ABSTRACT
The understorey origin of coffee trees and the strong plasticity of Coffea arabica leaves in relation to contrasting light environments have been largely shown. The adaptability of coffee leaves to changes in light was tested under controlled conditions by increasing the illumination rate on C. arabica var. Naryelis seedlings acclimated to low light conditions and observing leaf responses at three different developmental stages (juvenile, growing and mature). Only mature leaves proved capable of adapting to new light conditions. In these leaves, different major mechanisms were found to contribute to maintaining a good photosynthetic level. With increased illumination, a high photosynthetic response was conserved thanks to fast nitrogen remobilization, as indicated by SPAD values and the photorespiration rate. Efficient photoprotection was accompanied by a great ability to export sucrose, which prevented excessive inhibition of the Calvin cycle by hexose accumulation. In contrast, in younger leaves, increased illumination caused photodamage, observable even after 9 days of treatment. One major finding was that young coffee leaves rely on the accumulation of chlorogenic acids, powerful antioxidant phenolic compounds, to deal with the accumulation of reactive oxygen species rather than on antioxidant enzymes. Due to a lack of efficient photoprotection, a poor ability to export sucrose and inadequate antioxidant protection, younger leaves seemed to be unable to cope with increased illumination. In these leaves, an absence of induced antioxidant enzyme activity was accompanied, in growing leaves, by an absence of antioxidant synthesis or, in juvenile leaves, inefficient synthesis of flavonoids because located in some epidermis cells. These observations showed that coffee leaves, at the beginning of their development, are not equipped to withstand quick switches to higher light levels. Our results confirm that coffee trees, even selected for full sunlight conditions, remain shade plants possessing leaves able to adapt to higher light levels only when mature.
ABSTRACT
O sensoriamento remoto e o geoprocessamento são geotecnologias importantes no apoio ao levantamento de dados da agricultura, permitindo estudos e o entendimento das relações ambientais em que uma determinada cultura está inserida. Neste trabalho,objetivou-se, relacionar as variáveis físicas, como, altimetria, declividade e tipo de solo com o agrossistema cafeeiro existente no município de Umuarama-PR pelo uso de geotecnologias. Foi utilizada a imagem do satélite LANDSAT 5/TM (Thematic Mapper) com data de passagem em 02/07/2007 e o software SPRING 4.3.3. As bandas 3, 4 e 5 do sensor TM foram restauradas, resultando em imagens de 15 m de resolução espacial e, posteriormente, constituindo a composição colorida RGB, na sequência TM4, TM5, TM3, a qual foi empregada na identificação das lavouras cafeeiras por meio de interpretação visual. Para o estudo do relevo, foram utilizados dados da missão SRTM, os quais possibilitaram o conhecimento da altimetria e declividade da região. A imagem do sensor TM possibilitou a execução da classificação visual e consequente identificação das lavouras cafeeiras com alta precisão. Quanto ao relevo, verificou-se que aproximadamente 99 por cento das lavouras cafeeiras estão localizadas entre 380 e 480 metros de altitude e que 90 por cento destas estão situadas em declividades de até 8 por cento de inclinação. Em relação aos solos, observou-se que 89 por cento dos cafeeiros são cultivados sobre Latossolo Vermelho distrófico, de textura arenosa.
The remote sensing and geoprocessing are important geotechnologies in support of the survey data of agriculture, enabling studies and understanding of environmental relations in which a particular culture is insert. The objective of this work was to relate the physical variables, such as altimetry, slope and soil type with the coffee agrosystems in Umuarama-PR through the geotechnologies. The image of the LANDSAT 5/TM (Thematic Mapper) dated in 02/07/2007 and the software SPRING 4.3.3 were used for the image processing. The bands 3, 4 and 5 of the sensor TM were restored, which resulted in images of 15m spatial resolution and, later, creating the RGB color composition, which was used to identify the coffee crops through visual interpretation. For the relief map study, the data of the SRTM mission were applied, which enabled us to know the altimetry and declivity of the region. The image of the TM sensor enabled the visual classification and the consequent identification of the coffee crops with high precision. As for the relief area, it was noticed that about 99 percent of the coffee fields are located between 380 and 480 meters of altitude and that 90 percent of them are located in declivity of up to 8 percent of inclination. About the soils, it was observed that 89 percent of the coffee fields are grown over distrofic Red Latosol, of sandy texture.
