Seed germination is a fundamental process in the life cycle of most flowering plants. Within species, seeds can exhibit considerable variation in germination characteristics. Variation in germination, including seed dormancy, has significant implications for the stress tolerance of seeds and is often caused by environmental effects during seed development. However, another factor that may influence within-species variation in seed characteristics is polyploidy (the condition of having more than two sets of chromosomes). Polyploidy is common in plants and many polyploid species tend to be over-represented in invasive floras and disturbed environments, and often appear to have wider ecological tolerances than non-polyploids. In this project we will test the hypothesis that seeds of the study species Themeda triandra (kangaroo grass) from polyploid plants will be larger and more stress tolerant than those produced by non-polyploid plants. Kangaroo grass is a perennial C4 species which plays a key ecological role in many native grasslands across Australia.
We have collected seed from polyploid and non-polyploid T. triandra lines previously grown in a common garden experiment under an array of drought and atmospheric warming treatments (e.g. no stress, warming, drought, or warming + drought). Specifically, you will seek to determine the impact of developmental warming and drought on critical seed traits such as dormancy and germination, and assess the comparative fitness of diploid and polyploid individuals during germination in stressful environments. Few studies have experimentally investigated the role that polyploidy plays in the ecological differentiation and evolution of plant species, and this project will provide important insights into seed traits that are affected by chromosome duplication and their roles in adaptation to, or tolerance of, novel or stressful environments.
Potential research questions
How do environmental conditions during seed development affect germination and dormancy?
Is there a polyploidy advantage (e.g. higher germination success and rate)?
How do polyploidy, drought, temperature, and seed characteristics interact and what impact will this have on adaptation to, or tolerance of, novel or stressful environments?
Can we make predictions about the long-term effects of polyploidy and climate interactions on ecological differentiation and evolution in T. triandra?
Either February or mid-year; February preferred as this will coincide with seed maturation for a March harvest.
Image credit: Themeda triandra at Mulligans Flat Nature Reserve, ACT: Murray Fagg © ANBG