Assuntos
Ciclosporina/farmacologia , Sirolimo/farmacologia , Linfócitos T/imunologia , Administração Oral , Animais , Antígenos de Diferenciação de Linfócitos T/efeitos dos fármacos , Antígenos de Diferenciação de Linfócitos T/imunologia , Ciclosporina/administração & dosagem , Quimioterapia Combinada , Imunossupressores/farmacologia , Ratos , Ratos Endogâmicos Lew , Linfócitos T/efeitos dos fármacosAssuntos
Imunossupressores/farmacologia , Ácido Micofenólico/farmacologia , Tacrolimo/farmacologia , Administração Oral , Animais , Anticorpos Monoclonais , Antígenos de Superfície/genética , Interações Medicamentosas , Imunossupressores/administração & dosagem , Imunossupressores/farmacocinética , Técnicas In Vitro , Ativação Linfocitária/efeitos dos fármacos , Masculino , Taxa de Depuração Metabólica , Ácido Micofenólico/administração & dosagem , Ácido Micofenólico/análogos & derivados , Ácido Micofenólico/farmacocinética , Ratos , Ratos Endogâmicos Lew , Tacrolimo/administração & dosagem , Tacrolimo/farmacocinéticaRESUMO
We investigated the effects of an ambient dose of ultraviolet-B (UV-B) radiation on chamber-grown Pseudotsuga menziesii var. glauca (Beissn.) Franco (Douglas-fir) seedlings, to determine if the presence of UV-B radiation in the growth light regime induces tolerance to environmental stresses such as high light and drought. Douglas-fir seedlings were grown without UV-B radiation or with 6 kJ m-2 day-1 of biologically effective UV-B, which is ambient for the intermountain regions of Idaho. Non-stressed seedlings grown with UV-B radiation had 35% lower seedling dry mass, 36% higher concentrations of UV-B absorbing compounds per unit leaf area, 30% lower stomatal frequencies, 25% lower light-saturated photochemical efficiencies of Photosystem II and 45% lower light-saturated stomatal conductance than non-stressed seedlings grown without UV-B radiation. After 4 days of high-light stress, seedlings grown with UV-B radiation had 32% higher light-saturated carbon assimilation rates (A(CO2)) than seedlings grown without UV-B radiation. After water was withheld from the seedlings for up to 15 days, seedlings grown with UV-B radiation had 50% higher A(CO2) and 40% higher seedling water potentials than seedlings grown without UV-B radiation. The results support the hypothesis that UV-B radiation can act as an environmental signal to induce tolerance to high-light and drought stress in Douglas-fir seedlings. Possible mechanisms for the enhanced stress tolerance are discussed.