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ISHS Acta Horticulturae 454: III International Symposium on New Floricultural Crops

IRRIGATE FOR MORE SEEDS AND HEAT FOR BETTER GERMINATION IN AUSTRALIAN EVERLASTING DAISIES

Authors:   D. Choengsaat, J.A. Plummer, D.W. Turner
Keywords:   Rhodanthe chlorocephala, Schoenia filifolia, Helipterum, Helichrysum, Asteraceae, seed production, water deficit, dormancy
Abstract:
Commercial development of two Australian daisies, Rhodanthe chlorocephala subsp. rosea and Schoenia filifolia subsp. subulifolia, is limited by seed dormancy and there is little information on the agronomy of Australian daisies. The effect of irrigation on plant growth habit and seed yield was examined in glasshouse and field experiments. Water deficit substantially reduced branching which limited the sites for terminal inflorescence production. This reduced seed yield. In a field experiment with three irrigation regimes (25, 50 and 100% of class A pan evaporation), watering at 25% halved stem numbers and reduced seed yield to one third compared with 100% A pan. The effect of irrigation on seed germinability was monitored from 3–6 months after harvest at storage temperatures of 5, 15, 25, 30, 40, 55 or 65°C. R. chlorocephala seed stored at 30°C had 97% germination. Extreme temperatures (65°C and 5°C) decreased seed germination to 90%. Dormancy of R. chlorocephala increased with increasing water supply but disappeared within two months of harvest. Preharvest irrigation had no consequent effect on seed germinability of R. chlorocephala after three months storage. One month after harvest, 96% of S. filifolia seeds were viable and all seeds were dormant. Subsequent dormancy release depended on storage temperature. After 2 months storage at 65°C, germination was 80% and this fell to 60% after three months storage due to reduced viability. In contrast, seeds stored at 25, 30 or 40°C had approximately 90% germination after 3 months storage. Short term exposure of S. filifolia (1–14 days) to high temperature, 65 to 105°C, were examined and exposure to 80°C for 11–13 days overcame dormancy.
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