水淹对三峡水库消落带苍耳种子萌发的影响

The Effect of Flooding on the Germination of Xanthium sibiricum Seed in the Water-level Fluctuation Zone of the Three Gorges Reservoir

三峡水库实验性蓄水后,水库消落带内出现了罕见的苍耳(Xanthium sibiricum)带。通过对不同水淹处理后苍耳种子萌发特性的测定,研究水淹对苍耳种子萌发的影响。结果表明,苍耳种子具有较强的耐淹能力,即使受近8个月原位水淹胁迫,90%以上的苍耳种子依然保持有生活力。在25℃下,原位水淹的苍耳种子去总苞后的发芽率显著降低,并且发芽率随着水淹强度的增加而降低。在25℃且种子未去总苞条件下,室内干藏的苍耳种子的发芽率与三峡水库消落带海拔160m和150m处放置的苍耳种子的发芽率差异不显著,但显著低于放置在三峡水库消落带海拔170m处的苍耳种子的发芽率。室内浅水浸泡8个月后,苍耳种子各项发芽指标显著提高。短期的原位水淹可以促进具总苞的苍耳种子在常温下的萌发,而长期的原位水淹会降低苍耳种子的萌发,并且其发芽率随着水淹时间的延长和水淹深度的增加而逐渐降低。

Common cocklebur （Xanthium sibiricum） was widely distributed in the water-level fluctuation zone of the Three Gorges Reservoir after its impoundment to 156 m in elevation. Flooding maybe accelerated the germination of common cocklebur and it was likely to be the explanation of the phenomena. The aim of present paper was to determine the influence of water submergence on the germination of common cocklebur. The result showed that more than ninety percent of seeds even submerged in situ for even eight months were still alive. The germination rate of in situ inundated seeds at 25 ℃ was significantly depressed and was negatively related with submerged period. The germination rate of the seeds with bur stored in dry and airy indoor environment was not significantly different with the germination rate of seeds placed in the drawdown area with 160 m and 150 m in elevation respectively, but it was significantly lower than the germination rate of the seeds placed in the drawdown area with 170 m in elevation. All the germination indicators were significant improved after eight months’ indoor submergence. Thus, it is visible that short term in situ submergence can improve germination of the seeds with burr at common temperature, while long term in situ flooding would depress germination of the seed of common cocklebur. The negative effect of flooding on germination strengthened as the prolonging of submerged periods and increasing of water depth.