Browsing by Subject "Apfel"

Now showing 1 - 5 of 5
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    Changes in the concentration of particular hormones and carbohydrates in apple shoots after "bending" respectively chemical treatments and relationship to the flower induction process
    (2005) Boonplod, Nopporn; Bangerth, Fritz
    SUMMARY Apples are cultivated commercially throughout the temperate zone. A regular production however does not seem possible because of irregular yields from year to year. Main causes for this are the so called "alternate bearing" behavior which is the result of profuse flowering in one year but few or no flowers in the following year. It is reported that too vigorously growing shoots are part of the reasons for alternate bearing in apple trees. Applications of chemicals or conventional cultural practices, such as bending shoots have been widely used to restrict shoot growth and promote flower induction. However, the physiological mode of action of these methods in FI is still unknown. Phytohormones are thought to be involved in the process of flower induction (FI). In the above experiments, we investigated changes in endogenous hormones, starch and sugar contents after bending upright shoots into a horizontal position and spraying apple trees with the growth regulators Alar plus Ethrel to improve FI. The experiments were carried out during the years 2001 to 2003 at the Experiment Station, of the University of Hohenheim, Germany, whereby the apple cvs. ?Golden Delicious?, ?Boskoop?, ?Elstar? and ?Idared? were used. The apical part of growing shoots and non-growing bourse shoots, beside bark, wood and shoot diffusates were collected. Plant samples were frozen immediately in liquid nitrogen and freeze dried. Phosphate buffer 0.1M, pH 6.2 was used for collecting auxin in the shoot diffusates. All samples were stored at ?20C until extraction and purified, identified and quantified by Radio Immuno Assay (RIA). The results revealed, in general, that shoot bending and spraying with Alar plus Ethrel changed the endogenous hormone concentrations in the apical part of shoots, as well as in wood, bark and shoot exudates of apple trees. The ?Golden Delicious? cultivar and vigorously growing shoots showed clearer tendencies of hormonal changes than the other cvs. and non-growing bourse shoots. Cytokinin concentrations in the apical part of shoots, and in wood and bark increased after both treatments. Contrary to that, GAs and IAA concentrations in the apical part of shoots and in shoot exudates showed the opposite results. Both treatments had no effect on the concentration of ABA. Ethylene production in shoot tips was considerably stimulated by the combined treatment of Ethrel plus Alar probably due to Ethrel being a "synthetic precursor" of ethylene. Considerable variation existed in the mentioned hormonal changes in respect to the year of examination and the cv. under investigation. Time of treatments and in particular climatic conditions were probably the most influential variables. In spite of all this and on the basis of the above results the conclusion can be drawn that higher concentrations of cytokinins and lower concentrations of gibberellins and auxin are favorable for FI. Spraying with Alar plus Ethrel and bending of shoots seemed to decrease the reducing-sugars, as well as sucrose and starch concentrations in growing shoots and their leaves. In non-growing shoots, spraying seemed to reduce starch but to increase reducing-sugars and sucrose concentrations. A correlation between changes in carbohydrate contents (reducing sugar, sucrose and starch) caused by the spraying treatments and FI does not seem to exist. All the observed changes in the carbohydrate concentrations caused by spraying treatments were not particular impressive and did not really support the often published claim that the effect of spraying growth regulators, bending shoots or other cultural practices may mediate their stimulatory effect on FI via a change in carbohydrates. In contrast to that the above observed experimental results rather suggest that hormones are more effectively involved in the flower induction process of fruit trees.
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    Leg attachment and egg adhesion of the codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae) to different surfaces.
    (2014) Al Bitar, Loris; Zebitz, Claus P. W.
    Adults of Cydia pomonella live on host plant surfaces, differing considerably in their structural, chemical, and physicochemical characteristics according to host plant species, cultivar, plant organ, phenological stage, environmental conditions, and orchard management practices. This variable world provided by plant surfaces can profoundly affect many aspects of insect–plant interactions, such as attachment, locomotion, oviposition site selection, egg adhesion, and also survival of adults and their offsprings. Despite their importance, little attention has been given to the structural and wetting properties of the codling moth’s host plant surface and their effect on insect–plant interactions of this important pest. Therefore, studies in this thesis were undertaken to investigate the effect of structural and physicochemical characteristics of the substrate on two main codling moth-plant interactions: (1) the attachment ability of adults, and (2) the adhesion of their eggs. The first part of this thesis was performed to (1) analyze tarsal morphology of male and female C. pomonella to know more about their pretarsal attachment devices, and (2) to investigate their attachment ability on a variety of smooth and rough substrates, using a centrifugal force device. On all smooth artificial substrates tested, both sexes of C. pomonella adults achieved excellent attachment ability, by means of their smooth, flexible and well developed arolia. Hydrophobicity of the substrate had no considerable effect on friction forces. Cydia pomonella females showed a very good attachment ability to the smooth Plexiglas substrate in both horizontal and vertical positions. Thus, it can be concluded that the attachment system of C. pomonella is rather robust against physicochemical properties of the substrate and is able to achieve a very good attachment on vertical and horizontal plant surfaces. Results on the epoxy resin substrates, differing only in surface asperity size ranging from 0-12 µm revealed that the attachment ability of both sexes was significantly affected by surface roughness. Maximal friction force was measured on the smooth substrate whereas minimal friction force was assessed on microrough substrates with 0.3 µm and 1.0 µm size of asperities. On the remaining rough substrates, friction forces were significantly higher but still lower than on the smooth substrate. Both sexes generated similar friction forces on the same substrate, in spite of the considerable difference in their body mass, suggesting that both sexes attach effectively to variable rough plant surfaces in their habitat. However, since smooth surfaces have been reported previously to be the most favorable substrates for ovipositing females of C. pomonella, it is possible that they use their attachment system to sense the substrate texture and prefer those substrates to which their arolia attach the best. A better survival of the codling moth offspring is assumed to be ensured by the selection of suitable oviposition sites by females, as well as by a proper adhesion of deposited eggs to these sites. In apple orchards, eggs of the first generation of the codling moth are laid on leaf surfaces in the vicinity to small fruits, later in the growing season, most eggs are deposited directly on fruits. In the second part of this thesis, egg adhesion of the codling moth to different leaf and fruit surfaces of the domestic apple was investigated by measuring the pull-off force required to detach the eggs from the plant surface. Morphology, wettability, and free surface energy of the tested plant surfaces were analyzed to evaluate their role in egg adhesion. Furthermore, eggs and their adhesives covering leaf or fruit surfaces were visualized. Eggs on the smooth upper leaf sides of the tested cultivars were easily detached, requiring similar pull-off forces (total average of 6.0 mN). Up to 2-3 times stronger pull-off forces had to be applied to detach eggs from the trichome-covered lower leaf side, and these forces differed significantly between cultivars, owing mainly to different trichome covered areas. Whereas on the waxy fruit surface of all apple cultivars tested, eggs were very tightly adhered, and required 4-10 fold stronger pull-off forces than those previously measured on upper and lower leaf surfaces of the identical apple cultivars. Cydia pomonella eggs adhered stronger on the upper and middle fruit sections of all cultivars tested, than on the lower section. The influence of plant surface properties on egg adhesion, as well as the mechanisms used by the moth to overcome the presumable anti-adhesive properties of apple fruit surfaces, were discussed. Additionally, the results were debated in the context of the oviposition site selection, female attachment, as well as offspring survival of the codling moth.
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    Monitoring quality change of fruit during drying by application of laser light in the red spectrum
    (2011) Müller, Joachim; Nagle, Marcus; Romano, Guiseppe
    The main task of this research is to apply laser backscattering technology to simultaneously predict variations in moisture content and hardness of apples during drying. The backscattering area in pixel numbers, representing the illuminated area after laser light injection, and light luminescence measured by grey values were used for estimating changes in internal quality parameters during drying. Laser light measurement at 635 nm was found to be adequate for predicting changes in moisture content and SSC of apple during drying over different stages. On the contrary, photon scattering at 635 nm is not recommended as estimator of change in hardness during apple drying, based on the results.
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    Physiological, metabolic and molecular basis of biennial bearing in apple
    (2023) Kofler, Julian; Zörb, Christian
    Alternate or biennial bearing in apple (Malus ×domestica Borkh.) is characterized by ‘On’ years with high crop load and inhibited floral bud initiation and ‘Off’ years with little crop load and promoted formation of floral buds, respectively. Apple cultivars differ in their degree of biennial bearing behavior. The cropping irregularity has severe effects on quality and yield of apple harvests in commercial orchards and thereby directly poses an economic risk to apple growers. The aim of this study was to contribute to the understanding of the underlying mechanisms of biennial bearing in apple by analyzing the physiological processes in bud meristems during the time of flower bud induction. A field experiment was conducted during the growing seasons 2015 and 2016 and provided bud meristems of various developmental stages for a variety of analyses. The regular bearing cultivar ‘Royal Gala’ and the biennial bearing cultivar ‘Fuji’ allowed the comparison of two different developmental responses to high and low crop load treatments. Buds from 2-year-old spurs were sampled starting approximately four weeks after full bloom. Histological analysis of bud meristems successfully identified the time point of flower bud initiation in both cultivars at the experimental site. The onset of flower bud initiation was affected by crop load, cultivar and heat accumulation. While heavy cropping delayed the onset in ‘Royal Gala’ trees for 20 days compared to ‘Royal Gala’ trees with no crop load, bud initiation in heavy cropping ‘Fuji’ trees was negligible. ‘Fuji’ trees with no crop load started initiating buds 19 days earlier than ‘Royal Gala’ trees with the same cropping status. Proteomic profiling of the buds sampled during flower bud induction and during flower bud initiation revealed distinct differences in specific protein abundances depending on the cropping status. Buds from trees with a high crop load, where the flower bud initiation was inhibited and the buds primarily remained in a vegetative state, showed a decreased abundance of enzymes belonging to the phenylpropanoid and flavonoid pathways. Specifically, PAL was reduced, which could lead to less active auxin due to the reduced production of chlorogenic acid and thereby inhibiting flower bud formation. Furthermore, increased abundances of histone deacetylase and ferritins were also found in buds from high cropping trees, indicating that histone modification and building up enough iron storage capacities are involved in the vegetative bud development. Buds growing on non-cropping trees with a high rate of flower bud initiation, showed significantly higher concentrations of proteins involved in histone and DNA methylation. Metabolomic profiling and next-generation RNA sequencing showed that thiamine, chlorogenic acid, and an adenine derivative play a role in metabolic pathways promoting early flower bud development in apple, and that tryptophan was more abundant in buds collected from high-cropping trees compared to non-cropping trees. The selection of proteins, metabolites, and genes that the current work produced through its broad, non-targeted approach provides a comprehensive data base for future, more targeted analyses. The results of this study lay a thorough baseline to contribute to the identification of biological markers that are linked to a certain bearing behavior. Such markers can accelerate and facilitate breeding programs aimed at selecting apple cultivars, that are less prone to biennial bearing.
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    Sortenspezifische Veränderung der Fruchtfleischfestigkeit bei Apfel während der Lagerung unter Berücksichtigung des Signalmoleküls Ethylen
    (2019) Zimmermann, Telse; Wünsche, Jens Norbert
    Ripening of apples is initialized by ethylene, a ripening hormone, and the start of ripening is marked by an increase of ethylene production. During ripening fruit firmness is one of the changing processes and it is one of the major quality parameters for consumer and trade. After harvest the decline of apple fruit firmness consist of three distinct phase, in which the first phase, where no significant firmness reduce is observed, is the main part. The length of the first phase is different between the cultivars, so rapid softening cultivars have a short and cultivars, which obtain firmness over long time, have a long first phase. Application of ethylene will shorten this phase depending on the ethylene sensivity of the cultivars. The decline of fruit firmness is affected by changes in the cell wall. The aim of this study is to investigate this cultivar specific firmness decline by measuring gene expression of cell wall modifying enzymes and the activity of the cell wall modifying enzyme β galactosidase (GAL), and to find out the reason for the ethylene sensivity of the cultivars by recording ethylene production, gene expression and activity of ethylene biosynthesis enzymes also gene expression of the ethylene receptors and ethylene signal transduction proteins. To reach that goals three cultivars with different firmness and ethylene production are used and stored up to 4 month in a cool storage with 10 °C. The used cultivars are ‘Pinova’, which maintain firmness, ‘Elstar’ and ‘Golden Delicious’, which soften rapidly. ‘Pinova’ and ‘Elstar’ have a low ethylene production compared to ‘Golden Delicious’. Additional the ripening process is influenced by an inhibiting action of 1 Methylcyclopropen (1 MCP) and a promoting effect of ethylene. The main results are that correlation between ethylene production and fruit firmness persist just in softening cultivars although there are no difference between ‘Elstar’ and ‘Pinova’ in gene expression of ethylene biosynthesis enzymes. Also there are no differences between them in gene expression of ethylene receptors and ethylene signal transduction proteins while ‘Elstar’ shows an ethylene sensivity in contrast to ‘Pinova’. By comparison of the literature it is hypothesized that the amount of the ethylene receptors ERS1 and ERS2 is related to fruit firmness and the ethylene receptor ETR2 could be the sensor of ethylene sensivity. Furthermore the results about the changes/shifting of the cell wall refer to a difference between the cultivars in the gene expression of MdPG, MdAF, MdXTH2 und MdXYL with higher values for ‘Elstar’, but neither the expected inhibition of 1 MCP nor the promotion of ethylene in this genes happened. The activity of GAL shows indeed a cultivar specific pattern but it doesn´t correlate to fruit firmness. Also for other cell wall modifying enzyme activity or cell wall content exist no reference for a relationship to fruit firmness. So it is hypothesized that the interlinkage of the single cell wall components causes the fruit firmness on the one hand and limits the substrate availability of the respective cell wall modifying enzyme on the other hand.