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I believe all vascular plants produce root hairs (I need to double
check Lycophytes). I'm certain Gymnosperms do and 99% sure ferns do
(my plant anatomy book is not closeby at the moment,FYI Lycophytes
aren't ferns). As mentioned in the last letter Bryophytes (and
Algae) don't make roots and therefore cannot have root hairs. Their
root like structures are called rhizoids. A thallus refers to a
leaf-like structure and although it absorbs nutrients it doesn't
really fit the original posters criteria of being a hairlike
structure(rhizods come off the
thallus in many bryophytes though, just look at Ricciocarpus natans).
You can often see roothairs on floating plants with the naked eye.
Often when you see main roots with lots of fuzzy hair like roots
from the side of the root (hundreds of them, not just a few side
roots)they are root hairs (they could possibly be lateral roots
instead, see my next sentence). If you had a microscope you could
verify it because each root hair is an extension of a single
epidermal cell, not a distinct cell or cells itself. So in the end
the answer is either roots, root hairs or rhizoids depending on your situation.
Date: Thu, 16 Jan 2003 09:04:51 -0500
From: "Karpa-Wilson, Douglas" <dkarpawi at indiana_edu>
Subject: Root hairs and dangly thingies in floating plants
> Subject: Re: Please help finish this sentence
> ... Help please and feel free
> to correct me or suggest a term while you're at it.
> "Floating Plants - Plants which float on the surface of the water,
> deriving needed nutrients from the water via hairlike structures
> called ______. "
> The answer is--------root hairs
}"Thallus" and "leaves" would also be correct. e.g. : Riccia and
}Myriophyllum, the microphylls of moss.
}Hairlike structures, absorb nutrient through these structures, can
Until Tom posted I hadn't really read the original posting. Actually,
"root hairs" isn't correct. Root hairs are very small (usually
microscopic) protruberances from epidermal cells of angiosperm roots (at
least I think only angiosperms produce them), so the visible dangly
things in the case of duckweed and other flowering plants that float are
probably just roots. These roots may also have root hairs on them, but
they wouldn't be visible to the naked eye. In the case of ferns and
floating mosses, they'd be called something else, although I'd guess
their anatomy is a little tweaked from the usual fern anatomy. A
thallus refers to the undifferentiated vegetative mass of mosses,
liverworts, fungi, etc., that does not have leaves, stems and roots,
i.e. the gametophyte, haploid generation, which in the case of
liverworts (like Riccia) and mosses, that's what we're looking at. In
the case of ferns like Salvinia or Azolla, they'll be megaphylls or
So the short answer is: it depends on what the plant is.