Paper Reviewed
Wei, Z., Du, T., Li, X., Fang, L. and Liu, F. 2018. Interactive effects of elevated CO2 and N fertilization on yield and quality of tomato grown under reduced irrigation regimes. Frontiers in Plant Science 9: 328, doi: 10.3389/fpls.2018.00328.

Tomato is a key agricultural fruit crop grown throughout the world. It is a rich source of minerals, vitamins and antioxidants. However, according to Wei et al. (2018), the combined effects of elevated CO2, nitrogen (N) fertilization and drought on tomato fruit yield and fruit quality are not well known, despite interest in how these parameters might respond to possible changes in future climate.

And so it was that this team of five researchers set out to conduct an experiment to elucidate such responses. In doing so, they grew tomato plants (Solanum lycopersicum, cv. Elin) in a climate-controlled facility at the University of Copenhagen, Taastrup, Denmark, under a combination of two atmospheric CO2 concentrations (400 or 800 ppm), two N fertilization rates (100 or 200 mg N per kg soil) and two watering regimes (normal irrigation or drought, where drought conditions were approximately 70% of normal irrigation). At the end of the growing season, the scientists measured a number of tomato quality and yield parameters.

And what did their measurements reveal?

Focusing first on fruit yield, Wei et al. report that this parameter was enhanced by elevated CO2 regardless of N fertilization and irrigation regime. They also note that the positive effects of elevated CO2 "attenuated the negative influence of reduced irrigation on fruit yield," such that yields in the combined treatment of elevated CO2 and drought were similar to those under conditions of ambient CO2 and normal irrigation.

With respect to fruit quality, data from the authors' Table 1 reveal that elevated CO2 significantly increased the total soluble solid concentration and fruit sugar to acid ratio. In addition, data from their Table 2 reveal enhancements in fruit juice cation concentrations, anion concentrations, and total cation, anion and ionic concentrations, which combination of findings suggest that greater fruit quality is achieved in an elevated CO2 environment.