Abstract
BackgroundQuantification of leaf movement is an important tool for characterising the effects of environmental signals and the circadian clock on plant development. Analysis of leaf movement is currently restricted by the attachment of sensors to the plant or dependent upon visible light for time-lapse photography. The study of leaf growth movement rhythms in mature plants under biological relevant conditions, e.g. diurnal light and dark conditions, is therefore problematic.ResultsHere we present OSCILLATOR, an affordable system for the analysis of rhythmic leaf growth movement in mature plants. The system contains three modules: (1) Infrared time-lapse imaging of growing mature plants (2) measurement of projected distances between leaf tip and plant apex (leaf tip tracking growth-curves) and (3) extraction of phase, period and amplitude of leaf growth oscillations using wavelet analysis. A proof-of-principle is provided by characterising parameters of rhythmic leaf growth movement of different Arabidopsis thaliana accessions as well as of Petunia hybrida and Solanum lycopersicum plants under diurnal conditions. The amplitude of leaf oscillations correlated to published data on leaf angles, while amplitude and leaf length did not correlate, suggesting a distinct leaf growth profile for each accession. Arabidopsis mutant accession Landsberg erecta displayed a late phase (timing of peak oscillation) compared to other accessions and this trait appears unrelated to the ERECTA locus.ConclusionsOSCILLATOR is a low cost and easy to implement system that can accurately and reproducibly quantify rhythmic growth of mature plants for different species under diurnal light/dark cycling.
Highlights
Quantification of leaf movement is an important tool for characterising the effects of environmental signals and the circadian clock on plant development
The OSCILLATOR system for continuous analysis of plant growth under continuing diurnal light/dark cycles consists of three modules: (1) data acquisition in the experimental setup (2) image processing and (3) extraction of phase, period and amplitude using wavelet analysis
Data acquisition in the experimental setup The hardware of the system consists of a climate controlled growth cabinet fitted with two IR LED light units (890 nm) and two modified single-lens reflex (SLR) cameras with the IR filter removed
Summary
Quantification of leaf movement is an important tool for characterising the effects of environmental signals and the circadian clock on plant development. The first documented attempt to elucidate whether the rhythm of movement was inherent to the plant or the result of external stimuli was performed by de Mairan in 1729. He observed that the rhythmic leaf movements of his ‘sensitive plant’ (Mimosa pudica) continued even in continuous darkness [1,2]. Leaf movements of many species are controlled by the Analysis of rhythmic growth in seedlings Various systems have been described for the analysis of leaf movement in Arabidopsis seedlings [4,6] These systems are characterised by sequential imaging of seedlings from the side. FFT-NLLS provides the average phase and amplitude of cyclic processes, based on the best fitted sinusoidal curve over multiple days [9] and does not capture the daily changes in phase and amplitude upon transition to a different growth condition or during development
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