Are juvenile Lemna minor duckweed plants significantly smaller than their adult counterparts?

I bought some duckweed plants that are supposed to be of the species Lemna minor. They have been allowed to grow for about a month, and there are now two different sizes of plants. The larger plants are maybe a little smaller than the end of a pencil eraser. The smaller plants are about 2 millimeters length/diameter. I need to know if they are a different species, or if they are just juveniles because I am currently doing a high school science project with them. Thanks!

Are juvenile Lemna minor duckweed plants significantly smaller than their adult counterparts?
Lemna minor ==

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 a cup-shaped membranous scale containing a single ovule and two stamens. The seed is 1 mm long, ribbed with 8-15 ribs.



Excerpt above is from wikipedia .



http://koti.phnet.fi/jarkki/kasvit/Pikku...
Reply:On this site you find a lot of information incl a pic with different duckweed species to compare the sizes. It could help to find out if yours is contaminated and not L. minor only:

http://www.mobot.org/jwcross/duckweed/du...

and here another one incl specification:

http://www.mobot.org/jwcross/duckweed/du...



The maximum size is reported 0,0-2,0 cm ( http://www.aqua-fish.net/show.php?h=lemn... ) a rather large latitude to decide about your question.

This publication reports an influence of minerals on size:

http://209.85.135.104/search?q=cache:TYq...

"1.MINERAL SALT DEFICIENCY.—Duringthe experimentalwork approximately 850,000 plants of all species (about 460,000of Lemna minor) were "starved" by growing in various nutrientsolutions known to be deficient in one or more of all of theelements considered essential, in tap water or in various soil-water solutions. The plants became small in size"



Hope, one of these links will help!