Measurements of photosynthesis and respiration
Measurements of photosynthetic capacity were made using a LiCor LI-6400 infra-red gas analyser, at a temperature of 20°C in an atmosphere of 2000 µl l-1 CO2 and an irradiance of 2000 µmol m−2 s−1 provided by a warm white LED (colour temperature 2800–3200 K). Measurements of photosynthesis and respiration under growth conditions were carried out using the same gas analyser, in the growth cabinet where plants were grown, using ambient air. The gas analyser was placed in the cabinet and allowed to equilibrate for at least 1 hour prior to any measurements. The analyser chamber was placed to give a light intensity in the chamber equivalent to that of plants during growth. Respiration was measured by interrupting illumination, covering the plant and analyser chamber with aluminium foil. Data were analysed using Analysis of Variance, followed by Tukey post-hoc tests in SPSS (IBM).