1,720,996 research outputs found
Light quality regulates shoot cluster growth and development on MM 106 apple genotype in in vitro
No full textThe interaction between shoot proliferation and regulative action of light quality was investigated in terms of cluster growth and development. In the commercial laboratory, the shoot multiplication procedure is normally conducted by growing clusters of shoots during several sub-cultures. Thus in this work the regulative action of light quality was evaluated by analysing the shoot cluster proliferation rate, the evolution of axillary bud differentiation, the axillary shoot development on both initial explant stem (order 1 axis) and three representative lateral branches (order 2 axes), growing from the lateral buds located at the bottom of the initial explant. Experiments showed that light qualities regulate bud differentiation and interact with apical dominance, leading to strong control of axillary bud outgrowth, and, finally, resulting in a differentiated architectural formation of clusters and type of branching. Two independent actions were observed, one dependent on blue light and the other dependent on red light, evoking the role of specific photoreceptor systems in plant response. Blue and UV-A light increased the number of buds differentiated from the apical meristem, without affecting apical dominance. An opposite trend was induced by red, yellow and green light. The involvement of phytochrome became clear under red light, while possible specific receptors and/or specific interaction among the known photoreceptors can be postulated under the other two light qualities. Results confirm that in apple, proliferation is the product of the interaction between two biological responses, lateral bud differentiation, which can be defined as potential proliferation, and new shoot development, which is the effective proliferation, and both responses are regulated by light quality
Physiological dissection of blue and red light regulation of apical dominance and branching in M9 apple rootstock growing in vitro
No full textThis paper presents the results of the interaction of red light (R) with blue light (B), applied to shoots of M9 apple (Malus pumila paradisiaca Schmid) rootstock, on the regulation of stem growth, apical dominance and branching. These results are compared with the active form of phytochromes (PHYs) under monochromatic and dichromatic light treatments. The inhibition of internode elongation was determined by PHY photoequilibrium, with the additional effect of B, by means of a separate photoreceptor. The development of phytomers appeared to be primarily due to the active form of PHY, with a marginal effect from B. Shoot growth, which combines internode elongation and development of the phytomer, was highest under R and lowest under B and far red light (FR), showing the largely positive role of PHY photoequilibrium. Under FR, reduced stem elongation was due to the very small number of phytomers formed. Apical dominance was inhibited, while branching was increased under R, corresponding to the highest values of PHY photoequilibrium determined. Apical dominance was increased and branching was reduced by B, indicating a complex interaction between PHY and B receptor. In the shoot cluster system, photomorphogenic behavior was dependent on the time of exposure to the different light qualities. The information gained from the study will be helpful in improving the set up of in vitro growth light conditions, and in providing useful insights into research of the development of the woody plant canopy, an important factor in ecological plant communities. © 2008 Elsevier GmbH. All rights reserve
Il ruolo della qualità della luce nei processi di sviluppo e differenziazione delle colture in vitro. Italus Hortus, Review n.16: 37 - 49
No full textPhotoregulation of growth and branching of plum shoots: physiological action of two photosystems
No full textPlum shoot proliferation was investigated in terms of two distinct processes: axillary bud differentiation and axillary shoot development. Results showed that light quality influenced bud differentiation and interacted with apical dominance in determining shoot outgrowth, resulting in a differentiated structure of shoot clusters and type of branching. Results suggested that blue light, acting through its photoreceptor, increased the number of axillary buds differentiated from apical meristem, but did not remove the apical dominance. Red light removed apical dominance, while reducing the formation of axillary buds; both events appeared to be dependent on the putative amount of phytochrome active form, and independent of light photon fluence rate. On the contrary, blue light action appeared to be dependent on photon fluence rate. In addition, apparent blue-red interactions related to photomorphogenic events fit an antagonistic model for branching regulated by light via cryptochrome and phytochrome photoreceptors. Our results show that the dynamics of shoot cluster development is the product of two events: the formation of new axillary buds and their release from apical dominance
Modifications of some characteristics in nectarine fruit induced by light deprival at different times of fruit growth
No full textRelationship between evolution of CO2 and growth of plum shoot tips cultured in vitro under different light/dark regimes
No full textRuolo del fotoperiodo e della qualità della luce nella micropropagazione delle specie arboree da frutto
No full textRegeneration and selection of quince BA29 (Cydonia oblonga Mill.)somaclones tolerant to lime-induced chlorosis
No full textQuince is the most used rootstock in Italian pear orchards, but due to the its high susceptibility to calcareous soils it induces widespread chlorosis problems on the grafted pear cultivars. Until recently, the common breeding techniques have not allowed the simple production of tolerant quince selections. Thus, somaclonal variation, and the large genetic variability brought about during the in vitro processes, might be a suitable tool to obtain genotypes with better agronomic characteristics. The aim of the present research was to induce in vitro regeneration of quince shoots under Fe-limiting conditions from leaves (of quince clone ‘BA29’), and subsequently to evaluate their tolerance to lime-induced chlorosis. Leaves of explants were placed onto MS medium supplemented with TDZ and NAA, and the selective pressure conditions were obtained by reducing the normal MS iron content and/or by adding different concentrations of potassium bicarbonate (KHCO3). Selective conditions decreased both the percentage of shoot-forming leaves and the mean number of shoots per organogenetic leaf, as the iron content was reduced and/or the KHCO3 content was increased. A discrete number of putative somaclones, showing a range of severe chlorosis symptoms compared to a wild type clone, were chosen by visual assessments, and further tests were conducted under reduced amounts of Fe and the presence of 1.0 mM of KHCO3 conditions. DB-34 somaclone seemed to be the most promising one, because its chlorophyll content did not reduce as happened in the other somaclones and with the wild type clone. Stress conditions affected only the Fe2+ content of the DB-43 somaclone, even if under normal conditions the Fe2+ content was much higher than with all the other accessions. On the contrary, the medium acidification capacity of all somaclones was influenced similarly by treatments. A preliminary in vivo test confirmed these results. Moreover, preliminary RAPDs analyses disclosed polymorphism within the somaclones and among them and the wt clone. The sequence of chloroplastic protein D1, codified by the psbA gene, was determined in quince ‘BA29’ and pear ‘Conference’ to predict its hypothetical functions. Sequences showed differences in length and in amino acidic composition. In quince, the main modification is located in the ‘191’ position where tyrosine substitutes histidine, causing a loss of one of the iron-binding sites
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