TY - JOUR TI - The effect of ectopic expression of pine glutamine synthetase (GS1a) on water use efficiency in transgenic poplar DO - https://doi.org/doi:10.7282/T3RF5WNK PY - 2014 AB - Glutamine synthetase (GS) is a key factor in the assimilation of nitrogen in plants. Hybrid poplar plants (Populus tremula X P. alba, INRA 717-1-B4) ectopically expressing pine GS display increased growth rates, increased nitrogen use efficiency, and resistance to drought. In order to assess mechanisms associated with observed drought tolerance of GS poplars, we studied the ability of the GS poplars to perform photosynthesis under control and water-limiting conditions, as well as their nitrogen and carbon isotope contents. Included in this study were carboxylation efficiency, maximum assimilation rate, quantum yield of photosynthesis, maximum electron transport rate, dark respiration, triose phosphate utilization, light compensation point, intrinsic water use efficiency, stomatal conductance, and nitrogen-use efficiency. Rooted cuttings (12-18 months) were grown in a growth chamber (24o C; 16 hour photoperiod; approx. 330 μmol m-2 s-1). Well-watered conditions were defined as a soil moisture value of over 0.40 m3∙m-3, and drought conditions were defined as having a value of less than 0.20 m3∙m-3. The results showed significant differences between the GS transgenic and wild type. Under drought and control conditions, GS poplars showed carboxylation efficiencies similar to wild type grown under well-watered and drought conditions. Photosynthetic capacities were not different regardless of condition or genotype. However, the GS poplars showed lower water use efficiency when compared to the wild type, but higher nitrogen use efficiency. These data suggest that, compared to the wild type, GS poplars display a tradeoff between water and nitrogen use efficiency and are characterized by slightly enhanced photosynthesis, even during drought stress. KW - Biology KW - Poplar KW - Plants--Water requirement KW - Glutamine synthetase LA - eng ER -