Flowering and reproduction are highly regulated processes in composite plants like sunflower which produce disks that are clusters of many individual flowers. Environmental cues like light and temperature interact with the circadian clock regulate what time of the season buds first start to develop, and the same integration of internal and external signals likely occurs as new whorls individual florets open daily to present pollen and receptive stigmas at reproductive maturity. Because the timing and nature of environmental signals varies across the landscape, natural variation in how flowering responds to these cues evolves to allow plants to flower at the correct time of the season. For instance, we have found the wild sunflower populations change from being day-length insensitive to short-day responsive to long-day responsive in their flowering time as one moves from North to South over sunflower's range in the central US. We have mapped the genetic factors contributing to these evolutionary transitions to a handful of genomic regions, and the undergraduate(s) working on this project may help to conduct genotyping and gene expression studies to define those intervals and underlying candidate genes further. We are also curious to determine whether environmental control of floret maturation and daily patterns of solar tracking by sunflower stems show similar variation or geographic patterning in sunflower, and the undergraduate(s) working on this project will analyze time-lapse videos taken in the field this summer to investigate. Finally, because these field studies are ongoing, the students may have some opportunity to travel to field sites to assist with data collection or other field site needs.
The undergraduate researchers will grow and care for sunflowers being used for studies of natural variation, and they may also be involved in scoring of flowering time, solar tracking, and floret maturation of these plants under controlled photoperiod or greenhouse conditions. They will collect tissue for DNA or RNA extraction, and depending on progress and success, may also take part in DNA/RNA isolation and genotyping/qRT-PCR efforts.
Students with strong interests in plant-environment interaction, evolution, and ecology will find the experience most rewarding. Attention to detail and good record keeping skills are essential. The student should be comfortable and enthusiastic about intermittently working in greenhouse, growth chamber, or field conditions for extended periods, and they will be expected to follow guidelines for safely doing so.