bluuebunny/crossref_metadata_2025 huggingface dataset:
Adventitious shoot formation from embryonic explants of red pine (Pinus resinosa)
Authors: Noh E. W. , Minocha S. C. , Riemenschneider D. E.
Published: May 2006

Adventitious shoots were induced from excised embryos of Pinus resinosa Ait, on half‐strength Le‐Poivre (LP) medium containing 1–70 μMN6‐benzyladenine (BA). At lower concentrations of BA, only 2–3 shoot primordia (from as many as 22 formed per embryo) developed into shoots when subcultured onto medium containing 0.5% activated charcoal. Concentrations of 10 to 70 μM of BA produced significantly higher numbers of shoot primordia and most of them developed into shoots. Ten to 17 day culture on medium containing 10–25 μM BA proved optimal for maximum adventitious shoot production. Less than three days of incubation on the cytokinin medium did not stimulate the formation of adventitious shoots. Twenty‐four day culture on the same medium produced several shoots, but most of them failed to develop normally and formed callus. Coconut milk (0.1–5% v/v) inhibited adventitious shoot formation. Using optimal conditions, seeds from 11 open‐pollinated selected trees were compared to test for genetic differences in the potential to produce adventitious shoots from embryos. No significant differences were observed with regard to the shoots produced per embryo among the different seed collections. More than 200 plants produced through this technique were tested for variation in several isozymes by electrophoresis. No variations were observed.
Peroxidase and polyphenol oxidase activities in Cyperus esculentus leaves following glyphosate applications
Authors: Cañal María Jesús , Tamés Ricardo Sánchez , Fernández Belén
Published: May 2006

Following a 2‐week treatment with glyphosate [N‐(phosphonomethyl)glycine] changes in peroxidase (EC 1.11.1.7) and polyphenol oxidase (PPO; EC 1.14.18.1) activities of yellow nutsedge (Cyperus esculentus L.) plants, were determined. Glyphosate caused significant increases of both activities. Isoelectric focusing gave 3 species (F1, F2 and F3) of peroxidase activity, at pl 3.8, 4.4 and 4.8, and 4 species (Fa, Fb, Fc and Fd) of PPO activity at pl 7.0, 7.5, 7.8 and 9.5. The activity of the 4 active forms of PPO increased with increasing glyphosate dose up to 10−2M. The effect of the herbicide on the 3 fractions with peroxidase activity was to change their relative activities. Highest F1 activity was found in control plants whereas the F2 fraction was the predominant form in the plants treated with glyphosate at 10−2M and the highest F3 activity occurred in plants treated with 5 × 10−3M glyphosate. The increased PPO activity could produce phytotoxic o‐quinones, and variations in peroxidase isoenzymes activity could enhance isoperoxidases with lignin biosynthetic activity.
Immunological estimation of growth regulator distribution in phototropically reacting sunflower seedlings
Authors: Feyerabend Martin , Weiler Elmar W.
Published: May 2006

The distribution of immunoassayable xanthoxin (XA), abscisic acid (ABA) and indole‐3‐acetic acid (IAA) in all parts of sunflower (Helianthus annuus L.) seedlings was determined. During the course of phototropic curvature, including the lag phase (5 min), the distribution of these growth regulators was analyzed in the illuminated and shaded side of the hypocotyl, as well as in the peripheral and central tissues. All three growth regulators showed no detectable asymmetries between the illuminated and shaded hypocotyl halves during the lag phase and early phototropic curvature. Also, no indication for an exchange of XA, ABA or IAA between the peripheral and central tissues was observed. Partial removal of the peripheral cell layers revealed that changes in the growth properties of this tissue, preferentially at the illuminated side of the hypocotyl, are required for the phototropic reaction. Complete removal of the peripheral cell layers abolishes the phototropic response. In dark‐incubated, green sunflower seedlings, the loss of sensitivity to phototropic stimulation is correlated with decreasing levels of IAA immunoreactivity, whereas no changes in the levels of ABA‐ and XA immunoreactivity were recorded. The findings are discussed with respect to the involvement of ABA, XA and IAA in phototropic reactions of green dicotyledonous shoots.
Serine metabolism in legume nodules: Purification and properties of phosphoserine aminotransferase
Authors: Reynolds Paul H. S. , Hine Anna , Rodber Karen
Published: May 2006

Enzymes involved in serine metabolism were compared in the plant cytosol fraction of root nodules from soybean [Glycine max (L.) Merr., cv. Amsoy] and lupin [Lupinus angustifolius L., cv. Uniharvest]. Soybean nodules are ureide exporters and have a serine requirement in the synthesis of these compounds, whereas lupin nodules are amide transporters and do not have a serine requirement in asparagine synthesis. Specific activities were measured for phosphoserine aminotransferase (PSAT; EC 2.6.1.52) and phosphoglycerate dehydrogenase (EC 1.1.1.95), as representative activities of the ‘phosphorylated’ pathway, and for serine‐pyruvate aminotransferase (EC 2.6.1.51), and glycerate dehydrogenase (EC 1.1.1.29), as representative activities of the ‘non‐phosphorylated’ pathway. Phosphorylated pathway enzyme levels were higher in soybean nodules. During nodule development nonphosphorylated pathway activities fell in soybean nodules, whereas in lupin nodules the specific activities of these enzymes increased. These data are consistent with roles for the phosphorylated and non‐phosphorylated pathways in serine anabolism and catabolism, respectively.

PSAT was purified 250‐fold from soybean nodules. The enzyme showed linear reaction kinetics and was unaffected by serine. It had a molecular weight of 85 kDa, high specificity for its substrates and an optimum pH between pH 7.5 and 9. These results are discussed in relation to regulation of carbon supply to purine biosynthesis in ureide biogenesis in soybean root nodules.
Bundle sheath tissues of legume leaves as a site of recovery of solutes from the transpiration stream
Authors: Canny M. J.
Published: May 2006

The earlier observation that the fluorochrome sulphorhodamine G selectively enters cells of the extended bundle sheath system (paraveinal mesophyll) of soybean leaves from the transpiration stream, is extended to all the 26 species of legumes so far tested. The species examined were selected to include the three types of the system previously identified: Type 1 with complete systems, Type 2 with attenuated systems, and Type 3 with ordinary bundle sheaths. In Type 3 the dye selectively entered the bundle sheath cells. The hypothesis that the entry of the dye to a cell is caused by local low external pH, which suppresses its ionization, is confirmed by tests of the response of sulphorhodamine uptake to changing external pH, and of the inhibition of uptake by the ionophore dinitrophenol. An extension of this hypothesis identifies the local pH gradient as an energy source driving influx pumps to scavenge solutes from the transpiration stream and store them in special cells. It is proposed that this may be broadened to include many legumes. The activity of the proton extrusion pumps in this storage network is shown to be correlated with the flowering and fruiting of soybean, showing high activity before flowering, and disappearing during pod formation when nitrogenous materials are exported from the network.
Effects of excessive ammonium deposition on the nutritional status and condition of pine needles
Authors: van Dijk Harrie F. G. , Roelofs Jan G. M.
Published: May 2006

In the southeastern part of the Netherlands many Scots pine (Pinus sylvestris L.) trees show signs of yellowing. To investigate whether there is a relation between this phenomenon and the high ammonium deposition, needle and soil samples were analyzed. Soil samples from the discoloured forests contained more extractable nitrogen than samples from healthy stands, whereas differences in pH values were small. Needles from yellow trees had higher levels of total nitrogen than needles from green trees as well as severe imbalances of Mg, K+ and P relative to N. The amount of leaf pigments was substantially lower in needles of the diseased trees, but they contained much higher quantities of free arginine, which accounted for a major part of total nitrogen. This may be an indication of a severe nitrogen overload. The linkage between this excessive nitrogen nutrition and the observed process of yellowing is discussed.
The effects of nitrate on the enzymes involved in nitrogen assimilation in nodulated pea roots
Authors: Vézina L.‐P. , Joy K. W. , Hope H. J.
Published: May 2006

Pea Plants (Pisum sativaum L. ev. Little Marvel) were grown in N‐free medium and when well nodulated (28 days) were supplied for 8 days with nitrate or ammonium. Over the 8 days of nitrate treatment, total amino and amide N in sap declined, and the proportion of aspartate relative to the other amino acids increased. After 8 days of treatment, nitrogenase (EC 1.18.2.1) activity in nitrate‐treated plants declined to about 30% of the activity in controls even though nodules were not directly in contact with nutrient solution. Nitrogenase activity was also decreased by the addition of ammonium chloride (10 mM). With addition of nitrate or ammonium. clear signs of senescence began to show in the nodules after 4 days. Nitrate reductase (EC 1.6.6.1) activity was induced in roots by nitrate, but decreased sharply in nodules. In response to nitrate addition, newly formed root tissues showed 3‐ to 5‐times higher glutamine synthetase (GS. EC 6.3.1.4) activity than newly formed tissues of control plants, expressed on a protein or weight basis. In complementary experiments, when ammonium salts were used instead of nitrates, the increase in GS activity was significantly lower. GS activity decreased in nodules of treated plants and total extractable protein was 3 times lower in nodules of nitrate‐treated plants than in controls at day 8 of treatment.
Activities of Cu‐containing proteins in Cu‐depleted pea leaves
Authors: Ayala Matilde Barón , Sandmann Gerhard
Published: May 2006

The effect of Cu deficiency on Cu‐containing enzymes and on their activities was studied with two subsequent generations of Cu‐deficient pea plants (Pisum sativum L., cv. Progress) grown in low Cu2+ media. Cu deficiency caused growth inhibition and a decrease in photosynthesis as well as in the activities of 3 Cu‐containing enzymes: diamine oxidase (EC 1.4.3.6), ascorbate oxidase (EC 1.10.3.3) and superoxide dismutase (EC 1.15.1.1). Determinations of photosynthetic electron‐transport rates as well as the concentrations of several redox components showed that the target of Cu deprivation in the photosynthetic apparatus is the synthesis of Cu‐containing plastocyanin which is positively correlated to the Cu content of the leaves. Inhibited formation of plastocyanin resulted in low activities of photosynthetic electron transport in photosystem I. Under Cu‐deficient conditions, the activities of diamine oxidase and ascorbate oxidase were inhibited by about 50% in the first and 80% in the second generation of pea plants. Enzyme assays showed an inhibition of the activities of both the plastidic and cytoplasmic Cu/Zn‐containing superoxide dismutases. An observed simultaneous increase of Mn‐superoxide dismutase may be a compensation mechanism to partially maintain the total superoxide‐dismutase activity under Cu‐deficient conditions. This result indicates that the formation of superoxide‐dismutase isoenzymes is interdependent and coordinated.
Ionic channels in plant cell membranes
Authors: Satter Ruth L. , Moran Nava
Published: May 2006

The use of patch clamp methods for identifying ion‐specific channels and other transport structures in plant cell membranes is described. Methodology, basic concepts that underlie data analysis, and applications of this powerful technique are emphasized.
Photosynthesis and carbohydrate partitioning in sweet cherry: Fruiting effects
Authors: Roper Teryl R. , Keller John D. , Loescher Wayne H. , Rom Curt R.
Published: May 2006

The effect of fruiting on carbon fixation and retention in leaves was monitored by measuring net photosynthesis (Pn) and total non‐structural carbohydrates (TNC) on a seasonal basis on mature fruiting and non‐fruiting sweet cherry trees (Prunus avium L. cv. Bing). Pn was also measured diurnally during stages II and III of fruit development. Pn rates increased to between 18 and 20 mg CO2 dm‐2 h‐1 during stage II of fruit development and were maintained until harvest. Diurnally, Pn increased in the morning to 20 mg CO2 dm‐2 h‐1 and this rate continued until sunset. Leaf carbohydrate levels decreased in both fruiting and non‐fruiting trees beginning at the equivalent of stage II of fruit growth. Carbohydrates were lower in leaves and woody portions of current, 1‐ and 2‐year‐old shoots of fruiting trees. Although differences were found in levels of non‐structural carbohydrates, no differences in Pn were found in fruiting vs non‐fruiting plants on either a seasonal or a diurnal basis. Pn rates in swet cherry in the field were primarily affected by ontogeny and environment and not by sink strength.
No evidence for a pleiotropic relationship between male sterility and cyanide‐resistant respiration in Plantago lanceolata
Authors: Dijk Henk Van , Kuiper Pieter J. C.
Published: May 2006

Gynodioecy, the coexistence of hermaphrodites and male steriles, is frequent in populations of Plantago lanceolata L. A condition for the maintenance of gynodioecy in an obligatory outbreeding species like this is an increase in female fitness in male steriles compared with hermaphrodites. One of the possible underlying mechanisms, a lower cyanide‐resistant respiration in male steriles, which could lead to a higher metabolic efficiency, was investigated. For the experiments adult plants were used, because the effects which compensate for male sterility have been found in characters like seed production and longevity. No general correlation between sex phenotype and cyanide‐resistant respiration capacity, or with any other respiration component, was found. Only in a single cross a strong correlation between cyanide‐resistant respiration activity and sex phenotype was established, male steriles possessing the higher activity. The conclusion from these experiments is that there is no pleiotropic relationship between respiration levels and sex phenotype. The strongly significant correlation mentioned is ascribed to chromosomal linkage.
Effects of the triazole plant growth retardant BAS 111¨W on gibberellin levels in oilseed rape, Brassica napus
Authors: Hedden P. , Croker S. J. , Rademacher W. , Jung J.
Published: May 2006

Three‐week‐old shoots of the spring oilseed rape cv. Petranova (Brassica napus L. ssp. napus) were found by combined gas chromatography‐mass spectrometry to contain GA1, GA8, GA15, GA17, GA19, GA20, GA24, GA29, 3‐epi‐GA1 and a previously uncharacterised C19 dicarboxylic acid that is probably structurally related to GA24. Shoots of the winter cultivar Belinda, harvested at the early flowering stage, contained the same GAs with the exception of the C19 dicarboxylic acid and, in addition, GA34 and GA51 were identified. All material contained higher levels of GA20 than of GA1; the ratio of GA1 to GA20 was highest in shoots containing the largest proportion of young immature tissues. Soil treatment of cv. Petranova seedlings with the growth retardant BAS 111¨W [1‐phenoxy‐5,5‐dimethyl‐3‐(1,2,4‐triazol‐1‐yl)‐hexan‐4‐ol] caused 80% reduction in height 18 days after treatment and the levels of all GAs were 20% or less that of control plants. Foliar treatment at the same dosage reduced height by 50% and caused an 85% or greater reduction in the concentrations of the GA1 precursors GA20, GA19 and GA44. However, the levels of GA1, GA8 and GA29 were affected to a much smaller extent. Foliar application of BAS 111¨W to cv. Belinda 1 month after sowing resulted in only a 20% height reduction at flowering, but no uniform decrease in the concentrations of endogenous GAs at this stage.
Osmoregulation and role of nitrate during regrowth after cutting of ryegrass (Lolium perenne)
Authors: Ourry Alain , Gonzalez Boris , Boucaud Jean
Published: May 2006

The osmotic role of nitrate during aftermath growth of Lolium perenne L. cv. Réveille was investigated. Plants were grown from seed in a controlled environment using a liquid medium with 1.0 mM NH4NO3 as nitrogen source.

Eight‐week‐old plants were cut 4.0 cm above the root system and then harvested over a 14‐day period of regrowth on the same initial nutrient solution, except that nitrate was 15N labelled. Throughout the experimental period, nitrate storage and reduction in roots were low. In stubble and especially in leaves, nitrate accumulated during the first 6 days of regrowth whereas nitrate reduction mainly occurred after this period. Analyses of carbohydrate, chloride and potassium contents in stubble and leaves showed that the accumulation of nitrate osmotically compensated for the decrease in soluble sugars during the first 6 days of regrowth.

The cumulative osmotic potential of sugars, chloride and nitrate in differently treated plants was studied in stubble and leaves. Compared with uncut plants, the lower carbohydrate concentrations found in cut plants regrowing on 1.0 mM NH4NO3 were compensated for by an accumulation of nitrate. During aftermath growth on low nitrogen nutrition (0.2 mM NH4NO3), chloride replaced nitrate, supporting the proposed osmotic function of nitrate.

It is concluded that nitrate is involved in the osmotic adjustment of ryegrass during regrowth after cutting.
Lipoxygenases
Authors: Hildebrand David F.
Published: May 2006

Lipoxygenases (EC 1.13.11.12), commonly found in plant tissues, catalyze peroxidation of polyunsaturated fatty acids to various primary and secondary oxidation products. Some of these products affect the aroma of foods and some may be of significance in plant growth and development and/or pest resistance.
Comparative study of the composition of waxes extracted from isolated leaf cuticles and from whole leaves of Citrus: Evidence for selective extraction
Authors: Riederer Markus , Schneider Gerhard
Published: May 2006

The effect of different extraction methods on the composition of samples of soluble cuticular lipids (SCL) of Citrus aurantium L. was investigated. The variation of extraction yields, when whole leaves were immersed in solvent, was studied as a function of solvent type and duration of immersion. Cuticular waxes were also quantitatively extracted from isolated cuticular membranes of C. aurantium and their composition was compared to that of samples obtained by the immersion method. Significant differences were observed. Higher carbon number homologues of the aliphatic constituent classes were discriminated against when whole C. aurantium leaves were extracted by immersion. The alkyl ester fraction was almost entirely lacking in extracts from whole leaves. The dependence on carbon chain length of the saturation concentrations in chloroform of major aliphatic SCL constituents was determined. The results are discussed in terms of the major physico‐chemical processes involved in the extraction of SCL.
Thermosensitive genetic dwarfs of apple
Authors: Steffens G. L. , Jacobs F. W. , Engelhaupt M. E.
Published: May 2006

The role of environment on the dwarfing (short internode) phenomenon of apple (Malus domestisca Borkh.) was investi gated and defined in controlled environmental chambers. Orchard‐grown very dwarf, dwarf and semi‐dwarf trees obtained by natural sibcrossing of spur‐type cv. Golden Delicious and cv. Delicious, as well as standard cv. Golden Delicious, were propagated via in vitro techniques. Growth was rapid and none of the 4 types exhibited dwarf‐like characteristics when grown at constant 27°C with 12, 14 or 16 h daylengths. Standard and very dwarf plants grew at nearly the same rate at constant 30°C, whereas growth nearly ceased on both types at constant 35°C after 7 days. Dwarf and very dwarf plants responded differently from standard and semi‐dwarf plants when grown under alternating (ramped) night/day temperatures (15 or 20°C night ramped up to a daytime maximum over 8 h of 23, 28, 33 or 38°C, held for 2 h and then ramped down over 5 h to the night temperature). As the night/maximum day temperature differentia) increased from 0 to 23° under the ramping environments, growth of dwarf plants decreased markedly as compared to standard plants. When the same night/maximum day temperature differential occurred, the effect on decreasing shoot length was greater at the higher (20°C) night temperature. Increasing maximum day temperatures under the ramped environment also reduced leaf area plant−1 but did not markedly affect leaf number, resulting in short internodes. When a period of constant temperature was followed by ramped temperatures or vice versa, the sequence of constant vs ramped environments made little difference in the final growth of the 4 plant types. The data point to high temperature as the major factor for causing dwarfing of the sensitive plant types. Increasing the differential between night and maximum day temperature resulted in short internode. dwarf plants with small leaves similar to orchard‐grown dwarf trees.
Apical control of lateral bud development and shoot growth in mulberry (Morus alba)
Authors: Suzuki Takeo
Published: May 2006

Measurements of changes in the degree of dominance by upper laterals over lower ones in coppice shoots (1‐year‐old stems) of 12‐year old low‐ pruned stumps of mulberry (Morus alba L. cv. Shin‐ichinose) were made by removal of upper stem sections (pruning) or of lateral buds (debudding.) before spring bud burst, as part of a study of the factors involved in dominance relationships between the developing buds and elongating shoots. Besides inhibition of lower laterals by the upper, leading shoots, there was evidence for mutual inhibition (competition) of neighboring laterals along the stem. Thus in stems in which every other bud, or 4 out of every 5 buds were removed, there was a delay in growth cessation of lower laterals and their greater elongation than in controls. Such competition was seen to exist even between the uppermost and sub‐terminal laterals, since the former elongated more in the absence of the latter.

In contrast to high and middle pruned stems, the delay in sprouting of the buds in low‐pruned stems resulted in limited elongation of the shoots from such buds. This inhibition was removed when all the stems on a stump were pruned to the same length, suggesting that it was associated with intact stems with actively growing laterals. Patterns of regrowth of the short shoots (lower laterals) after summer pruning (middle‐pruned) depended on the extent of removal of other stems with vigorously growing, upper laterals. These results demonstrate that both acropetal and basipetal influences are important in bud and shoot dominance relationships.
Changes in osmotic pressure and cell wall properties during auxin‐ and ethylene‐induced growth of intact coleoptiles of rice
Authors: Hoson Takayuki , Maeda Sumiko , Sakaguchi Keiko , Onishi Iliroko , Ohta Hisashi
Published: May 2006

Indole‐3‐acetic acid and 1‐aminocyclopropane‐1‐carboxylic acid, the precursor of ethylene, stimulated elongation of coleoptiles of seedlings of intact rice (Oryza sativa L. cv. Sasanishiki) submerged in buffer solution with constant air‐bubbling. The osmotic pressure of the cell sap decreased during elongation of coleoptiles. In the presence of 30 μM aminooxyacetic acid, an inhibitor of ethylene biosynthesis, in‐dole‐3‐acetic acid at 30 μM accelerated the decrease in the osmotic pressure in the early stage of growth. 1‐Aminocyclopropane‐1‐carboxylic acid at 30 μM did not influence the decrease in the osmotic pressure.

Both indole‐3‐acetic acid and 1‐aminocyclopropane‐1‐carboxyIic acid decreased the minimum stress‐relaxation time and the relaxation rate of the cell wall, suggesting that both auxin and ethylene induce elongation of rice coleoptiles by stimulating cell wall loosening. These growth regulators caused an increase in the level of glucose in hemicelluloses in the early stage of growth and a decrease in the level in the subsequent last growth phase. Indole‐3‐acetic acid decreased the hydroxyproline and glucosamine levels per unit dry weight of the cell wall. These changes in the level of cell wall components may be associated with the changes in the mechanical properties of the cell walls caused by auxin and ethylene.
Glycolate metabolism in cyanobacteria. IV. Uptake, growth and metabolic pathways
Authors: Renström‐Kellner Eva , Bergman Birgitta
Published: May 2006

Anacystis nidulans (UTEX 625) and Anabaena cylindrical (CCAP 1403/2a) incorporated minor quantities of [14C]‐glycolate via diffusion, whereas Plectonema boryanum (PCC 73110) and Nostoc 268 rapidly incorporated [14C]‐glycolate. A carrier mediated uptake across the membrane is suggested for the two latter strains. In these strains the initial [14C]‐glycolate incorporation (>30 s) was inhibited by the uncoupler m‐chlorophenylhydrazone and the F0F1‐ATPase inhibitor N,N′‐dicyelohcxylearbodiimide (DCCD) but was not affected by inhibitors of glycolate metabolism: 2‐pvridyl‐hydroxymethanesulfonic acid (HPMS), glycidate, aminooxyacetic acid and aminoacetoniirile. The incorporation rate was about 0.5 and 40 umol (ma chl a)−1 h−1 at 17 μM and 5 mM glycolate, respectively, Anacystis nidulans did not grow on gtycolate. whereas Anabaena cylindrical to some extent did which suggests an inducible glycolate uptake system in this strain. Anahaena 7120 and Nostoc 268 grew photoheterotrophically on glycolate. The reduced [14C]‐glvcolale uptake by Anabaena 7120 in the presence of glycidate. aminooxyaeetic acid and aminoacetonitrile indicates that in the light, a large part of the [14C]‐glycolate incorporated was metabolized via glycine to serine. The net uptake of [14C]‐glycolate and the effect of different inhibitors was dependent on the source of nitrogen used (for growth and the nitrogen status during the assay. In cells cultivated in N‐free medium (nitrogen‐fixing cells) a larger part of the [14C]‐glycolate seemed to be metabolized via glycine to serine compared to that in cells cultivated in presence of NH4Cl (nonnitrogen‐fixing cells). The capacity to incorporate [14C]‐glyeolate by non‐nitrouen‐fixing cells was enhanced in presence of NH4CI.
Effects of temperature and photoperiod on vegetative growth of white clover (Trifolium repens) ecotypes
Authors: Junttila Olavi , Svenning Mette M. , Solheim Bjørn
Published: May 2006

Effects of photoperiod and temperature on vegetative growth of seedling populations and clones of white clover (Trifolium repens L.) originating from various latitudes (58°48′–69°54′N) and altitudes (up to 1100 m above sea level) were studied in a phytotron. Dry matter production, stolon elongation, petiole elongation and leaf lamina size were enhanced by long photoperiod. The requirement for long photoperiod increased with decreasing temperature. At 6°C the maximum growth was recorded under 24‐h daylength. At 18°C already an increase in photoperiod from 12 to 15 h significantly enhanced growth, and maximum growth was obtained at 21‐h photoperiod. The studied populations responded similarly to daylength, and the results did not indicate photoperiodic ecotypes in the material. The southernmost clones and populations generally had the highest dry matter production at all temperature treatments (6–18°C). Variation between clones within one location was, however, significant, and rapidly growing clones were found also in high‐latitude locations. Dry matter production was poorly correlated with the morphological characters observed, but in some cases significant correlation with leaf lamina size was found.
Characterization of a proton translocating ATPase and sucrose uptake in a tonoplast‐enriched vesicle fraction from sugarcane
Authors: Williams Lorraine , Thom Margaret , Maretzki Andrew
Published: May 2006

A sucrose gradient fraction was used to characterize the tonoplast ATPase from storage tissue of the sugarcane plant (Saccharum sp. var. H57–5175). Marker enzyme analyses and characterization of low‐density vesicles isolated on a sucrose gradient were consistent with a highly enriched tonoplast fraction. ATPase and proton transport activities were both substantially inhibited by nitrate (80%), but very little by vanadate (10%), indicating a high titer of tonoplast compared to plasma‐membrane vesicles in the fraction. Sensitivity toward other inhibitors, as well as ion effects, correlated closely among ATPase and proton translocation activities. Although the vesicles in this fraction showed good proton translocating activity there was no indication that ATP stimulated sucrose uptake in this tonoplast population.
Rapid growth responses of dark‐grown wheat seedlings to red‐light irradiation. II. Kinetic studies on the growth of different coleoptile zones
Authors: Bleiss W. , Ludwig M.
Published: May 2006

Continuous recordings of the effect of red light on the over‐all and zonal growth responses were made on intact, dark‐grown wheat (Triticum aestivum L., cv. Hatri) seedlings selected 70 or 90 h after sowing. The over‐all growth response of intact coleoptiles induced by bilateral continuous red light (660 nm, 17 W m−2) was complex and resulted from the overlapping of different zonal growth responses. During a 5 h investigation period, these responses can be divided into two phases. The first phase (short‐term response) was a transient growth inhibition. After a lag period of ca 15 min, the rate of extension decelerated to a minimum value at ca 60 min, after which an acceleration was seen. This response was qualitatively the same in all coleoptile zones investigated (tip, subapical zone, base) and independent of coleoptile age. The second phase (delayed response) became measurable between 1.8 and 3 h after onset of red light irradiation and exhibited zonal‐specific growth promotion or inhibition, dependent on the coleoptile age. A persistent growth promotion was observed only in the tip region of coleoptiles selected 70 h after sowing and became detectable about 3 h after the onset of red light.
Biochemical composition and photosynthetic activity of chloroplasts from Striga hermonthica and Striga aspera, root parasites of field‐grown cereals
Authors: Tuquet Christiane , Farineau Nicole , Salé Georges
Published: May 2006

Striga hermonthica(Del.) Benth. and Striga aspera (Willd.) Benth. are root parasites causing dramatic losses in field‐grown cereals in semi‐and tropics. Being achlorophyllous and obligate parasites during their underground development, upon emergence from the soil, they become green leafy plants; but, despite the presence of chlorophyll, they exhibit only low rates of photosynthesis. To investigate if deficiency in the photosynthetic apparatus could account for the low rates of photosynthesis, chloroplasts were isolated from S. hermonthica parasitizing sorghum [Sorghum bicolor (L.) Moench cv. Tiemarifing] and from S. aspera parasitizing maize (Zea mays L. cv. Tiémantié) grown under greenhouse conditions or in their natural surroundings. Isolated chloroplasts exhibited the characteristics of chloroplasts from C3 plants but displayed low levels of chlorophyll and polar lipids, while the protein content was less reduced. Main changes occurred in polar lipid composition, with decreases in monogalactosyldiacylglycerol and digalactosyldiacylglycerol. All polar lipids showed a decrease in the degree of unsaturation of fatly acids. All these changes were particularly pronounced in chloroplasts from plants that experienced heavy drought in Africa. On a chlorophyll basis, chloroplasts did not display a dramatic decrease in photosynthetic activities. These results are discussed in relation to parasitism and drought adaptation.
A novel shrunken endosperm mutant of barley
Authors: Sclulman Alan H. , Ahokas Hannu
Published: May 2006

Although mutations affecting several enzymes of the starch synthetic pathway in developing cereal endosperm have been isolated, none has a major effect on soluble starch synthase We report a new recessive shrunken endosperm mutant in barley (Hordeum vulgare L. cv. Bomi‐like), shx, which has 25% of normal starch content. We have assayed the activity of sucrose synthase (EC 2.4.1.13), ADP and UDP‐glucose pyrophosphorylases (EC 2.7.7.27 and 2.7.7.9), branching enzyme (EC.2.4.1.18), and granule‐bound and soluble starch synthase (EC 2.4.1.21) in shx. Sucrose synthase activity is reduced by 49% and UDP‐glucose pyrrphosphorylase is 80% of the normal level. Branching enzyme and starch‐bound starch synthase activities are normal, but ADP‐glucose pyrophosphorylase activity is reduced by 72%. The soluble starch synthase that is primer‐independent in the presence of sodium citrate shows 14% of normal activity in shx. whereas the primer‐dependent form is unaffected. This lower starch synthase activity in shx cannot be explained by inhibition, substrate destruction or lack of primer. Although several starch‐synthetic enzymes are affected, it is suggested that the primer independent from of soluble starch synthase may be the primary‐site of the mutation in shx.
The influence of plant water deficit on photosynthesis and translocation of 14C‐labeled assimilates in cacao seedlings
Authors: Deng Ximin , Joly Robert J. , Hahn Daniel T.
Published: May 2006

The effect of plant status on net assimilation and translocation of “C‐labeled assimilates in cacao (Theobroma cacao L.) was evaluated. As plant water potential (ψ) decreased from −0.5 to −1.0 MPa, neither net assimilation nor the rate of label translocation out of the l4CO,‐fed leaf were affected, but as iji fell between −1.0 and −1.5 MPa, net assimilation decreased sharply and label retention increased greatly. Translocation out of source leaves was strongly correlated with net assimilation (r =−0.93). Translocation velocity, assessed by detection of labeled assimilates in sink leaves, was sensitive to plant water deficit, and it declined linearly (r = 0.97) throughout the range of leaf water potentials observed. The results may be explained by reduction in the velocity of assimilate movement within the sieve elements, reduction in supply of labeled assimilates from source leaves, reduction in sink strength or diversion of assimilates to sites of storage or utilization.
Liposome‐mediated gene delivery into plant cells
Authors: Gad A. E. , Rosenberg N. , Altman A.
Published: May 2006

Liposomes may offer several advantages as vectors for gene delivery into plant cells: (1) enhanced delivery of encapsulated DNA by membrane fusion, (2) protection of nucleic acids from nuclease activity, (3) targeting to specific cells, (4) delivery into a variety of cell types besides protoplasts by entry through plasmodesmata, (5) delivery of intact small organelles. Realization of these advantages calls for the construction of efficient liposomes, for appropriate fusion conditions and for an understanding of the nature of liposome‐cell interactions. Various characteristics and techniques of the liposome‐cell system are described (mode of delivery, liposome types and composition, and means of promoting delivery of liposome contents). Data of liposome‐mediated delivery of various macromolecules into plant cells, with special reference to protoplasts, calli and pollen are reviewed. This includes data obtained by the use of fluorescent probes, radioactive‐labelled DNA, viral nucleic acids and expression of plasmid‐DNA. Structure and characteristics of plant surfaces and plasmodesmata are discussed with respect to DNA entry. It is suggested that liposome‐mediated gene delivery into plant cells, and not only protoplasts, will be advantageous in certain specific tissues and situations.
Aluminium interactions with K+(86Rb+) and 45Ca2+ fluxes in three cultivars of sugar beet (Beta vulgaris)
Authors: Lindberg Sylvia
Published: May 2006

Three cultivars of sugar beet (Beta vulgaris L.), which are sensitive to aluminium (Al) in the order Primahill > Monohill > Regina, were grown in water culture for 2 weeks. Nutrients were supplied at 15% increase of amounts daily, corresponding to the nutrient demand for maximal growth. The 2.4‐dinitrophenol (DNP)‐sensitive (metabolic) and DNP‐insensitive (non‐metabolic) uptake of aluminium, phosphate. 45Ca2+ and K+(86Rb+) in roots were measured as well as transport to shoots of intact plants. All 3 cultivars absorbed more aluminium if DNP was present during the aluminium treatment than in its absence. It is suggested that sugar beets are able to extrude aluminium activity or that they possess an active mechanism to keep Al outside the cell.

The presence of Al in the medium during the 1‐h experiment affected the metabolic and non‐metabolic fluxes of 45Ca2+ and K+(86Rb+) in different ways. In the presence of DNP, the influx of both 45Ca2+ and K+(86Rb+) and the efflux of 45Ca2+ were inhibited by Al in a competitive way. At inhibition of 45Ca2+ influx, 2 Al ions are probably bound per Ca2+ uptake site in cv. Regina (Al‐tolerant), but in cvs Primahill and Monohill only one Al ion is bound (more Al sensitive). Aluminium competitively inhibited the active efflux of 45Ca2+ (absence of DNP) in almost the same way in the 3 cultivars. In contrast, aluminium stimulated the influx of K+(86Rb+) in cvs Primahill, Monohill and Regina in the absence of DNP. Thus, the Al effects on active and passive K+(86Rb+) influx are different. The total influx of K+(86Rb+) increased in the presence of Al and might be connected to an active exclusion of Al. Regina is the least Al‐sensitive cultivar, probably because Al interferes less with the Ca2+ fluxes and because this cultivar actively excludes phosphate in the presence of Al. Thus Al‐phosphate precipitation within the plant could be avoided.
The effect of blue light on energy levels in epidermal strips
Authors: Agbariah Khaled‐Taha , Roth‐Bejerano Nurit
Published: May 2006

Red light applied together with blue enhanced stomatal opening in epidermal strips of Commelina communis L. more than red light alone. In red light, stomatal opening was enhanced by exogenously applied ATP and was inhibited by 3‐(3,4‐dichlorophe‐nyl)‐l,l‐dimethylurea (DCMU), while in the presence of blue light external ATP was almost without effect, and DCMU stimulated stomatal opening. Blue light increased the ATP levels in the epidermal strips. DCMU diminished the amount of ATP in both red light and red + blue light treatments, but did not abolish the stimulatory effect of blue light. Blue light also stimulated the respiration rate of the epidermal strips. Rotenone, which inhibited stomatal opening and respiration rate, abolished the effect of blue light in both processes. These results imply that blue light increases the ATP levels by stimulation of oxidative phosphorylation.
Characterization of a Ca2+‐translocating ATPase from corn root microsomes
Authors: Brauer D. , Schubert C. , Tsu S.–I.
Published: May 2006

Brauer, D., Schubert C. and Tu, S,‐I. 1990. Characterization of a Ca2+‐translocating ATPase from corn root microsomes. ‐ Physiol. Plant. 78: 335‐344.

The existence of a Ca2+‐translocating ATPase in microsomes from maize (Zea mays L. cv, WF9 × Mo17) roots was evaluated using assays to follow Ca2+‐stimulation of ATP hydrolysis and Ca2+ transport by changes in the fluorescence of chlorotetracycline, ATP hydrolysis by microsomes was stimulated by the addition of Ca2+ and further enhanced by the Ca ionophore A23187 and bovine brain calmodulin only in the presence of Ca2+, Stimulation by these agents was additive and sensitive to vanadate. These results were consistent with the presence of a Ca2+‐translocating ATPase in microsomal membranes. The fluorescence of chlorotetracycline in the presence of microsomes and Ca2+ increased upon the addition of ATP, indicating the transport of Ca2+, The initial rate and extent of change in fluorescence were stimulated by calmodulin and quenched by the addition of either A23187 or EGTA, but not by protonophores. Changes in chlorotetracycline fluorescence were prevented by vanadate. Therefore, results using chlorotetracycline also indicated the presence of a Ca2+‐translocating ATPase, Localization experiments indicated that the majority of the Ca2+‐translocating ATPase was on the endoplasmic reticulum.
Large‐scale purification procedure of spinach leaf mitochondria —isolation and immunological studies of the F1–ATPase
Authors: Hamasur Beston , Birgersson Ulf , Eriksson AnnaCarin , Glaser Elzbieta
Published: May 2006

A large–scale purification procedure for mitochondria from spinach (Spinacia oteracea L, cv Medania) leaves is described. It involves differential centrifugation and density gradient centrifugation on a self–generating gradient of Percoll, From 3 kg of spinach leaves, 150 mg mitochondrial protein are obtained. The thylakoid contamination is lower than 0.2% on a chlorophyll basis. The mitochondria oxidize malate and glycine with state 3 rates of 108 and 140 nmol (mg protein)‐1 min‐1, with respiratory control ratios of 2,7 and 3,8 and ADP/O ratios of 2,0 and 2.1, respectively. The present large–scale purification procedure will facilitate further biochemical and molecular biological studies of leaf mitochondrial proteins.

A pure and active catalytic moiety of the F1–ATPase (EC 3,6,1,3) was purified from the isolated mitochondria. The yield was 5 mg of F1–ATPase from 150 mg mitochondria. The F1–ATPase contained five polypeptides of apparent molecular mass 54 kDa (α), 52 kDa (β), 33 kDa (γ), 22 kDa (ω) and 11 kDa (ɛ). An additional component at 24 kDa was present in variable amounts in some preparations and was therefore not ascribed to the ATPase complex. The enzyme catalyzed ATP hydrolysis at a rate of 12.5 nmol (mg protein)‐1 min‐1. Antibodies against the spinach mitochondrial F1–ATPase cross–reacted only with the a and β subunits of F1–ATPases of spinach chloroplasts, photosynthetic bacteria Rhodospirillum rubrum and beef heart mitochondria.
Cell wall changes during the expansion and senescence of carnation (Dianthus caryophyllus) petals
Authors: de Vetten N. C. , Huber D. J.
Published: May 2006

Senescence of carnation (Dianthus caryophyllus L. ev. White Sim) petals coincided with a decrease on a per flower basis in the yield of cell wall and ethanol‐insoluble solids. The decrease in cell wall yield per flower was due largely to a loss of neutral sugars, primarily galactose (45%) and arabinose (23%). On a per flower basis, water‐and chelator‐soluble pectins increased throughout development, comprising in senescent petals 18 and 58%, respectively, of total pectin. Alkali‐soluble pectins ranged from 35 to 45% of the total pectin and decreased during senescence. Gel chromatography of chelator‐ and alkali‐soluble pectins revealed no change in molecular size and polygalacturonase activity was not detected. Large‐molecular‐size hemicelluloses decreased during development, an observation reminiscent of the changes affecting hemicelluloses during the ripening of a number of fruit types. Compositional analysis of the large hemicellulosic polymers revealed a decrease in xylose and galactose content.
The water status of the roots of soil‐grown maize in relation to the maturity of their xylem
Authors: Wang X.‐L. , Canny M. J. , McCully M. E.
Published: May 2006

The long delayed maturation of the late metaxylem of maize (Zea mays) roots imposes a high‐resistance barrier between the immature apices and the negative water potential of the leaves. These apices (20+ cm) bear strongly adhering soil sheaths to within 0.5 to 2 cm of the distal end. It was hypothesized that the sheathed immature apices should show less response to transpiration stress than bare regions. Measurements were made of the relative water content (RWC) of the sheathed and bare zones of the axile roots, both at different ages of the plant, and early and late in the day's transpiration. Sheathed roots maintained a steady RWC of about 83% irrespective of age or transpiration. Bare roots had RWCs of about 63% in the morning, but this fell to 55% in the afternoon. The first‐order branches on the bare roots in the morning had still lower values of RWC, near 50%. Plots of RWC against water potential were indistinguishable for the three root types. It is concluded that the immature apices are indeed relatively isolated from the fluctuating tensions in the stem xylem, and that these tensions reduce the water content of bare roots and their branches to low values.
Regulation of ethylene biosynthesis in citrus leaves infected with Xanthomonas campestris pv. citri
Authors: Dutta Sunil , Biggs Robert Hilton
Published: May 2006

Inoculation of Poncirus trifoliata (L.) Raf. x Citrus Paradisi Macf. (Swingle citrumelo) leaves with Xanthomonas campestris pv. citri (Hasse) Dye (Xc). a nursery strain of bacteria causing citrus canker, induced significant ethylene production. No ethylene biosynthesis was induced by Xanthomonas campestris pv. dieffenbachiae (McCulloh and Pirrone) Dye (Xd), a non pathogen to citrus. Leaves inoculated with Xc had a higher endogenous 1‐aminocyclopropane‐1‐carboxylic acid (ACC) content than the leaves treated with aminoethoxyvinylglycine (AVG) or streptomycin before inoculation. All the inhibitors of ethylene biosynthesis tested were effective in suppression of ethylene production from Xc inoculated leaves. The inhibitors also suppressed the rate of disease progression. Major points of regulation of pathogen induced ethylene appear to reside at the transcriptional and/or translational levels, as indicated by the inhibitor studies. It appears that the pathogen‐induced ethylene biosynthesis in this case is closely associated with disease progression and that denovo induction and activation of ACC synthase is the key step in the induction of ethylene production. The induction of ethylene production as a result of pathogen invasion may be a plant defense response as it leads to the abscission of leaves which helps retard the spread of the pathogen into the plant‐system.
Nonstructural carbohydrate metabolism during leaf ageing in tobacco (Nicotiana tabacum)
Authors: Crafts‐Brandner Steven J.
Published: May 2006

Nonstructural carbohydrate status and activities of ADP‐glucose pyrophosphorylase (EC 2.7.7.27, ADPG pyrophosphorylase) and sucrose phosphate synthase (EC 2.4.1.14, SPS) were determined during ageing of tobacco (Nicotiana tabacum L., cvs KY 14 and Speight G28) leaves sampled from control plants and from plants that had the apical meristem and subsequent axillary growth removed (detopped plants). Over the 30‐day period shoot growth increased much more for control compared to detopped plants, but the increase in root growth was similar for both treatments. Dry matter and leaf area of the individual leaf used for enzyme and metabolite analysis were constant over time for controls but increased 5‐fold for detopped plants. Ageing of control leaves was indicated by a progressive loss of chlorophyll and ribulose 1, 5‐bisphosphate carboxylase (EC 4.1.1.39, Rubisco) activity; loss of these components was diminished for detopped plants. In contrast to chlorophyll and Rubisco activity, activities of ADPG pyrophosphorylase and SPS remained relatively constant over time for controls. Thus, under normal ageing conditions, changes in activities of ADPG pyrophosphorylase and SPS were not closely associated with changes in the standard senescence indicators chlorophyll and Rubisco activity. The activities of ADPG pyrophosphorylase and SPS were enhanced, relative to controls, within 6 days after applying the detopping treatment and activities remained high for the duration of the 30‐day period. Detopping also led to increased concentrations of starch and sucrose, but the increases were not well correlated with changes in enzyme activities. The data indicated that the leaves of detopped plants functioned as both source leaves, with enhanced ability to synthesize carbohydrate, and sink leaves, with enhanced growth. Therefore, activities of ADPG pyrophosphorylase and SPS were more responsive to changes within an individual leaf than to changes in whole plant growth.