For all experiments temperatures in the phytotron were
controlled to 1.0 8C and a water vapour pressure deficit of
530 Pa was maintained at all temperatures. Throughout the
experiments the plants were grown in a peat-based potting
compost (90% peat, 10% clay) with an additional 1:5 volume of
granulated perlite. The plants were fertilized twice weekly with
a complete fertilizer solution (conductivity 1.7 mmho), and
otherwise watered with tap water as required.