bluuebunny/crossref_metadata_2025 huggingface dataset:
A role for young leaves in vernalization of cauliflower: I. Analysis of leaf development during curd induction
Authors: Williams C. A. , Atherton J. G.
Published: May 2006

Growth analysis techniques are used to test the hypothesis that chilling induces curd (flower) initiation in the cauliflower (Brassica oleracea Botrytis L. cv. Perfection) through inhibiting leaf growth, thereby increasing the availability of growth factors to the stem apex and enabling differentiation of the curd. Effects of chilling on leaf growth and curd induction are compared in juvenile and mature, vegetative plants. Chilling at 5°C reduced dry matter accumulation in the total leaf complement by ca 60% in juvenile plants and 40% in mature plants, compared to control plants growth at 20°C. Juvenile plants showed slower rates of leaf initiation than mature plants. Leaf initiation was retarded by chilling in both plant types with the most marked effect seen in the juvenile plants. This was consistent with dry matter availability to the stem apex limiting differentiation more severely in juvenile plants than in mature plants. The rate of dry matter accumulation in existing leaves, however, was faster in juvenile plants than in mature plants at 20°C. Plants that were juvenile during chilling produced an average of 43 leaves below the curd whereas those that were mature produced 25.

Dry matter accumulation in younger leaves was more markedly inhibited by chilling than in older leaves. Chilling also reduced the rate at which enlarging leaves became positionally more remote from the stem apex. Possible roles for such leaves in regulating apical development are considered.
Reversion of the apical hook of pea in the dark and its promotion by a red light pulse.
Authors: Takagi Toshihiro , Tsurumi Seiji , Hashimoto Tohru
Published: May 2006

At the developmental stage at which the apical hook passed the 3rd and 4th nodes, dark‐grown seedlings of pea (Pisum sativum L. cv. Progress No.9) opened the hook upright and then formed a new hook above the node nearly in the opposite direction to the previous one. In cv. Alaska, in contrast, many (about 84%) seedlings closed the hook in the original direction after they partially (up to about 110°) opened it at the 3rd node, thus doing a wagging movement, while a small percentage (about 16%) of the seedlings reversed the hook direction. Exposure to red light of cv. Alaska seedlings for 10 min increased the percentage of the hook reversion up to 71% or more. The hook reversion was never observed except when the hook part passed the nodes, suggesting the involvement of the nodes in the phenomenon.
Influence of aluminium on biomass, nutrients, soluble carbohydrates and phenols in beech (Fagus sylvatica)
Authors: Påhlsson Anna‐Maj Balsberg
Published: May 2006

The effects of aluminium on biomass, nutrients and soluble carbohydrates and phenols were studied in beech (Fagus sylvatica L.) seedlings. After germination, seedlings with cotyledons and the buds of the first leaf‐pair developed, were preconditioned for two weeks and then grown for 31 days in nutrient solutions containing 0.1, 0.5, 1.0 or 2.0 mM A1C13. Aluminium did not affect the dry weights of roots but at Al concentrations ≥ 1.0 mM the development of the terminal shoot above the first leaf pair, was reduced by 80% or more. The concentrations of most nutrients (P, Ca, Mg, Zn, Cu) in the plant tissues decreased strongly even at the lowest Al levels, but K increased in the shoots. The tissue concentration of N was not affected of Al. but the distribution between the organs was changed to a higher content of N in the roots. At ≥1.0 mM Al the concentrations of starch in both the shoots and the roots were significantly increased, and at ≥ 0.5 mM the roots contained more of total phenols than untreated seedlings. The elevated concentrations and contents of starch and phenols in the seedlings may partly be related to the reduced shoot growth. The observed effects of Al were marked already at Al levels found in soil waters from beech forests in southern Sweden.
Carbohydrates and carbohydrate enzymes in developing cotton ovules
Authors: Hendrix Donald L.
Published: May 2006

Patterns of carbohydrates and carbohydrate enzymes were investigated in developing cotton ovules to establish which of these might be related to sink strength in developing bolls. Enzymatic analysis of extracted tissue indicated that beginning 1 week following anthesis, immature cotton seeds (Gossypium hirsutum L. cv. Coker 100A glandless) accumulated starch in the tissues which surround the embryo. Starting at 15 days post anthesis (DPA), this starch was depleted and starch simultaneously appeared in the embryo. Sucrose entering the tissues surrounding the embryo was rapidly degraded, apparently by sucrose synthase; the free hexose content of these tissues reached a peak at about 20 DPA. During the first few weeks of development these tissues contained substantial amounts of hexose but little sucrose; the reverse was true for cotton embryos. Embryo sucrose content rose sharply from the end of the first week until about 20 DPA; it then remained roughly constant during seed maturation. Galactinol synthase (EC 2.4.1.x) appeared in the embryos approximately 25 days after flowering. Subsequently, starch disappeared and the galactosides raffinose and stachyose appeared in the embryo. Except near maturity, sucrose synthase (EC 2.4.1.13) activity in the embryos predominated over that of both sucrose phosphate synthase (EC 2.4.1.14) and acid invertase (EC 3.2.1.26). Activities of the latter enzymes increased during the final stages of embryo maturation. The ratio of sucrose synthase to sucrose phosphate synthase was found to be high in young cotton embryos but the ratio reversed about 45 DPA, when developing ovules cease being assimilate sinks. Insoluble acid invertase was present in developing cotton embryos, but at very low activities; soluble acid invertase was present at significant activities only in nearly mature embryos. From these data it appears that sucrose synthase plays an important role in young cotton ovule carbohydrate partitioning and that sucrose phosphate synthase and the galactoside synthesizing enzymes assume the dominant roles in carbohydrate partitioning in nearly mature cotton seeds. Starch was found to be an important carbohydrate intermediate during the middle stages of cotton ovule development and raffinose and stachyose were found to be important carbohydrate pools in mature cotton seeds.
Monoterpene glycoside biosynthesis in detached grape berries grown in vitro
Authors: Bravdo B. , Shoseyov O. , Ikan R. , Altman A.
Published: May 2006

A procedure for the culture in vitro of isolated small berries of Vitis vinifera L. cv. Muscat of Alexandria in a Murashige and Skoog basal medium supplemented with N6‐benzyladenine and indoleacetic acid is described. Berries developed well in culture during 60 days and tripled in size, but remained green and smaller than normal berries grown in vivo. Some callus formed on the distal end of the berry, and where major skin damage occurred, callus emerged from the cracked berries. In order to examine their biosynthetic competency, berries which were previously cultured in vitro for 60 days were incubated for 48 h in a Murashige and Skoog medium containing a [14C]‐labelled water‐soluble fraction. This fraction was isolated from grape berries located adjacent to a leaf that had been exposed to gaseous 14CO2 in full sunlight for 5 h. The berries were then recultured for 48 h after which a glycosidic fraction was isolated on a C18 reversed phase column and further separated by thin layer chromatography (TLC). The major labelled band corresponded to the geranyl‐β‐rutinoside marker, indicating that grape berries have the ability to synthesize monoterpene glycosides. This band also consisted of other monoterpene glycosides as revealed by the gas chromatography‐mass spectrometry (GC‐MS) analysis of their aglycones (released by enzymatic hydrolysis).
Adenylate control of respiration in plants: the contribution of rotenone‐insensitive electron transport to ADP‐limited oxygen consumption by soybean mitochondria
Authors: Bryce James H. , Azcon‐Bieto Joaquim , Wiskich Joseph T. , Day David A.
Published: May 2006

The aim was to test the hypothesis that rotenone‐insensive electron transport (bypass of complex I) may underlie rapid state 4 (ADP‐limited) mitochondrial respiration. A comparison of mitochondria from soybean (Glycine max L. cv. Bragg) cotyledons and nodules showed that ADP‐sufficient (state 3) malate plus pyruvate oxidation by mitochondria from 7‐day‐old cotyledons was inhibited 50% by rotenone and state 4 rates were rapid, whereas nodule mitochondria were 80% inhibited by rotenone and had slower state 4 rates of malate plus pyruvate oxidation. Respiration of malate alone (pH 7.6) by cotyledon mitochondria was slow, especially in the absence of ADP; subsequent addition of pyruvate dramatically increased state 4 oxygen uptake concomitant with a rapid rise in mitochondrial NADH (determined by fluorimetry). Rotenone had no effect on this increased rate of state 4 respiration. The rate of malate oxidation by nodule mitochondria was relatively rapid compared with cotyledon mitochondria. The addition of pyruvate in state 4 caused a slow increase in matrix NADH and only a slight stimulation of oxygen uptake. Rotenone inhibited state 4 malate plus pyruvate oxidation by 50% in these mitochondria. From a large number of cotyledon and nodule mitochondrial preparations, a close correlation was found between the rate of state 4 oxygen uptake and rotenone‐resistance. During cotyledon development increased rotenone‐resistance was associated with an increase in the alternative oxidase. Addition of pyruvate to cotyledon mitochondria, during state 4 oxidation of malate in the presence of antimycin A, significantly stimulated O2 uptake and also almost eliminated respiratory control. Such combined operation of the rotenone‐insensitive bypass and the alternative oxidase in vivo will significantly affect the extent to which adenylates control the rate of electron transport.
Supercooling ability in apple seeds as affected by temperature‐induced modifications in water relations in the seed parts
Authors: Nguyen Xuan Vingh , Kacperska Alina
Published: May 2006

Prolonged storage of apple fruits (Pyrus malus L. cv. Golden Delicious) at different temperatures (0, 12 and 35°C) decreased the water content in seed coats and endosperms, higher temperatures being much more effective than the lower (0°C) one. No effect of the temperature on the embryo hydration was found. However, a pronounced decrease in water potential in the embryos was observed during the first 9 weeks. The decrease was much faster and the water potential reached lower levels in embryos isolated from seeds pretreated with higher temperatures (12 or 35°C) than from cold‐pretreated (0°C) material. Higher temperatures of fruit storage also resulted in a decreased permeability of the embryo membranes to electrolytes and sugars. At the same time, membrane permeability to water was not modified. It is proposed that the previously observed occurrence of the discontinuous type of freezing in apple seeds (Nguyen and Kacperska, Physiologia Plantarum (X): 000‐000, 1989) is associated with the temperature‐induced dehydration of seed coat and endosperm, whereas a higher super cooling ability of the high‐temperature‐pretreated embryos is due to a decrease in the free energy of water in the system, and to the effective protection of embryo cells against heterogenous ice nucleation. The changes in water potential showed a high negative correlation with the embryo phospholipid content determined in the other work (Nguyen et al. Plant Physiol. Bio chem. 25: 697–703, 1987). Therefore, it is proposed that changes in matrix potential play an important role in the regulation of the water potential in the embryo cells.
Soret absorption of intermediate(s) in protochlorophyllide to chlorophyllide photoreduction trapped at low temperature
Authors: Dujardin Esther , Kahn Albert , Mathis Paul
Published: May 2006

Absorption spectra at ca 100 K from 400 to 750 nm and fluorescence emission spectra at 77 K from 600 to 750 nm were obtained from: 1) etiolated leaves of the H‐ordeum vulgare L. (barley) mutant albozonata 2 and SAN 9789‐treated Avena sativa L. (oat) with low levels of carotenoids, and 2) preparations of protochlorophyllide holo‐chrome from Phaseolus vulgaris L. cv. Commodore (bean).

This allowed clear resolution for the first time of the Soret bands of the green pigments before and after light‐induced accumulation of intermediate(s) in protochlorophyllide to chlorophyllide photoreduction and after conversion of the intermediate(s) to chlorophyllide by warming the samples to 233 K in darkness. Although the intermediate(s) differ(s) in absorption and fluorescence in the red wavelength region from both protochlorophyllide and chlorophyllide, the extinction in the Soret band is not distinguishable from that of chlorophyllide. These observations indicate that the C7‐C8 double bond in ring IV of protochlorophyllide has been altered in intermediate(s) accumulated at low temperature in intense light, such that the transition state exhibits the character of a π complex.
Time‐dependent changes in polypeptide and translatable mRNA levels caused by NaCl in barley roots
Authors: Robinson Nina L. , Tanaka Chariene K. , Hurkman William J.
Published: May 2006

The effect of salt stress on polypeptide and translatable mRNA levels was examined in roots of barley (Hordeum vulgare L. cv. CM 72). A salt‐shock time course (200 mM NaCl added to the nutrient solution of 5‐day old seedlings for up to 24 h) and a 6‐day salt treatment (seedlings grown in nutrient solution containing 200 mM NaCl for 6 days) were compared. Roots of intact seedlings were labeled in vivo with [35S]‐methionine. Poly(A)+ RNA was isolated and assayed in an in vitro translation system. The changes in the levels of the labeled polypeptides and translation products were analyzed following separation on two‐dimensional polyacrylamide gels. Over the salt‐shock time course, the majority of the changes in polypeptides and translation products were quantitative, as were the changes at 6 days. Qualitative changes occurred during the salt‐shock time course, but were not observed at 6 days. The levels of polypeptides and translation products differed at each point of the salt‐shock time course and at 6 days. In addition, changes were observed at the shortest time points examined, indicating a rapid response to salt.
NH+4 release by non‐growing cultures of the cyanobacterium Mkrocystis firma
Authors: Abarzua Sibylle , Nietz Kathleen
Published: May 2006

The rhythmic changes in NH+4 concentration previously observed in an eutrophic shallow estuary under conditions of growth limitation, NH+4 addition and dominance of cyanobacteria were studied in laboratory cultures of the cyanobacterium Microcystis firma (Breb et Lenorm.) Schmidle, strain Gromov/Len. 398. The rhythm was induced in M. firma by means of carbon limitation and light/dark alternation, and was characterized by a decrease in NH+4 in the growth medium during the first hours of the light phase and an increase in NH+4 in the late light phase lasting until the end of the dark phase. Inhibition of the glutamine synthetase/glutamate synthase pathway [darkness, lack of C skeletons, inhibitors such as L‐methionine‐D,L‐sulfoximine (MSX)] brought about NH+4 release by the cells. From the various processes generating NH+4 intracellularly (active NH+4 uptake. NO−3 reduction, protein and amino acid degradation, photorespiration), NO−3 reduction appears the most important one. This has been concluded from experiments with and without nitrate and/or ammonium in the growth medium and from experiments with 3‐(3.4‐dichlorophenyl)‐1,1‐dimethyl‐urea (DCMU) and MSX. NO−3 was also taken up and reduced in the presence of external ammonium, probably because of the C limitation under otherwise optimal conditions for photosynthesis. It appears, moreover, that glutamine restricts nitrate uptake during the first hours of the light phase but less in subsequent light periods, when carbon limitation might be more severe. The present results may help explain previous observations under natural conditions, provided that nitrate is available in the water samples. Furthermore, this system enables the occurrence of a new, cheaper and more efficient method of photoproduction of ammonium from nitrate.
UDP‐glucose pyrophosphorylase from the plant fraction of nitrogen‐fixing soybean nodules
Authors: Vella John , Copeland Les
Published: May 2006

UDP‐glucose pyrophosphorylase (EC 2.7.7.9) has been highly purified from the plant fraction of soybean (Glycine max L. Merr. cv Williams) nodules. The purified enzyme gave a single polypeptide band following sodium docecyl sulphate polyacryla‐mide gel electrophoresis, but was resolved into three bands of activity in non‐denaturing gels. The enzyme appeared to be a monomer of molecular weight between 30 and 40 kDa. UDP‐glucose pyrophosphorylase had optimum activity at pH 8.5 and displayed typical hyperbolic kinetics. The enzyme had a requirement for divalent metal ions, and was highly specific for the substrates pyrophosphate and UDP‐glucose in the pyrophosphorolysis direction, and glucose‐1‐phosphate and UTP in the direction of UDP‐glucose synthesis. The Km values were 0.19 mM and 0.07 mM for pyrophosphate and UDP‐glucose, respectively, and 0.23 mM and 0.11 mM for glucose‐1‐phosphate and UTP. The maximum velocity in the pyrophosphorolysis direction was almost double that for the reverse reaction. UDP‐glucose pyrophosphorylase did not appear to be subject to a high degree of fine control, and activity in vivo may be regulated mainly by the availability of the substrates.
Plant hormone response mutants
Authors: Scott I. M.
Published: May 2006

A variety of plant hormone response mutants has now been described, and is surveyed in this article. In addition to hormone‐insensitive mutant phenotypes with defects in hormone‐related features, there exist mutants apparently constitutive for the gibberellin responses, and also a mutant hyper‐responsive to gibberellin. Although there is still little biochemical evidence on the nature of these mutants, the emerging picture of their genetic dominance relationships has given rise to tentative suggestions of the involvement of represser functions in hormonal control systems.
Lipid modulation of plasma membrane‐bound ATPases
Authors: Cooke David T. , Burden Raymond S.
Published: May 2006

The plasma membrane cation‐pumping ATPase is a key regulatory enzyme in cellular events. However, the mechanism by which its activity is controlled is still unclear. Lipid modulation is acknowledged to be a potentially important mechanism in this respect, although precisely how it is achieved remains controversial. This review examines the modulation of plant, animal, yeast and fungal plasma membrane‐bound ATPases by sterols and phospholipids as well as discussing critically two putative modulating mechanisms, the ‘Annulus Hypothesis’ and membrane fluidity. The use of xenobiotics in helping to elucidate the role played by lipids in ATPase regulation is examined and a sequence of events by which lipid modulation may occur is suggested.
Effects of salt wash on the structure of the prolamellar body iembrane and the membrane binding of NADPH–protochlorophyllide oxidoreductase
Authors: Widell–Wigge Anna , Selstam Eva
Published: May 2006

NADPn–protochlorophyllide oxidoreductase (EC 1.6.99.1; PCR) is the major protein component of the prolamellar body (PLB) membrane of the etioplast. The interaction between the pigment–protein complex of PCR and the membrane lipids is of importance for the induction and maintenance of the regularly branched PLB structure. The isoelectric point of the PLB surface and the impact of salt treatment on the PLB structure, the PCR absorbance properties and the association of PCR to the membrane, have been studied in isolated fractions of PLBs from dark–grown wheat (Triticum aestivum L. cv. Starke 11). We conclude that the PLB membrane has its isoelectric point at pH 4.5. which is similar to that of other plastid membranes. The PLB membrane and the pigment–protein complex of PCR are both affected by salt treatment. Concentrations below 50 mM MgCl2, or 250 mM KCI tend to stabilize the regularly branched strueture. while higher concentrations of both mono– and divalent cations lead to disintegration of the membrane and shifts towards shorter wave–lengths of the in vivo absorbance spectra of protoehlorophyllide. PCR. the dominant PLB protein, however, seems to be intimately associated with the membrane lipids and is not washed off the membrane by repeated salt treatment.
Effects of light on phospholipid metabolism in DunaUella salina
Authors: Peeler Thomas C. , Thompson Guy A.
Published: May 2006

Dunalliella salina (Teodoresco) is a unicellular, wall‐less, halotolerant green alga. Previous work has shown that levels of inositol phospholipiils in whole cells of D. salina fluctuate in response to hyper‐ and hypo‐osmotic shock. In this paper, we report the effects of changes in the light environment on levels of phospholipids, including inositol phospholipids, in D. scilina. Utilizing both short‐term and long‐term labeling of phospholipids with 32PO4, we were able to compare both immediate and long‐term changes in lipid metabolism during changes in the light environment. Relative to the other phospholipids. phosphotidic acid and the inositol phospholipids phosphatidylinositol, phosphatidylinositol 4‐phosphate and phosphatidylinositol 4,5‐bisphosphate were rapidly labeled, even in the dark, suggesting that the metabolism of these compounds is more active than that of the bulk cellular phospholipids. There was little change in inositol phospholipid metabolism when cells were illuminated following a 1 h dark adaptation period, Furthermore, the inositol phospholipid signal transduction pathway did not respond to severe photoinhibition treatment. Apparently this plasma‐membrane‐based signal transduction pathway, which responds to changes in the external environment, is relatively insensitive to major changes in chloroplast metabolism.
Stimulation or inhibition of K+(86Rb+)influx in wheat roots depending on different ABA treatments
Authors: Gunvor A , Erlandson L. , Jensen Paul
Published: May 2006

The regulatory role of abscisic acid (ABA) and kinetin on influx of K+(86RB+) IN tools of 7day old intact winter wheat which plant (Fritieun aestivum I ass starke 1 and 11) Was studied the inhibitory effect of 40,80 μM ABA in the uptake solution on K+(86RB+)influx was transiently stipulated pretreatment of the plants with ABA kinetin content enacted inhibitors effect caused by ABA. At low water potential in the uptake solution (05MPa)K+(86RB+) influx was slights higher in the presence of ABA than in is absence High humidity 123kpa ca 100% relative humidity (RID)around the shoots counteracted the inhibitory effect on k+(86RB+) influx caused by A,B,A IN the uptake solution the present data contain the hypothesis that when plants are subjected to conditions such as low water potential and low temperature. ABA stimulates K influx to facilitate water uptake.
Photosynthetic carbon fixation in the corollas of Petunia hybrida
Authors: Weiss David , Shomer‐Ilan Adiva , Vainstein Alexander , Halevy Abraham H.
Published: May 2006

Corollas of Petunia hybrida (cv. Hit Parade Rosa) flowers fixed 14CO2 under both light and dark conditions. Rates of light fixation were much higher in mature pink corollas than in young, green corollas [57 and 9 nmol (ngchl)1 min‐1], paralleling the development of chloroplasts in these tissues. Stomatal conductance in corollas was only 12% of that in green leaves, mainly due to the presence of few, and non‐functioning stomata in the corolla. The activity and concentration of ribulose bisphosphate carboxylase (EC 4.1.1.39) in corolla extracts were only about 30% (per unit Chi) of those in extracts from green leaves. These results, together with previous results, might indicate a coordinated reduction in activity of systems participating in photosynthesis in corollas. The fixation products following a 6 s pulse with 14CO2, were typical of C, plants in both corollas and green leaves, but a higher level of β‐carboxylation products was found in the corollas. The activity of phosphoenol‐pyruvate carboxylase (EC 4.1.1.31) (per unit protein) was similar in both tissues. Although the total carbon fixed by the corolla constituted only a small part of the metabolites required for flower development, certain photosynthetic metabolites might have a regulatory role in flower development.
The effect of butyrate on the cell cycle in root meristems of Pisum sativum
Authors: Tramontano W. A. , DeCostanzo D. C. , DeLillo A. R.
Published: May 2006

Sodium butyrate at 5 mM in aerated White's medium reduced the mitotic index in root meristems of seedlings of Pisum sativum to < 1% after 12 h. This effect was lessened as the butyrate concentrations were lowered. The fraction of the root meristem nuclei in G2 increased to ~ 70% after 12 h in butyrate. After 12 h exposure to butyrate, seedlings transferred lo medium without butyrate gradually re‐established their normal root meristem mitotic pattern, with a burst of mitosis at 10 h after the transfer. Even a brief exposure to butyrate inhibited DNA synthesis, and nuclei released from butyrate exposure were still unable to resume normal DNA synthesis even after 12 h. This information suggests that butyrate halts progression through the cell cycle by arresting meristem nuclei in G2 and inhibiting DNA synthesis.
Abscisic acid and indole‐3‐butyric acid regulation of maturation and accumulation of storage proteins in somatic embryos of interior spruce
Authors: Roberts Dane R. , Flinn Barry S. , Webb David T. , Webster Fiona B. , Sutton Ben C. S.
Published: May 2006

The ontogenetic course followed by somatic embryos of interior spruce is highly dependent on the media concentration of abscisic acid (ABA). Little or no organized development occurs in the absence of ABA and as the level of ABA is increased, a range of embryo types is produced. “Shooty embryo” structures predominate in many callus lines at low levels of ABA (1‐10 μM), while 10‐20 μM ABA promotes the formation of bipolar embryos that germinate precociously. When ABA is increased to 30‐40 μM, precocious germination is inhibited and opaque cotyledonary embryos characteristic of their zygotic counterparts are formed which enter a period of quiescence. Only “mature” somatic embryos contain significant amounts of storage proteins and the level to which these proteins accumulate is dependent on the concentration of ABA. Indole‐butyric acid (IBA) included with ABA increases the number of mature embryos. Root elongation, which was used as a measure of embryo quality, was never observed from shooty embryo Structures and was 2‐3 fold higher in mature embryos compared to those that germinated precociously.
Seasonal variation in nitrogen storage reserves in the roots of leafy spurge (Euphorbia esula) and responses to decapitation and defoliation
Authors: Cyr David R. , Bewley J. Derek
Published: May 2006

Seasonal fluctuations of carbohydrates and nitrogenous components in the roots of the noxious perennial leafy spurge (Euphorbia esula L.) are strongly associated with overwintering strategy, Amino acids and distinct soluble proteins accumulate during fall and remain at elevated levels throughout winter. The formation of carbohydrate reserves in roots was not significantly affected by decapitation or selective defoliation; however, maximum amino acid and soluble protein contents were markedly reduced. In particular, the accumulation pattern of a 26 kDa protein was altered. This protein may play a role in plant conditioning and regenerative potential.
Translation of heterologous mRNAs by chloroplast stroma components
Authors: Maiek Ladislav , Kozieradzki Ivona
Published: May 2006

In vitro translation of exogenous mRNAs has been difficult to achieve using chloroplast components. An in vitro protein synthesis system is described, based on a pea (Pisum sativum L, cv. Spring) chloroplast stroma 30000 g supernatant, which was capable of translating polyuridylie acid and MS2 phage RNA into corresponding proteins. The kinetics of label incorporation and fluorograms of unique translation products are presented. The unusual steps which may have contributed to successful translation include the following: the removal of exogenous unlabeled amino acids from the incubation mixture, ultrafiltration of the stromal supernatant and the removal of thylakoid‐bound polyribosomes. The system could be further developed to study translational control of gene expression in the chloroplasts.
Induction and repression of phenylalanine ammonia‐lyase and chalcone synthase enzyme proteins and mRNAs in carrot cell suspension cultures regulated by 2,4‐D
Authors: Ozeki Yoshihiro , Komamine Atsushi , Tanaka Yoshiyuki
Published: May 2006

Changes in the amounts of enzyme proteins and mRNAs for phenylalanine ammonia‐lyase (PAL, EC 4.3.1.5) and chalcone synthase (CHS, EC 6.‐.‐.‐) were investigated in suspension cultures of carrot (Daucus carola L. cv. Kurodagosun), in which anthocyanin synthesis was induced and repressed in the absence and presence of 2,4‐dichrolophenoxyaeetic acid (2,4‐D), respectively. The amounts of enzyme proteins were measured using anti‐PAL and anti‐CHS sera. In a medium lacking 2,4‐D, enzyme proteins and mRNAs for both PAL and CHS were induced 5 days after transfer, when the anthocyanin synthesis was induced. They all increased coordinately during days 5‐7 after transfer, when anthocyanin was rapidly synthesized, and then they decreased. In contrast, in a medium containing 2,4‐D, the amount of enzyme protein and mRNA for CHS were below detectable levels throughout the culture time. As regards PAL, however, whether 2,4‐D was present or not, both enzyme protein and mRNA rapidly increased after the transfer of cells to fresh medium, and then decreased and remained at low levels in a medium containing 2,4‐D. The addition of 2,4‐D to cells cultured for 6 days in a medium lacking 2,4‐D caused an immediate decrease in the amounts of enzyme proteins and mRNAs for both PAL and CHS.

All the results obtained here indicate that the induction and suppression of the synthesis of PAL and CHS were probably due lo increase and decrease, respectively, in the amounts of their mRNAs. Thus, it is suggested that the induction and suppression of anthocyanin in this system may be regulated at the transcriptional level by 2,4‐D.
Effect of alcohols on the association of photosynthetic fructose‐1,6‐bisphosphatase to thylakoid membranes
Authors: Andres A. Rodriguez , Lazaro J. J. , Chueca A. , Hermoso R. , Gorge J. Lopez
Published: May 2006

Aliphatic alcohols have a positive effect on the assoociation of pea (Pisum sativum L. cv. Lincoln) chloroplast fructose‐ 1,6‐bisphosphatase (FBPase; EC 3.1.3.11) with thylakoid membranes. The alcohol concentration needed to obtain a fixed percentage of enzyme association decreased with increased length of the aliphatic chain of the alcohol; maximum binding was obtained when the lysis medium contained, in molar fractions (or v/v percentages): 48×10‐4(T4 (2.4%), 26×10‐3 (10%), 40×10‐3 (15%), 76×10‐3 (21%), and 13×10‐2 (24%), of 1‐butanol, 1‐propanol, 2‐propanol, ethanol, and methanol, respectively. A good correlation of binding with the octanol/water partition coefficient was observed. Since this coefficient constitutes a measure of hydrophobicity, we suggest that the binding of FBPase to the membranes occurs via hydrophobic clusters of both components.
Elicitor‐induced hydroxycinnamoyl‐CoA:tyramine hydroxycinnamoyltransferase in plant cell suspension cultures
Authors: Villegas Mirza , Brodelius Peter E. , Kylin A.
Published: May 2006

Treatment of Nicotiana glutinosa L. cell suspension cultures with chitosan results in the co‐induction of phenylalanine ammonia lyase, 4‐eoumarate:CoA ligase, tyrosine decarboxylase and tyramine hydroxycinnamoyltransferase, all involved in the biosynthesis of hydroxycinnamoyltyramines. The highest enzyme activities were observed around 12 h after addition of 0.8 to 1 mg chitosan per g fresh weight of cells. No hydroxycinnamoyltyramines could be detected by TLC or HPLC of extracts made from non‐treated or elicited cells. [14C]‐Tyramine was incorporated into insoluble polymeric material at a higher rate in elicitor‐treated than in non‐treated cells of N. glutinosa. Tyramine hydroxycinnamoyltransferase could be induced in suspension cultured cells of Eschscholtzia califortnca Cham, but not in cells of Phaseolus vulgaris L. or Catharanthus roseus (L.) G. Don by addition of a yeast elicitor to the growth medium.
Anaerobic induction in conifers: Expression of endogenous and chimeric anaerobically‐induced genes
Authors: Good A. G. , Bekkaoui F. , Pilate G. , Dunstan D. I. , Crosby W. L.
Published: May 2006

Alcohol dehydrogenase (ADH; EC 1.1.1.1) activity was measured in Picea glauca (Moench) Voss cell suspensions under differing conditions of hypoxia. ADH activity increased 4.5 fold after 48 h of induction. When cells were induced under different levels of hypoxia (2, 5 and 20% O2) changes in ADH activity were found to increase with lower levels of oxygen. Alanine aminotransferase (AlaAT; EC 2.6.1.2) activity increased under hypoxia in a pattern similar to ADH, however lactate dehydrogenase (LDH; EC 1.1.1.27) activity did not increase under hypoxic conditions. The ability of white spruce cells to accurately regulate heterologous anaerobic promotors was tested by electroporating chimeric ADH reporter genes into protoplasts. While protoplasts were capable of anaerobically regulating a maize ADH reporter construct, constructs with dicotyledonous promoters (pea and Arabidopsis) were not expressed.
Reduced irradiance and applied auxin influence carbohydrate relations in Pinus banksiana cuttings during propagation
Authors: Haissig Bruce E.
Published: May 2006

Untreated and indole‐3‐butyrie acid‐treated (IBA) cuttings from 90‐day‐old Pinus banksiana Lamb, stock plants were propagated under normal greenhouse irradiance (max. 900 $$mol m‐2 s‐1) and shade (max. 120 $$mol m‐2 s‐1) to determine effects on adventitious rooting and on reducing sugar and starch concentrations in needles and basal stems. In one experiment, cuttings were assessed at days 15 and 25 of propagation for basal 1‐cm stem fresh weight, proportion rooted, number of roots and longest root length. In a second experiment with cuttings, basal 1‐cm stem fresh weight and concentrations of reducing sugar and starch in needles and basal stems were measured each day for the first 10 days of propagation. Carbohydrate measurements were also made for seedling stock plants as controls for the second experiment. Carbohydrate data for cuttings were primarily evaluated based on net (cutting minus seedling) concentrations, to correct for changes in cuttings not related to adventitious rooting. Increase of basal stem fresh weight and rooting of cuttings, based on all measured variables, occurred in the order: light + IBA > light > shade + IBA > shade. The best rooting required the greater irradiance. Compared to results from cuttings in the light, shading resulted in lesser accumulations of reducing sugars and starch in needles and basal stems. Reducing sugar: starch concentration ratios were significantly greater in shade‐ vs light‐propagated cuttings, IBA treatment did not offset the effects of shade on rooting or on reducing sugar and starch concentrations or ratios. Overall, the results suggested that decreased reducing sugar and starch concentrations and/or their increased ratios are associated with shade‐induced poor rooting of P. banksiana cuttings.
Leaf morphology and water status changes in Triticum durum under water stress
Authors: Rascio A. , Cedola M. C. , Toponi M. , Flagella Z. , Wittmer G.
Published: May 2006

Water relations, leaf morphology and the chemical composition of cell walls in irrigated and unirrigated plants of three durum wheat eultivars were measured at two growth stages (booting and flowering). Plant response to water stress differed at the two stages: cell wall elasticity increased at booting and osmotic potential values decreased at flowering; this may be due to the changes in stress history, leaf development and plant growth stage between the two harvests. Leaf tissue characteristics were modified by water stress only at flowering: accumulation of fibrous constituents and hemicellulose in the cell walls, reduction of acid detergent fiber (ADF) per unit of leaf area, increase in specific leaf weight (SLW), decrease in turgid weight/dry weight ratio (TW/DW) and alteration in mesophyll cell morphology (cell area / ceil perimeter ratio) were observed.

Generally, cv. Valforte (the less drought‐resistant cultivar) had the greatest mesophyll cell area and perimeter and it had greater values of neutral detergent fiber (NDF) at the booting stage than cv. Appulo. Reactivity to water stress differed in the eultivars: Valforte showed the greatest increase in hemicellulose content and decrease in cell dimensions under drought at flowering.

No significant relationships between osmotic potential and mesophyll cell characters were observed; there were no correlations among cell wall elasticity, cell morphology and the chemical components of leaf tissue. The total fiber content and the hemicellulose per unit of leaf area were correlated with the TW/DW ratio at flowering. This parameter decreased more in plants subjected to water stress owing to accumulation of hemicellulose. Correlations between leaf structural constituents and $$ suggest that the absorptive capacity of the cell wall may significally affect the osmotic volume of the cell.
Polyamines and ethylene in relation to adventitious root formation in Prunus avium shoot cultures
Authors: Biondi Stefania , Diaz Teresa , Iglesias Isabel , Gamberini Grazia , Bagni Nello
Published: May 2006

An attempt was made to identify some of the hormonal factors that control adventitious root formation in our Prunus avium micropropagation system in order to improve rooting in difficult‐to‐root genotypes. Changes in endogenous contents of free polyamines were determined at intervals during auxin‐induced rooting of shoot cultures. Accumulation of putrescine and spermidine peaked between days 9 and 11. Spermine was only present in traces, Exogenously supplied putrescine or spermine (50‐500 μM), in the presence of optimal or suboptimal levels of indolebutyric acid (IBA), had no effect on rooting percentage or root density, except for spermine at 500 μM. At this external concentration spermine caused a substantial accumulation in both free spermine and putrescine. The use of several inhibitors of polyamine biosynthesis, namely α‐difluoromethylornithine (DFMO), α‐difluoromethylarginine (DFMA), dicyclohexylammonium sulphate (DCHA) and methylglyoxal‐bis‐guanyl‐hydrazone (MGBG) alone or in combination in the 0.1 to 5 μM range, resulted in an inhibition of rooting that was partially reversed by the addition of the corresponding polyamine. Cellular polyamine levels were significantly reduced by DFMO and DFMA but not by DCHA and MGBG, Labeled putrescine incorporation into spermidine increased somewhat in the presence of the ethylene synthesis inhibitor aminoethoxyvinylglycine (AVG). A system based on [3,4‐14C]methionine incorporation was used to measure ethylene synthesis by the in vitro cultured shoots. Label incorporation was drastically reduced by 10 μM AVG and increased 3.5‐fold in the presence of 50 μM IBA with respect to controls (no IBA). Labeled methionine incorporation into spermidine increased to some extent when ethylene synthesis was inhibited by AVG. Adding the ethylene precursor 1‐aminocyclopropane‐l‐carboxylic acid (ACC) to the rooting medium significantly inhibited rooting percentage; AVG caused the formation of a greater number of roots per shoot but delayed their growth. Supplying the shoots with both compounds resulted in an intermediate rooting response, in which both rooting percentage and root density were affected. These results indicate that polyamines may play a significant role at least in some stages of root formation. The polyamine and ethylene biosynthetic pathways seem to be competitive but under our conditions, the enhancement of one pathway when the other was inhibited, was not dramatic. Although IBA promoted ethylene synthesis, AVG, which drastically reduced it, also promoted root formation. Thus, the auxin effect on root induction cannot be directly related to its ability to enhance ethylene synthesis.
DNA replication and the development of preprophase bands in soybean protoplast cultures
Authors: Wang Hong , Cutler Adrian J. , Fowke Larry C.
Published: May 2006

Nuclear DNA replication and the development of preprophase bands (PPBs) are two chronologically close processes during the higher plant cell cycle. However, it is not clear whether occurrence of PPBs is coupled with DNA replication. A soybean protoplast culture with a high frequency of PPBs was used to study the relationship between the two processes when treated with aphidicolin, a potent and specific inhibitor of eukaryotic DNA polymerase‐α. When DNA replication was partially inhibited by 10 mg l‐1 aphidicolin, both the percentage of cells with PPBs and the mitotic index (MI) decreased in absolute terms, but there were proportionately more PPBs than mitoses. Since PPBs change in appearance as they develop, they were divided into categories of early (interphase associated) and late (prophase associated). The increased PPB/MI ratio was associated with an increased proportion of early stage PPBs relative to late stage PPBs. When DNA replication was completely blocked by 50 mg l‐1 aphidicolin, both MI and the percentage of cells with PPBs were close to zero. These results suggest that development of PPBs was to a large extent coupled DNA replication. We propose that the increased PPB/MI ratio at 10 mg l‐1 aphidicolin was due to a linkage between the duration of interphase and the time period in which early stage PPBs are visible. The increased duration of early PPBs partially compensates for the reduced number of nuclei reaching the stage of PPB initiation. Furthermore, in cultures containing aphidicolin, the percentage of PPBs with simultaneous perinuclear fluorescence (PNF, accumulation of microtubules on nuclear envelope) was reduced and whenever PNF was prominent and dense on the nuclear envelope the nucleus showed chromatin condensation. These observations indicated that the transition from PPB to PNF and then to the prophase spindle is closely related to the progress of the nuclear cycle.
Effects of photoperiod and temperature on sugars and fructans in leaf blades, leaf sheaths and stems, and roots in relation to growth of Poa pratensis
Authors: Solhaug K. A.
Published: May 2006

Vegetative plants of Poa pratensis L. cv. Holt were cultivated in short days (SD; 8 h summer daylight) and in long days (LD; 8 h summer daylight + low intensity extension of 5 μmol m‐2 s‐1) at 12, 18 and 24°C in one experiment and at 9, 12, 15 and 18°C in another. Relative growth rate (RGR) as the mean of both experiments and all temperatures was 32% higher in LD than in SD between start of daylength treatment and first harvest, and 18% higher in LD than in SD between first and second harvest. Early in the daylength treatment period, more assimilates were allocated to storage in SD than in LD, so that at first harvest leaf sheaths and stems had 175% higher concentration of fructans in SD. Later this allocation pattern changed, and for the larger plants at the second harvest the differences in fructan concentrations were much smaller between the two daylengths. Both sugar and fructan concentrations were highest at low temperatures. The distribution of sugars and fructans varied from mostly sugars in the leaves to mostly fructans in leaf sheaths and stems and roots. The fructans were mainly high degree polymerization fructans. At least two series of fructans were present, and the dominant one was probably based upon kestose. It is concluded that allocation of assimilates to growth in leaf area instead of to storage may be important for the observed LD stimulation of dry matter production.
Sucrose phosphate synthase and other sucrose metabolizing enzymes in fruits of various species
Authors: Hubbard Natalie L. , Pharr D. Mason , Huber Steven C.
Published: May 2006

Recent reports have suggested that sucrose phosphate synthase (EC 2.4.1.14), a key enzyme in sucrose biosynthesis in photosynthetic “source” tissues, may also be important in some sucrose accumulating “sink” tissues. These experiments were conducted to determine if sucrose phosphate synthase is involved in sucrose accumulation in fruits of several species. Peach (Prunus persica NCT 516) and strawberry (Fragaria x ananassa cv. Chandler) fruits were harvested directly from the plant at various stages of fruit development. Kiwi (Actinidia chinensis), papaya (Carica papaya), pineapple (Ananas comosus) and mango (Mangifera indica) were sampled in postharvest storage over a period of several days. Carbohydrate concentrations and activities of sucrose phosphate synthase, sucrose synthase (EC 2.4.1.13), and acid and neutral invertases (EC 3.2.1.26) were measured. All fruits contained significant activities of sucrose phosphate synthase. Moreover, in fruits from all species except pineapple and papaya, there was an increase in sucrose phosphate synthase activity associated with the accumulation of sucrose in situ. The increase in sucrose concentration in peaches was also associated with an increase in sucrose synthase activity and, in strawberries, with increased activity of both sucrose synthase and neutral invertase. The hexose pools in all fruits were comprised of equimolar concentrations of fructose and glucose, except in the mango. In mango, the fructose to glucose ratio increased from 2 to 41 during ripening as sucrose concentration more than doubled. The results of this study indicate that activities of the sucrose metabolizing enzymes, including sucrose phosphate synthase, within the fruit itself, are important in determining the soluble sugar content of fruits of many species. This appears to be true for fruits which sweeten from a starch reserve and in fruits from sorbitol translocating species, raffinose saccharide translocating species, and sucrose translocating species.
Cloning and expression of a gene encoding a root specific nitrate reductase in bean (Phaseolus vulgaris)
Authors: Hoff Tine , Stummann Bjarne M. , Henningsen Knud W.
Published: May 2006

A structural gene encoding nitrate reductase (NR) in the legume Phaseolus vulgaris cv. Saxonia has been cloned and sequenced. The NR gene encodes a protein of 881 amino acids with a MW of 99.2 kDa. The coding sequence is interrupted by three introns, which are located in the molybdopterin cofactor binding domain. In the flanking regions the signals of a functional eukaryotic gene are present. The gene is the smallest NR gene so far identified in higher plants. Comparison to other NRs shows homology ranging from 65 to 74% at the amino acid level. The similarity is highest for the three functional domains, and lowest in the N‐terminal end of the protein. mRNA studies demonstrate that the gene is nitrate inducible and expressed exclusively in the roots of bean. Southern blot analysis indicates the presence of a second NR gene in bean. This gene may encode a NR enzyme expressed in leaves.