Several aspects of the maternal environment (e.g. air temperature, soil moisture, soil nutritional status and photoperiod) are known to influence seed production and quality in a range of plant species. However, little is known about the effect of other environmental factors, such as the light intensity perceived by the developing plant, on these seed characters. This is particularly important when elucidating the persistence mechanisms of annual weeds that may produce seeds under a crop canopy. Therefore, the aim of the present study was to determine the effect of light intensity on the reproductive characteristics of a number of wild oat (Avena fatua L.) lines originating from a range of locations in Australia. Under a reduced light intensity and in the absence of competition, the overall plant growth, seed production, seed weight and depth of seed dormancy (but not seed viability) were all reduced compared with that seen in plants growing in full sunlight. In addition, the reduced light intensity conditions significantly increased plant height and reduced tiller production, but did not affect leaf area production. In general, these responses were the same for all six lines studied and indicate that the reduced light intensity perceived by late germinating weeds present within a crop canopy causes the production of seeds with traits that are likely to result in rapid loss from the soil seed bank. In addition, all lines grown under the reduced light intensity conditions had an extended development time (up to 70 days), that it would be unlikely that they would reach maturity before the crop was harvested, and therefore would not be able to return any seed to the soil seed bank.
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