EMBRYO DEVELOPMENT, SEED BANK POTENTIAL AND GERMINATION OF THE FEDERALLY ENDANGERED HERB OF PINE SAVANNAS, THALICTRUM

ECU Author/Contributor (non-ECU co-authors, if there are any, appear on document)

Erika M Dietrick (Creator)

Institution

East Carolina University (ECU )

Web Site: http://www.ecu.edu/lib/

Abstract: Plant conservation efforts strongly rely on knowledge of species seed biology and viability for further propagation. Virtually nothing is known about the seed biology of the federally endangered Thalictrum cooleyi Ahles (Cooley’s meadowrue, Ranunculaceae). Thalictrum cooleyi is a dioecious wind-pollinated herb with short-stalked, clustered achenes, native to the fire-adapted wet pine savannas of NC, FL, and GA. Congeners have underdeveloped embryos, some of which require cold stratification to germinate. I studied embryo presence and development, the effect of temperature (specifically, high heat and cold) on mean total germination rates, and the potential of T. cooleyi to form a seed bank. Stereo- (SM) and scanning electron microscopy (SEM) are both viable options for embryo evaluation, but SEM more readily identifies underdeveloped embryos and cavities. Half (50%) of 100 seeds had embryos, suggesting low viability. Both methods showed T. cooleyi to have small, linear underdeveloped embryos with peripheral attachment. The point of attachment is at the base of the carpel, suggesting basal placentation of ovules. My results showed that T. cooleyi has simple morphophysiological dormancy and seed biology characteristics similar to that of the rest of the family Ranunculaceae. Seeds were dormant at maturity; longer periods of cold (8 vs. 2 wk) at 1 ºC resulted in higher mean total germination. Moist cold breaks seed dormancy and embryos elongated upon subsequent exposure to germination conditions (25:15 ºC, light:dark, 14:10). Germination studies in the field, including burial of seed, showed that Thalictrum cooleyi can also form a seed bank of at least 1 year and overwintering is required for germination. High heat did not increase germination, but fire is necessary for maintaining an open canopy. Although low germinability remains a challenge for this species, seed propagation in cultivation and in the field hold promise for restoration efforts. Further research is necessary to ascertain long-term natural seed bank potential, but my work confirms the presence and importance of seed banks in pine savannas, offering another tool for conservation efforts.

Additional Information

Publication

Thesis

Language: English

Date: 2016

Keywords

conservation, rare, seeds, embryo morphology, endangered, pine savanna, seed bank

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