School of BioSciences - Theses

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End date: 2019 × Start date: 2017 × Type: Masters Research thesis × Subject: Cakile edentula ×

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    Characterisation of seed germination in sea rockets (Cakile spp.)
    Sun, Qi ( 2017)
    The sea rocket genus (Cakile) includes several species; two of these are C. edentula and C. maritima. Both are invasive and have become widely distributed throughout the world. C. edentula was introduced earlier than C. maritima in Australia, and quickly expanded. However, after C. maritima was introduced to Australia, C. edentula disappeared from many regions. This replacement of C. edentula by C. maritima has occurred in other areas of the world. An exception also exists where the two species show coexistence in climates where the winters are cold and summers are wet. Several hypotheses have been raised to explain this replacement. In this thesis, a difference in the germination timing of the two species was hypothesised to be of importance in different climates. In order to work towards understanding and predicting germination of Cakile species, the germination of C. edentula from two different climates was examined in this thesis. A hydrothermal time model was used to describe seed germination. The results showed that populations from different climates differ in seed germination behaviour. The C. edentula population from temperate area showed lower base temperature and smaller hydrothermal time accumulation requirement than that from sub-tropical area. Overall, the sub-tropical population germinated more readily than the temperate population across almost all experimental conditions. Dormancy was found in C. edentula seeds during the germination experiment. Further study therefore investigated methods in relieving dormancy of the two Cakile seeds to see whether they responded differently. Two treatments (i.e. damage on seed coat and cold stratification) were applied. The results indicate that C. edentula generally had a higher percentage germination than its counterpart in each treatment (including the control group) while C. maritima germinated faster than C. edentula under most damage levels. The data generated by this thesis could be used as the basis of comparing germination timing between the two Cakile species. For predicting the germination timing more effectively, populations of both species from more climates are required, and dormancy needs to be studied under field conditions.