TY - THES ID - 3438309 TI - Evaluation of flower induction and outgrowth of bromeliad plants under natural conditions as a tool for species management and conservation in nature. AU - Racines Oliva, Mauricio Andrés AU - De Proft, Maurice. AU - KU Leuven. Faculty of bioscience engineering. Department of biosystems. PY - 2013 VL - 1135 SN - 9789088263248 PB - Leuven KU Leuven. Faculteit Bio-ingenieurswetenschappen DB - UniCat KW - Academic collection KW - Theses UR - https://www.unicat.be/uniCat?func=search&query=sysid:3438309 AB - Abstract Indiscriminate deforestation is endangering some regions all over the globe. Localities in tropical forests that feature exceptional concentrations of species with exceptional levels of endemism and that face exceptional degrees of threat are defined as hotspots (Myers, 1988). One of them is “Tropical Andes” and Ecuador is part of it. In highly deforested areas of the Ecuadorian lowland rain forests, Vriesea is one of the most representative genera among bromeliads. Therefore this genus, represented by Vriesea ‘Ginger’, was used as model plant in this study. In the future, Ecuadorian management of natural resources and conservation legislation have to be improved to avoid even more ecological damage. In the scope of creating tools to improve management and conservation of plant species, this PhD research focuses on possible spontaneous flowering induction “SFI” triggers in order to improve our understanding of this event. Flowering synchronization is utmost important for the continuity of a healthy gene pool for a species. Moreover, a better knowledge about the way a plant species controls flowering constitutes the core of any project that aims to preserve a plant species in his natural habitat.The experimental plant material is described and the time it takes the model plant to show anthesis is determined. Juvenile and mature stages are defined. Juvenility is left behind when plant reaches a fresh weight of 20 g (18 weeks of growth in the greenhouse). This is further confirmed by the analysis of ACC and MACC before and after the plant reaches that fresh weight. Based on the knowledge that bromeliads are flower induced by means of ethylene, treatments believed to spur its biosynthetic pathway were applied to Vriesea ‘Ginger’ plants.On the one hand, mechanical, geotropical and drought treatments applied to assess plants response did not yield any flower induction. However drought did induce “tubing”. “Tubing” is a kind of protection against drought of the apical meristem by the young leaves creating a tube of leaves at the center of the central tank of the plants and by this limiting water loss. “Tubed” plants did not become flower inducible using ethylene. On the other hand, light treatments induce Vriesea ‘Ginger’ plants prone to flower. This is achieved by first decreasing the irradiation light intensity followed by increasing irradiation light intensity. Plants exposed to 0.5 µmol m-2s-1 for four weeks (400 W high pressure sodium lamps) with subsequent increase to 15 or 30 µmol m-2s-1 (400 W high pressure sodium lamps) yielded flower induction of 165 g fresh weight or heavier plants. Higher flower induction was achieved by finalization with 30 µmol m-2s-1 thence suggesting the need of a specific Δ irradiation level to induce plants more efficiently. This was confirmed by the exposure to 100 µmol m-2s-1 (400 W high pressure sodium lamps) of the same plant material under the same initial conditions, showing no flower induction at all for plants up to 225 g fresh weight. High Δ irradiation level proved to have no or even an inhibiting effect on flower induction. Not only light intensity but also light quality definitely plays a role during flower induction. Whereas the 12h exposure of Vriesea ‘Ginger’ plants to one LED light source UV-A (350 nm) and NIR (920 nm) had no effect on flower induction, the exposure of the plants to: 660 nm (11.5 µmol m-2s-1), 630 nm (9.8 µmol m-2s-1), 530 nm (8.6 µmol m-2s-1) and 420 nm (9.7 µmol m-2s-1) made plants from 315 g and heavier prone to flower induction, resulting in at least 40% of the plants to bloom. None of the lighter plants, exposed to the same light intensity or less, were flower induced. The only exceptions were 30% of the plants of 145 and 225 g fw exposed to 5 µmol m-2s-1 (420 nm). 420 nm was the only LED light treatment able to induce 145 g plants, highlighting the importance of blue light during the flower inducive process. 530 nm (8.6 µmol m-2s-1) made 100% of the plants prone to flower induction. This proves against the traditional thought that green light has no major influence on plant physiology behavior.Exposure of plants to two LED-types sources for 12h a ratio ≈ 2:1 of 480 nm (12 µmol m-2s-1) and 630 nm (6.1 µmol m-2s-1) yielded in a flower induction of 40% (225 g plants) and 60% (145 g plants), therefore highlighting once again the importance of blue light. By changing the ratio ≈ 1:2 of 480 nm (6.1 µmol m-2s-1) and 630 nm (12.5 µmol m-2s-1) it was possible to obtain at least 40% of flower induction of 205 g or heavier plants. 660 nm (11.5 µmol m-2s-1) and 730 nm (3.2 µmol m-2s-1) induced 60% of 285 g plants. Irradiating 730 nm (3.2 µmol m-2s-1) for 1h after 12h of 660 nm (11.5 µmol m-2s-1) yielded 60% of induction (327 g plants) and 30% (205 g plants), suggesting that other photoreceptor other than phytochrome might play a role in Vriesea ‘Ginger’ flower induction. Almost with all light treatments it can be said that the higher the fresh weight of the plants, the higher the potential to flower. A total of two “SFIs” were witnessed and both origins were traced down to January: the first one being on 12/01/2009 ± 8 days and the second and last one on 21/01/2010 ± 8 days. Spectral analysis during December 2010-January 2011 showed subtle variation in the values of R:FR ratio (660:730 nm), R/B (660:450 nm) and B:FR (450:730 nm) compared with February, March and April 2011. This suggests that under natural conditions, far-red light (730 nm), blue light (450 nm) and low PAR irradiance might be important in creating flower inducive conditions, which is coherent with the other light experiments conducted. Furthermore, “SFI” is linked with clouding in the rainy seasons in nature as it increases the amount of blue light that reaches plants and at the same time decreases the light intensity plants are exposed to. Both being environmental cues that can trigger SFI under natural conditions. ER -