Lopez-Smith, Renee A. , Renzaglia, Karen S. .
Sperm cell architecture and the neck canal in diploid and tetraploid Ceratopteris cytotypes: does size matter?
With a nearly 2300-fold range, genome size is one of the most variable features of plants. Despite this, its functional and evolutionary significance is poorly understood. Genome size is known to be correlated with cell sizes as seen in guard cells. It is also known that genome size is positively correlated with sperm cell size and complexity in land plants. Episodic changes in genome size, such as events of polyploidy, may decrease reproductive success through constraints on gamete development and alterations in mature sperm architecture. Preliminary results regarding the establishment of polyploid species in culture suggests that significant, asymmetric reproductive isolation exists among Ceratopteris cytotypes. It is hypothesized that diploid sperm cells are too large to enter haploid archegonia. However, there have been no studies that document differences in gamete and archegonial neck sizes between diploid and tetraploid Ceratopteris cytotypes. In the present study, sperm architecture in the tetraploid C. thalictroides (n = 78) is described and related to the archegonial neck dimensions in the diploid C. richardii (n = 39). With an approximate cell length of 70 µm and an average nuclear diameter of 3µm, the sperm cells of C. thalictroides are both wider and longer than those of C. richardii. At its entrance, the archegonial neck canal of C. richardii measures approximately 10 µm in diameter, although it quickly narrows to an estimated 8 µm. Consequently, the archegonia of C. richardii could easily accommodate C. thalictroides sperm. These data increase our understanding of how genome size variation influences reproductive success and polyploid species establishment in archegoniates.
Log in to add this item to your schedule
1 - Southern Illinois University, Department of Plant Biology, 1125 Lincoln Drive, Carbondale, IL, 62901-6509, USA
2 - Southern Illinois University, Department of Plant Biology, 1125 Lincoln Drive, Carbondale, Illinois, 62901-6509, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Lake Michigan/Hilton
Date: Monday, July 9th, 2007
Time: 2:00 PM