Morfogenese da folha do cafeeiro (Coffea arabica L.)
The origin of new leaves in Coffea arabica L. cv. "Mundo Novo" and the modifications which occur during their growth were studied. Apical buds from adult plants and leaves in various stages of development were collected during the spring and summer, fixed in FAA and Craf, respectively, and embedded in paraffin. Longitudinal and transverse sections whose thicknesses varied from 10 to 15¿ m were stained according to Delafield's hematoxylin and Heidenhain's ferric hematoxylin methods. Apical buds are covered by interpetiolar stipules which produce on their adaxial surface numerous glandular appendices whose epidermal cells secrete a viscose, sticky liquid in which the whole apical bud with its foliar and stipular primordia remains immersed. When dry, this secretion forms a protective, waxy film over the abaxial surface of the primordia and young leaves. The initiation of foliar primordia in coffee occurs in a series of periclinal divisions in the second layer of the tunica and gives rise to protuberances lateral to the apical bud. While the primordia are elongating, the procambium differentiates in continuity with the leaf traces; and soon thereafter, the phloem differentiates. When the primordia are 2,0 mm long, all growth activity becomes concentrated in the marginal meristems. After the leaves emerge from the stipules, they show intense meristematic activity and morphological modifications that bring about structural differentiation. The mesophyll begins to differentiate through the anticlinal elongation of cells of the fundamental meristem, forming the cells which constitute the palisade parenchyma. Afterwards, certain protodermall cells divide, differentiating into stomata. Simultaneously the spongy parenchyma begins to differentiate with the formation of intercellular spaces. Once formed in this manner, the incipient leaf structure the epidermal cells as well as the mesophyll cells divide only anticlinally and grow until the leaf blade completes its
| Principais autores: | , , |
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| Formato: | biblioteca |
| Publicado em: |
1978
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| Assuntos: | COFFEA ARABICA, ANATOMIA DE LA PLANTA, MORFOGENESIS, HOJAS, YEMA (PLANTA), ETAPAS DE DESARROLLO DE LA PLANTA, MUNDO NOVO, ANATOMIA FOLIAR, MORFOLOGIA FOLIAR, |
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