萍家故事（步雨清韻）

舊魂一夢帶泥香，浮上春湖不話傷。

把水同歡嘻日短，將星共語敘情長。

時逢雨迫知兄弟，處有心連見故鄉。

可笑千帆南北散，萍家獨聚享清涼。

 

 

 

Lemna minor (common duckweed or lesser duckweed) is a species of Lemna 

 

(duckweed) with a subcosmopolitan distribution, native throughout most of 

 

Africa, Asia, Europe and North America, occurring everywhere that 

 

freshwater ponds and slow-moving streams occur, except for arctic and 

 

subarctic climates. It is not reported as native in Australasia or South 

 

America, though is naturalised there.[1][2]

 

It is a floating freshwater aquatic plant, with one, two or three leaves 

 

each with a single root hanging in the water; as more leaves grow, the 

 

plants divide and become separate individuals. The root is 1-2 cm long. The 

 

leaves are oval, 1-8 mm long and 0.6-5 mm broad, light green, with three 

 

(rarely five) veins, and small air spaces to assist flotation. It 

 

propagates mainly by division, and flowers are rarely produced; when 

 

produced, they are about 1 mm diameter, with a cup-shaped membranous scale 

 

containing a single ovule and two stamens. The seed is 1 mm long, ribbed 

 

with 8-15 ribs.[3][4][5]

 

It grows in water with high nutrient levels and a pH of between 5 and 9, 

 

optimally between 6.5 and 7.5, and temperatures between 6 and 33 °C.[6] 

 

Growth of colonies is rapid, and the plant frequently forms a complete 

 

carpet across still pools when conditions are suitable. In temperate 

 

regions, when temperatures drop below 6 to 7 °C it develops small, dense, 

 

starch-filled organs called 'turions', which become dormant and sink to the 

 

water bottom for winter; the following spring, these recommence growth and 

 

float back to the surface.[6][7]

 

 

 

Colony on a small pool

It is an important food resource for many fish and birds (notably ducks); 

 

it is rich in protein and fats.[6] Birds are also important in dispersing 

 

the species to new sites; the root is sticky, enabling the plant to adhere 

 

to the plumage or feet while the bird flies from one pond to another.[8]

 

Cultivation and uses[edit]

It is often used as a plant in both coldwater and tropical aquaria as well 

 

as in outdoor ponds, though it must be frequently thinned by seining 

 

because of its rapid growth rate and may be considered a pest.[9] It is 

 

also grown as a commercial crop for animal feed, primarily for fish and 

 

poultry, as it is fast-growing and easy to harvest by surface skimming.[6]

 

Population and Competition[edit]

Lemna minor is structurally adapted to grow quickly. That enables it to 

 

populate bodies of water rapidly. It overcomes inter-species competition by 

 

growing a thick carpet over still water bodies, thereby shading out other 

 

plant species below it and eliminating the competition. With intra-specific 

 

competition, it will compete by absorbing as much of its surrounding 

 

resources as possible so that it has the energy to grow and reproduce.