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Ultrastructural analysis and programmed cell death in the tracheary elements in leaves of Ruschioideae: a novel investigation of vascular tracheids and the formation of peripheral vascular bundles

Grant number: 12/11260-0
Support Opportunities:Scholarships abroad - Research Internship - Master's degree
Effective date (Start): September 01, 2012
Effective date (End): October 31, 2012
Field of knowledge:Biological Sciences - Botany - Plant Morphology
Principal Investigator:Gladys Flávia de Albuquerque Melo de Pinna
Grantee:Aline Siqueira Nunes
Supervisor: Sara Beatriz Maldonado
Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Research place: Universidad de Buenos Aires (UBA), Argentina  


Popularly known as flowering stones or ice plants, the Aizoaceae (Caryophyllales) form a family of succulent leaves plants with center of origin in South Africa. Most of the species are classified in the diverse subfamily Ruschioideae, which present since dorsiventral flat leaves until species with three angled and cylindrical leaves, which in notable the presence of connation in opposite leaves bases. In anatomical studies carried out in Ruschioideae so far, we observed that connation of leaf bases implies the occurrence of peripheral vascular bundles with particular arrangement, regardless of the morphology of mature leaves. Our results suggest that the peripheral vascular bundles originate from the marginal blastozone region which is responsible for the expansion of the leaf lamina during leaf ontogenesis. These peripheral bundles present a particular type of tracheary element, called wide-band tracheid (WBT), found in other families of Caryophyllales. However, the distinction between the WBTs of peripheral vascular bundles and vessel elements of the midrib is not that clear in Aizoaceae in relation to other families. There is, therefore, a need for ultrastructural analysis to confirm the identity of these xylem vascular elements. With the TUNEL test, used for detection of programmed cell death, will be possible to visualize the formation of new conductive cells of the xylem in the marginal blastozone region, in order to confirm the hypothesis established in this study (FAPESP bag 2011/04286-0) that this the new peripheral bundles forming region in Ruschioideae. Besides the scientific relevance directly linked to the master's project mentioned above, this stage will be an enhancement in research, being carried out between the two Universities, creating new opportunities for continuing studies on the anatomy and ultrastructure of Aizoaceae. Under the academic aspect, the experience acquired from the exchange of information with the expert in plant histochemistry, Dr. Sara Beatriz Maldonado, will be an important addition in the formation of the candidate, who has played with great dedication her research in this plant group. (AU)

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