Browsing by Subject "Phytohormones"

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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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    Innovative propagation techniques in banana and plantain
    (2020) Opata, John; Wünsche, Jens Norbert
    Despite the significant role of banana and plantain (Musa spp.) in the livelihood of millions of people mostly in developing countries and in particular Sub-Saharan Africa, cultivation of these important crops is impeded by numerous challenges. Against this backdrop, research attempts were made to improve shoot proliferation in banana and plantain by employing innovative macropropagation techniques. Banana and plantain suckers were harvested in the greenhouses of the University of Hohenheim, Stuttgart, Germany and research fields of the Crops Research Institute, Ghana. These were subjected to Plants Issus de Fragments de tige technique (PIF), which is a mechanical preparation technique. It involves paring, thus cutting off the roots of the corms with a sharp sterilized knife. Thereafter, the leaf sheaths of the corms were carefully removed, consequently exposing latent axillary buds and the apical shoot meristem. Some of the corms had the exposed meristem destroyed with crosswise incision whiles others had the meristem left intact. Various hormonal treatments with the synthetic plant hormone 6-benzylaminopurine (0, 2.25 and 225.25 mg L-1 BAP) and natural plant hormones derived from coconut water were used. Fresh and autoclaved coconut water and other additives such as papain and root growth biostimulant from seaweed were employed in various combination to treat banana and plantain corms by either soaking or vacuum infiltration. The treated corms were planted in germination beds filled with growth substrates inside growth chambers. Evaluation of solution uptake from the two application methods and subsequently effects on number and growth characteristics of lateral shoots from the treated corms were carried out. Field evaluation of growth and yield of acclimatized plantlets from the PIF technique and hormonally derived plantlets were also undertaken. The hormonal solution application method demonstrated a higher solution uptake with the method of infiltration which was about 33% more compared to the method of soaking. Results revealed an earlier shoot emergence in corms which had the apical meristem destroyed with crosswise incision, demonstrating the breakdown of apical dominance. Nonetheless, this did not contribute to significantly higher shoot numbers when compared to corms with intact apical meristem. BAP treated corms had triggered greater number of strong shoots with comparatively higher number of roots than untreated controls, however, the effect was independent of the concentration applied. The study further revealed the importance of natural growth hormones particularly the application of autoclaved coconut water as an alternative to the expensive plant growth hormone, 6-benzylaminopurine. There was a marked effect of autoclaved coconut water, resulting in earlier shoot development characterized with higher root numbers compared to corms subjected to 6-benzylaminopurine and the PIF technique, respectively. Moreover, the addition of the proteolytic enzyme papain and the root growth biostimulant seaweed extract to coconut water did not influence the growth performance of the treated corms. Vegetative growth performance, specifically pseudostem length of the main crop, was significantly influenced by the treatment at 6 and 9 months of growth in the field. BAP and seaweed extract recorded the highest numbers of suckers. Uniformity of acclimatized plantlets with well-developed roots and active leaves at the nursery stage might have contributed immensely for the uniform vegetative growth. Treating the corms with BAP and seaweed significantly influenced the bunch weight of the main crop resulting in a bunch weight of about 11 kg. However, there was no significant difference among treatments regarding bunch weight of the first sucker crop with each treatment recording a bunch weight of 11 kg.
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    Tissue-specific hormone signalling and defence gene induction in an In vitro assembly of the rapeseed verticillium pathosystem
    (2023) Hafiz, Fatema Binte; Geistlinger, Joerg; Al Mamun, Abdullah; Schellenberg, Ingo; Neumann, Günter; Rozhon, Wilfried
    Priming plants with beneficial microbes can establish rapid and robust resistance against numerous pathogens. Here, compelling evidence is provided that the treatment of rapeseed plants with Trichoderma harzianum OMG16 and Bacillus velezensis FZB42 induces defence activation against Verticillium longisporum infection. The relative expressions of the JA biosynthesis genes LOX2 and OPR3, the ET biosynthesis genes ACS2 and ACO4 and the SA biosynthesis and signalling genes ICS1 and PR1 were analysed separately in leaf, stem and root tissues using qRT-PCR. To successfully colonize rapeseed roots, the V. longisporum strain 43 pathogen suppressed the biosynthesis of JA, ET and SA hormones in non-primed plants. Priming led to fast and strong systemic responses of JA, ET and SA biosynthesis and signalling gene expression in each leaf, stem and root tissue. Moreover, the quantification of plant hormones via UHPLC-MS analysis revealed a 1.7- and 2.6-fold increase in endogenous JA and SA in shoots of primed plants, respectively. In roots, endogenous JA and SA levels increased up to 3.9- and 2.3-fold in Vl43-infected primed plants compared to non-primed plants, respectively. Taken together, these data indicate that microbial priming stimulates rapeseed defence responses against Verticillium infection and presumably transduces defence signals from the root to the upper parts of the plant via phytohormone signalling.