RESUMEN
Considering the prevalence of ever-changing conditions in the natural world, investigation of photosynthetic responses in C4 plants under fluctuating light is needed. Here, we studied the effect of dynamic illumination on photosynthesis in totally 10 C3, C3-C4 intermediate, C4-like and C4 dicots and monocots at CO2 concentrations of 400 and 800 µmol mol-1. C4 and C4-like plants had faster photosynthetic induction and light-induced stomatal dynamics than C3 plants at 400 µmol mol-1, but not at 800 µmol mol-1 CO2, at which the CO2 supply rarely limits photosynthesis. C4 and C4-like plants had a higher water use efficiency than C3 plants at both CO2 concentrations. There were positive correlations between photosynthetic induction and light-induced stomatal response, together with CO2 compensation point, which was a parameter of the CO2-concentrating mechanism of C4 photosynthesis. These results clearly show that C4 photosynthesis in both monocots and dicots adapts to fluctuating light conditions more efficiently than C3 photosynthesis. The rapid photosynthetic induction response in C4 plants can be attributed to the rapid stomatal dynamics, the CO2-concentrating mechanism or both.
Asunto(s)
Dióxido de Carbono , Luz , Fotosíntesis , Estomas de Plantas , Fotosíntesis/fisiología , Dióxido de Carbono/metabolismo , Estomas de Plantas/fisiología , Estomas de Plantas/efectos de la radiación , Hojas de la Planta/fisiología , Hojas de la Planta/efectos de la radiación , Hojas de la Planta/metabolismo , Agua/metabolismoRESUMEN
In the past, nitobegiku (the herb of Tithonia diversifolia (Hemsl) A. Gray) has been used as a medicinal plant for diabetes. Antidiabetic effect of the water extract of Nitobegiku (NG) was investigated in KK-Ay-mice--one of the animal models of type 2 diabetes. NG (1,500 mg/kg body weight) reduced the blood glucose of KK-Ay mice from 509 +/- 22 mg/dl to 340 +/- 14 mg/dl (p < 0.001) and also lowered the plasma insulin (p < 0.05) 7 hours after single oral administration. No change in blood glucose of NG-treated normal mice (ddY) was seen. These results support that NG improve glucose metabolism by reducing insulin resistance. Therefore, NG may be useful for treatment of type 2 diabetes.