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At least 1,297 records · Page 72Linked to original sources
PubMed1997

Sources of N for leaf growth in a high-density apple (Malus domestica) orchard irrigated with ammonium nitrate solution.

Elstar apple trees (Malus domestica Borkh.) on M.9 rootstock received either 5 or 35 g N tree(-1) year(-1) during the first two growing seasons after planting, applied as Ca(NO(3))(2) on a daily basis for nine weeks through a drip irrigation system. During the third growing season (1994), all trees were treated with 20 g N tree(-1) year(-1) as (15)NH(4) (15)NO(3) with applications starting on April 22 and continuing for 10 weeks. Soil solution nitrate-N and ammonium-N were monitored weekly with suction lysimeters located 30 cm beneath the drip emitters. Spur and shoot leaves were sampled intensively from full bloom to the end of rapid shoot growth. During the period of nitrogen application, soil solution nitrate-N and ammonium-N were relatively constant, at about 24 and 1.0 mg l(-1) respectively. Growth of the spur leaves was completed by one week after full bloom (May 12), whereas biomass of the shoot leaves increased until mid-June. Nitrogen for growth of the spur leaves was supplied mainly from remobilization, which was dependent on previous N supply. Accumulation of fertilizer N in spur leaves was independent of previous N treatments and continued until the end of the monitoring period (June 24), but contributed only 13% to total spur leaf N. Nitrogen for shoot leaf growth was independent of previous N treatments and was initially supplied primarily by remobilization, but by the end of extension growth, fertilizer N contributed 48% to total shoot leaf N. Linear increases in leaf N uptake throughout the period of rapid shoot growth and the large contribution of fertilizer N to total shoot leaf N were attributed to the constant supply of N available in the root zone through daily N fertilization.

Journal Article↗
PubMed1997

Effect of crop load on fruiting and leaf photosynthesis of 'Braeburn'/M.26 apple trees.

Four-year-old apple (Malus x domestica Borkh.) trees cv. 'Braeburn' on M.26 rootstock were thinned at full bloom to establish six crop loads ranging from a heavy crop to a deflowered treatment. At harvest, mean yield per tree varied from 0 to 38 kg and mean fruit weight ranged from 225 g in the heaviest cropping treatment to 385 g in the lightest cropping treatment. Light cropping resulted in a significant advance in fruit maturity as indicated by background color, starch/iodine score and soluble solids. There were small differences in leaf photosynthetic rate among the treatments when shoot growth was active. However, in early January, coincident with cessation of shoot growth and maximum rate of accumulation of fruit weight, leaf assimilation rate was reduced by as much as 65% on the deflowered trees compared to the trees carrying the heaviest crop. Leaf assimilation rate showed a curvilinear response to crop load at this time, with little increase in leaf assimilation when crop load exceeded 12 fruit m(-2) leaf area.

Journal Article↗
PubMed2002

Nitrogen absorption, translocation and distribution from urea applied in autumn to leaves of young potted apple (Malus domestica) trees.

We studied the absorption, assimilation, translocation and distribution of nitrogen (N) from urea applied in autumn to leaves of 1-year-old potted Fuji/M26 apple (Malus domestica Borkh) trees. In early October, all leaves of each tree were painted with either 3% urea (enriched to 10 atom % with 15N) or water (control trees). Four trees were harvested before the treatment and N and amino acid contents were determined. Four trees from each treatment were harvested at 2, 4, 7, 10, 15 and 20 days after urea or water application. Total N, amino acids and 15N in leaves, bark, xylem, shank and roots were analyzed to determine uptake and mobilization of N from urea. Most uptake of 15N by leaves occurred during the first 2 days following application of urea. The mean rate of absorption during these 2 days was 0.29 g m-2 day-1. Amino acids in leaves, bark and roots increased significantly after urea application compared with control values. The highest concentrations of amino acids in leaves and bark occurred 4 days after application, whereas the highest concentrations of amino acids in roots occurred 10 days after application. Total 15N content in leaves peaked 2 days after urea application and then decreased, whereas 15N content in roots and bark increased throughout the experiment. Total 15N content in xylem and shank was low. Leaves absorbed 35% of the 15N applied as urea, and 63.6% of absorbed 15N was translocated out of leaves within 20 days after urea application. We conclude that N from urea was converted to amino acids in leaves after foliar application in autumn, and roots and bark were the main sinks of N from urea applied to leaves.

Absorption↗
PubMed2005

Physiological and biochemical leaf and tree responses to crop load in apple.

Seven-year-old apple (Malus x domestica Borkh.) trees cv. 'Braeburn' on rootstock M.26 were flower-thinned to establish four crop loads, resulting in final mean fruit numbers per tree of 0, 100, 225 and 400. Mean fruit mass decreased by about 35% with each decrease in cropping density. Fruit from light-cropping trees had significantly advanced maturity as indicated by the harvest management criteria of background color and starch/iodine score, and other fruit quality characteristics such as soluble solids. Flesh firmness and dry matter also increased with decreasing crop load. Compared with fruiting trees, mean leaf photosynthetic rates of non-cropping trees were significantly lower (40%) between 75 days after full bloom (dafb) and fruit harvest, with a maximum reduction of almost 60% at 118 dafb. Photosynthetic activity decreased linearly with increasing concentration of leaf starch, but was positively and significantly related to stomatal conductance. Consequently, the accumulation of nonstructural carbohydrates in leaves of light-cropping or non-cropping trees may have led to end-product inhibition of photosynthesis. Increases in xanthophyll cycle carotenoids mediated non-radiative thermal energy dissipation in non-cropping trees, providing increased capacity for photoprotection but reducing photochemical efficiency.

Carbohydrate Metabolism↗
PubMed2005

Leaf responses of micropropagated apple plants to water stress: nonstructural carbohydrate composition and regulatory role of metabolic enzymes.

We examined changes in nonstructural carbohydrate biosynthesis and activities of related enzymes in leaves of micropropagated apple plants (Malus domestica Borkh. cv. 'NaganoFuji') in response to water stress, with particular emphasis on the enzymes associated with sorbitol, sucrose and starch metabolism. Water stress resulted in the accumulation of photosynthates in leaves, mainly sorbitol, sucrose, glucose and fructose, accompanied by a reduction in starch concentration. Correlation and path analysis indicated that water stress affected the partitioning of newly fixed carbon among terminal products. In response to water stress, ADP-glucose-pyrophosphorylase (ADPGPPase) activity decreased, becoming a critical and limiting step in shifting partitioning of photosynthetically fixed carbon. Amylase and ADPGPPase affected sucrose and sorbitol metabolism, mainly by regulating substrate supply; however, competition for limited substrate had a greater effect on the biosynthesis of sorbitol than of sucrose. Starch metabolism was also strictly regulated by ADPGPPase and amylase, whereas other related enzymes were downstream of the pathway for synthesis and degradation of carbohydrates and thus had relatively little effect on starch metabolism. Sorbitol dehydrogenase and sucrose phosphate synthase were critical regulators of sorbitol and sucrose metabolism, respectively.

Adaptation, Physiological↗
PubMed2006

Hyperhydricity in apple: ultrastructural and physiological aspects.

We studied the effects of hyperhydricity on subcellular ultrastructure and physiology of leaves during in vitro regeneration of apple plants. Morphological, anatomical and ultrastructural differences between healthy leaf tissues obtained from greenhouse-grown plants and healthy and hyperhydric leaves obtained from shoots raised from nodal shoot explants in a bioreactor were investigated by electron microscopy and confocal laser scanning microscopy. Compared with healthy leaves, hyperhydric leaves showed abnormal, often discontinuous development of the epidermis and cuticle. Stomata were malformed. The leaf lamina appeared thickened and was characterized by poor differentiation between the palisade and spongy mesophyll tissue. Hyperhydric leaves had a significantly lower chloroplast number per cell and chloroplasts showed reduced thylakoid stacking compared with healthy leaves. Hyperhydricity resulted in a general decrease in concentrations of reduced and oxidized pyridine nucleotides, reflecting a reduction in metabolic activity. The activities of antioxidant enzymes, such as superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase were higher in hyperhydric leaves than in healthy leaves, indicating that hyperhydricity was associated with oxidative stress. Chlorophyll fluorescence measurements provided evidence of oxidative damage to the photosynthetic machinery in hyperhydric leaves: photochemical efficiency of photosystem II, effective quantum efficiency and photochemical quenching were all lower in hyperhydric leaves compared with healthy leaves.

Antioxidants↗
PubMedDate not supplied

Training community health workers to reduce health disparities in Alabama's Black Belt: the Pine Apple Heart Disease and Stroke Project.

African American women have significantly higher mortality rates from heart disease and stroke than White women despite advances in treatment and the management of risk factors. Community health workers (CHWs) serve important roles in culturally relevant programs to prevent disease and promote health. This article describes the Pine Apple Heart and Stroke Project's activities to (1) revise the Women's Wellness Sourcebook Module III: Heart and Stroke to be consistent with national guidelines on heart disease and stroke and to meet the needs of African American women living in rural southern communities; (2) train CHWs using the revised curriculum; and (3) evaluate the training program. Revisions of the curriculum were based on recommendations by an expert advisory panel, the staff of a rural health clinic, and feedback from CHWs during training. Questionnaires after training revealed positive changes in CHWs' knowledge, attitudes, self-efficacy, and self-reported risk reduction behaviors related to heart disease, stroke, cancer, and patient-provider communication. This study provides a CHW training curriculum that may be useful to others in establishing heart disease and stroke programs in rural underserved communities.

Black or African American↗
PubMedDate not supplied

CT-guided bone biopsy in a cancer center: experience with a new apple corer-shaped device.

In this article we report our experience with CT-guided bone biopsy (CTGBB) using a new nondisposable bone biopsy device with in a uniform protocol for all lesions and compare our results with data from bone biopsies obtained with other techniques. With this biopsy device, the specimen is collected in a 20 x 2 mm chamber of an apple corer-shaped needle. In 46 consecutive cancer patients that were candidates for bone biopsy, 50 CTGBB procedures were performed and analyzed. Lesions with cortical defects and/or surrounding soft tissue infiltration were excluded. There were no complications. Of 50 CTGBB procedures, 90% were diagnostic. Four of the five inconclusive biopsies were repeated: All were conclusive, one malignant. Of 19 with CT-indistinguishable lesions (detected on MRI or isotope studies), 35% were malignant. Thirty-eight percent of the lesions were not accompanied by pain. The procedure was less painful than injection of the local anesthetic prior to biopsy in 90% of the cases. With the new device, CTGBB procedures can be carried out safely. Biopsy with the described technique has a high diagnostic output, better results than those of biopsy with reported uniform techniques, and equal results to the best results of combined techniques. If a lesion is not distinguishable on CT and/or not accompanied by pain, malignancy is not ruled out. CTGBB in the described technique is less or equally time consuming, less painful, and cheaper than reported for other bone biopsy procedures.

Adult↗
PubMed1992

Pear blister canker viroid is a member of the apple scar skin subgroup (apscaviroids) and also has sequence homology with viroids from other subgroups.

The sequence of pear blister canker viroid (PBCVd), the putative causal agent of pear blister canker (PBC) disease, has been determined. PBCVd consists of a single-stranded circular RNA of 315 nucleotide residues which assumes a branched conformation when it is folded in the model of lowest free energy. PBCVd has highest sequence similarity with grapevine 1B viroid (52.4%), but also contains sequences related to regions present in viroids that belong to different subgroups, suggesting that PBCVd could have developed from RNA recombination between viroids replicating in a common host plant. PBCVd contains almost the entire central sequence which is conserved in the members of the apple scar skin subgroup (apscaviroids) as well as a conserved sequence located in the left-terminal region of apscaviroids and pospiviroids (whose type member is potato spindle tuber viroid). A consensus phylogenetic tree has been obtained in which PBCVd and other viroids previously classified as apscaviroids appear closely related, allowing consideration of PBCVd as a new member of this subgroup.

Base Sequence↗
PubMed1992

Analysis of the dsRNAs of apple chlorotic leaf spot virus.

Double-stranded RNAs were isolated from plants infected with five different isolates of apple chlorotic leaf spot virus (ACLSV). Analysis by PAGE and by Northern blot hybridization showed that six major species of viral dsRNA of approximately 7.5, 6.4, 5.4, 2.2, 1.1 and 1.0 kbp can be detected in infected plants, irrespective of the ACLSV isolate used. In addition to the dsRNA of 7.5 kbp corresponding to the full-length genome, the size and position on the genome of the 2.2 and 1.1 kbp species indicate that these are very probably double-stranded forms of subgenomic RNAs allowing the expression of the internal open reading frames coding respectively for the ACLSV 50K and coat proteins. The subgenomic messenger for the coat protein was indeed detected in total RNA preparations from infected plants. Surprisingly, the two most abundant dsRNA species, of 6.4 and 5.4 kbp, were found to be 5'-coterminal with the genomic RNA. A model for the expression of the genome of ACLSV and for the production of the molecules 5'-coterminal with the genomic RNA is presented.

Base Sequence↗
PubMed1992

Evidence for translation of apple stem grooving capillovirus genomic RNA.

Apple stem grooving virus (ASGV) RNA was translated in a rabbit reticulocyte lysate system and shown to direct the synthesis of several polypeptides of Mr ranging from 200K to 43K. A polypeptide of 200K was a major product, but no polypeptide with electrophoretic mobility the same as that of the ASGV coat protein was synthesized. Immunoprecipitation experiments showed that a polypeptide of 200K was selectively precipitated by antiserum against purified ASGV. These results indicate that ASGV coat protein is translated as part of a 200K polyprotein.

Cell-Free System↗
PubMed1994

The nucleotide sequence of apple mosaic virus coat protein gene has no similarity with other Bromoviridae coat protein genes.

A double-stranded cDNA was synthesized from in vitro polyadenylated apple mosaic virus (ApMV) RNA 3 using oligo(dT) and sequence-specific primers, and was cloned into plasmid vectors. A set of overlapping cDNA clones was used to determine the nucleotide sequence of RNA 4. ApMV RNA 4 was found to contain an open reading frame (ORF) of 666 nucleotides, which was flanked by 5' and 3' non-translated sequences of 55 and 264 nucleotides, respectively. The ORF encoding the coat protein was identified by comparing the predicted amino acid sequence with that obtained from direct protein microsequencing of the native viral coat protein. The ORF encodes a protein with an M(r) of 25,056. The nucleotide sequence of the ApMV coat protein gene showed no similarity to those of alfalfa mosaic virus, tobacco streak virus (TSV), brome mosaic virus or cucumber mosaic virus. The predicted amino acid sequence of the amino-terminal region of the ApMV coat protein is basic, rich in cysteine residues and may contain a zinc finger motif similar to that found in TSV.

Amino Acid Sequence↗
PubMed1994

Nucleotide sequence of apple mosaic ilarvirus RNA 4.

The complete nucleotide sequence of apple mosaic ilavirus RNA 4 was obtained from cloned cDNAs and direct sequencing of the 5'-terminal RNA region. The sequence is 891 nucleotides long and can encode a protein of 226 amino acids (M(r) 25,171) that, by analogy to alfalfa mosaic virus (AlMV) and tobacco streak virus (TSV), should correspond to the coat protein (CP). Database comparisons showed that no significant similarity to other proteins was apparent. Analysis of the CP sequence revealed a putative 'zinc finger' domain and a region rich in basic residues at the amino-terminal portion of the protein, similar to that of TSV. The secondary structure proposed for the 3'-terminal region of RNA 4 shows the presence of three hairpin structures flanked by the tetranucleotide AUGC that are highly similar to those previously described in the RNA 4 species from AlMV and TSV. These results support the idea that both features (metal-binding domain and highly conserved hairpin structures) are characteristics of ilarviruses and are probably involved in the peculiar 'genome activation' phenomenon described in these viruses.

Amino Acid Sequence↗
PubMed1994

Nucleotide sequences of apple stem pitting virus and of the coat protein gene of a similar virus from pear associated with vein yellows disease and their relationship with potex- and carlaviruses.

The nucleotide sequence (9306 nucleotides) of cDNA clones of apple stem pitting virus (ASPV) obtained from a double-stranded RNA template, extracted from diseased plant tissue, was determined. The genome is composed of five open reading frames (ORFs) encoding putative proteins with M(r)s of 247083, 25147, 12832, 7429 and 43712, and has a poly(A) tail. Using two oligonucleotides designed from the ASPV sequence information a 1598 bp fragment from near the 3' terminus of the viral RNA, containing the coat protein of M(r) 43,766, was amplified from vein yellows (VY)-infected pear plants by PCR. The sequence determined showed eight nucleotide changes resulting in five amino acid substitutions compared with the sequence of ASPV. When compared to potex-, carla-, clostero- and capilloviruses, the ASPV genome organization appeared to be most closely related to that of potexviruses, but with a larger coat protein of M(r) 44K (ORF5). The predicted coat protein size was confirmed by immunoblot analysis. The results show that ASPV does not fall into subgroup A of the closteroviruses but that it probably belongs in an as yet undefined group of viruses. They also suggest that the virus associated with VY is a strain of ASPV.

Amino Acid Sequence↗
PubMed1995

Expression, subcellular location and modification of the 50 kDa protein encoded by ORF2 of the apple chlorotic leaf spot trichovirus genome.

A putative movement protein of molecular mass 50 kDa encoded by the ORF2 of the apple chlorotic leaf spot virus (ACLSV) genome was expressed in Escherichia coli using an expression vector and was then used to produce an antiserum. Immunoblot analysis using an antiserum raised against this protein showed that the ORF2 protein of ACLSV was detected in both cell wall and cell membrane fractions prepared from infected Chenopodium quinoa tissues. The ORF2 protein from infected tissues had a molecular mass of 52 kDa, larger than that of the full-length ORF2 protein (50 kDa protein) expressed in E. coli. Incubation of the 52 kDa protein with alkaline phosphatase resulted in a decrease in its apparent molecular mass from 52 kDa to 50 kDa, strongly suggesting that the ORF2 protein of ACLSV is phosphorylated in infected plant tissues.

Base Sequence↗
PubMed1998

Nucleotide sequence and genome structure of grapevine rupestris stem pitting associated virus-1 reveal similarities to apple stem pitting virus.

Rupestris stem pitting (RSP), a component of the rugose wood complex, is one of the most widespread graft-transmissible diseases of grapevines. Here we report on the consistent association of a high molecular mass dsRNA (ca. 8.7 kbp) with RSP. The dsRNA was reverse-transcribed and cDNAs generated were cloned into Lambda ZAP II. Sequence analysis of the cDNA clones showed that the dsRNA was of viral origin and the putative virus was designated rupestris stem pitting associated virus-1 (RSPaV-1). The genome of RSPaV-1 consists of 8726 nt excluding a poly(A) tail at the 3' terminus. It has five potential open reading frames which have the capacity to code for the replicase (ORF1), the triple gene block (ORF2-4) and the coat protein (ORF5). Comparison of the genome structure and nucleotide and amino acid sequences indicated similarities of RSPaV-1 to apple stem pitting virus, and to a lesser extent, to potato virus M carlavirus. The possibility that different strains of RSPaV-1 or other viruses are associated with RSP is discussed.

Amino Acid Sequence↗
PubMed2000

Intracellular distribution, cell-to-cell trafficking and tubule-inducing activity of the 50 kDa movement protein of Apple chlorotic leaf spot virus fused to green fluorescent protein.

The 50 kDa protein (50KP) encoded by ORF2 of Apple chlorotic leaf spot virus (ACLSV) fused to green fluorescent protein (GFP) was expressed transiently in cells of Nicotiana occidentalis and Chenopodium quinoa leaves. Its intracellular distribution, cell-to-cell trafficking in leaf epidermis and tubule formation on the surface of protoplasts were analysed. The 50KP-GFP fluorescence was distributed as small irregular spots or a fibrous network structure on the periphery of epidermal cells and protoplasts of both plant species. In leaf epidermis of N. occidentalis, the protein spread from the cells that produced it into neighbouring cells in both young and mature leaves and targetted plasmodesmata in these cells. In contrast, GFP was restricted to single cells in most cases in mature leaves. When 50KP and GFP were co-expressed in leaf epidermis of N. occidentalis, GFP spread more widely from the initial cells that produced it than when GFP was expressed alone, suggesting that 50KP facilitated the cell-to-cell trafficking of GFP. 50KP-GFP was able to complement local spread of 50KP-deficient virus when expressed transiently in leaf epidermis of C. quinoa. Expression of 50KP-GFP in protoplasts resulted in the production of tubular structures protruding from the surface. Mutational analyses showed that the C-terminal region (aa 287-457) was not essential for localization to plasmodesmata, cell-to-cell trafficking, complementation of movement of 50KP-deficient virus or tubule formation on protoplasts. In contrast, deletions in the N-terminal region resulted in the complete disruption of all these activities.

Green Fluorescent Proteins↗
PubMed1999

Isolation of the gene encoding an immunodominant membrane protein of the apple proliferation phytoplasma, and expression and characterization of the gene product.

An immunodominant membrane protein (IMP) of the apple proliferation (AP) phytoplasma was detected in preparations from AP-diseased periwinkle plants using monoclonal and polyclonal antibodies to the AP agent. Following isolation from Western blots and partial sequencing, degenerate oligonucleotides derived from the IMP sequence were used as probes to identify a DNA fragment containing the ORF encoding the IMP. Complete sequencing and subsequent analysis of the cloned DNA fragment revealed the presence of two ORFs, predicted to encode proteins with molecular masses of 25 kDa (P-318A) and 19 kDa (P-318B). Whilst database searches failed to assign a possible function to P-318A, analysis of P-318B predicted an amphiphilic membrane protein with a positively charged N-terminal portion, followed by a hydrophobic segment forming an alpha-helix, and a hydrophilic C-terminal part located outside of the cell. The amphiphilic nature of P-318B was confirmed by its solubility in Triton X-114. The gene encoding P-318B was expressed in Escherichia coli and the resulting protein was used to immunize rabbits. The antiserum obtained reacted specifically with P-318B. The same protein was also detected by an antiserum raised against antigen preparations from AP-diseased plants. The P-318B antiserum did not react with antigen preparations from plants infected with the closely related pear decline phytoplasma. However, in Southern hybridization studies, the gene encoding the IMP hybridized to genomic fragments of the pear decline and European stone fruit yellows phytoplasmas. It also showed significant sequence similarity to a gene encoding an antigenic membrane protein of the sweet potato witches' broom phytoplasma, but not to a gene encoding a major immunogenic membrane protein of an aster yellows group phytoplasma. Since it appears that most phytoplasmas possess a major immunogenic membrane protein which may have a function in pathogenesis, this work may be a basis for further studies on fundamental aspects of host-pathogen interactions. It also describes a new approach to obtain suitable immunogens to produce specific antibodies for detection and characterization of the non-culturable phytoplasmas.

Amino Acid Sequence↗