Posted by Zackary Gran on April 10, 2006

Q: I'm a little confused with my science fair project. Does the taproot actually take in water and help the growth of the plant or is it the root hairs that supply the water to the plant? The taproot seems to be searching for water, but from all that I have read, it is the roothairs that take in the water? thank you for whatever you can tell me.

A: I can easily see why you might be confused about this structure - I'm not so sure myself. I looked up some references in botany books and there was no discussion about the taproot directly taking up water and nutrients. The taproots main function, as I'm sure you already know, is to anchor the plant and provide a base from which the "active" roots can grow.

However, what about its initial development at germination? Seems to me that this is the only root availabe at first that can take up water and nutrients. It would seem that it is possible then that the taproot does in fact take up water but quickly ceases this function once other roots are growing and absorbing water and nutrients. You are correct in noting that the root hairs are where "the action is".

I'm going to email a botany professor at Cornell University and see what he thinks. I'll get back to you ASAP. Sure hope I haven't confused you more. Thanks.

John Wiessinger ( April 11, 2006)

A: Zackary, my botany connection at Cornell provided an answer that needs a bit of explanation. Iím including his answer along with some ìclarificationî that Iíve put in () for you. I sure hope this helps. Thanks for your excellent question.

Immediately after germination, the hypocotyl (this becomes the plantís first root structure) is the seminal (original structure that gives rise to the) root responsible for all uptake. In an annual, the "taproot" continues to function until the plant dies. In perennials, once the root differentiates (has different parts for different functions) and the outer surface becomes suberized (cells thicken and can no longer can absorb water and nutrients), there is little direct water uptake. Root hairs per se are single cells growing from roots. In nature, root hairs are uncommon and short lived. Fine roots are a better term for what your friend refers to, I think.

John Wiessinger ( April 12, 2006)