This thesis presents the results of a series of trials using controlled incubation conditions to improve germination percentages and germination synchrony in Eucalyptus horistes, E. loxophleba ssp lissophloia and E. polybractea. Information on the phenological development of these little known mallee species is also provided. Germination percentages ranged from 33 to 99% after 10 days in E. horistes, with 40% of seedlots showing less than 80% germination. Similarly, germination percentages ranged from 47 to 100% after 10 days in E. loxophleba ssp lissophloia with 20% of seedlots showing less than 80% germination. In the slower germinating E. polybractea, germination percentages ranged from 54 to 87% after 18 days, with 90% of seedlots showing less than 80% germination. Dry heat stimulus followed by cold moist stratification enhanced germination in poorly germinating cohorts of Eucalyptus horistes, narrowing the period to reach 90% germination by more than seven days. Similar increases were achieved with dry heat stimulus followed by endogenous application of 25mg/L GA3. The characteristics influencing germination in Eucalyptus horistes, under constant (20 C) temperature conditions included genetic variation (family), seed size and duration of canopy storage (seed age). Timing of seed collection also influenced germination in poorly performing cohorts. Germination was also enhanced following the sequential cues of heat stimulus followed by cold moist stratification in Eucalyptus loxophleba ssp lissophloia. The requirement for specific environmental cues was successfully overcome with 20g/L KNO3, narrowing the period to reach 90% germination by 5 days. The characteristics influencing germination in Eucalyptus loxophleba ssp lissophloia included seed age, size and light conditions (8 hour light/16 hour dark versus 24 hour dark) under constant (20 C) temperature incubation conditions. Alternating temperature regimes (20 C day/10 C night) adversely impacted on germinability in this species. Dry heat stimulus followed by cold moist stratification also increased germination in Eucalyptus polybractea. However, endogenous exposure to 20g/L KNO3 increased germination to a larger extent, narrowing the period to reach 90% germination by 10 days. Seed size, age and collection season influenced germination in E. polybractea under constant (20C) temperatures regimes. Germination was also adversely affected by alternating temperature (20 C day/10 C night) regimes. Although seed viability remained high, germinability was severely reduced after six months of both cold and ambient storage. The factors affecting germination in these commercially important mallees require management to improve the economics and efficiency of nursery propagation. Based on the findings of this research, recommendations are made for altering seed processing techniques. Seed pre-treatments to improve germination in poorly performing cohorts are also described.

This publication provides an approach by which conservationists can determine whether or not long-term seed storage is feasible for a particular species, i.e. whether or not that species shows orthodox seed storage behaviour, and provides advice on the implementation of the protocol, examples of ways in which the results from seed storage studies could be misinterpreted due to confounding factors, as well as several alternative approaches for estimating seed storage behaviour prior to carryng out actual investigations with the seeds. In particular, the latter section introduces the concept of a multicriteria approach for estimating seed storage behaviour.

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