Genetics/Genomics

Abstract

CS-22-2 - The circadian clock and environmental cues co-ordinate flower maturation and pollinator visits in sunflower

Tuesday, July 17
8:53 AM - 9:13 AM

Plant reproduction requires the co-ordination of several developmental and external events, such as the co-occurrence of anther maturation and pollen presentation with pollinator activity and the availability of receptive stigmas. Almost all organisms possess an internal circadian clock, which enables them to co-ordinate diverse biological processes with daily diurnal cycles. Here, we investigate the role of the sunflower circadian clock and external environmental cues in co-ordinating floret maturation and pollinator visits. Sunflower has a complex inflorescence with each floret maturing in a step-wise fashion, displaying anthers and pollen on one day and then a receptive stigma the next. This development occurs centripetally in whorls across the flower head throughout anthesis, with dozens of florets presenting pollen in a remarkably coordinated manner each morning. Under constant controlled conditions using time-lapse photography we show that this rhythmic, centripetal, maturation is maintained without external cues, suggesting that the circadian clock regulates the timing of floret maturation. The clock, however, does not act alone in this process. Anther filament elongation is inhibited in constant light conditions but a three-hour dark period per day is sufficient to restore male organ development. The timing of this dark treatment affects the phase and synchronicity of floret maturation, demonstrating circadian gating of this process. In related studies, we find that modest differences in temperature affect the timing of floret development and pollen release by affecting the rate of style elongation. These results may explain our previous finding that sunflower head orientation, which is also regulated by the circadian clock, affects floral temperature and influences the frequency of morning pollinator visits. Together, our data demonstrate ways in which the circadian clock and external environmental cues such as light or temperature affect the co-ordination of floral organ development, pollen extrusion and pollinator visits.


 

Co-Authors

Stacey Harmer, Dr – University of California, Davis

Nicky M. Creux, PhD

Postdoc
University of California, Davis

Presentation(s):

Send Email for Nicky Creux


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CS-22-2 - The circadian clock and environmental cues co-ordinate flower maturation and pollinator visits in sunflower



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