Raphael A. Stern
Bio: Raphael A. Stern is an academic researcher from Tel-Hai Academic College. The author has contributed to research in topic(s): Pyrus communis & PEAR. The author has an hindex of 24, co-authored 81 publication(s) receiving 1546 citation(s).
Topics: Pyrus communis, PEAR, Malus, Pollination, Fruit tree
Papers published on a yearly basis
TL;DR: A new response curve for vegetative budbreak is proposed in 'Golden Delicious∑ apple, within a temperature range between 0 to 15 OC', based on the data collected here.
Abstract: ADDITIONAL INDEX WORDS. rest, chilling requirements, apical dominance, Malus sylvestris ABSTRACT. The relative contribution of various temperatures to dormancy completion of lateral vegetative apple (Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.) buds was studied quantitatively on whole container-grown trees. Trees were exposed continuously to 10 different temperatures and also to daily alternating temperatures in a 24-hour cycle. In addition, fully chilled vertically and horizontally positioned shoots were compared under forcing conditions. No budbreak occurred in shoots chilled above 12.5 OC. There was a steep increase in budbreak as the chilling temperature fell from 12.5 to 7.5 OC. There was little difference in the level of budbreak on shoots chilled between 7.5 and 0 OC. The relative contribution of temperature to chilling accumulation in apple found in our study differs from what has been proposed for stone fruit and for apple in previous studies, especially at temperatures <6 OC. The length of exposure to forcing conditions required to initiate budbreak diminished as the chilling temperature was reduced. No additional bud- break was apparent on shoots chilled longer than 2100 chilling hours. The chilling requirement found here for lateral vegetative buds is much higher than that needed for terminal vegetative and flower buds. Trees that were exposed to daily alternating temperatures had lower levels of budbreak when the high temperature in the diurnal cycle was greater than 14 OC. Practically no budbreak was apparent on trees that were exposed to diurnal cycles with a high temperature of 20 OC for 8 hours. Budbreak on horizontally positioned trees was more than twice that on the vertically positioned trees, emphasizing the magnitude of the apical dominance effect and its strong masking of the chilling effect on lateral buds in vertically grown apple trees. Based on the data collected here we propose a new response curve for vegetative budbreak in 'Golden Delicious∑ apple, within a temperature range between 0 to 15 OC. Buds of most temperate-zone deciduous trees have a dormancy period in the winter. Low temperatures are the most significant fac- tor affecting dormancy completion, although, there are indications that heat, light intensity, and mist, during the endodormancy phase affect dormancy completion to a certain extent (Chandler, 1960; Erez et al., 1966; Erez et al., 1968; Freeman and Martin, 1981). Knowing the exact response of apple (Malus sylvestris var. do- mestica) buds to temperature is important for a basic understanding of dormancy and for the practical application of dormancy release or bloom delay techniques. Spring frost may cause severe damage to flowers and young foliage in temperate zones; therefore, predic- tion of the date of budbreak is an important issue for growers in those regions. Budbreak is affected by two temperature-dependent processes: a) the accumulation of chilling to the level required for dormancy completion; and b) the accumulation of the heat units required for the buds to develop to bloom and foliation. These two processes were shown to be interdependent, i.e., fewer degree-days of heating are required as the previously accumulated chilling in- creases (Couvillon and Erez, 1985a). In warm regions, temperatures in the winter are not low enough, or the duration of exposure is not
TL;DR: It seems that a large number of foragers per tree directly increases the amount of pollination, high bee mobility between rows increases the amounts of cross-pollination, and a high proportion of “topworkers” increases pollination efficiency.
Abstract: SummaryThe ‘Red Delicious’ apple exhibits full self-incompatibility, therefore its fruit production depends totally on cross pollination, especially by honeybees, which are the ultimate apple pollinators. In the present study, the technique of sequential introduction of honeybee colonies and doubling their density was applied to determine effects on yield. In three consecutive season it was found that sequentially increasing the density of colonies in the apple orchards from 2.5 colonies per ha., as recommended previously, to 5.0 colonies per ha, and introducing them sequentially (half at the 10% full bloom (FB) and half at FB), increased the number of bees per tree, their mobility among the rows, and the proportion of “topworkers” compared with “sideworkers” . It seems that a large number of foragers per tree directly increases the amount of pollination, high bee mobility between rows increases the amount of cross-pollination, and a high proportion of “topworkers” increases pollination efficiency. All th...
••27 Jul 2010
20 Nov 2007-Scientia Horticulturae
TL;DR: Applying synthetic auxins to the main cherry cultivar grown in the warm climate of Israel caused appreciable and significant increases in fruit size and total yield, except when the crop load was heavy.
Abstract: The main cherry cultivar grown in the warm climate of Israel, ‘Bing’, produces relatively small fruit. Over three consecutive years (2003–2005), application of 50 mg l−1 2,4-dichlorophenoxypropionic acid [2,4-DP; as its butoxyethyl ester (Power™)], 10 mg l−1 3,5,6-trichloro-2-pyridyloxyacetic acid [3,5,6-TPA; as the free acid (Maxim®)], or 25 mg l−1 2,4-dichlorophenoxyacetic acid (2,4-D) plus 30 mg l−1 naphthaleneacetic acid (NAA; 0.3% Amigo™), at the beginning of pit-hardening when fruitlet diameter was ca. 13 mm caused appreciable and significant increases in fruit size and total yield, except when the crop load was heavy. Anatomical studies revealed that the main effect of these synthetic auxins was via direct stimulation of fruit cell enlargement. The above auxins had no negative effect on fruit quality, either at harvest or after 1 month of storage at 0 °C, or on return yield in the following year.
19 Aug 2004-Sexual Plant Reproduction
TL;DR: It is shown that Sn-RNase does not prevent fertilization by Si-pollen haplotype, thus presenting a case in which RHV is not required for the determination of specific pollen rejection by S- RNase, and implying that other regions in the enzyme may be sufficient for this specificity.
Abstract: In the gametophytic self-incompatibility system, growth of self-pollen tubes in the style is inhibited in a haplotype-specific manner by S-RNase. The mechanism by which S-RNase confers its specificity is unknown. However, a hypervariable region (RHV in Rosaceae and HVa-HVb in Solanaceae) that differs among the many cloned S-RNase alleles has been proposed to be involved in conferring the S-haplotype specificity of the S-RNase. Region swapping experiments between S-RNases and crystallography of the enzyme support this assumption. However, the deduced amino acid sequences of Sn-RNase and Si-RNase alleles from the European pear (Pyrus communis) were recently found to have an identical RHV. In the present study it is shown that Sn-RNase does not prevent fertilization by Si-pollen haplotype, thus presenting a case in which RHV is not required for the determination of specific pollen rejection by S-RNase, and implying that other regions in the enzyme may be sufficient for this specificity.
01 Nov 2006-Plant Physiology
TL;DR: It is concluded that MdMYB1 coordinately regulates genes in the anthocyanin pathway and the expression level of this regulator is the genetic basis for apple skin color.
Abstract: Anthocyanins are secondary metabolites found in higher plants that contribute to the colors of flowers and fruits. In apples (Malus domestica Borkh.), several steps of the anthocyanin pathway are coordinately regulated, suggesting control by common transcription factors. A gene encoding an R2R3 MYB transcription factor was isolated from apple (cv Cripps' Pink) and designated MdMYB1. Analysis of the deduced amino acid sequence suggests that this gene encodes an ortholog of anthocyanin regulators in other plants. The expression of MdMYB1 in both Arabidopsis (Arabidopsis thaliana) plants and cultured grape cells induced the ectopic synthesis of anthocyanin. In the grape (Vitis vinifera) cells MdMYB1 stimulated transcription from the promoters of two apple genes encoding anthocyanin biosynthetic enzymes. In ripening apple fruit the transcription of MdMYB1 was correlated with anthocyanin synthesis in red skin sectors of fruit. When dark-grown fruit were exposed to sunlight, MdMYB1 transcript levels increased over several days, correlating with anthocyanin synthesis in the skin. MdMYB1 gene transcripts were more abundant in red skin apple cultivars compared to non-red skin cultivars. Several polymorphisms were identified in the promoter of MdMYB1. A derived cleaved amplified polymorphic sequence marker designed to one of these polymorphisms segregated with the inheritance of skin color in progeny from a cross of an unnamed red skin selection (a sibling of Cripps' Pink) and the non-red skin cultivar Golden Delicious. We conclude that MdMYB1 coordinately regulates genes in the anthocyanin pathway and the expression level of this regulator is the genetic basis for apple skin color.
30 Jul 2009
TL;DR: In an age of accelerating biodiversity loss, this timely and critical volume summarizes recent advances in biodiversity-ecosystem functioning research and explores the economics of biodiversity and ecosystem services.
Abstract: In an age of accelerating biodiversity loss, this timely and critical volume summarizes recent advances in biodiversity-ecosystem functioning research and explores the economics of biodiversity and ecosystem services. The book starts by summarizing the development of the basic science and provides a meta-analysis that quantitatively tests several biodiversity and ecosystem functioning hypotheses. It then describes the natural science foundations of biodiversity and ecosystem functioning research including: quantifying functional diversity, the development of the field into a predictive science, the effects of stability and complexity, methods to quantify mechanisms by which diversity affects functioning, the importance of trophic structure, microbial ecology, and spatial dynamics. Finally, the book takes research on biodiversity and ecosystem functioning further than it has ever gone into the human dimension, describing the most pressing environmental challenges that face humanity and the effects of diversity on: climate change mitigation, restoration of degraded habitats, managed ecosystems, pollination, disease, and biological invasions.However, what makes this volume truly unique are the chapters that consider the economic perspective. These include a synthesis of the economics of ecosystem services and biodiversity, and the options open to policy-makers to address the failure of markets to account for the loss of ecosystem services; an examination of the challenges of valuing ecosystem services and, hence, to understanding the human consequences of decisions that neglect these services; and an examination of the ways in which economists are currently incorporating biodiversity and ecosystem functioning research into decision models for the conservation and management of biodiversity. A final section describes new advances in ecoinformatics that will help transform this field into a globally predictive science, and summarizes the advancements and future directions of the field. The ultimate conclusion is that biodiversity is an essential element of any strategy for sustainable development.
TL;DR: The data demonstrate that Cd perturbs the DNA methylation status through the involvement of a specific methyltransferase, linked to nuclear chromatin reconfiguration likely to establish a new balance of expressed/repressed chromatin.
Abstract: In mammals, cadmium is widely considered as a non-genotoxic carcinogen acting through a methylation-dependent epigenetic mechanism. Here, the effects of Cd treatment on the DNA methylation patten are examined together with its effect on chromatin reconfiguration in Posidonia oceanica. DNA methylation level and pattern were analysed in actively growing organs, under short- (6 h) and long- (2 d or 4 d) term and low (10 mM) and high (50 mM) doses of Cd, through a Methylation-Sensitive Amplification Polymorphism technique and an immunocytological approach, respectively. The expression of one member of the CHROMOMETHYLASE (CMT) family, a DNA methyltransferase, was also assessed by qRT-PCR. Nuclear chromatin ultrastructure was investigated by transmission electron microscopy. Cd treatment induced a DNA hypermethylation, as well as an up-regulation of CMT, indicating that de novo methylation did indeed occur. Moreover, a high dose of Cd led to a progressive heterochromatinization of interphase nuclei and apoptotic figures were also observed after long-term treatment. The data demonstrate that Cd perturbs the DNA methylation status through the involvement of a specific methyltransferase. Such changes are linked to nuclear chromatin reconfiguration likely to establish a new balance of expressed/repressed chromatin. Overall, the data show an epigenetic basis to the mechanism underlying Cd toxicity in plants.
14 Sep 2011-Scientia Horticulturae
TL;DR: A complete picture of dormancy is shown, using results from the early, pioneering work to the molecular basis, also emphasising dormancy modelling and measurement and their implication in temperate fruit production.
Abstract: Dormancy is the mechanism that plants use to protect sensitive tissue from unfavourable climatic conditions. In a changing global environment, temperate fruit crop adaptation might be at risk due to changes in temperature cues. A complete picture of dormancy is shown in this review, using results from the early, pioneering work to the molecular basis, also emphasising dormancy modelling and measurement and their implication in temperate fruit production. This description is completed by the variability that climatic change might induce in plants through direct or indirect changes in dormancy. Future avenues for the correct adaptation of temperate fruit crops are proposed that span basic questions, from temperate fruit distribution to more-applied questions of dormancy, such as application of rest-breaking agents, depth-of-dormancy markers, breeding strategies, cross-pollination and host–pest interaction. In the context of global climate change, a linkage among the cited fields is intended in this review in order to raise awareness in the scientific community.
TL;DR: The effect of the environment, interactions with vegetative growth, the roles of plant growth regulators and carbohydrates, and recent advances in molecular biology, are discussed.
Abstract: The intention of this review is to discuss floral initiation of horticultural trees. Floral initiation is best understood for herbaceous species, especially at the molecular level, so a brief overview of the control of floral initiation of Arabidopsis (Arabidopsis thaliana (L.) Heynh.) precedes the discussion of trees. Four major pathways to flowering have been characterized in Arabidopsis, including environmental induction through photoperiod and temperature, autonomous floral initiation, and regulation by gibberellins. Tropical trees are generally induced to flower through environmental cues, whereas floral initiation of temperate deciduous trees is often autonomous. In the tropical evergreen tree mango, Mangifera indica L., cool temperature is the only factor known to induce flowering, but does not ensure floral initiation will occur because there are important interactions with vegetative growth. The temperate deciduous tree apple, Malus domestica Borkh., flowers autonomously, with floral initiation dependent on aspects of vegetative development in the growing season before anthesis, although with respect to the floral initiation of trees in general: the effect of the environment, interactions with vegetative growth, the roles of plant growth regulators and carbohydrates, and recent advances in molecular biology, are discussed.