Heppner, S. (2010): <b>Vegetative Vermehrung einheimischer Baumarten in Südecuador Physiologische Grundlagen und deren Umsetzung</b> University of Bayreuth, <i>phd thesis</i>
Resource Description
Title:
Vegetative Vermehrung einheimischer Baumarten in Südecuador Physiologische Grundlagen und deren Umsetzung
FOR816dw ID:
1098
Publication Date:
2010-03-30
License and Usage Rights:
Resource Owner(s):
Individual:
Sina Heppner
Contact:
email:
sina.heppner <at> web.de
Abstract:
Parallel to the proceeding destruction of the megadiverse mountain forests of Ecuador more and more plantations with exotic Pinus and Eucalyptus species are being established. An ecologically reasonable reforestation could help to solve the problem. Such a reforestation can only be achieved by using indigenous species. As the harvest of seeds is problematic, plant material has to be produced by means of vegetative propagation. However, we have been lacking a knowledge base and efficient methods for cloning native tree species so far.<br/>
<br/>
? In the present thesis the potential to vegetatively propagate as well as the carbohydrate and phytohormone content of the following six tree species ? naturally occurring in the mountain forests of Southern Ecuador ? were examined: Clethra revoluta (Clethraceae), Heliocarpus americanus (Tiliaceae), Isertia laevis (Rubiaceae), Myrica pubescens (Myriaceae), Piptocoma discolor (Asteraceae) and Tabebuia chrysantha (Bignoniaceae).<br/>
? Despite variegated variations of the propagation conditions over 1 ½ years we did not succeed in obtaining rooted stem cuttings of adult trees. The plants withered rapidly. Measurements of stomatal leaf conductance show an insufficient regulation of the stomata associated with high transpiration rates. Although the production of rooted stem cuttings of adult trees by air-layering was successful, these plants withered after placing them in soil, too.<br/>
? The carbohydrate measurements resulted in annual fluctuations in several species concerning their starch and soluble sugar content ? especially for the raffinose family (Tabebuia); an increased inositol content during the drier months could also be observed in all species. Although the total carbohydrate content showed clear seasonal fluctuations in the leaves (Heliocarpus-, Myrica and Tabebuia plants) no definite fluctuations could be detected in the twigs at all. Whereas Heliocarpus and Tabebuia trees stored reserve carbohydrates with a content of 6 or 9.5 %, respectively (especially in the form of starch as well as glucose, fructose and sucrose) the low carbohydrate supply in the twigs of Clethra and Piptocoma during the whole year could have been detrimental to successful adventive rooting.<br/>
? It is presumed that the endogenous content of cytokinins (initiation of root primordia) and auxins (root growth) is especially important for the rooting of cuttings. The measured phytohormone status fluctuates depending on season and species. A hormone status suitable for the root formation (= a high auxin : cytokinin ratio) was found in Heliocarpus and Tabebuia in the months with the highest precipitation rates. On the contrary Clethra and Myrica contained hardly any auxin but relatively much cytokinin. Thus rooting seems to be especially difficult with these species.<br/>
? As it is not possible to interfere in the hormone status of adult trees, young plants were used as donor plants for their hormone and metabolic reserve status can be changed adequately by stressing treatments. We especially aimed at lowering the cytokinin level endogenously. For these experiments Heliocarpus and Tabebuia were selected and exposed to shortage of water, nutrients or root space as well as combinations of these stress factors. Additionally wildlings (saplings) were used.<br/>
? This strategy turned out to be successful because from all treatments 42 % of the Heliocarpus and 15 % of the Tabebuia cuttings rooted on average. The most successful cuttings originated from Heliocarpus treelets exposed to water shortage (70 % rooting) and from Tabebuia plants exposed to nutrient shortage (15 %). Wildlings of Tabebuia also grew roots effectively (45 %). Even better results in the two species were achieved by air-layering.<br/>
? The pretreatments resulted in an increase of the carbohydrate content (except for Tabebuia plants under water shortage). However, no statistically significant correlation aroused between the carbohydrate content of the differently stressed donor plants and the rooting percentage.<br/>
? As assumed the stressful pretreatment of the donor plants of both species caused a lower cytokinin level whereas at least in Tabebuia a significantly negative correlation between the rooting of cuttings and the cytokinin content of the donor plants was found (rs up to -0.93).<br/>
? The results of this thesis clearly show that even young twigs of adult tropical trees have virtually no rooting potential. In young plants this potential can be activated by stress whereas the accumulation of metabolic reserves and the decrease of the cytokinin level had a beneficial influence on the rooting percentage. This constellation was rather developed in Tabebuia than in Heliocarpus.<br/>
? Due to the possibility of making at least two cuttings from one donor plant the establishment of a cultivation of cloned material for reforestation is ? although time-consuming ? definitely feasible.
Literature type specific fields:
THESIS
Degree:
phd
Degree Institution:
University of Bayreuth
Total Pages:
192
Metadata Provider:
Individual:
Kristin Roos
Contact:
email:
biene.tomate <at> gmx.net
Faculty of Biology, Chemistry and Geoscience
Department of Plant Physiology
Universitätsstr. 30
95440 Bayreuth
Germany
