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Phase shift in leaf movements of xanthium attributed to age and rhythm patterns
W L Koukkari1, L C Hobbs, F B Salisbury
1Department of Plant Biology, University of Minnesota, St. Paul, Minnesota 55108.
Plant Physiology
|April 1, 1992
Summary
Cocklebur (Xanthium strumarium L.) leaf orientation during the night is not due to ecotype, but rather leaf age and light-dark cycle. Leaf age causes significant phase shifts in the plant
Area of Science:
- Plant biology
- Chronobiology
- Plant physiology
Background:
- Cocklebur (Xanthium strumarium L.) leaves exhibit varying positions (upright/downward) during the dark span.
- Previous research suggested ecotype differences might explain these variations.
Purpose of the Study:
- To investigate the factors influencing cocklebur leaf position during the 24-hour cycle.
- To determine if ecotype, leaf age, or light-dark cycle patterns affect leaf orientation.
Main Methods:
- Analysis of leaf position data across different leaf ages and light-dark cycle stages.
- Application of statistical models, including linear regression and harmonic analysis, to waveform patterns.
Main Results:
- Leaf position differences are primarily attributed to leaf age, not ecotype.
- Younger leaves show maximum upright position near mid-dark, older leaves near the end of the dark span.
- Leaf aging induces phase shifts of 6–10 hours, with waveform troughs differing significantly between young and old leaves.
Conclusions:
- Leaf age is a critical determinant of cocklebur leaf movement patterns during the circadian cycle.
- The observed variations in leaf position are linked to age-related changes in the rhythm's waveform, particularly the trough.
- Understanding these age-dependent shifts is crucial for interpreting plant circadian rhythms.
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