Leaf movement imaging and analysis
A. thaliana seeds were sown in-vitro individually, with an approximately 1 cm gap in between each seed. To promote hypocotyl elongation plants were grown under the same condition as described above in individual 5 cm tall cardboard boxes for 10 - 12 days. Individual seedlings were cut out in 1 cm2 blocks of agar with a scalpel and transferred to vertical standing 25-well 10 cm2 culture dishes (Sterilin, UK) in constant white light (100 µmol m-2 s-2). Circadian rhythms of leaf movement were recorded using time-lapse image capture from an array of video cameras controlled by MetamorphTM software (Molecular Devices LLS, USA). Images were captured every 20 minutes for seven days. Leaf position data were extracted from images using MetamorphTM software. Rhythmic traces were analysed using Biological Rhythms Analysis Software System (BRASS) software package which obtains period estimates and relative amplitude error (RAE) values using a Fast-Fourier Transform non-linear least squares (FFT-NLS) method. The first 24 hours of data were excluded from analysis, and movements were considered rhythmic if they had a period between 15 and 35 hours.