Thesis

Reproductive biology and germination requirements of the California state threatened species Hazardia orcuttii (Asteraceae)

This research investigates the reproductive biology of the California state threatened plant, Hazardia orcuttii (Asteraceae). The only documented U.S. location of this perennial shrub. is in Encinitas, San Diego County, California. Very little ecological or life history data existed for this plant, since its first local record in 1981. Shrub and inflorescence reproductive phenology studies reveal long flowering and seed-producing seasons (6 months and 5.5 months respectively). Shrubs of different sizes show little difference in their flowering phenology (budding and seeding at the same times). Smallest shrubs bloom longer and start producing seeds later. Germination was tested under varying conditions of temperature, light, soil type and soil moisture. Hazardia orcuttii germinates better in alternating photoperiods than in dark, indicating soil or leaf cover may not be a favored environment for recruitment. Four temperature regimes were tested (temperatures oscillated with light and dark, high temperatures correlating with light). These regimes were alternating 20°CI12°C, 25°C/18°C, 15°C/8°C and steady15°C. H orcuttii germinated best in steady 15°C (average temperature of a Southern California fall day) (83 percent). The most achenes germinated in loamy sand (7 5 percent )percent) compared to sandy loam or sandy clay and in higher soil moisture (20 percent) compared to 15 or 10 percent. Of significance is zero (0) seeds germinated in 10 percent moisture/sandy clay, which is the soil ~exture in native areas surrounding existing shrubs. There is a strong interaction between soil texture and soil moisture variables. In soil types sandy loam and sandy clay, 5 to 50 percent of achenes did not germinate but were viable. Viable achene production was estimated over monthly intervals. Achenes produced by shrubs greater than 55 em, averaged 6.5 percent viability, while shrubs 55 em or less produced zero (0) percent viable seeds. The most and least viable achenes were produced in November and March respectively. There was a high amount of insect damage to achenes, affecting number of viable achenes. The percentage of insect damaged achenes was between 24 and 63 percent. This research substantially increases the understanding of the reproductive ecology of this rare plant and can serve to aid in developing better conservation and restoration efforts, because the soil germination data obtained will assist with future re-introduction projects. Keywords: reproduction, seed, germination, phenology, Asteraceae, Hazardia orcuttii.

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