SEED GERMINATION PLASTICITY OF TWO ENDANGERED SPECIES OF FERULA IN THE CONTEXT OF CLIMATE CHANGE

Ferula assa-foetida and F. gummosa, Apiaceae, are important endemic and endangered medicinal plants. Survival of the species is threatened by climate change, overexploiting (as source of oleo-gum resin and for-age) and lack of organized cultivation. Cultivation of these valuable medicinal plants is restricted by insuffi-cient domestication knowledge. Germination characteristics of different populations of Ferula taxa were studied with the aim of describing and comparing their responses to continuous cold stratification condition. Germination cues for the species were complex, with dormancy mechanisms present to restrict germination until cold stratification are fulfilled. Results indicated that a period of 4 weeks of stratification is sufficient for germination of F. assa-foetida, but optimal germination of F. gummosa require stratification for periods of 8 weeks. Both species were able to germinate at very low temperatures (4°C). Within-taxon differences in dor-mancy breaking and seedling emergence may interpret as local adaptations. The continued regeneration and propagation of the species in the wild will depend on the temperature and moisture status of the soil during winter and the maintenance of conditions suitable for stratification for an appropriate length of time.

SEED GERMINATION PLASTICITY OF TWO ENDANGERED SPECIES OF FERULA IN THE CONTEXT OF CLIMATE CHANGE

Ferula assa-foetida and F. gummosa, Apiaceae, are important endemic and endangered medicinal plants. Survival of the species is threatened by climate change, overexploiting (as source of oleo-gum resin and forage) and lack of organized cultivation. Cultivation of these valuable medicinal plants is restricted by insufficient domestication knowledge. Germination characteristics of different popula-tions of Ferula taxa were studied with the aim of describing and comparing their responses to continu-ous cold stratification condition. Germination cues for the species were complex, with dormancy mechanisms present to restrict germination until cold stratification are fulfilled. Results indicated that a period of 4 weeks of stratification is sufficient for germination of F. assa-foetida, but optimal germi-nation of F. gummosa require stratification for periods of 8 weeks. Both species were able to germi-nate at very low temperatures (4°C). Within-taxon differences in dormancy breaking and seedling emergence may interpret as local adaptations. The continued regeneration and propagation of the species in the wild will depend on the temperature and moisture status of the soil during winter and the maintenance of conditions suitable for stratification for an appropriate length of time.

Seed dormancy and germination of three grassy woodland forbs required for diverse restoration

Restoration is vital for the re-establishment and maintenance of biodiversity of temperate grassy woodlands, but limited understanding of species’ reproductive biology restricts the efficiency of restoration practice. The present study aimed to explore germination cues and seed dormancy of Dianella longifolia R.Br., Dianella revoluta R.Br., and Stackhousia monogyna Labill., three native Australian forb species that have been difficult to germinate in large-scale restoration projects. A series of experiments investigated the effect of various dormancy-alleviation or germination-promoting treatments on germination of these three species. Significant interactions were found between some treatments and germination temperatures for D. longifolia and S. monogyna, but no significant interactions were observed for D. revoluta. At optimal temperatures, scarification treatment produced the highest mean germination for D. longifolia and S. monogyna, and this was significantly higher than for control seeds. Storage conditions (ambient, dry, frozen) did not decrease viability after 10 weeks of storage, suggesting that seeds of all species are likely to be orthodox. To maximise the effectiveness of seed use in restoration programs, it is recommended that scarification of D. longifolia and S. monogyna seed be undertaken to improve field germination. Further work should focus on how to scale up application of the scarification treatment, optimise methods for alleviating dormancy in D. revoluta, and examine the ecological cues that naturally alleviate dormancy and promote germination of these three species.

Fire-related cues and the germination of eight Conostylis (Haemodoraceae) taxa, when freshly collected, after burial and after laboratory storage

The genus Conostylis (Haemodoraceae) is endemic to fire-prone south-western Australia. To gain an understanding of the effect of some fire-related germination cues, eight Conostylis taxa were tested in response to water, nitrate, smoke water and karrikinolide (KAR1) under light and dark conditions, when seeds were freshly collected and after a year of burial. The germination of all taxa tested was higher in response to smoke water and KAR1 than in water alone, whereas nitrate did not stimulate germination. Germination was higher in all taxa following 1 year of burial than in fresh seeds. Recently, glyceronitrile has been identified as another chemical in smoke water, apart from KAR1, that can stimulate the germination of certain species. The relative response of eight Conostylis taxa to KAR1, glyceronitrile and smoke water was examined in laboratory-stored seeds. Germination of these taxa was promoted by both smoke water and KAR1, except for C. neocymosa, which had high germination regardless of treatment. Four of the other seven taxa germinated to higher levels in at least one of the glyceronitrile concentrations tested (10, 50 or 100 μM) than in water alone. However, in only two of these taxa, C. aculeata subsp. septentrionora and C. juncea, was germination in glyceronitrile as high as that in smoke water. Thus, the response to glyceronitrile is not uniform across Conostylis taxa. Generally, germination was higher with KAR1 than glyceronitrile, suggesting that although some Conostylis taxa have the capacity to respond to glyceronitrile, KAR1 is the more important germination stimulant for this genus.

Introduced and native grass-derived smoke effects on Cymbopogon obtectus germination

Introduced grasses, such as buffel, alter the dynamics of grassy ecosystems by replacing native species and influencing recruitment. Several different smoke-derived chemicals are separately responsible for the promotion and inhibition of germination of various plant species. We tested whether smoke derived from the introduced buffel grass (Cenchrus ciliaris) produced the same density of germination as provided by smoke derived from a native spinifex grass (Triodia brizoides). Smoke from both spinifex and buffel grass significantly enhanced the germination of a native lemon grass (Cymbopogon obtectus) in comparison to untreated seed, reflecting the significant role of fire in woodlands across northern Australia. This is the first record of smoke-promoted germination in a species of Cymbopogon. However, smoke from the exotic buffel grass provided the same level of germination as that from the native spinifex, suggesting similarity in smoke chemicals involved. Further research is required to test the effect of buffel smoke on the germination of other species and whether exotics such as buffel grass provide the same temperature profile in the topsoil as does spinifex, and therefore equivalent germination cues to heat-shock responsive native plants.