Plant Science Department, Marrone Bio Innovations, Davis, California, United States of America.
PLoS One. 2013 Sep 5;8(9):e71457. doi: 10.1371/journal.pone.0071457. eCollection 2013.
Echinochloaoryzicola(syn.E. phyllopogon) is an exotic weed of California rice paddies that has evolved resistance to multiple herbicides. Elimination of seedlingsthroughcertain weed control methods can limit the spread of this weed, but is contingent on accurate predictions of germination and emergence timing, which are influenced by seed dormancy levels.In summer annuals, dormancy can often be relieved through stratification, a period of prolonged exposure to cold and moist conditions.We used population-based threshold models to quantify the effects of stratification on seed germination of four E. Oryzicola populations at a range of water potential (Ψ) and oxygen levels. We also determined how stratification temperatures, moisture levels and durations contributed to dormancy release. Stratification released dormancy by decreasing base Ψ and hydrotimerequired for germination and by eliminating any germination sensitivity to oxygen. Stratification also increased average germination rates (GR), which were used as a proxy for relative dormancy levels. Alternating temperatures nearly doubled GR in all populations, indicating that seeds could be partially dormant despite achieving high final germination percentages. Stratification at Ψ = 0 MPa increased GR compared to stratification at lower water potentials, demonstrating that Ψ contributed to regulating dormancy release. Maximum GR occurred after 2-4 weeks of stratification at 0 MPa; GR were often more rapid for herbicide-resistant than for herbicide-susceptible seeds, implying greater dormancy in the latter. Manipulation of field conditions to promote dormancy alleviation of E. oryzicola seeds might improve the rate and uniformity of germination for seed bank depletion through seedling weed control. Our results suggest field soil saturation in winter would contribute towards E. oryzicola dormancy release and decrease the time to seedling emergence.
稗草（Echinochloaoryzicola）是加利福尼亚稻田中的一种外来杂草，已经对多种除草剂产生了抗性。通过某些杂草控制方法消除幼苗可以限制这种杂草的传播，但这取决于对发芽和出苗时间的准确预测，而这又受到种子休眠水平的影响。在夏生一年生植物中，休眠通常可以通过层积来缓解，即长时间暴露在寒冷和潮湿的条件下。我们使用基于种群的阈值模型来量化层积对四个稗草种群在一系列水势（Ψ）和氧水平下种子发芽的影响。我们还确定了层积温度、水分水平和持续时间如何促进休眠的释放。层积通过降低种子发芽的基础 Ψ 和需水时间以及消除对氧的任何发芽敏感性来解除休眠。层积还增加了平均发芽率（GR），GR 可作为相对休眠水平的替代指标。所有种群的交替温度几乎使 GR 增加了一倍，这表明尽管最终发芽百分比很高，但种子可能部分休眠。在 Ψ=0 MPa 下的层积与在较低水势下的层积相比，增加了 GR，这表明 Ψ 有助于调节休眠的释放。在 0 MPa 下，经过 2-4 周的层积后达到最大 GR；对除草剂抗性种子的 GR 通常比除草剂敏感种子的 GR 更快，这意味着后者的休眠程度更大。操纵田间条件以促进稗草种子休眠的缓解可能会提高通过幼苗杂草控制耗尽种子库的发芽率和均匀性。我们的结果表明，冬季田间土壤饱和会有助于稗草休眠的释放，并减少种子出苗的时间。
