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入侵植物少花蒺藜草种子异型性及种群维持策略

花匠小妙招
2024-11-10 18:27

摘要： 少花蒺藜草（Cenchrus pauciflorus Benth.）是科尔沁沙地入侵最为严重的杂草之一。以少花蒺藜草的异型性种子为对象，通过分析其生物学特征、萌发特性以及人工去除对P型种子萌发的影响，探究少花蒺藜草在科尔沁沙地的种子异型性和种群维持策略。结果表明，少花蒺藜草一个刺苞内有两粒或以上种子（以两个种子为多）；同一刺苞内相对较大、外形似芒果的种子（M型种子）大于另一个相对较小、外形似李子的种子（P型种子），两异型种子在长、宽、高及百粒重上存在较大差异，P型种子各特征的变异系数均略高于M型种子；自然生境下，一个刺苞内萌发一粒种子（M型）的概率可达到93%，萌发2粒种子（M型、P型）的概率仅为7%，萌发3粒种子的概率为0；室内实验显示，同一刺苞内萌发一粒种子的概率为69.3%，萌发2粒种子的概率为22.2%，萌发3粒种子的概率为8.5%；野外早期去除少花蒺藜草植株地上部分对当年种群数量的影响不大，晚期去除会导致少花蒺藜草种群数量减少；室内去除刺苞内已萌发的M型种子的胚根和胚芽后，P型种子的萌发率仅为20.15%，P型种子可能对少花蒺藜草种群的维持起独特的作用，并受环境条件制约且有一定的阈值。

关键词: 少花蒺藜草, 种子多型性, 萌发机制, 生活史对策

Abstract: Cenchrus pauciflorus Benth. is one of the most invasive weeds in Horqin Sandy Land. To explore the seed heteromorphism and population maintenance strategy of C. pauciflorus, we assessed the biological characteristics and germination traits of seeds, and the effects of artificial removal on the germination of P-type seeds. The results showed that two or more seeds were detected in the same bur of the C. pauciflorus (most contained two seeds). One type of seeds was bigger and looks like mango (type M), and the other type was smaller and looks like plum (type P). Seed length, width, height and weight were significantly higher for M-type seeds than P-type seeds. However, the variations of seed characteristics for P-type seeds were higher than M-type seeds. In natural habitats, the probability of one seed (M-type) germinated in one bur reached 93%, while the rate of two seeds (both M-type and P-type) germinated in the same bur was only 7%. We did not detect three seeds germinated in the same bur in the natural habitats. In laboratory germination experiment, the germination rate of one seed germinated in one bur was 69.3%, that of two seeds germinated in the same bur was 22.2%, and that of three seeds germinated in the same bur was 8.5%. Results from the field artificial removal experiment showed that clipping C. pauciflorus seedlings in spring had weak effect on its population size, while clipping C. pauciflorus adult plants in summer significantly reduced the population size of C. pauciflorus. The germination rate of P-type seeds was only 20.15% after removal of the radicle and germ of the germinated M-type seeds. Our results indicated that P-type seeds may play a unique role in maintaining C. pauciflorus population, which is subject to environmental factors and with a threshold.

Key words: Cenchrus pauciflorus Benth., seed heteromorphism, germination mechanism, life history strategy.