Agüera Eloísa, Ruano David, Cabello Purificación, de la Haba Purificación
Departamento de Biología Vegetal, Area de Fisiología Vegetal, Facultad de Ciencias, Universidad de Córdoba, Campus de Rabanales, Edificio Celestino Mutis (C4), E-14071 Córdoba, Spain.
J Plant Physiol. 2006 Jul;163(8):809-17. doi: 10.1016/j.jplph.2005.08.010. Epub 2005 Oct 25.
Expression and activity of nitrate reductase (NR; EC 1.6.6.1) and glutamine synthetase (GS; EC 6.3.1.2) were analysed in relation to the rate of CO(2) assimilation in cucumber (Cucumis sativus L.) leaves. Intact plants were exposed to different atmospheric CO(2) concentrations (100, 400 and 1200microLL(-1)) for 14 days. A correlation between the in vivo rates of net CO(2) assimilation and the atmospheric CO(2) concentrations was observed. Transpiration rate and stomatal conductance remained unaffected by CO(2) levels. The exposure of the cucumber plants to rising CO(2) concentrations led to a concomitant increase in the contents of starch and soluble sugars, and a decrease in the nitrate content in leaves. At very low CO(2), NR and GS expression decreased, in spite of high nitrate contents, whereas at normal and elevated CO(2) expression and activity were high although the nitrate content was very low. Thus, in cucumber, NR and GS expression appear to be dominated by sugar levels, rather than by nitrate contents.
分析了黄瓜（Cucumis sativus L.）叶片中硝酸还原酶（NR；EC 1.6.6.1）和谷氨酰胺合成酶（GS；EC 6.3.1.2）的表达及活性与二氧化碳同化速率的关系。将完整植株置于不同大气二氧化碳浓度（100、400和1200 μL L⁻¹）下处理14天。观察到净二氧化碳同化的体内速率与大气二氧化碳浓度之间存在相关性。蒸腾速率和气孔导度不受二氧化碳水平的影响。黄瓜植株暴露于不断升高的二氧化碳浓度下，导致叶片中淀粉和可溶性糖含量随之增加，硝酸盐含量降低。在极低二氧化碳浓度下，尽管硝酸盐含量很高，但NR和GS的表达仍降低，而在正常和升高的二氧化碳浓度下，尽管硝酸盐含量很低，但表达和活性却很高。因此，在黄瓜中，NR和GS的表达似乎受糖水平而非硝酸盐含量的主导。
