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- Factors affecting rind pitting in the mandarin hybrids "fortune" and "nova". The influence of exogenous growth regulatorsPublication . Duarte, Amílcar; Guardiola, J. L.The commercialization of the mandarin hybrids "Fortune" and "Nova" is hindered by the development of cold-induced pitting in the fruit rind which may develop either in the orchard or during storage and transport. In the late cropping cultivar "Fortune", the pitting develops on tree during the winter months and affects mainly the exposed fruit from the north-west quadrant of the tree. The induction of symptoms under uniform conditions in the cold-room reveals differences in the susceptibility to chilling injury among the fruits and the fruit sides. The green fruit is not susceptible. Susceptibility develops as pigmentation progresses, and it is higher for the exposed than for the non-exposed (covered by the foliage) fruits. The application of GA3 at colour-break delays pigmentation and retards the development of susceptibility. The waxing of the fruit offers some protection to cold in the cold-room. However, the incidence of pitting is not related to the wax content of the fruit rind and the application of a wax coverage on tree had only a marginal protective effect. No pitting is usually found on tree in the fruit of the early ripening "Nova" cultivar, which is usually harvested before the winter chilling. The pitting develops during cold storage (8-10 C), and is reduced by GA3 application at colour break, an effect related to the delay in rind pigmentation.
- The anatomy of the fruit in relation to the propensity of citrus species to splitPublication . García-Luis, Amparo; Duarte, Amílcar; Kanduser, Masa; Guardiola, José LuísThe anatomy of the fruit has been compared in three prone-to-split mandarin hybrids (Nova, Ellendale and Murcott), several cultivars of clementine mandarin (Fino, Clementina de Nules and Orogrande), and in Owari satsuma mandarin. The fruit of the hybrids is oblate to subglobose and usually presents an open stylar end disrupted by a navel formed by the floral meristem, which is conserved near the apex of the fruit. In the non-prone-to-split clementines as well as in Owari satsuma, the floral axis protrudes inside the style, and the flower meristem is lost through abscission shortly after petal fall. The abaxial side of the carpels fuses with the flower axis forming at the stylar end of the fruit a solid tissue which externally has a small scar at the place of style abscission. Most of the fruits in these cultivars have no navel. In addition, the fruit of clementine is slightly oblate or globose. The relevance of these anatomical characteristics as regards to splitting is supported by the differences between the split and non-split fruits in Nova, the split fruit being more oblate in shape and having a bigger navel than non-split fruit. However, the effect of applied growth regulators on fruit splitting could not be correlated with their effect on the anatomy of the fruit. Additional factors not contemplated in the study also influence fruit splitting.
- Uso de desbrozadora como alternativa a los herbicidas en el control de malas hierbas, en naranjo ‘Rhode’Publication . Duarte, Amílcar; Martins, A.La lucha contra malas hierbas en cítricos constituye un problema por el coste de las operaciones, el gasto de energía y el impacto ambiental cuando se usan herbicidas. Por estas razones, es importante estudiar y divulgar métodos alternativos al uso de los herbicidas. El presente estudio demuestra que en el cultivo del naranjo ‘Rhode’, el uso de una desbrozadora es igualmente eficaz que el uso de un herbicida. Los resultados demuestran que la cosecha y el calibre del fruto no son afectados por el cambio de método de control de malas hierbas. Además, se facilita la movilidad de maquinaria dentro del huerto. El coste de las operaciones de lucha contra las malas hierbas fue inferior en el tratamiento en que se usó la desbrozadora.
- Introduction to the citrus waste valorisationPublication . Duarte, AmílcarThe term citrus is used to denote a wide range of fruit species, among which the most important are sweet orange, mandarin, lemon and grapefruit. In addition to being used as fruit trees, some citrus species are also used as ornamental plants in public spaces, in private gardens and as indoor plants.
- Pre-harvest rindstain of ‘Encore’ mandarin: initial histological signs of epicarp disturbance and extent of the disorderPublication . Maia, M. I.; Medeira, M. C.; Pinto, M. J.; Duarte, AmílcarPre-harvest rindstain in ‘Encore’ mandarin starts by the injury of a few epidermal cells. The connection between the damaged epidermis and the collapsed layers of flavedo, extending in parallel with rind surface was only visible on cross-sections containing the narrow zone of injured epidermal cells. The individual cell alteration including loss of membrane integrity and the accumulation of large amounts of osmiophilic materials in the cytoplasm are the result of a degrading process. Minute disruptions in the cuticle may provide shelters for resting forms of amoeboid or plasmodial-like organisms living on the rind. Our results suggest that these organisms could be involved in the disorder expression.
- Utilização de reguladores de crescimento na citricultura. O caso da citricultura portuguesa, em comparação com outros paísesPublication . Duarte, AmílcarA aplicação de reguladores de crescimento tem sido amplamente estudada em citrinos, em diferentes países. Em alguns casos, esses trabalhos levaram a uma ampla utilização de reguladores de crescimento na produção e na cadeia de comercialização dos frutos. O estímulo do vingamento do fruto permite aumentar a produtividade dos pomares, sobretudo em tangerineiras e seus híbridos. Nestas espécies, o aumento do calibre do fruto assume também uma grande importância. A aplicação de auxinas é usada com esse objectivo em alguns países. Os reguladores de crescimento são também usados para diminuir a incidência de defeitos na casca do fruto em cultivares susceptíveis a estes problemas, tanto em campo como em pós-colheita. Algumas cultivares de citrinos caracterizam-se por uma forte queda de frutos na fase de maturação. A aplicação de algumas auxinas é amplamente usada para diminuir a intensidade da queda. Dado o desfasamento nos processos de maturação interna e externa do fruto, a desverdização é praticada frequentemente em algumas cultivares temporãs de laranja e tangerina e ainda noutros casos. A aplicação de reguladores de crescimento é complexa, devido, por exemplo, aos efeitos diferentes e até opostos que algumas substâncias têm, em função do estado fenológico em que são aplicadas. A toxicidade das auxinas e de outros produtos aplicados torna ainda mais difícil a utilização dos reguladores de crescimento de plantas. Em Portugal foram realizados vários trabalhos de investigação que provaram a eficácia destas substâncias para aumentar a produtividade e o calibre do fruto. Algumas substâncias são usadas na citricultura portuguesas mas a legislação do nosso país é mais restritiva que a de outros países, quanto ao uso de reguladores de crescimento. A generalização da produção integrada e o modo de produção biológico colocam novas questões quanto aos métodos de controlo da frutificação, abrindo portas à sua substituição por outras técnicas, como é o caso da incisão anelar. Interessa analisar ainda a intensidade de utilização de reguladores de crescimento em países que competem com Portugal no mercado europeu e ainda naqueles que exportam fruta para Portugal.
- Saline stress and cell toxicity evaluation using suspended plant cell cultures of horticultural crops grown in a bioreactorPublication . Lima-Costa, Maria Emília; Ferreira, A. L.; Duarte, Amílcar; Beltrão, JoséCrop salt damage consists, usually, of leaf burn and defoliation, and it is associated with accumulation of toxic levels of sodium and/or chloride in leaf cells (Storey and Walker, 1999). The cell and tissue culture are simple biological systems that offer a direct approach to the metabolic changes. The plant cell growth in a controlled environment, as a bioreactor, is a unique tool for cell ion transport studies. Cell suspension culture of citrus cell line was exposed to a medium containing different sodium chloride concentrations (0mM, 42.7mM and 85.5mM). The growth profile of control cells (absence of NaCl) and 85.5mM cells were similar. The lack of inhibition of biomass accumulation, of all tested saline conditions clearly showed that the level of NaCl concentration used was not toxic for the cell metabolism. Also its ability to resist to 85.5mM NaCl can be on evidence that this suspension cel culture might have salt tolerance characteristics.