摘 要

外来物种入侵已成为严重的全球现象，并对生态、经济和社会体系产生影响。入侵种植物会大大减少本地种的丰富度或存活率，并且能够完全改变陆地和淡水生境的自然生态系统。研究入侵种成功入侵的原因有助于预测和控制外来种入侵，也可以阐明入侵种和本地种在生态系统中的相互作用。然而，我们对造成植物入侵的原因的了解仍然十分有限。

与陆生植物相比，无性繁殖在水生植物中更为频繁。断枝在部分水生植物的传播和散布中尤为重要。与其他无性繁殖方式相比，断枝拓殖的优势在于：易产生和传播；生存时间长；高拓殖和再生能力。断枝的散布在许多外来种入侵和建立新生境中起到重要作用。但是对外来种水生植物断枝拓殖和建群仍缺乏研究。

本文研究了五种外来种沉水植物的拓殖（根部生长）和再生（萌芽生长）能力对不同水体营养的响应。这些能力可能从根本上影响淡水生境中水生植物传播的成功与否。本实验中使用了5种外来种沉水植物的断枝：伊乐藻(Elodea nuttallii (Planch.) H. St. John)；白花水盾草(Cabomba caroliniana A. Gray)；红花水盾草(Cabomba furcate Schult. amp; Schlult.f.)；大石龙尾(Limnophila aquatica (Willd.) Santapau)；瓦氏水猪母乳(Rotala wallichii (Hook. f.) Koehne)。经过8周的生长后，大多数断枝存活，并且各物种与营养梯度并无相互作用。除了大石龙尾外，其余4种外来种在高营养梯度下倾向于将更多生物量用于侧枝的生长。而这些外来种植物的拓殖能力也因物种和营养梯度的不同而有异。外来种植物拓殖和再生能力的不同说明了外来种沉水植物在散布潜力上的差异。实验结果提供的证据表明：水体营养是促进繁殖体在淡水生境中传播的重要因素。

关键词：传播；植物入侵；沉水植物；植物茎段

Dispersal Abilities of Fragments of Introduced Exotic Submerged Macrophytes Are Improved by Water Nutrients

ABSTRACT

The invasion of exotic species is considered to be a serious global phenomenon, resulting in ecological, economic, and social systems consequences. Plant invaders can greatly diminish the abundance or survival of native species and can completely alter the native ecosystem in terrestrial and fresh water habitats. Identifying the factors associated with the success of invasive species is helpful in predicting its invasion and controlling exotic species and to elucidate the interaction between invasive and native species in ecosystems. However, our understanding of the characteristics that contribute to invasion is still limited.

Compared with terrestrial plants, asexual reproduction is more frequent in aquatic plants. Stem fragments are important for propagation and dispersal in some aquatic plants. Compared to other means of asexual propagation, fragments have advantages in its easy production and dispersal, long periods of survival and high colonization and regeneration abilities. The dispersal of fragments plays an important role in invading and establishing a new habitat for many invasive weeds. However, researches of fragment production and establishment in exotic aquatic species are lacking.

This study tested the colonization (root production) and regeneration (shoot production) abilities of five exotic submerged macrophytes in response different water nutrient gradients. These abilities may ultimately influence the success of macrophyte dispersal in aquatic habitats. Fragments of five common exotic submerged macrophytes were used in this experiment Elodea nuttallii (Planch.) H. St. John, Cabomba caroliniana A. Gray, Cabomba furcate Schult. amp; Schlult.f., Limnophila aquatica (Willd.) Santapau, Rotala wallichii (Hook. f.) Koehne. After 8 weeks growth, most of the fragments survived, and there was no interactions between nutrients gradients and species. Except for R. wallichii, the other four exotic species tended to invest more biomass into the shoot growth in high water nutrients conditions. The colonization abilities of these exotic species were also varied among species and nutrients gradients. The differences in colonization and regeneration abilities among fragments of exotic species indicate that these exotic submerged macrophytes differed much in their dispersal potential. Our results provide evidence that water nutrients are important factors that drive the propagule dispersal in aquatic habitats.

Key words:dispersal； plant invasions；submerged macrophytes； vegetative stem fragment

目录

1 前言 1

1.1 水生植物无性繁殖的类型：断枝（stem fragment） 1

1.2 水体营养对水生植物无性繁殖的影响 2

1.3 水生植物无性繁殖与生物入侵 2

1.4 太湖水质及沉水植物群落现状与主要问题 3

1.5 本研究的内容、目的与意义 4

2 实验材料、实验方法和植物的化学分析 4

2.1 实验材料 4

2.2 实验设计 6

2.3 统计方法 6

3 实验结果 7

4 讨论 19

4.1断枝的再生 19

4.2根系与茎叶 20

4.3生物量的分配 21

结 论 22

致 谢 23

参考文献 24

1 前言

1.1 水生植物无性繁殖的类型：断枝（stem fragment）

水生植物在全球大多数淡水生态系统中都是重要的组成部分，并且绝大部分水生植物分布广泛，在不同类型的淡水水体中均被发现(Cook, 1985)。与陆生植物不同，水生植物的传播主要依赖植物断枝，并且该繁殖体在维持种群数量上起到了显著的作用(Santamaría, 2002)。然而种子的传播对维持种群数量的作用却甚微(Barrat-Segretain, 1996)。一般情况下，部分物种很少产生种子(Orchard, 1979)如粉绿狐尾藻（Myriophyllum aquaticum (Vell.) Verdc.）。即使部分物种产生大量种子，在其原产地种子也极少萌发。其他外来种如伊乐藻（Elodea canadensis Michx.）在其入侵地如欧洲不产生任何种子(Cook and Urmi-Ko¨ nig, 1985)。虽然外来种沉水植物种子萌发率极低，在其入侵地仍依靠无性繁殖体大量繁殖入侵。

水生植物断枝的产生有多种原因：如穗状狐尾藻（Myriophyllum spicatum L.）可由自身诱导脱落产生断枝；也可由于水流扰动，洪水带动沉积物，水鸟、鱼类或人类的干扰而产生（Umetsu et al.）。断枝一旦产生便可漂浮到水面，通过水流、水鸟或人类活动被传播到各处(Riis et al., 2009)。部分断枝甚至能抵抗干燥环境得以存活(Barnes et al.,2013)。第一个被发现可在根部产生断枝的沉水植物为穗状狐尾藻，甚至在其断枝接触底泥之前，根部就可产生随水漂流的断枝。