[Truncated abstract] A common response of plants to flooding is the formation of an adventitious root system. These stem-borne roots can stay suspended in the water column (aquatic roots), or grow down into the sediment. Previous research has focused on features of sediment adventitious roots, such as aerenchyma and radial O2 loss that enhance root function in anaerobic soil. Unlike sediment adventitious roots, aquatic adventitious roots grow in aerobic floodwaters and have the potential to form photosynthetically active chloroplasts, and, therefore, have additiional O2 sources to that supplied via the aerenchyma. This thesis contains a series of experiments investigating full and partial submergence tolerance and aquatic root growth and physiology in two herbaceous perennials, Cotula coronopifolia L. and Meionectes brownii (Hook. f.). Both species tolerated 4 weeks of complete submergence in glasshouse experiments and grew an extensive aquatic adventitious root system from submerged stems when partially or completely submerged. Aquatic root systems were a major constituent of the total plant drymass (up to 26.3 ± 2 % in C. coronopifolia and 20.8 ± 1 % in M. brownii, in partially submerged plants) and contributed up to 90% of the total root drymass. Aquatic roots potentially confer some benefits to plant health and growth during flooding. An aquatic root pruning experiment conducted on both completely and partially submerged plants found, compared to controls with intact aquatic roots, reduced relative growth rates in both completely and partially submerged plants and reduced stem and leaf Chla in completely submerged plants when these roots were removed.
|Qualification||Doctor of Philosophy|
|Publication status||Unpublished - 2011|