the light dependent 14CO2 incorporation. At 0.5% CO2 the cell suspensions assimilated about 100 μmol CO2/mg chlorophyll × h. In the presence of 1% CO2 the light driven assimilation was raised up to 185 μmol CO2/mg chlorophyll × h. In both cases, the dark incorporation of CO2 was merely 1.8% of the values obtained in light.
Peroxidases in Relation to Removal of Dormancy and Germination of Apple Embryos
Authors: THÉVENOT CLAUDINE , GASPAR THOMAS , LEWAK STANISLAW , CÔME DANIEL
Published: April 2006

The changes in germination, peroxidase activity and isoperoxidase spectrum have been studied in apple embryos at 5°C (stratification) and at 20°C in the presence or absence of seed coats. The embryo dormancy is progressively released at 5°C, but not at 20°C. The peroxidase activity in embryos covered with seed coats is very low at 5°C as well as at 20°C which corresponds to a restricted number of isoenzymes. In isolated embryos the peroxidase activity increases significantly. This is due to an increase in both the number and the activity of the isoperoxidases and it is more pronounced at 20°C than at 5°C.

The obtained results suggest that the soluble peroxidases are not involved in the process of the release of embryo dormancy. The variations observed are attributed to the growth process following germination, which can occur even at low temperature.
Metabolisme du γ‐aminobutyrate chez Agaricus bisporus III. La succinate‐semialdehyde:NAD(P)+ oxydoreductase
Authors: BALDY PIERRETTE
Published: April 2006

Metabolism of γ‐Aminobutyrate in Agaricus bisporus. III. The Succinate‐Semialdehyde: NAD (P)+ Oxidoreductase.

The succinate‐semialdehyde:NAD(P)+ oxidoreductase (E.C. 1.2.1.16) is responsible for the second step in the catabolism of γ‐aminobutyrate: the irreversible enzymatic conversion of succinic semialdehyde (SSA) to succinate. Succinate semialdehyde dehydrogenase was extracted from mitochondrial fraction of fruit‐bodies of Agaricus bisporus Lge. The mitochondrial pellet was sonicated and centrifuged at 110,000 g; the supernatant obtained was designated the “crude extract”. The enzyme was extremely unstable on storage, unless 1 mM EDTA and 20% glycerol were added.

Kinetic studies were carried out at 30°C, and the formation of NADH or NADPH was followed by measuring increase of absorbance at 340 nm with a spectrophotometer. The dehydrogenase was completely inactive when the reaction was run in the absence of thiol and was more active with NAD+ than with NADP+. In the “crude extract” the activity with NADP+ had a pH optimum between 8.6 and 9.1 and the Km values for SSA and NADP+ were 2.0 × 10−4M and 1.4 × 10−4M respectively. The pH optimum with NAD+ was found between 8.6 and 8.8 and the Km value for SSA is 4.8 × 10−4M and for NAD+ 2.0 × 10−3M. With NAD+, the kinetic values (pH, Km) of the “crude extract” chromatographed on hydroxylapatite were unchanged. Inhibition by thiamine pyrophosphate (TPP) was uncompetitive with respect to NAD+, those by malate, ATP, ADP and NADPH non‐competitive and that by NADH competitive. These results and the fact that activity with NAD+ was lost more slowly than with NADP+ indicate the possibility of at least two mitochondrial succinate‐semialdehyde dehydrogenases, even though the activities of this enzyme assayed with NAD+ and NADP+ respectively were not able to be separated from each other by hydroxylapatite column chromatography.

Some speculations on the metabolic regulation of this dehydrogenase and considerations on the significance of these results in the physiology of respiration in Agaricus bisporus Lge are given.
The Influence of a Strong Reducing Agent upon the Initiation of Callus from the Germinating Seedlings of Gossypium barbadense
Authors: KATTERMAN FRANK R. H. , WILLIAMS M. DALE , CLAY WILLARD F.
Published: April 2006

Hard compact calluses were initiated from the cotyledons of germinating cotton seedlings (Gossypium barbadense L.) by use of a strong reducing agent (dithiothreitol) and a higher than normal concentration of an auxin, naphthalene‐acetic acid. Dithiothreitol was superior to other compounds such as ascorbic acid and polyvinyl‐pyrrolidone in preventing a toxic brown coloration of the initiated callus. After eight to ten subculturings, some of the hard callus tissues (c. 2 to 3%) proliferated into larger and faster growing cells.
Determination of Prenylquinones in Green Photosynthetically Active Moss and Liver Moss Tissues
Authors: LICHTENTHALER HARTMUT K. , KARUNEN PIRJO , GRUMBACH KARL H.
Published: April 2006

The prenylquinone composition of two species of mosses (Polytrichum formosum Hedw., Sphagnum acutifolium Ehrh.) and two species of liver mosses (Lunularia cruciata (L.) Dum., Pellia epiphylla (L.) Cord.) was determined and compared with the chlorophyll content and the photosynthetic activity of the intact moss and liver moss tissues.

Green moss and liver moss tissues possess in principle the same prenylquinone composition as higher plants with plastoquinone‐9, α‐tocopherol, α‐tocoquinone and the phylloquinone K1 as main components. On a chlorophyll basis the lipoquinone levels are lower than in higher plants. Differences among the individual mosses as well as within one species only occur in the quantitative levels of the chloroplast prenylquinones, but there are no differences between musci and liver mosses.

There are differences in the maximal fluorescence of liver mosses and mosses. The variable fluorescence in turn, which is a measure of in vivo photosynthetic activity, is very similar for all examined species of mosses and liver mosses (values from 0.7 to 1.0) but somewhat lower than in leaf pieces of higher plants. DCMU blocks the variable fluorescence and the concomitant oxygen evolution in all mosses and liver mosses.

From the lower prenylquinone levels and the low values for the variable fluorescence it is concluded that mosses and liver mosses exhibit on a chlorophyll basis fewer reaction centres and electron transport chains than chloroplasts of higher plants.
Photosynthetic Response to Water Stress in Phaseolus vulgaris
Authors: O'TOOLE J. C. , OZBUN J. L. , WALLACE D. H.
Published: April 2006

Water stressed Phaseolus vulgaris L. plants were monitored to detect the relationships between net photosynthesis, transpiration, boundary layer plus stomatal resistance, mesophyll resistance, CO2 compensation point, ribulose, 1,5‐diphosphate carboxylase activity and leaf water potential.

At full expansion, the first trifoliate leaves of greenhouse grown bean plants were subjected to water stress by withholding irrigation. Gas exchange and enzyme activity of the central trifoliolate leaflets were monitored as leaf water potential decreased.

Although increased stomatal resistance appeared to be the primary causal factor of reduced net photosynthesis, increased mesophyll resistance and decreased ribulose 1,5‐diphosphate carboxylase activity further documented the role of non‐stomatal factors.
Rise in the Ratio Heavy to Light Extractable Ribosomal RNA during Sprouting of Birdcherry Buds
Authors: EKELUND R.
Published: April 2006

Using the diethyl pyrocarbonate method, nucleic acids have been extracted from buds of European bird‐cherry (Prunus padus L.) in different developmental stages and analysed by sucrose gradient centrifugation. The ratio heavy to light ribosomal RNA was about I in extracts from dormant and non‐dormant but slowly growing buds. In extracts from sprouting buds the ratio was about 1.7. This increase probably reflects an increased extractability of heavy ribosomal RNA and may depend on a change of ribosomal structure during sprouting.
Changes in Metabolite Levels during Growth of Acer pseudoplatanus (Sycamore) Cells in Batch Suspension Culture
Authors: SHIMIZU TOMIKO , CLIFTON ANNE , KOMAMINE ATSUSHI , FOWLER MICHAEL W.
Published: April 2006

Measurements were made of the levels of key glycolytic intermediates and co‐factors during the growth of Acer pseudoplatanus L. cells in batch culture. Mass action ratios were calculated for the enzymes phosphoglucoseisomerase, phosphofructokinase and pyruvate kinase. The ratio for phosphofructokinase was greatly displaced from equilibrium.

Major increases in the level of NADPH and ATP and energy charge were observed in the initial or lag period of culture. The data indicate that the energy generating system of the cells is most active in the lag phase.
The Role of Malate, Oxalate, and Mustard Oil Glucosides in the Evolution of Zinc‐Resistance in Herbage Plants
Authors: MATHYS WERNER
Published: April 2006

Malate, oxalate and mustard oils were analysed in zinc‐resistant and zinc‐sensitive ecotypes of Silene cucubalus Wib., Rumex acetosa L., Thlaspi alpestre L. and Agrostis tenuis Sibth. The effect of zinc on the activities of carbonic anhydrase and peroxidase in Siiene cucubalus was tested. Carbonic anhydrase of the zinc‐resistant ecotypes was stimulated by addition in vivo of high amounts of zinc. The high activity of peroxidase in the non‐zinc‐resistant ecotypes after the addition of zinc documented a poisoning of the sensitive plants by zinc. The amount of oxalate differed greatly between ecotypes. There was, however, no direct correlation between zinc‐resistance and oxalate. When applying zinc to the nutrient medium, the synthesis of oxalate was inhibited in zinc‐sensitive, but stimulated in zinc‐resistant ecotypes of Silene cucubalus and Rumex acetosa. In Thlaspi alpestre high concentrations of mustard oil glucosides were found. Zinc‐resistant plants produced twice as much glucosides as sensitive ones. A possible role of mustard oils in zinc‐resistance is discussed. In the content of malate there were great quantitative differences between zinc‐resistant and zinc‐sensitive plants. All zinc‐resistant ecotypes of all the species contained much higher concentrations in their green organs than the sensitive ones. It is assumed that malate is a major factor in the evolution of zinc‐resistance. Malate may act as a complexing agent for zinc within the plasma, whereas oxalate and mustard oils may function as “terminal acceptors” of large amounts of zinc. The role of malate may be extended by a special transport mechanism, by which zinc is eliminated from the plasma into the vacuole.
Internal Leaf Area and Cellular CO2 Resistance: Photosynthetic Implications of Variations with Growth Conditions and Plant Species
Authors: NOBEL PARK S.
Published: April 2006

The influences of illumination, temperature, and soil water potential during development on leaf thickness, mesophyll cell wall area per unit leaf area (Ames/A), and the cellular CO2, resistance expressed on a mesophyll cell wall area basis (rCO2cell,) were examined for Plectranthus parviflorus Henckel. Although the ranges of all three growth conditions caused at least 9‐fold variations in the leaf biomass produced in 4 weeks, only the illumination had a major effect on internal leaf morphology, e.g. the thickness went from 279 to 831 μm and Ames/A from 10.5 to 34.8 as the photosynthetically active radiation was raised from 3 to 53 nEinsteins cm−2 s−1, while rCO2cell remained close to 154 s cm−1. Variations in the growth temperature, soil water potential, and the nutritional status of the plant, affected photosynthesis mainly by changes in rCO2cell.

To compare the influence of internal leaf area on photosynthesis for other plants, especially those with low Ames/A values, the maximum rates of CO2 uptake at light saturation and photosynthetically optimal temperatures were also determined for a moss, Mnium ciliare (C. Muell.) Schimp., and two ferns, Adiantum decorum Moore and Alsophila australe R. Br. As Ames/A went from 2.00 for the moss to 3.8, 7.5, 11.7, and 20.8 for the fens, the illumination at light saturation and the maximum rate of photosynthesis both progressively increased. The cellular CO2 resistance, which theoretically might have a lower limit of 20 s cm−1, ranged from 85 to 190 s cm−1.
Enzymatic Activity in Mitochondria from Orobanche
Authors: SINGH PRIKHSHAYAT , KRISHNAN P. S.
Published: April 2006

Mitochondria from Orobanche were analysed for the activities of aconitate hydratase, isocitrate dehydrogenase, succinate dehydro‐genase, fumarate hydratase, malate dehydrogenase, NADH oxidase, substrate‐cytochrome c oxidoreductases, glutamate dehydrogenase, aminotransferases, ATPase and “malic” enzyme. The specific activities of isocitrate dehydrogenase, NADH oxidase, substrate‐cytochrome c oxidoreductases and glutamate dehydrogenase in the mitochondria) fraction from parasite tissue compared favourably with those reported for most of the mitochondria from growing and storage tissues. Succinate dehydrogenase, fumarate hydratase and aspartate aminotransferase were of intermediate activity, while aconitate hydratase and malate dehydrogenase had rather low activity, and “malic” enzyme had very low activity in comparison with other preparations. The relevance of these findings in relation to mitochondrial metabolism in the parasite is discussed. No evidence was obtained to suggest any basic abnormality in the biochemical properties of the mitochondria from Orobanche centua which may be correlated with its obligatorily parasitic existence.
The Effects of Shoot Water Status on Some Photosynthetic Partial Processes in Sitka Spruce
Authors: BEADLE C. L. , JARVIS P. G.
Published: April 2006

Clonal cuttings of Picea sitchensis (Bong.) Carr. were grown in a controlled environment and, after completion of shoot extension and maturation, subjected to a drying cycle. Photosynthesis and stomatal conductance were measured in situ using 14CO2 and a porometer, respectively. Shoot water potential was measured with the pressure chamber. Photosystem and carboxylase activities of chloroplast preparations were measured in vitro. A considerable fall in photosynthetic rate occurred at low water potential. This was associated with stomatal closure and a decrease in CO2 transfer or fixation processes in the mesophyll. Little change in activity of photosystem I, photosystem II, and ribulose 1,5‐diphosphate carboxylase was detected during the drying cycle. Any decline in activity of the photosynthetic partial processes in vivo under severe water stress (Ψ < – 30 bar) was probably masked in vitro as a result of rehydration prior to assay.
Antisenescent Activity of Natural Cytokinins
Authors: KUHNLE JUDITH A. , FULLER GLENN , CORSE JOSEPH , MACKEY BRUCE E.
Published: April 2006

The antisenescent activity of naturally occurring cytokinins (bases and ribosides) has been evaluated by measuring chlorophyll retention in detached wheat (Triticum vulgare) leaf segments. 6‐(3‐Methyl‐2‐butenylamino)‐2‐methylthiopurine (ms2ip) was the most active cytokinin followed by 6‐(4‐hydroxy‐3‐methyl‐trans‐2‐butenylamino)purine (tZ). 6‐(4‐Hydroxy‐3‐methyl‐cis‐2‐butenylamino)‐9‐β‐D‐ribofuranosylpurine (cZR), 6‐(4‐hydroxy‐3‐methyl‐trans‐2‐butenylamino)‐2‐methylthio‐9β‐D‐ribofuranosylpurine (MstZR), and 6‐(4‐hydroxy‐3‐methyl‐cis‐2‐butenylamino)‐2‐methylthio‐9‐β‐D‐ribofuroanosylpurine (mscZR) were essentially inactive. 9‐Ribosyl substitution did not affect the activity of tZ, (±)‐6‐(4‐hydroxy‐3‐methylbutylamino)purine (DHZ), or 6‐(3‐methyl‐2‐butenylamino)purine (2ip), but lowered the activity of 6‐(o‐hydroxybenzylamino)purine (OHBA) and 6‐(4‐hydroxy‐3‐methyl‐cis‐2‐butenylamino)purine (cZ). 2‐Methylthio substitution increased the activity of 2ip and DHZ, decreased the activity of tZ, and had no effect on the activity of cZ. The activities of the simultaneously substituted 2‐methylthio‐9‐ribosyl compounds are lower than those of their corresponding unsubstituted or 2‐methylthio substituted bases with the exception of DHZ.

Structure‐activity relationships for chlorophyll retention did not parallel many of the relationships found for callus tissue growth stimulation.
Effect of Low Temperature upon Lipid and Fatty Acid Composition of Roots and Leaves of Winter Rape Plants
Authors: SMOLEŃSKA GABRIELA , KUIPER PIETER J. C.
Published: April 2006

When winter rape plants were transferred from favourable temperature conditions (25/20°C day/night temperature) to 5°C, the frost resistance of the leaves was increased whereas the frost tolerance of the roots remained unaffected. This permitted an analysis of the changes in lipid and fatty acid composition both as related to functioning of the plant at low temperature alone (roots) and as related to adaptation to freezing and functioning at low temperature (leaves). — Transfer of the plants to 5°C lead to an increase in the level of linolenic acid in roots and leaves. This increase was most evident in the phosphatidyl choline and ethanolamine fractions of the leaves, and in the neutral lipids and in an unidentified phospholipid from the roots. It was concluded that upon transfer of the plants to 5°C a general and non‐specific increase in linolenic acid level contributed to functioning of the rape plants at low temperature; and that parallel but minor increases in linolenic acid level of digalactosyl diglyceride, phosphatidyl inositol and the unknown phospholipid in roots and leaves could only contribute to low‐temperature functioning in specific membrane enzyme locations. Combined adaptation of the leaves to freezing tolerance and low‐temperature functioning was correlated with a higher level of phosphatidyl choline and ethanolamine, predominantly esterified with linolenic acid.
Oscillatory Transpiration and CO2 Exchange of Citrus Leaves at the CO2 Compensation Concentration
Authors: BRAVDO BEN‐AMI
Published: April 2006

CO2 and H2O vapor exchange were measured by enclosing citrus (Citrus sinensis cv. Sour Orange) leaves in a temperature controlled transparent leaf chamber. Introduction of dry air into the closed circuit gas flow caused cyclic oscillation in CO2 and H2O vapor exchange. It is suggested that oscillation in the CO2 exchange at the CO2 compensation concentration is due to oscillation in non‐stomatal resistance to CO2. Three types of oscillation were observed: 3–6 min (peak to peak) in young leaves, 30 min in mature leaves, and 160 min in old leaves.
Dipeptides and Amino Acids as Nitrogen Sources for the Callus of Atropa belladonna
Authors: SALONEN MAIJA‐LIISA , SIMOLA LIISA KAARINA
Published: April 2006

Stem callus of Atropa belladonna was grown on media containing seven dipeptides and the corresponding amino acids, given as the only nitrogen sources and in combination with inorganic nitrogen. Of the eight amino acids studied, only alanine and proline were used effectively by the callus. Three dipeptides (glycyl‐alanine, glycyl‐glycine and prolyl‐proline) promoted growth slightly, but none of them was better than inorganic nitrogen (KNO3, 2.5 mM) as the sole nitrogen source. In combination with KNO3 (2.5 mM), these three peptides stimulated growth more than, or at least as much as, KNO3 (5 mM). Growth was better with glycyl‐alanine and glycyl‐glycine (1.25 mM) than with glycine (2.5 mM), which inhibited growth. Arginine, a usually favourable compound, did not give any growth when used as the sole nitrogen source. Leucyl‐tyrosine, prolyl‐hydroxyproline and prolyl‐methionine inhibited growth when given alone or with inorganic nitrogen. In the case of the prolyl peptides the inhibition seemed to be due to the unfavourable effects of methionine and hydroxy‐proline, which were not counteracted by an equimolar concentration of proline. Both leucine and tyrosine were also strongly growth‐retarding.
The Radial and Longitudinal Path of Ion Movement in Roots
Authors: SINGH CHANCHAL , JACOBSON LOUIS
Published: April 2006

The existence of a barrier to lateral outward diffusion of ions from roots was demonstrated quantitatively and by autoradiography. Ions applied to the apical zone were excreted through the basal cut end with no lateral outward diffusion from the central zone. The ions moving through the conducting tissues showed no leakage to the external solution regardless whether the treatment roots came from seedlings grown under low or high salt conditions. However, when dinitrophenol (DNP) was also applied to the central zone in the external salt solution, leakage of apically applied calcium occurred from the conducting tissues. Autoradiographic studies with labeled calcium suggested that the endodermal layer was an effective barrier preventing the lateral outward diffusion of ions. The ions moved longitudinally through the stele. In the stelar tissues the autoradiographic studies failed to detect the presence of any radioactive calcium in the central duct and in the mature xylem vessels, although high concentrations of labeled ions were found in the living cells of the stele, particularly the xylem parenchyma. It is suggested that xylem parenchyma cells may be involved in the longitudinal transport of ions.
Improved Growth of Tissue Cultures of the Onion, Allium cepa
Authors: DUNSTAN D. I. , SHORT K. C.
Published: April 2006

A forty‐fold increase in tissue fresh weight has been achieved for Allium cepa stem tissue callus grown on a modified B5 medium with increased ammonium, phosphate and nitrogen levels; and decreased level of 2,4‐dichlorophenoxyacetic acid. Growth was examined on several standard media, using fresh weight, dry weight and cell number as parameters over an 8‐week growth period. Further, tissue grown upon this medium is more friable than on other media. The value of such friable callus for suspension culture initiation and for single cell cloning experiments is discussed.
Uptake and Distribution of Mercury within Higher Plants
Authors: BEAUFORD W. , BARBER J. , BARRINGER A. R.
Published: April 2006

The uptake and distribution of inorganic mercury (HgCl2) within higher plants (Pisum sativum and Mentha spicata) was examined using solution culture and radiotracer techniques. Plants were found to tolerate an external level of 1 mgHg/kg of solution but both physiological and biochemical processes were affected at 5 mgHg/kg and 10 mgHg/kg. The uptake of Hg into plants grown in hydroponic solution was a function of external concentration. Over the concentration range considered the accumulation of Hg in the roots was linear on a log‐log basis although the uptake of the element into the shoots appeared to be two‐phased. The distribution of Hg in plants was asymmetrical with much greater amounts of the element in the roots than the shoots. Although the level of Hg increased generally in plant tissues with increasing external levels, the proportion retained in the roots, relative to the shoots, was constant (approximately 95%). Two binding characteristics of the Hg within plant tissue were detected. A major proportion of Hg was tightly bound, being unaffected by treatment with ethanol and hydrochloric acid. The remaining Hg in the tissue was removed by either water or hydrochloric acid treatment. Cell fractionation indicated that the major binding component of Hg in plant tissues was the cell wall.
The Effect of Ringing on Cytokinin Distribution in Salix baylonica
Authors: VAN STADEN J. , BROWN N. A. C.
Published: April 2006

Although quantitative differences were observed in the cytokinin content of mature leaves and bark of Salix babylonica it would appear as if these tissues contained the same cytokinin complement. Ringing resulted in a decrease in the level of cytokinins in the leaves and an increase in the bark, both above and below the girdle. In the leaves the decrease was due mainly to a drop in the level of those compounds that co‐chromatographed with the cytokinin glucosides. These compounds were also almost undetectable in the bark above the girdle, where callus was formed. The observed increase in the cytokinin content of the bark above the girdle was due to higher activity in those parts of the chromatograms where zeatin and zeatin riboside occurred. Ringing stimulated the growth of lateral buds below the girdle. These developing buds as well as the bark below the girdle contained very high levels of cytokinins that cochromatographed with zeatin and zeatin riboside.
Induction of Secondary Abscission in Apple Pedicels in vitro
Authors: PIERIK R. L. M.
Published: April 2006

In vitro cultivated apple pedicels without a primary abscission layer can form a secondary (adventitious) abscission layer, especially under the influence of auxins.

In the apple cv. Cox's Orange Pippin abscission can only be induced by auxins, while the site of the abscission layer, a few millimetres from the basal ends of the pedicels, is fixed and independent of the auxin concentration. The auxin treatment has to last at least 5–6 days to induce abscission, which is not affected by the presence of a flower. A secondary layer does not occur when pedicels are placed inverted on the media. Although abscission occurs both in light and in darkness, it is strongly promoted by light. Abscission is also accelerated by raising the temperature from 9°C to 21–25°C. High concentrations of 2,3,5‐triiodobenzoic acid reduce the percentage of auxin‐induced abscission. Sugar is required, but the presence of macro‐elements is not essential.
Bark Banding of Pinus radiata with Morphactin (IT3456): Influence on Trunk Anatomy Assimilate Transport and Growth
Authors: DOSS ROBERT P. , NEUMANN PETER M. , BACKHAUS RALPH A. , SACHS ROY M.
Published: April 2006

A morphactin formulation containing methyl‐2‐chloro‐9‐hydroxyfluorene‐9‐carboxylate as the major component caused abnormal stem growth in Pinus radiata D. Don seedlings when applied as a bark band. The banded region swelled due to increased cell division in the periderm and cambium. The abnormal stem development in treated trees did not cause a localized girdling effect. The morphactin treatment inhibited shoot elongation and root growth. Treated trees exposed to 14CO2 translocated significantly less assimilate to the roots than did control trees although fixation of 14CO2 by the shoots was not reduced. Label from a bark band of 14C‐morphactin was rapidly translocated to the roots indicating that direct inhibition of root growth by the inhibitor probably occurred.
Control of Ethylene Induced Permeability of Plant Cells by a Substituted Benzothiadiazole
Authors: PARUPS E. V.
Published: April 2006

The permeability of bulb tissues of onion (Allium cepa L.), amaryllis (Hippeastrum hybrids), tulip (Tulipa × hybrida) and daffodil (Narcissus tazetta L.) treated with Ethephon and 5‐methyl‐7‐chloro‐4‐ethoxycarbonylmethoxy‐2,1,3‐benzothiadiazole (TH6241), to water and solutions of 1,3‐dimethylurea was determined by the plasmometric methods. Ethylene treatments promoted, while those with TH6241 generally decreased the cell membrane permeability; TH6241 negated the effects of ethylene on cell permeability.
Initiation, Growth and Nuclear Characteristics of Tissue Cultures of Paeonia suffruticosa
Authors: GILDOW F. E. , MITCHELL J. P.
Published: April 2006

Tissue cultures of the garden paeony, Paeonia suffruticosa have been established using explants of etiolated stems. Callus formation was induced on agar‐solidified media containing ammonium ions or amino acids together with the hormones 2,4‐dichlorophenoxyacetic acid and kinetin, but not on media lacking the reduced nitrogen component. Attempts to induce callus from explants from green plants were completely unsuccessful and were characterized by the production of intense brown colorations, both of the explant and the medium. Subcultured tissue without the added hormones produced roots, both on solid and liquid media.

Growth was tested on a range of liquid media, SH/2, SH, SH × 2 and SH—M, containing 1250, 2500, 5000 and 2500 mg/l potassium nitrate. The SH—M medium also contained 1650 mg/l ammonium nitrate. Growth measured as increased fresh weight was best in the SH/2, SH and SH—M media and was curtailed in the SH × 2 medium. Soluble protein content was highest at the lowest nitrogen concentration.

A histochemical comparison of tissue grown on the SH/2, SH—M and SH—M lacking hormones showed that the cells in all the cultures remained diploid while differences were established in total nuclear protein, measured using the ninhydrin‐Schiff procedure. Nuclei from SH—M grown cells have a higher protein content than those from the SH/2 medium while cells from the SH—M medium lacking hormones show a further increase in nuclear protein. This raises the question whether this change in nuclear protein is related to the morphogenesis of roots which occurs in this medium.
Effects of Low Root Temperature on Ion Uptake and Ion Translocation in Wheat
Authors: NORDIN ÅSA
Published: April 2006

Roots of wheat seedlings (Triticum aestivum L. cv. Weibulls Starke) were cooled (+1°C) for 24 h while the shoots were kept at 25°C. The treatment induced an increased water deficit in the leaves. Fresh weight, dry weight, and the uptake and distribution of potassium and calcium were measured before and after cooling. Growth, measured both as fresh weight and dry weight increase, was reduced during the cold treatment. Afterwards (at 20°C), growth recovered to nearly pre‐stress rates.

Analysis of the potassium fluxes in and out of the roots by 86Rb techniques showed that influx, and to a lesser extent efflux, were inhibited at low temperature. The result was a net potassium uptake rate of one‐third that of unstressed plants. After the cooling period the potassium influx increased to the rate of control plants. The potassium efflux increased to one and one‐half times the rate of unstressed wheat so that net uptake was negative. The increase in potassium efflux was explained by a higher permeability of the root cell membranes after cooling. The net uptake of calcium was reduced to one‐third by root cooling. Contrary to potassium uptake, calcium uptake increased under post‐stress conditions, partly due to a low efflux rate.

During root cooling there was a redistribution of dry matter from the leaves down towards the lower part of the shoot. Afterwards the original distribution of dry matter was reestablished. The net flow of potassium and calcium followed a similar pattern as dry matter, suggesting a growth‐regulated flow.
The Effect of Canopy Wetting on Plant Water Status, CO2 Fixation, Ion Content and Growth Rate of ‘Baccara’ Roses
Authors: PLAUT Z. , ZIESLIN N.
Published: April 2006

The effect of canopy wetting of rose (Rosa hybrida) plants on transpiration rate, stomatal resistance, plant water potential, ion concentration in leaves, and several growth parameters was investigated. Plants were grown in a greenhouse and their canopies were exposed to wetting cycles during the daytime. Canopy wetting decreased transpiration rate and increased diffusive resistance to water vapor transfer. Plant water potential was only slightly increased by wetting, mainly in the spring.

Canopy wetting did not prevent the decrease in CO2 fixation, which took place before midday when plant water potential dropped below – 10 bars during a rise in radiation intensity. The concentrations of Cl− and Ca2+ decreased in wetted leaves, while the concentration of Na+ was increased and other cations were hardly affected. Canopy wetting inhibited growth rate of rose shoots and flower formation, and increased the average flower weight.
The Occurrence of Phytylpyrophosphate and Acyl Esters of Phytol in Irradiated Dark‐Grown Barley Seedlings and Their Possible Role in Biosynthesis of Chlorophyll
Authors: LILJENBERG CONNY
Published: April 2006

Dark‐grown barley seedlings which had been irradiated for 6 to 8 h have been shown to contain fatty acid esters of phytol. No such esters could be found in non‐irradiated seedlings. The fatty acids were saturated or had only one double bond. The most prominent acid was palmitic acid.

Isolated etio‐chloroplasts from non‐irradiated and irradiated barley seedlings also contained phytylpyrophosphate. The ratio of free phytol to phytylpyrophosphate is only little changed when the seedlings are irradiated for 6 to 8 h. The chemical identifications of free phytol and the phytol derivatives are based upon combined gas chromatography/mass spectrometry.
Patterns of Hormones, Respiration and Ripening Enzymes during Development, Maturation and Ripening of Cherry Tomato Fruits
Authors: ABDEL‐RAHMAN M.
Published: April 2006

Changes in growth, endogenous levels of hormones, ethylene evolution and cellulytic and pectolytic enzyme activities of cherry tomato fruits (Lycopersicon esculentum Mill. cv. Small Fry) were assayed from anthesis through ripening. After anthesis, growth of cherry tomato fruit follows a three‐dimensional and sigmoid growth pattern which consits of cell division, cell enlargement, mature green, pink and red stages. Cytokinins and auxins were abundant and reached their peak during early development (cell division). Gibberellin levels were more prominent during the period of cell enlargement and reached a peak before the green mature stage. Levels of abscisic acid increased gradually during maturation and reached a maximum in the advanced green mature stage. Respiration pattern was characterized by a climacteric peak at the pink stage. Ethylene production remained less than 2 μl/kg fresh weight an hour until shortly before mature green stage, then rose rapidly to a maximum at pink stage. Activities of cellulytic and pectolytic enzymes were first detected at the green mature stage and increased rapidly during fruit ripening.
Inhibitory Effect of Gibberellins on Archegonial Differentiation in Lygodium japonicum
Authors: TAKENO KIYOTOSHI , FURUYA MASAKI
Published: April 2006

Archegonial differentiation in light‐grown gametophytes of Lygodium japonicum was partially inhibited by exogenously applied gibberellin A3 (GA3) at a concentration of 10−6M, and fully prevented at 10−5M. The inhibitory effect was nullified by transferring the GA3‐treated samples onto fresh media omitting GA3, so that the archegonial formation became discernible 6 days after the transplantation. The application of 10−4M GA3 to younger gametophytes brought about a complete inhibition of archegonial differentiation, whereas the same concentration applied to older gametophytes did not influence the process at all, indicating the timing of archegonial differentiation during the ontogeny. Activity spectrum of authentic gibberellins on the basis of concentrations inducing 50% inhibition of archegonial formation was obtained as follows: GA4= GA9 > GA7 > GA3 > GA1= GA5= GA8.
Stimulation of Growth and Nucleic Acid Biosynthesis at Low Concentration of Abscisic Acid in Tissue Culture of Spinacia oleracea
Authors: NEŠKOVIĆ M. , PETROVIĆ J. , RADOJEVIĆ LJ. , VUJIČIĆ R.
Published: April 2006

The effect of abscisic acid on growth, ultrastructure and nucleic acid biosynthesis was studied in tissue culture of spinach (Spinacia oleracea L.). Low concentration (0.01 mg l−1) of abscisic acid increased fresh and dry weight of calluses, whereas 1.0 mg l−1 was inhibitory. The stimulating effect was observed only in the presence of a relatively high concentration of kinetin (1 mg l−1). The inhibitory effect was partly overcome by the same kinetin concentration. The low concentration of abscisic acid probably accelerated the induction of callus growth after subculture and stimulated cell division in the exponential phase of growth.

Electron microscopy showed the presence of numerous polysomes and rough endoplasmic reticulum in callus cells grown at the stimulating abscisic acid concentration. Control cells and cells at the inhibitory concentration had slightly hyaline cytoplasm and were more vacuolated.

Incubation of callus tissue with 32P in the presence of stimulating concentration of abscisic acid showed a significant increase in the rate of biosynthesis of all nucleic acid classes after 8 h, whereas inhibitory concentration produced a decrease in 32P incorporation. However, when the tissue was grown in the presence of abscisic acid for 20 days, both concentrations decreased the rate of nucleic acid biosynthesis, as compared to the controls.
Growth and Maintenance Respiration in Whole Plants, Tops, and Roots of Lolium multiflorum
Authors: HANSEN G. K. , JENSEN C. R.
Published: April 2006

Continuous measurements of CO2‐exchange were separately carried out on tops and roots of small swards of Lolium multiflorum grown in nutrient solution in growth chamber during 3–4 weeks. From these measurements, a daily carbon balance and accumulated dry matter could be established. The data were used to distinguish between two components of respiration, one proportional to growth or photosynthesis (growth respiration), the other proportional to plant dry weight (maintenance respiration).

The separation of respiration in the two components was made by multiple regression analyses with daily photosynthesis or growth rate and accumulated dry matter as the independent variables. To ensure independency between the independent variables during the growth period, photosynthesis was varied by application of alternate three‐day periods of high and low irradiance. From the two regression coefficients, the efficiency of converting assimilates into constructive growth (YG) and the maintenance coefficient (M) could be derived.

Three experiments with varying length of photoperiod and dark period were carried out. The analyses were carried out for whole‐plant respiration, respiration of tops and respiration of roots separately. Growth respiration for whole plants as well as for tops and for roots was lower — and hence the efficiencies higher — the longer the photoperiods were. Growth respiration and maintenance respiration were higher for roots than for tops. The high rate of root respiration may originate from release of HCO3− in exchange for NO3−. The parameters found can be utilized quantitatively in computer models of crop photosynthesis and respiration.
Levels and Aggregation of Ribosomes during Dormancy and Dormancy Break of Peach Flower Buds
Authors: BAGNI N. , MARINO G. , TORRIGIANI P. , AUDISIO S.
Published: April 2006

The level of ribosomes and their aggregation state (monosomes‐polysomes) have been investigated in relation to dormancy in peach flower buds (Prunus persica). The ribosomes were analysed by a linear sucrose gradient. The ribosomal content hardly changes in the bud before dormancy and until dormancy breaks; on the other hand after this period there is a remarkable increase in the ribosomal level strictly related to the increase in bud weight. The ribosomal content reaches the highest value at flowering. During dormancy break the largest portion of ribosomes is localized in flower primordia, not in scales. Polysomes, which are always present in buds, remain constant during dormancy (35%), increase at dormancy breaking, reaching the highest level at flowering.
Freeze Preservation of Cultured Plant Cells. III. The Pregrowth Phase
Authors: WITHERS LYNDSEY A. , STREET H. E.
Published: April 2006

There is an inverse relationship between cell size and capacity to survive the freeze‐preservation protocol. Pregrowth of cell suspensions in media rendered more negative in water potential by addition of mannitol enhances the survival capacity of Acer pseudoplatanus and Capsicum annuum cells but this effect can only partially be explained in terms of the associated reduction in mean cell size. Studies with cell suspensions of Daucus carota indicate the importance for successful freeze‐preservation of the stage in the growth cycle of suspensions propagated in batch culture; highest survival was recorded for cells taken at lag phase or early exponential phase. Regrowth of recovered cells depends upon the establishment of an appropriate inoculum density of cells which have retained the capacity to divide. The dividing cells only achieve a growth rate equal to that of untreated cells after a number of cell generations. A proportion of the recovered cells giving an initial positive fluorescein diacetate reaction lose this capacity rapidly (within 24 h), others lose the capacity more slowly and others, in which the positive reaction persists, are incapable of division. These observations indicate that different levels of injury are inflicted by the freeze‐preservation protocol and that only in a proportion of the cells is the injury reparable or compatible with growth by cell division.