Re: Why do lotus roots have big holes in them.

There are a lot of misapplications of botanical terms such as referring to an
underground stem as a root (Hershey 2004, 2005). Another example of that is
ginger root, which is actually a rhizome, a type of underground stem. The "root"
of the lotus (Nelumbo nucifera) is actually a rhizome as well.

The holes, shown in the first reference, are termed aerenchyma (Comis 1997,
Evans 2004). They provide a pathway for air from above the water surface to
reach the underwater parts. Plant cells require oxygen. I'm not sure if the
holes have to be that large or not.

Rhizomes are often the main reproduction method under natural conditions. The
plants just spread via rhizomes to cover the available area. If a piece of
rhizome is separated from the original plant (termed fragmentation) it becomes a
separate plant. The last reference discussed how seeds can remain viable for
decades and serve as a backup reproduction mechanism or to spread into new
environments not already occupied by lotus. Rhizomes are an important method of
reproduction for gardeners who want a specific cultivar.

The last refence mentions that some seeds float and some sink but either can
germinate.

Do a google.com search for Nelumbo nucifera and you can find lots of information
on lotus. Shen-Miller et al. (1995) germinated 1,300 year old lotus seeds. At
the time, it was the oldest seed longevity known but has now supposedly been
surpassed by a 2,000 year old date seed.

References


Lotus


Lotus


Comis, D. 1997. Aerenchyma: Lifelines for Living Underwater. Agricultural
Research 45(8):4-8. August 


Evans, D.E. 2004. Tansley review: Aerenchyma formation. New Phytologist 161:
35-49


Hershey, D.R. 2004. Avoid Misconceptions When Teaching about Plants.


Hershey, D.R. 2005. More Misconceptions to Avoid When Teaching about Plants


Shen-Miller, J., Mudgett, M.B., Schopf, J.W., Clarke, S. and Berger, R. 1995.
Exceptional seed longevity and robust growth: Ancient sacred lotus from China.
American Journal of Botany 82: 1367-1380.


Nelumbo (Lotus) Germination & Seedling Growth