Reproductive and stress resistance characteristics of wild oat and its allelopathic effects on common wheat

As a widespread malignant weed in farmlands, wild oat has strong survival ability and can adopt multiple strategies to cope with various and changing environmental stresses. This high adaptive ability always makes wild oat to occupy a dominant place in the interspecific competition. In this study, the reproductive and dispersal characteristics of the population, stress resistance of seeds and seedlings, and allelopathic effects (root exudates) on common wheat seedlings of wild oat were investigated. The study aimed to understand the survival strategies of wild oat and find effective methods of controlling natural spread of this plant species. The main results of the study were as follows:1) Wild oat had a strong sexual reproduction and population dispersal ability in farmland ecosystems. This included earlier flowering and higher grain-setting than common wheat, high seed yield, huge seed bank, far seed dispersal distance, etc. 2) The germination of wild oat seed occurred within a wide temperature range and could germinate normally under room or varying temperature conditions. Room temperature was the optimum condition for wild oat seed germination after freezing treatment, which was highly benefited the plant by breaking seed dormancy and increasing total germination rate to up to 93.33%. 3) Wild oat seed had some adaptable responses to the salt stress, but germinated normally when NaCl concentration was below 1.80%. 4) Wild oat seedling was also adapted very well to both salt and drought stresses. Proline accumulation in seedling leaf of wild oat increased significantly (P < 0.01) with gradual increase in NaCl or PEG concentration. However, catalase activity of wild oat seedling leaf increased at the start of NaCl or PEG stress and then declined as NaCl or PEG concentration increased. 5) Root aqueous extract of wild oat negatively affected the plant height, plant dry weight, root length and root vitality of wheat, which was significant at P < 0.01 level. This demonstrated that the root of wild oat had a strong allelopathic effect on the growth of common wheat seedling. The above results suggested that the competitive advantage of wild oat was reflected in several ways-strong sexual reproduction and seed dispersal ability, high resistance to salt and drought adversities, and significant allelopathic effect on adjacent plants. Related in depth studies were required to provide firm theoretical basis for controlling wild oat dispersal in farmlands, especially in wheat fields.