Climate change: a response surface study of the effects of CO₂ and temperature on the growth of French beans

Abstract

The possible impact of global rises in atmospheric CO₂ concentration and temperature on the growth and development of French beans (Phaseolus vulgaris) was examined using growth cabinets. Five CO₂ concentrations of 350, 450, 550, 650 and 750 vpm and five temperatures of 14·5, 15·5, 16·5, 17·5 and 18·5°C were tested using a fractional factorial design comprising nine treatment combinations of the two factors. Plants were grown under constant irradiance, common atmospheric humidities (vpd 0·5 kPa) and non-limiting supplies of water and mineral nutrients. The plant growth response was modelled by fitting polynomial response function curves to the times to first flower opening, first bean set, 50% maturity and the number and yield of beans. The effects of temperature were large and positive for most of the measured variables, whereas the effects of CO₂ were small and negative or non-existent. Increased temperature substantially reduced the time to flowering and the time from bean set to 50% maturity and increased the number and yield of mature beans whereas increased CO₂ concentration had little effect on plant growth except that bean yield was very slightly reduced. There was no significant evidence of interaction between the CO₂ concentration effects and the temperature effects.

The time to maturity and yield of mature beans was simulated for the 2020s (2010 to 2039) and the 2050s (2040 to 2069) using the fitted polynomial models and four climate change scenarios suggested by the UK Climate Impacts Programme. These simulations showed that, depending upon the assumed scenario, the 2020s yields could rise by 39–84% and time to maturity reduce by between 6 and 15 days whereas the 2050s yields could rise by 51–118% and time to maturity reduce by between 9 and 25 days.