Georgia plume (Elliottia racemosa) is a threatened woody plant endemic to the Coastal Plain region of Georgia in the southeastern United States. Seed set is low in most populations, and sexual recruitment has not been observed in recent times. The objective of this study was to describe the floral biology of georgia plume. which is fundamental information needed to develop an understanding of the causes for lack of sexual reproduction in natural populations. Floral development was characterized and morphological characteristics at key developmental stages ranging from small, unopened buds to open flowers with receptive stigmas were examined using light and scanning electron microscopy. Flowering is protandrous, and anthers dehisce releasing pollen within closed buds before stigmas are receptive. Pollen tetrads, aggregated by viscin strands, are presented on unreceptive stigmas when petals reflex. Receptive stigmas developed a raised and lobed central region with a clefted opening leading to a stylar canal containing exudate produced in secretory regions. Receptivity of the non-papillate stigma is indicated by the formation of an exudate droplet, which is formed within 1 day after flower opening. Pollen viability was low to moderate; tetrad germination ranged from 20% to 40% using in vitro germination assays indicating poor pollen quality and may contribute to lack of seed development in some populations. No developmental abnormalities in stigmas or styles were observed indicating other factors are responsible for lack of sexual recruitment in the wild.
Georgia plume (Elliottia racemosa, Ericaceae) is a threatened, woody plant endemic to Georgia's Coastal Plain region in the southeastern United States. Populations of the plant have a fragmented distribution within a restricted range and are characterized by low genetic diversity and a lack of sexual recruitment. Georgia plume cannot be effectively propagated using conventional methods. We have developed an in vitro shoot regeneration system that is effective with explants obtained from mature plants in the wild. The objective of this study was to determine the efficacy of using this in vitro protocol to regenerate proliferating shoot cultures from 34 georgia plume genotypes obtained from divergent populations. Young expanding leaves were cultured on Gamborg's media supplemented with 10 μM thidiazuron and 5 μM indole-3-acetic acid. After 8 weeks, tissues were transferred to a shoot elongation medium with 25 μM 2-isopentenyl adenine. Of the 34 genotypes tested, 91% formed shoot primordia and 85% regenerated shoots within 6 months of inoculation. This study verifies that tissue culture can be used to produce adventitious shoots from a wide range of georgia plume genotypes. Within a coordinated conservation program, tissue culture is a feasible system to use for safeguarding and reintroduction of genetically diverse plant material, which may be critical to the survival of this rare species.