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| Author(s): |
Natalia Paganotti Antonucci
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB) |
| Defense date: | 2010-03-10 |
| Examining board members: |
Gladys Flávia de Albuquerque Melo de Pinna;
Nanuza Luiza de Menezes;
Emerson Alves da Silva
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| Advisor: | Gladys Flávia de Albuquerque Melo de Pinna |
| Abstract | |
The Kranz syndrome is a set of anatomical, ultrastructural and biochemical features that culminate in the C4 photosynthesis. This syndrome has a huge diversity among Angiosperms, so it became suitable to survey all the levels above cited for its complete characterization. In the present work the Kranz syndrome of Gomphrena arborescens and G. scapigera (Amaranthaceae) is studied, with emphasis on the ontogenetic origin of the Kranz sheath, on the ultrastructural description, and on the biochemical confirmation about the C4 photosynthesis kind. The foliar development of these species shows that the Kranz sheath is originated from the inner layer of the mesophyll, the foliar endodermis. A discussion about the literature terms used to describe the Kranz sheath, all of them referring to the function of this layer in C4 photosynthesis, demonstrates the importance of using terms that inform the ontogenetic origin of this layer, such as endodermis and perycicle. The ultrastructural analysis identified possible factors that interfere on the C4 photosynthesis of both species, such as wall thickening and composition of Kranz sheath cells, the centripetal position of chloroplasts and the peripheral reticulum in chloroplasts. Although biochemical analysis has resulted in no conclusive information, the chloroplast dimorphism suggests the NADP-ME C4 photosynthesis. This work, in a general way, contributes to the knowledge of the Kranz syndrome among Amaranthaceae s.s., a group that has the ultrastructure and the biochemistry of C4 photosynthesis poorly known. It also draws attention to the importance of anatomical surveys concerning the ontogenetic origin of Kranz sheath for a better understanding on the diversity of Kranz syndrome among Angiosperms. (AU) | |