RESUMOAvaliou-se o efeito de diferentes épocas de irrigação (A -entre 1 de junho a 30 de setembro; B -entre 1 a 30 de setembro, e, C (Testemunha) -sem irrigação), sobre a produtividade, o rendimento de grãos e o potencial hídrico foliar do cafeeiro (Coffea arabica L.), cultivar Catuaí Vermelho, IAC 44. O experimento foi instalado sobre uma cultura com 18 anos, com espaçamento de 3,5 m entre as linhas de planta por 0,8 m entre plantas. O potencial hídrico foliar foi monitorado, as 6 h e 12 h, no período de maio a outubro, nos anos de 2003 e 2004. Identificou-se elevada sensibilidade deste indicador fisiológico às épocas de irrigação sendo que a irrigação realizada no período de 01/06 a 30/09 (Tratamento A) mostrou sempre o melhor status hídrico, bem como maior produtividade, com valor médio de 4617 kg ha -1 . Esses resultados ratificam o fato de que a produtividade da cultura guarda relação direta com o seu status hídrico e, sobretudo, o potencial hídrico foliar, que demonstrou ser um indicador fisiológico com poder discriminante, portanto, adequado para ser utilizado como referencial no manejo da irrigação, nas condições estudadas. The high sensitivity of this physiological indicator to irrigation was identified, and that the irrigation from 06/01 to 09/30 (treatment A) always showed the best leaf water status, as well as the best performance of productivity, with a mean value of 4617 kg ha -1 . The results corroborate with the fact that the productivity of the crop maintained a direct relationship with its leaf water status and especially with the leaf water potential, which showed itself to be a physiological indicator with good discriminating powers, and for this reason, suitable to be utilized as a reference in the irrigation management.
Summary Oral tolerance (OT) is being studied with great interest because of its therapeutic potential in allergy and autoimmunity. In the present study, two mouse strains with extreme phenotypes of OT susceptibility (TS) or resistance (TR) to ovalbumin (OVA) were used to demonstrate whether the tr and ts genes, cumulated during 18 generations of bi‐directional genetic selection, influence expression of immunobiological traits in naive or antigen‐gavaged TR/TS mice. The difference in anti‐OVA titres was 2048‐fold between OVA‐gavaged TS and TR mice. Tolerance susceptibility to OVA gavage in individuals from a (TS × TR)F2 population was 24% high‐susceptibility, 62% low‐susceptibility and 14% non‐tolerant. Different antigens, unrelated to OVA, were tested by gavage and TS mice were generally susceptible while TR mice were resistant. The stability of TS and TR phenotypes was not affected by the use of strict protocols of intraperitoneal immunization or feeding over 30 consecutive days. The levels of interleukin‐2 (IL‐2), IL‐4, interferon‐γ and IL‐10 cytokines evaluated in concanavalin A‐stimulated spleen cells from naive mice and in OVA‐stimulated spleen cells from OVA‐gavaged mice were higher in TS mice. Interleukin‐10 was up‐regulated in OVA‐gavaged TS mice and down‐regulated in TR mice. In naive mice, the percentage of CD4+ CD25+ and CD4+ Foxp3+ spleen cells and IL‐10 expression by CD4+ cells was significantly higher in TS mice. These results indicate that regulation of IL‐10 expression could be an important factor contributing to the mechanisms controlling OT susceptibility, and that the OT responses of TR and TS individuals strongly correlate with their innate potential to secrete this cytokine.
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