Xiaoxi Li1, Michael Weiss1, Richard Richards1
1 CSIRO Agriculture and Food, GPO Box 1700, Canberra, ACT 2601, Australia Xiaoxi.Li@csiro.au
Differential carbon allocation between the shoots and the roots has a potential impact on crop yield as well as water and nutrient use. A pot experiment in 2-m long tubes was established to monitor the shoot and root growth at different stages in wheat until anthesis, and to obtain detailed root distribution data at different soil depths. Two Australian cultivars, Suntop and Westonia, and two Indian cultivars, C306 and HI1500 were compared. After root washing, the seminal roots were sectioned along the root axis into 20-cm segments to measure morphological traits and dry weight. Preliminary results showed that from fully emerged flag leaf to heading, root biomass did not increase while the shoot growth was rapid in all four cultivars. Subsequently, from heading to anthesis, the roots of the two Indian cultivars grew more rapidly than the two Australian ones. The Indian cultivars tended to have smaller root systems than the Australian cultivars. However, the Indian cultivar HI1500 tended to grow more roots at depth (below 1 m) by anthesis, compared with other cultivars. These preliminary results highlight that the carbon allocation to roots declined markedly during the fast stem and ear growth, but variation among cultivars existed in root growth at depth at later growth stages. The study provides information on competition for carbon between roots and shoots which may be useful in modelling. Genetic variation in root growth may be useful for accessing deep soil water during grain-filling and may result in greater yields, especially under terminal drought conditions.