Effect of water stress during seed development on morphometric characteristics and dormancy of wild radish (Raphanus raphanistrum L.) seeds

The effects of water stress on morphometric characteristics of wild radish seeds as well as the expression of its seed dormancy were investigated in a pot trial at Roseworthy, South Australia in 2005. This experiment was carried out in a completely randomised design with five water regimes (control, S4, S5, S6 and S8) and four replicates. The water stress was exerted by withholding irrigation and placing the pots under a rain shelter at different growth stages starting with the onset of flowering (S4) and ending with the completion of flowering (S8). Wild radish pods from all the treatments were collected fortnightly from November 11 to December 23, 2005 (four collection dates). Seed dormancy was tested with and without pod for all treatments in January and May 2005. All morphometric characteristics of pods including pod wall weight and seed weight were negatively affected by water stress. Pods sampled earlier had thicker pod walls and greater pod segment weight. The germinability of all treatments increased with pod removal. The dormancy level tended to be lower in later collected pods. This Study showed that expression of seed dormancy was influenced by water stress during reproductive development. Therefore, variability in spring rainfall could have a major influence on the level of dormancy in seeds of this weed species produced in different growing seasons.