Developmental and Structural Section
Williams, Joseph H. .
Are there forms of pre-zygotic self-recognition in Austrobaileya scandens (Austrobaileyaceae)?
The origin of angiospermy (carpel closure) involved shifting the sites of pollen germination and pollen tube growth from the ovule to carpelar structures, the stigma and an internal pollen tube pathway. Pre-zygotic self-incompatibility systems may have first evolved within these novel tissue types, or alternatively, early forms of self-recognition might have arisen within the ovule. Austrobaileya scandens is the sole species within Austrobaileyaceae, a family that is sister to the rest of Austrobaileyales, which is in turn sister to all angiosperms other than Nymphaeales and Amborella. It is endemic to the wet tropics area of northeastern Queensland, Australia. I climbed trees to conduct hand-pollinations on flowering vines of Austrobaileya in order to compare the performance of self (S) versus outcrossed (OC) pollen up to the time of fertilization. There were no significant differences in pollen germination rates over the first six hours after pollination (hap), pollen tubes grew at equivalent rates to the base of the style (6-18 hap), and did not differ significantly in length at that time (18 hap). Nor were there differences in the rate of formation of sperm nuclei within the pollen tube. Results from a second field season indicate that self pollen tubes often reached and penetrated ovules. The pattern of S and OC pollen tube entry into ovules and female gametophytes (24, 48, 72 hap) will be discussed. A separate paternity analysis on 17 seed families and 3 seedling families (20 vines) using microsatellite markers indicates fruits contained very few self-fertilized seeds. Taken together, these results indicate that Austrobaileya has strong self-sterility that acts at a late stage of pollen tube development or soon after fertilization. Late-acting self-sterility has been documented in several other basal angiosperms, but it is not yet known whether any of these cases, including Austrobaileya, represent genetically-based self-incompatibility systems.
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Williams lab website
1 - University of Tennessee, Ecology and Evolutionary Biology, Knoxville, TN, 37996, USA
pollen tube growth
Presentation Type: Oral Paper:Papers for Sections
Location: 555B/Convention Center
Date: Wednesday, August 4th, 2010
Time: 10:15 AM