VARIATION IN RADICLE ELONGATION RATE IN MACROPTILIUM ATROPURPUREUM

The northern Australian environment is characterised by high temperature and unreliable rainfall during spring and summer and seedling establishment under these conditions is frequently risky. Plants with rapid radicle elongation should be better able to establish under these conditions, as they would be able better to keep in pace with the receding front of moist soil after rainfall, enabling them to capture soil water. A controlled experiment was carried out in which differences in radicle elongation between accessions of the pasture legume Macroptilium atropurpureum were investigated. There were large differences between accessions in radicle elongation rate during the first four days after germination, and these were negatively related to provenance rainfall. Variation in radicle elongation may also exist in other tropical forage species and there may be benefit in examining this variation when seeking germplasm adapted to arid climates.